Monday Morning Key

26 ODP related abstracts

Section Session Location Title Author Time

GP11 A MCC level2

Marine Controlled Source Electromagneticsfor Gas Hydrate Evaluation on the CascadiaMargin: Correlation Between ResistivityAnomalies and Seismic Blank Zones

Schwalenberg, Ket al. 8:00

GP11 B MCC level2

Age Offsets of the Matuyama-BrunhesPolarity Transition in Records From theAtlantic: Lock-in Depth Variations or SiteDependent Field Behavior?

Clement, B. et al. 8:00

Paleomagnetic and Rock MagneticInvestigation of Leg 210 Cores,Newfoundland Basin

Liu, Q et al. 8:00

Paleomagnetic and Rock MagneticSignature of Upper Oceanic Crust Generatedby Superfast Seafloor Spreading: Resultsfrom ODP Leg 206

Acton, G. et al. 8:00

Paleomagnetic Paleolatitudes of the OntongJava Plateau From 120 Ma to 55 Ma:Implications for the Apparent Polar WanderPath of the Pacific Plate.

Hall, S. et al. 8:00

Geomagntismand

Paleomagnetism

GP11 D MCC level2

Magnetic Properties and Paleointensity of aMid-Miocene Gabbro from the Costa RicaAccretionary Wedge, ODP Leg 170

Hawkins, L. et al. 8:00

Mineral and RockPhysics MR11 A MCC level

2

Calibration of Mobile NMR Instruments inRespect to Porosity and Pore SizeDistribution of Drill Cores

Arnold, J et al. 800

New Insights into Inferring ClimateVariability from Records of PlanktonicForaminiferal Mg/Ca, Oxygen Isotope andShell Weight in the Southern Ocean

Greaves, M. et al. 8:00

Paleoceanographyand

PaleoclimatologyPP11 A MCC level

1 Changes in Deep Sea Temperature and IceVolume Based on Paired Measurements ofBenthic Foraminiferal Mg/Ca and d18O:Evidence from ODP Site 849, EquatorialPacific for Marine Isotope Stages 1-3

Healey, S L 8:00

Section Session Location Title Author Time

The Nature of the d13C of PeriplatformSediments: Implications for stratigraphy

Swart, P K 8:00

Orbitally Paced Climate VariabilityDuring the Middle Miocene: HighResolution Stable Isotopes and FeRecords From the Western andSoutheastern Pacific

Holbourn, A 8:00

Middle Eocene to early Oligocenepaleoceanography of the Southern Oceanfrom foraminiferal stable isotope andMg/Ca records

Bohaty, S et al. 800

PP11 A MCClevel 1

Cenozoic variations in the SouthAtlantic carbonate saturation profile:Insights from the Walvis depth-transect(ODP Leg 208)

Schellenberg, Sand Nielsen, J 800

New Data On The Distribution OfCalcareous Nannofossils During AndAfter The Paleocene/Eocene Transition

Raffi, I 800

Depth Dependant Variations in BenthicForaminiferal Assemblages and StableIsotopes Across the P-E Boundary,Walvis Ridge (ODP Leg 208)

McCarren, H etal. 800

Marine carbonate dissolution eventacross the Eocene/Oligocene boundary:the Walvis Ridge transect, SouthAtlantic (ODP Leg 208)

Liu, Z et al. 800

Tracers of Productivity across thePETM, Walvis Ridge, ODP Sites 1262and 1263

Quartini, J C etal 800

The Composition and Flux ofTerrigenous Material from the latePaleocene to the early Eocene in theIndian Ocean

Nicolo, M J 800

Paleoceanographyand

Paleoclimatology

PP11 B MCClevel 1

Extreme Acidification of the Deep Seaat the Paleocene-Eocene Boundary: NewConstraints From Ocean DrillingProgram Leg 208

Zachos, J et al. 800

Section Session Location Title Author Time Paleoceanographic changes inthe western tropical Atlanticduring the late Paleocene (59-55Ma): high-resolution stableisotope records from ODP Leg207 Site 1258

Romano, M et al. 800

PP11 B MCClevel 1

Decoupled Shelf-OceanPhytoplankton ProductivityResponses Across the Paleocene-Eocene Thermal Maximum

Gibbs, S J et al. 800

Paleoceanographyand

Paleoclimatology

P11 C MCC2004

Late Quaternary BiosiliceousLaminated Marine SedimentsFrom Antarctica: SeasonalityDuring a Period of RapidClimate Change

Pike, J et al 815

Ice shelf drill sites proposed tostudy Pre-Late Oligocene climateand tectonic history, CoulmanHigh, Southwestern Ross Sea,Antarctica.

Decesari, R et al. 800

T11 A MCClevel 2

Evidence That Early to MiddleMiocene ice Streams From WestAntarctica cut Into SoutheasternRoss Sea Continental Shelf

Sorlien, C et al. 800

Holocene Turbidite RecurrenceFrequency off NorthernCalifornia: Insights for SanAndreas Fault Paleoseismicity

Nelson, H et al. 1205

Tectonophysics

T12 B MCC3002 Cascadia Great Earthquake

Recurrence: Correlation Evidencefor Repeated Margin WideRupture

Goldfinger, C etal. 1050

Monday Afternoon Key

21 ODP Related abstracts

Section Session Location Title Author Time

Union U14 A MarriottSalon 7

LGM to Holocene Africanclimate variability and the Sr, Nd,and Pb isotope ratios of eoliandeposits off northwest Africa

Cole, J et al. 1700

Data Management for the Ridge2000 Program Chayes, D et al. 1340

 Biogeoscience

 B13 A

MCClevel 1

Evidence for Along-StrikeHydrothermal Circulation WithinYoung Oceanic Crust on theEastern Flank of the EndeavourAxis, Juan de Fuca Ridge

Hutnak, M et al 1340

Teaching Biostratigraphy UsingReal Cores and IODP Data: Theuse of Information Technology onSpatial Visualization Skills,Motivation and Transfer ofUndergraduate Science Majors

Hilding-Kronforst et al. 1340Education

andHuman Resources

ED13 E MCClevel 2

Writing and Visualization forTeaching Plate Tectonics

Thomas, S F 1340

Geomagnetism andPaleomagnetism GP13 A MCC

3112 A Pilot Marine EM Study ofHydrate Ridge, Oregon.

Weitemeyer, Ket al. 1455

Timing of Late Quaternary seasurface temperature change:Evidence from high-resolution {\itGlobigerina bulloides} Mg/Carecords from the CaliforniaMargin

Pak, D et al. 1300

Primary Productivity Changes inthe subtropical western NorthAtlantic During Marine IsotopeStages 11-12: Inferences fromBenthic Foraminifera

Poli, M et al. 1340PP13 A MCClevel 1

MILLENNIAL-SCALECLIMATE VARIABILITY INTHE SUBTROPICALATLANTIC DURING THEMIDDLE PLEISTOCENE

Gibbons, F et al 1340

   

Paleoceanographyand

Paleoclimatology

PP13 B MCC2004 Sea-surface and deep-sea Tripati, A 1455

Section Session Location Title Author Time Calcareous Nannofossils andOrbitally Tuned Cyclostratigraphyin the Cenozoic

Raffi, I 1425

PP13 B MCC2004

Oxygen Isotopic Stratigraphy andGeomagnetic Field Intensity

Meynadier, Land

Valet, J1440

Revisiting ODP Site 690 toAssess the Responses of MarineCarbonate Chemistry to thePaleocene-Eocene ThermalMaximum

Kelly, D et al 1645

Paleoceanographyand

Paleoclimatology    

PP14 A MCC2004

Multiple Early Eocene ThermalMaximums Roehl, U et al. 1615

T13 A MCClevel 2

Airborne Gravity GradiometerSurvey Over the San AndreasFault

Talwani, M 1340

Magnetic Properties of OceanCrust from the Walls of EndeavorDeep: Implications for the SourceLayers of Marine MagneticAnomalies

Richmond, R etal. 1340

T13 B MCClevel 2

Structure of the Upper CrustExposed at Endeavor Deep:Implications for Crustal Accretionat Ultra-Fast Spreading Rates

Popham, C et al. 1340

Tectonophysics 

T14 C MCC3002

Analysis of the Growth of ActiveDetachment Folds Applying thenew Thickness Relief Method,With Examples From the Tien-Shan and Nankai Trough

Gonzalez-Mieres,R andSuppe, J

1650

Along Strike Hf-Nd IsotopicComposition of Aleutian ArcLavas

Gerseny, M et al. 1340

The Hf-Nd isotopic diversity ofsubducting oceanic sediments

Vervoort, J et al. 1340Volovanology,Geochemistry,

Petrology 

V13 B 

MCClevel 2 Characterizing Sedimentary

Carbon and Nitrogen SubductionFluxes in the Central AmericaConvergent Margin (ODP Legs170, 205)

Li, Land

Bebout, G1340

Tuesday Morning Key

13 ODP Related abstracts

Section Session Location Title Author Time

Union U21 A MCClevel 2

Late Pleistocene Paleoclimate RecordFrom the SW African Margin

Shackford, J 800

Biogeoscience B21 D MCClevel 2

Carbon Biogeochemistry of MarineSediments at the ODP Leg 204, HydrateRidge

Li, Y et al. 800

Educationand

HumanResources

ED21 C MCClevel 1

Experiences and Results from theIntegrated Ocean Drilling Program(IODP) Teacher at Sea Program,Expedition 301

Rice, J et al. 800

Geodesy G21 A MCClevel 1

An Experiment on GPS/A SeafloorPositioning in the Central Part of Kumano-nada, Central Japan

Fujimoto, H etal. 800

OS21 A MCClevel 2

Authigenic Dolomite in MarineMarginal Sediments: An Indicator ofFossil Microbial Activity

Vasconcelos, Cet al. 800

OS21 E MCC3011

Slope Instability and Gas Hydrates in theHudson Canyon Region, U.S. AtlanticContinental Margin

Rona, P et al 930Ocean Sciences

  

OS22 B MCC3011

Size and Age Characteristics for WestCoast Tsunamigenic Landslides

Lee, H et al. 1120

Tectonophysics T21 C MCClevel 1

Long-Term Observations of ActiveHydrothermal Processes on the GordaRidge: The Sea Cliff Hydrothermal Fieldand Escanaba Trough

Von Damm, Ket al. 800

Tephrochronology of North PacificVolcanic Arcs - data from ODP Leg 145

Prueher, L 850Volcanology,Geochemistry,

Petrology   

V21 C MCC3008 Terrestrial-marine Correlation of the 24

kyr BP Dawson Tephra: Implications forDispersal and Preservation of AlaskanTephra Deposits

Beget, J et al. 820

Section Session Location Title Author Time An ocean floor prospecting: Implicationsfrom the petrological insights of theabyssal chromitites from ODP Leg 209,MAR 15 20 N FZ

Abe, N 1055

Geochemical Study of Mid AtlanticRidge Peridotites From 15\deg N:Preliminary Results From ODP Sites1272 and 1274

Godard, M et al 1125Volcanology,Geochemistry,

PetrologyV22 A MCC

3008

Upper Mantle Geochemistry atPeridotites of Site 1274 (ODP Leg 209):Relation to Melt-Rock Reaction andProcesses at the Base of the Lithosphere

Suhr, Gand

Paulick, H1140

Tuesday Afternoon Key15 ODP Related abstracts

Section Session Location Title Author Time

Union U23 A MarriottSalon 7

MIS 11 and the mid-Brunhes DissolutionInterval Barker, S et al. 1440

Geomagnetismand

PaleomagnetismGP24 A MCC

3024

Hotspot motion, scales of mantleconvection and the long-term history of thegeydynamo

Tarduno, J 1610

Ocean Sciences OS23 A MCClevel 2

Secondary Teachers and Their Students;Why you Need Them, Where to Find Themand How to Make Them Your Number OneAudience!

Peart, L 1340

Do Tropical SST Changes Lead HighLatitude Climate Change, Or Are OurProxies Misleading Us?

Dekens, P et al. 1340

High Latitude and Tropical ClimatesLinked Prior to the Onset of NorthernHemisphere Glaciation: Evidence Fromthe Eastern Tropical Pacific

Lawrence, K et al. 1340

Early Onset and Origin of 100-kyr Cyclesin a Tropical Pleistocene SST Record

Liu, Zand

Herbert, T1340

PP23 A   

MCClevel 2

Detrital Sediment Supply And LateQuaternary Environmental Changes OffTaiwan, ODP Site 1202

Hofmann, J et al 1340

High resolution paleoceanography of thecentral Gulf of California during the past15,000 years

Barron, J et al. 1340

Pleistocene North Atlantic Deep WaterProduction; A Southern HemispherePerspective

Foote, J et al. 1340

Optical Dating of Marine Sediment FromODP Core 658B - An IntercomparisonWith an Independent AMS 14CChronology

Armitage, S et al. 1340

 Paleoceanography

andPaleoclimatolgy

     

PP23 B  

MCClevel 2

Fulfilling the Promise of the DSDP/ODPLegacy with Multiparameter Logging ofArchive Cores

Schultheiss, P et al 1340

New insights into serpentinization atAtlantis Massif, 30° N Mid-Atlantic Ridge,using wide-angle seismic method

Singh, S et al. 1340

Magnetization Of Gabbroic Rocks andPeridotites Recovered From Mid AtlanticRidge 14N - 16N, ODP Leg 209

Kikawa, E et al. 1340

Lithium and strontium isotopecompositions of serpentinite-hostedcarbonate veins from the MAR (ODP Leg209): Records of different stages ofseafloor metamorphism

Rosner, M et al. 1340

Volcanology,Geochemistry,

PetrologyV23 B MCC

level 1

Extensional Faulting at 15\deg North on theMid-Atlantic Ridge, ODP Leg 209 Schroeder, T et al. 1340

Wednesday Morning Key

11 ODP Related abstracts

Section Session Location Title Author Time

Union U31 A MCClevel 1

Warmer tropics during stage 11 - evidencefrom the Cariaco Basin Lea, D

ED31 A MCClevel 2

Out To Sea: Life as a Crew Member Aboard aGeologic Research Ship'' - Production of aVideo and Teachers Guide.

Rack, Fand

Tauxe, K800

Educationand

Human ResourcesED31 C MCC

level 2

Learning Activities Developed at TheUniversity of Texas at Austin Institute forGeophysics Using Ocean Drilling Science,Technology and Data

Bailey, D et al. 800

Volcanic Influence on the SusceptibilitySignal: a Case Study in Indian Ocean

Salome, A et al 800Geomagnetism and

Paleomagnetism 

GP31 B MCClevel 2

Rock Magnetic Properties Across Paleocene-Eocene Boundary Sediments from the NorthAtlantic, South Atlantic, and Eastern Pacific

Lippert, P et al. 800

Evidence For Deep-water Production In TheNorth Pacific During The Early Cenozoic Thomas, D 800

PP31 B MCC2000 Planktonic Foraminifera Study at Site ODP

999A (Caribbean Sea): Insights into OceanicExchange and Paleocirculation During the last

450 Kyrs.

Vautravers, M etal. 800

Tracking Warm Saline Deep Water on MaudRise Using Nd Isotopes Martin, E et al. 815

Paleoceanographyand

Paleoclimatology

PP32 AMCC2000 Structure of the Penultimate Deglaciation

Along the California Margin and Implicationsfor Milankovitch Theory

Cannariato, K etal. 1120

V31 A MCClevel 2

Evidence for Extremely Large Lava Flows onOntong Java Plateau from High PrecisionMeasurements of Volatiles and MajorElements in Natural Glasses

Michael, P 800Volcanology,Geochemistry,

Petrolgy 

V31 B MCClevel 2

Gabbro fracturing and elemental analysis inthe Costa Rica margin (ODP Leg 205): Core-log integrated high-resolution study

Thu, M et al. 800

Wednesday Afternoon Key

16 ODP Related abstracts

Section Session Location Title Author Time Rapid true polar wander: Aquixotic search?

Cottrell, R etal. 1340

Union U33 A MCClevel 1

Paleomagnetic Data FromOntong Java Plateau areAnomalous $\sim$ Did thePlateau Form on Another Plate?

Sager, W 1340

Biogeoscience B33 B MCClevel 1

Testing the Molecular ClockUsing the Best Fossil Record:Case Studies from the PlankticForaminifera

Steel, B et al. 1340

Geomagnetismand

PaleomagnetismGP34 A MCC

2000

Determination of RelativeContributions from Marine andTerrestrial Sediment Sources inthe Cariaco Basin using aMagnetic Mixing Model

Verosub, K etal. 1630

OS33 A MCClevel 1

Holocene and Glacial Variabilityof the Hydrologic Cycle in theTropical Atlantic: Evidence fromthe Cariaco Basin

Dulski, P et al 1340

Sediment Accumulation Rates ofLate Quaternary Deposits in SanPedro Basin, the Gulf of SantaCatalina, and San Diego Trough,Offshore Southern California

Normark, Wet al. 1340

OS33 B MCClevel 1 Relations Between Basement

Tectonics, Sediment Deformationand Fluid Flow at the Eastern Juande Fuca Ridge Flank: ResultsFrom Very High ResolutionSeismic Data

Zuehlsdorff,L and

Spiess, V1340

Mechanism for free gas migrationthrough South Hydrate Ridgehydrate system

Liu, X andFlemings, P 1630

Ocean Sciences

OS34 B MCC3010 Structural Controls on Hydrate

Distribution and Morphology atHydrate Ridge, Oregon

Weinberger, Jand Brown, K 1615

Section Session Title Author Time

An Excess $^{226}$RaGeochronology for Saanich Inlet

Grayson, R etal 1340

Differentiation of CenozoicEolian Dust Sources in theEastern Pacific by Nd-Sr-PbRadiogenic Isotopes

Stancin, A etal. 1340

PP33 A MCClevel 2

High Resolution Record ofSeawater Osmium Isotopes Overthe Last 100,000 Years

Zylberberg, Det al 1340

Paleoceanographyand

Paleoclimatology

PP33 B MCClevel 2

High Resolution CalcareousNannofossil Fluctuations Acrossthe Oligocene/Miocene Boundary,ODP Hole 1168A

McGonigal, K 1340

V33 E MCClevel 2

Trace Element and Isotopic (Re-Os, O) Systematics of RobertsVictor Eclogites: Evidence for 3Ga Subduction-Incorporation ofArchean Oceanic Lithosphere intothe South African KaapvaalCraton Keel

Shirey, S etal. 1340

Plume-Ridge Interaction on theCocos Plate (ODP Leg 205, CostaRica): Implication for FluidCirculation

Chavagnac, Vet al. 1630

Volcanology,Geochemistry,

Petrolgy

V34 B MCC3006 Hawaiian Hotspot - Spreading

Ridge Interaction in the LateCretaceous: A Fair and BalancedLook at the Evidence

Keller, R 1745

Thursday Morning Key

17 ODP Related abstracts

Section Session Location Title Author TimeData Acquisition,

Management,Display

SF41 A MCClevel 2

High Tech High School Interns Developa Mid-Ocean Ridge Database forResearch and Education

Staudigel,D et al. 800

Education andHuman Resources ED41 C Marriott

Salon 4Undergraduate Student Research with theIntegrated Ocean Drilling Program onExpedition 301

Hawkins, Let al. 900

MCC2000

Field Geometry During the IcelandBasin Event Observed from the NorthAtlantic Ocean, North Pacific Ocean andthe South China Sea

Laj, C et al. 830

GP41 B A 300 kyr Record of GeomagneticExcursions and Paleointensity From theIrminger Basin: Candidates for MonoLake, Laschamp, Iceland Basin, Jamaicaand Pringle Falls?

Channell, J 815

Geomagnetism andPaleomagnetism

A paleomagnetic record of the last 640kyr from an eastern Mediterranean pistoncore and a review of geomagneticexcursions in the Brunhes

Oda, H etal. 945

MCClevel 1

Estimation of Free Gas Saturation UsingAVO Analysis on 3D Seismic Data atSouth Hydrate Ridge, CascadiaAccretionary Complex

Xun, H etal. 800

OS41 C Analysis of Sonic Velocity in an ActiveGas Hydrate System, Hydrate Ridge,Offshore Oregon

Guerin, Get al. 800Ocean Sciences

OS42 A MCC3011

Medusa-Isosampler: A modular,network-based observatory system forcombined physical, chemical andmicrobiological monitoring, samplingand incubation of hydrothermal and coldseep fluids

Schultz, Aet al. 1135

Paleoceanographyand

PaleoclimatologyPP41 A MCC

level 1

Late Cenozoic reduction in AntarcticCircumpolar Current flow from analysesof drift deposits along the AntarcticPeninsula, ODP Site 1095

Hassold, Net al. 800

Section Session Location Title Author Time Enriched MORB in the NortheasternPacific, Petrological and GeochemicalFeatures of igneous Basement at Site1224, ODP Leg200

Haraguchi, Set al. 800

T41 A MCClevel 2

Atlantis Bank as a Key to Understandingthe Nature of the Moho and Crust-MantleBoundary

Matsumoto, Tet al. 800

Varying Rates and Modes of SubductionErosion Along the Peruvian Margin

Kukowski, Net al. 800

T41 C MCClevel 2

Structural vergence variation andclockwise block rotation in the Cascadiaaccretionary wedge, offshore centralOregon

Johnson, J etal. 800

T41 C MCClevel 2

Metamorphic Tectonites and DifferentialExhumation Reveal 3D Nature ofExtension and Lower Crustal Flow in theActive Woodlark Rift, Papua New Guinea

Little, T et al. 800

Distribution of Post-Rift Sills on theNewfoundland Nonvolcanic MarginAround the ODP Leg 210 Transect FromWaveform Inversions and SyntheticSeismograms

Shillington, Det al. 800

T41 E MCClevel 2

Opal diagenesis and sediment propertiesin the Nankai Trough, Japan

Spinelli, G etal. 800

Tectonophysics

T42 B MCC3000

Stratigraphic Control on Excess PorePressure at the Plate Boundary Fault ofNankai Trough

Underwood,M et al 1120

Thursday Afternoon Key19 ODP Related abstractsSection Session Location Title Author Time

Late Miocene-Recent Magnetic PolarityStratigraphy and Astro-Chronology From ODPSites 1207, 1208, 1209, 1210, 1211 and 1212-Shatsky Rise

Evans, H et al. 1340

30 Myr of polarity stratigraphy and relativepaleointensity from Equatorial Pacificsediments (ODP Sites 1218 and 1219, Leg199)

Lanci, L et al. 1340

Deep-tow Study of Magnetic Anomalies in thePacific Jurassic Quiet Zone

Tominaga, Met al. 1340

Holocene relative paleointensity andpaleosecular variation from the SouthernOkinawa Trough (ODP Hole 1202B)

Richter, C etal. 1340

Geomagnetismand

Paleomagnetism GP43 BMCClevel 2

Different magnetostratigraphic approaches:Lake Baikal sediments and the J/K boundarystrata in the Tethyan realm

Pruner, P et al. 1340

OS43 A MCClevel 2

Global Distribution of Microbial Alteration ofthe Ocean Crust Josef, J et al. 1340

A Three-Dimensional Subseafloor ObservatoryNetwork for Cross-Hole, HydrogeologicExperiments Established in the NortheastPacific Ocean

Fisher, A et al. 1340Ocean SciencesOS43 B MCC

level 2Geology of Smooth Ridge: MARS-IODPCabled Observatory Site

Jordahl, K etal. 1340

PP43 A MCClevel 1

Excess Aluminum and the Quantification ofTerrigenous Material in Pelagic BiogenicSediment: An Update and Eye for the Furture

Murray, R. etal. 1340

Antarctic Timing of Surface Water Changesoff Chile and Patagonian Ice-sheet ResponseBased on ODP Site 1233

Lamy, F et al. 1340

Pliocene Shoaling of the Central AmericanSeaway and its Effect on Caribbean andTropical East Pacific Upper OceanStratification

Steph, S et al. 1410

Regime Shifts in Climate Forcing of PeruDenitrification

Altabet, M etal 1440

Paleoproductivity and Paleoclimate offSouthern Chile During the last Deglaciation.Diatom and Phytoliths Records from Site 1233

Abrantes, F etal. 1455

Linking Global Climates BetweenHemispheres and Ocean Basins: Millennial-Scale Temperature and Isotopic Variability ofIntermediate and Mid-Depth Watermasses ofthe Equatorial and Southeast Pacific.

Mix, A et al 1510

PP43 B MCC2000

Paleomagnetic Results From ODP Leg 202:The Chilean Margin Sites Stoner, J et al. 1525

Paleoceanographyand

Paleoclimatology

PP44 A MCC2000

Deep Ocean Temperature and Salinity at theLast Glacial Maximum

Adkins, J andSchrag, D 1600

Friday Morning Key

32 ODP Related abstracts

Section Session Location Title Author Time

Education andHuman Resources ED51 C MCC

level 1USIO-IODP Developing a NewFellowship for HBCU Students

Castner, A etal. 800

Data Modeling, Development,Installation and Operation of the

ACEX Offshore Drilling InformationSystem for the Mission Specific

Platform Expedition to the LomonosovRidge, Arctic Ocean.

Conze, R et al 800Global Climate

Change GC51 D MCClevel 2

A Test for Extending the High-Resolution Global Climate Record in

Santa Barbara Basin

Hopkins, S etal. 800

Ocean Sciences OS52 A MCC3011

Jack Dymond's "Fingerprints" onSediment Chemistry, Biogeochemical

Fluxes, and my Career

Leinen, Met al. 1055

PP51 A MCClevel 2

Duration of Pliocene Ice-RaftingEvents Offshore of Prydz Bay,

Antarctica, Derived FromExtraterrestrial Helium-3

McAuley, A etal. 800

Radiolarian and SedimentologicPaleoproductivity Proxy Record From

the Benguela Upwelling System,DSDP Site 532, 0-6 Ma

Bittniok, BEt al. 800

PP51 B MCClevel 2

The Late Miocene Carbon Isotope Shiftand Marine Biological Productivity.

Diester-Haass,L et al. 800

The early Eocene in the SouthernOcean; an integrated dinocyst and

geochemical analysis of ODP Leg 189sites 1171 and 1172, Tasman Sea.

Deltrap, R et al. 800

Eocene-Oligocene Southern OceanPaleo-bathymetry maps generated with

geophysical, sedimentological andmicrofossil data.

Brown, B et al 800

Radiolarian and SedimentologicEvidence for Late Eocene Origin of

Southern Ocean EnvironmentsLazarus, D et al 800

Evolution of North AtlanticThermohaline Circulation: From the

Greenhouse to the Icehouse

Via, Rand

Thomas, D800

Paleoceanographyand

Paleoclimatology

PP51 D MCClevel 2

Orbital forced sea level fluctuationsduring the Middle Eocene (ODP site

1172, East Tasman Plateau)

Warnaar, J etal. 800

Friday Afternoon Key

21 ODP Related abstracts

Section Session Location Title Author Time

Biogeosciences B53 A MCClevel 2

Poroelastic Parameters of Peru MarginSediments: Implications for Flow andTransport at Multiple Scales in the MarineBiosphere

Gettemy,G et al. 1340

Global ClimateChange GC53 A MCC

3020

Late Quaternary Paleoenvironmental Historyof the Peru-Chile Current System and AdjacentContinental Chil

Lamy, Fet al. 1340

Hydrology H53 E MCC3009

Marine Sedimentary Record of CenozoicMonsoon Intensity Preserved in the AsianMarginal Seas

Clift, P 1525

$^{15}$N depleted nitrogen isotope values inCretaceous black shales: paleoceanographicevent or diagenesis

Junium, Cand

Arthur, M1340

Evaluation of Geochemical Proxies Preservedin the Sapropel Record from the EasternMediterranean Within the Pliocene-HoloceneTime Interval

Gallego-Torres, D

et al.1340PP53 B MCC

level 2

Implications of Mn-Mg-rich ContaminantPhases for Mg/Ca Past TemperatureReconstructions

Pena, L etal. 1340

The evolution of atmospheric carbon dioxidesince the middle Eocene: a biomarkerperspective

Pagani, Met al 1355

A Cenozoic terrestrial isotope record and theevolution of C$_{4}$ photosynthesis

Gr”cke, Det al. 1410PP53 D MCC

2000 A 10 Million Year, High-Resolution Record ofC4 and C3 Plant Evolution from Arabian SeaODP Site 722

Huang, Yet al. 1530

Evidence for an Open Drake Passage in theLate Middle Eocene

Scher, Hand

Martin, E1600

Exploring the CarbonateProduction/Dissolution Paradox in the Mid-Bruhnes of the Southern Ocean Using CoupledRecords of Biological and Chemical Dynamics

Flores, Jet al. 1615

Paleoceanographyand

Paleoclimatology

PP54 A MCC2008

Two Highly-Resolved Geochemical Recordsof Holocene Variability: A ComparisonBetween West and East Antarctica

Kryc, K etal 1655

Section Session Title Author Time

PP54 A MCC2008

Paleoceanography and Paleoclimatology of theSouthern Ocean: A Synthesis of Three Decadesof Scientific Ocean Drilling

Warnke,D et al. 1710

Timing and Nature of the Deepening of theTasmanian Gateway

Stickley,C 1620

ACEX: A first Look at Arctic Ocean CenozoicHistory

Moran, Kand

Backman,J

1635

Paleoceanographyand

Paleoclimatology

PP54 B MCC2000

From Greenhouse to Icehouse: Evidence forLate Early Eocene Concomitant Cooling ofSouthern Ocean Surface Waters and GlobalDeep Waters From Dinoflagellate Endemism

Brinkhuis,H et al. 1650

Tectonophysics T53 A MCClevel 1

Extremely Rapid and Localized Erosion in theHimalaya Recorded in Sediments of the BengalFan

Stewart Ret al. 1340

V53 B MCC3006

Thallium Isotope Constraints on HydrothermalWater Fluxes at Mid-Ocean Ridge Axes andFlanks

Rehkamper, M et al. 1455

V53 C MCC3008

The Mantle Plume Hypothesis Pro and Con:Evidence from Earth's Most Voluminous Large

Igneous Provinces

Ingle, Sand

Coffin, M1425

Pb and Other Trace Elements in MeltInclusions From Modern Seafloor TectonicSettings

Beaudoin,Y et al. 1615

Volcanology,Geochemistry,

Petrology

V54 B MCC3006 Deep Marine Sediment Diagenesis of

Germanium, Silica, Lithium and LithiumIsotopes in ODP-177: The "Missing OceanicGe Sink"

Froelich,P and

King, S1730

HR:14:40h AN: U23A-05 TI: MIS 11 and the mid-Brunhes Dissolution Interval AU: * Barker, S et al.

AB: The mid-Brunhes dissolution interval (MBDI) represents a prolonged period ofmarine carbonate dissolution centred around Marine Isotope Stage 11 (MIS 11). TheMBDI has been observed in all the major ocean basins and at all water depths. Wepresent a 1Myr foraminiferal shell weight record from ODP site 982 in the North Atlantic(57.5N, 15.9W, 1134m) which is strongly affected by dissolution over this period,demonstrating the vulnerability of even shallow sites to the effects of dissolution. From acompilation of carbonate mass accumulation rates (MARs) we suggest that a globalincrease in marine carbonate production was responsible for the carbonate crash at thistime. This is a variant on the basin to shelf hypothesis which argues that enhanced growthof shallow water carbonates in low latitudes during MIS 11 resulted in a globaldissolution event. We model the effects of the proposed increase in carbonate productionwithin the constraints of observed atmospheric CO2 variability.

HR: 1340h AN: U33A-0024 TI: Rapid true polar wander: A quixotic search? AU: * Cottrell, R D et al.

AB: Studies in the 1960's emphasized that polar wander could be a significantcomponent of apparent polar wander curves. These concerns were assuaged whensubsequent tests revealed that polar wander components were very small andoverwhelmed by plate motion. Nevertheless, the concept of large and rapid polar wanderhas been surprisingly resilient. It gained new support in the 1980's when polar wanderwas defined in a fixed hotspot frame of reference and called ``true polar wander" (TPW).This new TPW was correlated to a wide variety of phenomena, from the rate ofgeomagnetic reversals to anomalous volcanism, but the linkages often differed sharplybetween studies. And renewed investigations, including paleomagnetic studies of theEmperor seamounts (ODP Leg 197), have emphasized that hotspot drift can be relativelyrapid (over 40 mm/yr). We trace problems in some past and recent TPW hypotheses to anoverreliance on the hotspot reference frame. The failure to scrutinize independently thetwo key components (APWPs and hotspot tracks) in directional space has led to illusoryshort-term spurts of TPW and overestimates of long-term rates. We review tests that canbe used to detect these artifacts. The exclusion of hotspot drift reduces total ``TPW"displacements so that they are near the level of other competing explanations that mightaccount for variation in global paleomagnetic pole positions (e.g. reconstructionuncertainities and inadequate geomagnetic field averaging). This vanishingly smallamount of polar wander suggests that locally developing mantle mass heterogeneitiesmay have been naturally balanced by global mantle flow in the post-Jurassic Earth.

0800h AN: U31A-0011

TI: Warmer tropics during stage 11 - evidence from the CariacoBasin AU: * Lea, D and Peterson, L EM AB: Marine Isotope Stage (MIS) 11 stands out as the most extreme interglacial episodeof the last million years. But evidence for unusual warmth in the tropics at this timeremains equivocal. A proxy SST record from the equatorial western Pacific (ODP 806B -Lea et al., 2000; Medina et al., this meeting) suggests that MIS 11 was the warmest timeinterval of the last million years. A key question that directly addresses the hypothesesproposed to explain MIS 11 is whether anomalously warm SSTs were a common featureof the tropics at this time. The Cariaco Basin, an anoxic marine basin on the northernshelf of Venezuela, preserves a unique high resolution climate record of the southeasternCaribbean/tropical Atlantic. This record is continuous through the last 580,000 years andincludes multiple varved intervals. Records from this basin have been instrumental inestablishing ties between tropical climate records and high latitude ice core and oceanicrecords. Paleothermometry based on planktic foraminiferal Mg/Ca works well in theCariaco Basin because of the presence of a wide range of planktic species and superbpreservation of carbonates, including pteropods. We have analyzed Mg/Ca in samplesfrom ODP Hole 1002C (10ø42.73'N, 65ø10.18'W, 893ÿm water depth) that span MIS 11.Our preliminary results, covering the interval 402-409 ky BP, from surface dwellingGlobigerinoides ruber yield Mg/Ca values of 4-5 mmol/mol, equivalent to SSTs of 26.5-28 degrees C. For comparison, Mg/Ca values in the Holocene range from 4-4.5mmol/mol, equivalent to SSTs of 26-27.5. We are in the process of adding further resultsto evaluate how systematic this difference is. Poore and Dowsett (2001) reported oxygenisotope results from the same sequence and species and found that MIS 11 values were0.3 permil more depleted than the Holocene. Our preliminary Mg/Ca-SST results suggestthat most of this difference is not due to higher SST, suggesting either lower Cariacosalinity at this time and/or a negative shift in mean ocean O18 related to higher sea levelduring MIS 11. These findings will be considered in light of the unusual climate state thatprevailed during MIS 11. HR:

17:00h AN: U14A-04 TI: LGM to Holocene African climate variability and the Sr, Nd,and Pb isotope ratios of eolian deposits off northwest Africa AU: Cole, J M et al. EM: AB: Abrupt changes in African climate from the last glacial period through the Holocenehave been documented in a core located off Cap Blanc, northwest Africa, ODP Hole658C (deMenocal et al, 2000). Large changes in terrigenous sedimentation to the ocean,due in large part to humid-arid shifts in terrestrial vegetation, are observed in the percentterrignous and Th-230 normalized terrigenous flux measurements. While there is overallhigh biogenic and eolian terrigenous sedimentation, terrigenous input decreased duringthe African Humid Period (AHP, 14.8-5.5 kyr). Additionally sea surface temperatureswere lower during that time compared to the later Holocene. Others have shown thatradiogenic isotope isotope ratios of terrigenous deposits from marine and ice cores varyover time and provide provenance information. Alternatively, it has been suggested thatchanges in Sr isotope ratios of dust may relate to the degree of chemical weathering. Wesampled the <63 micron detrital fraction to measure the Sr, Nd and Pb isotope ratios inorder to quantify the eolian dust proportion and potential source regions. Nd and Pbmeasurements record source area contributions. However, Sr isotope data indicate a clearshift toward less radiogenic values during the African Humid Period, where as there is nocorresponding change in Nb and Pb values. Additionally, we observe an abrupttermination of the AHP and other rapid events. This research seeks to enhance ourunderstanding of African and low-latitude responses to global climate forcings over thelast deglaciation. \

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0800h AN: U21A-0704 TI: Late Pleistocene Paleoclimate Record From the SW AfricanMargin AU: Shackford, J K et al.

AB: Late Pleistocene sediments recovered from ODP Leg 175, Site 1085 are used togenerate a high-resolution (500 yr) record of continental climate change in SouthernAfrica. Sedimentological, geochemical, and clay mineralogical variations of the CapeBasin sediments for the last 200 k.y. are used to determine transport pathways ofterrigenous load and continental climate change in southern Africa. The location of Site1085, the SW African continental slope, provides a continuous hemipelagic section witha significant terrigenous component. Terrigenous sediments are either fluvial or eolian,with fluvial load possibly being controlled by monsoonal circulation and insolation(Christensen et al., 2002; Murray et al., 2002) and eolian by glacial intensification oftrade winds. Analyses, including grain size (transport), color reflectance (terrigenousinput), biogenic sediment geochemistry including %CaCO3, % organic carbon, and C:N(terrigenous input, productivity), bulk sediment geochemistry (continental climate,terrigenous sediment source, and productivity), benthic foraminiferal stable isotopes(chronology), and clay mineralogy (source, continental climate, transport pathways), areused to identify continental climate conditions in southern Africa, and to address possibleforcing mechanisms of climate change in the region during the last 200 k.y. Analysesindicate significant glacial and interglacial variation. Color reflectance and %CaCO3covary down section, with highest values during MIS1, while there is an inversecorrelation between color reflectance, median grain size and C:N ratios, with greatestterrigenous carbon during MIS 1. Peaks in median grain size are associated withboundaries between MIS 1 and 2 as well as MIS 2 and 3. Our results differ from Stuut etal. (2002), who find increased eolian sediments from grain size within glacial stages onthe Walvis Ridge, north of the Cape Basin, rather than at the boundaries. Claymineralogy, determined after removal of calcite, indicates the presence of smectite,different from the modern regional maps of Petschick et al. (1996). Presence of smectitedowncore may attest to increased continental weathering and possibly a more humidclimate in Southern Africa. D

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1340h AN: U33A-0032 TI: Paleomagnetic Data From Ontong Java Plateau areAnomalous $\sim$ Did the Plateau Form on Another Plate? AU: * Sager, W W EM AB: A recent study of Ocean Drilling Program basalt core paleomagnetic data fromOntong Java Plateau (OJP) found paleolatitudes that disagree with previous estimates ofthe Early Cretaceous Pacific APWP, a result attributed to poor quality of data used inprior pole calculations [Riisager, P., S. Hall, M. Antretter, X. Zhao, Earth Planet. Sci.Lett., 208, p. 235, 2003]. My compilation of paleomagnetic data from Cretaceous Pacificbasalt cores drilled by the Deep Sea Drilling Project and Ocean Drilling Program showsthat paleocolatitude data in of ages 118-129 Ma display greater scatter than other agebins. The only factor that allows this data group to be coherently subdivided is whetheror not the coring site is located on OJP. Without OJP data, paleocolatitude scatter is muchless and gives a similar pole position (48.9$\deg$N, 327.1$\deg$E, N=40) to data in the110-118 Ma interval. Data from the plateau give a pole that is 15$\deg$ farther north(64.9$\deg$N, 323.4$\deg$E; N=37), indistinguishable from late Jurassic and earliestCretaceous skewness poles. The OJP and non-OJP poles are distinct at the 95$%$confidence level despite having indistinguishable mean ages of 121.6 $\pm$1.1 Ma (OJP)and 123.4 $\pm$4.1 (non-OJP). Because Ontong Java Plateau data come from 6 differentsites spread over the northern plateau, tectonic tilting is not a likely explanation for thedifference. Also unlikely are systematic errors such as incomplete averaging of secularvariation (large number of independent magnetic units sampled), inaccurate radiometricdates (many high quality dates), or inadequate paleomagnetic techniques (detailed studiesby several different investigators). Rapid true polar wander does not seem a plausibleexplanation because global true polar wander curves have a different trend. Perhaps thesimplest explanation is the one often used when anomalous data are found within a plate:the anomalous region had a different history of tectonic drift. In this scenario, OJPformed on a separate plate that drifted southward relative to the Pacific plate beforebecoming attached. This finding is similar to theAŸ’'A+ƒ_TAŸƒ_sA,A›AŸ’'A,A›AŸA›A›ƒ_sAªA.A_AŸƒ_sA,AªAŸ’'A›ƒ,ªA_AŸA›A›ƒ_sAªA.ƒ_oStealthPlateAŸ’'A+ƒ_TAŸƒ_sA,A›AŸ’'A,A›AŸA›A›ƒ_sAªA.A_AŸƒ_sA,AªAŸ’'A,A_AŸƒ_sA,A¨AŸƒ_sA,A« hypothesis [Larson, R. L., and W. W. Sager, Proc. ODP, Sci. Res.,129, p. 471, 1992], which was formulated to explain a similar angular difference betweenskewness-derived paleolatitudes from the Hawaiian and Japanese magnetic lineationsrelative to the Phoenix lineations. The most significant challenge for this hypothesis,however, is to account for the space and plate boundaries. If true, this hypothesis implieseither that much of the Jurassic Quiet Zone seafloor was created by Pacific-Stealthspreading or that an unknown plate boundary near OJP separated the plateau from the restof the Pacific plate.

HR: 0800h AN: SF41A-0764 TI: High Tech High School Interns Develop a Mid-Ocean RidgeDatabase for Research and Education AU: Staudigel, D et al.

Ridges (MOR) represent one of the most important geographical and geological featureson planet Earth. MORs are the locations where plates spread apart, they are the locationsof the majority of the Earths' volcanoes that harbor some of the most extreme life forms.These concepts attract much research, but mid-ocean ridges are still effectivelyunderrepresented in the Earth science class rooms. As two High Tech High Schoolstudents, we began an internship at Scripps to develop a database for mid-ocean ridges asa resource for science and education. This Ridge Catalog will be accessible viahttp://earthref.org/databases/RC/ and applies a similar structure, design and data archivalprinciple as the Seamount Catalog under EarthRef.org. Major research goals of thisproject include the development of (1) an archival structure for multibeam and sidescandata, standard bathymetric maps (including ODP-DSDP drill site and dredge locations) orany other arbitrary digital objects relating to MORs, and (2) to compile a global data setfor some of the most defining characteristics of every ridge segment including ridgesegment length, depth and azimuth and half spreading rates. One of the challengesincluded the need of making MOR data useful to the scientist as well as the teacher in theclass room. Since the basic structure follows the design of the Seamount Catalog closely,we could move our attention to the basic data population of the database. We have pulledtogether multibeam data for the MOR segments from various public archives(SIOExplorer, SIO-GDC, NGDC, Lamont), and pre-processed it for public use. Inparticular, we have created individual bathymetric maps for each ridge segment, whilemerging the multibeam data with global satellite bathymetry data from Smith & Sandwell(1997). The global scale of this database will give it the ability to be used for any numberof applications, from cruise planning to data

HR: 0800h AN: B21D-0908 TI: Carbon Biogeochemistry of Marine Sediments at the ODPLeg 204, Hydrate Ridge AU: * Li, Y et al. EM AB: ODP Leg 204 was drilled on the Oregon continental margin to determine thedistribution and concentration of gas hydrates in an accretionary ridge. Themicrobiological communities and biogeochemical properties of the hydrates are ofspecial interest. Our goal was to study carbon biogeochemistry in the marine sedimentscollected from boreholes 1245B, 1245C, 1250D, 1244E and 1244F. The total organiccarbon of all boreholes had a narrow range of \delta$^{13}$C values (-21.3 to -22.3\permil), indicating the predominance of a homogeneous source. Lipids wereextracted from bulk sediment and separated into neutral-, glycol- and polar-fractionsusing silicic acid columns. The polar lipids were treated further for analyses ofphospholipids fatty acids (PLFA) and compound-specific carbon isotope ratios. TotalPLFA was low (less than 80 pmol/g) in boreholes 1245B and 1245C and generallydecreased with depth. Total PLFA in borehole 1250D, however, increased with depth,ranging from 33 pmol/g at 30.24 mbsf (meters below seafloor) to 426 pmol/g at 134.7mbsf. On the other hand, total PLFA in boreholes 1244E and 1244F were high (338.1 to444.2 pmol/g) but without any obvious trends with depth. Overall, saturated fatty acidswere predominant (less than 45% to 82%) in these borehole sediments and terminallybranched fatty acids, indicative of sulfate-reducing bacteria, were up to 15% of totalPLFA. In borehole 1250D, saturated fatty acids decreased from greater than 80% at thetop of the core to less than 45% at depth. Meanwhile, the monounsaturated fatty acidsincreased from several percent to more than 20% with depth. The \delta$^{13}$C valuesof PLFA ranged from -45\permil to -50\permil, which were significantly lower than bulkorganic carbon. It is unclear, however, whether these low values are attributed to theanaerobic oxidation of methane, which is known to occur in other gas hydrates of theHydrate Ridge and Gulf of Mexico. DE HR

: 1340h AN: B13A-0158 INVITED TI: Data Management for the Ridge 2000 Program AU: * Chayes, D N et al. EM AB: Since the start of this effort (September 1, 2003) we have developed a data baseschema, selected and installed a relational data base management system (PostgreSQL),designed, developed and, deployed a draft set of metadata forms, ingested data from tenRidge2000 cruises as of September 2004 and deployed a web accessible Ridge2000 dataportal: http://www.marine-geo.org/ridge2000/ . At the portal, one can get content usingwith pre-constructed queries for survey targets and deployed instruments at each of theR2K Integrated Study Sites. Alternatively, our data link allows spatial, temporal andkeyword searches to identify and download data. The current metadata forms have beenused for 6 cruises and we have received constructive feedback (in addition to the actualmetadata) from all three R2K integrated study sites. We are working on incorporating thisfeedback into an updated set of forms which we expect to release early in 2005. Otherrecent include substantial improvements to GeoMapApp, links to other data repositories,a major update of our web site, integration with data from Arctic, Antarctic, Marginsdata sets and the pre-constructed queries on the R2K portal page. Our plans for 2005include: A second major revision of the metadata forms in early '05, improvements in themetadata ingestion process, enhanced authentication using LDAP, continued activeparticipation in the broader data community developing interoperability as well asimplementing direct interoperability with a number of complementary databasesincluding the underway geophysical and multibeam databases at National GeophysicalData Center, the National Deep Submergence facility at Woods Hole, the GeologicalData Center of the Scripps Institute of Oceanography, and the databases of the ODP(JANUS at TAMU, and Borehole Geophysics at LDEO) UR

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1340h AN: B13A-0183 TI: Evidence for Along-Strike Hydrothermal Circulation WithinYoung Oceanic Crust on the Eastern Flank of the Endeavour Axis,Juan de Fuca Ridge AU: * Hutnak, M et al. EM AB: Many geological, geophysical, and geochemical indicators at spreading centerssuggest that the dominant direction of fluid circulation may be along-strike, subparallel tothe primary orientation of neovolcanic and near-ridge faulting. Researchers are beginningto identify additional evidence from young ridge flanks for along-strike fluid (and heatand solute) flow. We present newly-compiled thermal, swath-map, and seismic datacollected on young crust east of the Endeavour Segment of the Juan de Fuca Ridge.Hydrosweep data reveal several prominent basaltic outcrops just north of the ODP Leg168 drilling transect, within an area experiencing a hydrothermal transition (HT) fromexposed to sediment-covered basement. Seafloor heat flow is strongly suppressed 20 kmeast of the spreading center, and the pattern of thermal rebound with increasing distancefrom the ridge has been interpreted as evidence for dominantly across-strikehydrothermal circulation. We show that within one part of the hydrothermal transition,located on 1.2-1.3 Ma seafloor, the data are at least as well explained by along-strikefluid circulation, with cold seawater recharging through outcrops to the north of the HTarea. Application of a simple analytical model for coupled heat and fluid flow suggestsspecific discharge in basement on the order of 1 m/yr, a rate consistent with earlierestimates of across-strike circulation, and with independent estimates of driving forcesand crustal permeability. Dominantly along-strike circulation has also been inferred on3.5 Ma crust to the east of the HT area, suggesting that this mode of fluid transport maybe the rule, rather than the exception, on this young ridge flank. Since primary flow pathsare likely associated with tectonic processes that occur during and soon after the crust isformed, it seems probable that along-strike fluid flow is also important today at theEndevaour Segment. DE HR:

1340h AN: B53A-0985 TI: Poroelastic Parameters of Peru Margin Sediments:Implications for Flow and Transport at Multiple Scales in theMarine Biosphere AU: * Gettemy, G L et al. EM AB: As part of a broader investigation of the deep marine subsurface environment, thefirst biosphere-focused drilling expedition, Leg 201, of the Ocean Drilling Program(ODP) occupied five unique sites in the Peru Margin (in a 1200 km$^2$ region centeredat 10 S, 80E). These sites represent the entire range of shallow biogeological conditionsassociated with this convergent margin:deep-water, mixed clay-pelagic sediments ocean-ward of the trench; slope-apron and prism toe sediments at the deformation front; andseveral distinct lithostratigraphic sequences on the continental shelf. Microbialenumeration and pore-water geochemistry results show that each particular site is bothconsistent and unique--consistent in terms of general biotic quantity and activity aspredicted by energy flux and redox potential given the depositional environment andsedimentary record, but unique at key biogeological boundaries such as lithologic and/orphysical property interfaces. This research addresses questions related to ourunderstanding of how and why these boundaries form by looking at poroelastic andhydrologic parameters measured at multiple scales, from sub-millimeter to severalcentimeters. The issue of measurement scale, especially in regard to permeability anddiffusivity characterization, is vital to interpreting observations of biologically-mediateddiagenetic fronts (e.g., dolomitic lenses, depth- or time-varying barite fronts). Theseparameters are derived from (i) hydrologic and wave propagation experiments, (ii) SEMimages, and (iii) shipboard split-core measurements, and structured in a modified Biotporoelasticity framework. This approach also allows quantification of the localheterogeneity of these parameters at the scale applicable to (and controlled by) microbiallife; these results can then be used to formulate predictive models of the impact ofbiogeochemical processes. Ultimately, these models could then be used in interpretationof new remote-sensed data (e.g., from borehole tools, high-frequency backscatterdevices), a fundamental challenge for all types of biospheric imaging everywhere. DE

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1340h AN: B33B-0265 TI: Testing the Molecular Clock Using the Best Fossil Record:Case Studies from the Planktic Foraminifera AU: * Steel, B A EM AB: Criticism of molecular clock studies often centres on inadequate calibration and aperceived lack of correlation between reproductive isolation and recognisablemorphological evolution. Since many major groups (e.g. birds, mammals, reptiles) havea poor fossil record, it is often difficult to test and refute these limitations. Plankticforaminifera represent an exception to this rule. Deep-sea sediments are super-abundantin foraminifera, and large numbers of specimens and occurrences are easily garneredfrom Ocean Drilling Programme cores. Planktic foraminifera therefore represent an idealmodel group with which to test and refine molecular clock studies. Since the1990AŸA›A›ƒ_sAªA›ƒ_zA›s, genetic sequences (principally 18S r-RNA) have beenextracted from living planktic foraminifera, and a large genetic library has developed.Our study attempts to contextualise and test molecular data, particularlyAŸA›A›ƒ_sAªA<"molecular clockAŸA›A›ƒ_sAªA›ƒ_zA› dates, utilising material fromtwo ODP cores (Site 926A (Atlantic) and 806 (Pacific), to examine the evolutionaryhistory of two sibling-species complexes (Globigerinella siphonifera and Globigerinoidesruber, both common shallow-water species and both of considerable palaeoceanographicutility). Recent genetic studies have suggested that these two AŸA›A›ƒ_sAªA<"super-speciesAŸA›A›ƒ_sAªA›ƒ_zA› in fact consist of a number of isolated forms, withcontrasting ecologies and longevities, which in Recent and sub-Recent sediments can bedistinguished either on the basis of pore ultrastructure (Gl. siphonifera) or test colouration(Gs. ruber). In both cases, molecular clock estimates are indicative of ancient (7-11 Ma)intra-species cryptic divergences, which seem to be considerably older than fossil dates.In particular, the calculated molecular split between the two forms of Gs. ruber(AŸA›A›ƒ_sAªA<"whiteAŸA›A›ƒ_sAªA›ƒ_zA› andAŸA›A›ƒ_sAªA<"pinkAŸA›A›ƒ_sAªA›ƒ_zA›) of around 11 Ma is considerablydiscordant with the fossil date of around 0.7 Ma. At first glance, this may appear to be aclassic case of molecular over-estimation, often a feature of clock models, especiallywhere, as in the foraminifera, substitution rates may vary widely. However, there is goodreason to suspect that fossil range of the derivedAŸA›A›ƒ_sAªA<"pinkAŸA›A›ƒ_sAªA›ƒ_zA› form may have been artificially truncatedby diagenetic degradation of the meta-stable test pigmentation. The deep molecular splitsfor Gl. siphonifera (around 7 Ma for the two main morphologically distinguishable sub-types), whilst not so obviously at odds with the fossil record, still belie the very smallamount of morphological evolution observed within the plexus. We have usedmorphometric methods on a large (over 2000 pooled specimens) dataset in an effort toindependently test the molecular clock, using SEM-based measurement of pore metrics(for Gl. siphonifera) and a multivariate analysis of whole-test characteristics (for Gs.ruber). Comparison of results for the two species suggests interesting patterns; whilst thetwo cryptic sub-types of Gl. siphonifera seemingly can be traced through time and seemto respond to external oceanographic forcing, the sub-types of Gs. ruber appear to betruly cryptic, and cannot be distinguished in the fossil record beyond 0.7 Ma. This raises

two important points; firstly, the molecular clock (at least for foraminifera) bearsconsiderable scrutiny, appears to be relatively robust to substitution bias and is seeminglybroadly in accordance with morphological data; and secondly, the relationship betweenform and function in planktic foraminifera appears to be ill-defined, raising importantquestions for functional morphology.

HR: 0800h AN: ED31A-0734 TI: ``Out To Sea: Life as a Crew Member Aboard a GeologicResearch Ship'' - Production of a Video and Teachers Guide. AU: * Rack, F and Tauxe, K EM AB: In May 2002, Joint Oceanographic Institutions (JOI) received a proposal entitled"Motivating Middle School Students with the JOIDES Resolution", from a middle schoolteacher in New Mexico named Katie Tauxe. Katie was a former Marine Technician whohas worked aboard the R/V JOIDES Resolution in the early years of the Ocean DrillingProgram (ODP). She proposed to engage the interest of middle school students using theODP drillship as the centerpiece of a presentation focused on the lives of the people whowork aboard the ship and the excitement of science communicated through an activeshipboard experience. The proposal asked for travel funds to and from the ship, the loanof video camera equipment from JOI, and a small amount of funding to cover expendablesupplies, video editing, and production at the local Public Broadcasting Station in LosAlamos, NM. Katie sailed on the transit of the JOIDES Resolution through the PanamaCanal, following the completion of ODP Leg 206 in late 2002. This presentation willfocus on the outcome of this video production effort, which is a 19 minute-long videoentitled "Out to Sea: Life as a Crew Member Aboard a Geologic Research Ship", and ateacher's guide that can be found online. UR:

1340h AN: ED13E-0747 TI: Writing and Visualization for Teaching Plate Tectonics AU: * Thomas, S F EM AB: The Theory of Plate Tectonics is probably the most important paradigm forunderstanding the workings of our planet. As such it is an integral part in anyIntroductory Geology course. Whereas geology majors usually easily embrace the Theoryof Plate Tectonics, the enthusiasm for the coherence and elegance of this theory appearsto be much more subdued among the majority of non-science majors. While visual andelectronic media certainly support the teaching of the theory, pretty pictures andanimations are not sufficient for many non-science majors to grasp the concepts ofinteracting lithospheric plates. It is well known that students do better in learningscientific concepts if they create their own understanding through research and inquiry-based learning, by working in the field, manipulating real earth-science data, and throughwriting. Writing assignments give instructors the opportunity to assess their students'learning and to clarify misconceptions yet they also have to be willing to teach studentshow to craft a science paper. Most electronic media and textbook-added CD-ROMs arenot useful for making the structure of a science paper transparent. I found many of thenecessary ingredients for effectively teaching plate tectonics in the interactive CD-ROM,"Our Dynamic Planet", developed by Wm. Prothero together with G. Kelly (University ofCalifornia at Santa Barbara). It allows students to select and manipulate real earth-science data of plate-tectonically active regions, and provides an electronic interface thatlets students create graphical representations of their collected data. A downloadableTeacher's Manual provides suggestions on teaching students to write a scientificargument, rooted in sound pedagogy. Originally designed for a large oceanography class,the material was modified for use in a small introductory geology class for non-sciencemajors. Various assignments were given to instruct students in writing a scientificargument based on their own collected data and observations. The main goals are forstudents o To see the relationship between data and the development of a scientific theoryo To understand the elements of scientific discourse o To learn how to derive conclusionsfrom interpretations and observations o To back interpretations with observations o To beable to write a scientific argument o To understand the Theory of Plate Tectonics, and oTo gain a better understanding about how science works The results of several surveyswill be presented that confirm that most of the expected outcomes continue to be met.

0800h AN: G21A-0139 TI: An Experiment on GPS/A Seafloor Positioning in the CentralPart of Kumano-nada, Central Japan AU: * Fujimoto, H et al. EM AB: Kumano-nada, northeast of Kii Peninsula in the central part of Japan, is aseismogenic zone of the M-8 class Tonankai earthquakes that occurred repeatedly at aninterval of about 100 years. The MEXT (Ministry of Education, Culture, Sports, Scienceand Technology, Japan) initiated a 5-year program in 2003 for seafloor observations inand around Kumano-nada. Nagoya and Tohoku Universities initiated experiments onGPS/A seafloor positioning to monitor crustal deformation in the subduction zone with afocus on investigation of the effect of sound velocity structure in the ocean on seafloorpositioning (e.g., Tadokoro et al., this meeting). Tohoku group deployed five precisionacoustic transponders (PXPs) jointly developed with Scripps Institution of Oceanographyin the central part of Kumano-nada at depths of about 2,000m. The deployed PXPs A, B,C, and D form a diamond on the seafloor, and PXPs C, D, and E form a triangle.Although three typhoons were in the way of our 12-day cruise in August this year, wecarried out GPS/A observation for several days. After an observation for locating theprecise position of each PXP, we tried to keep the buoy near the center of the diamond orthe triangle. The vessel held the position within 20-30m from the center, and the buoy_fsposition was kept with 100m from the center. Kinematic GPS positioning is now underprocessing with GEONET data observed in Kii Peninsula. We also tried monitoring thesound velocity structure with 3 sets of inverted echo sounders (IESs) deployed near thePXPs C, D, and E. The IESs can monitor temporal and spatial variation in the soundvelocity structure in the triangle array of PXPs. We plan to carry out the second GPS/Aobservation in November. The result is worthy of notice. Strange earthquakes ofmagnitude 6.9, 7.4, and 6.4 occurred on the nearest Nankai Trough axis on September 5-7, 2004. Co-seismic crustal deformation observed by the GEONET was about 4 cm nearthe coast of Kii Peninsula. The seismogenic zone is in the list ocean drilling under theIODP (Integrated Ocean Drilling Program).

HR: 08:30h AN: GP41B-03 TI: Field Geometry During the Iceland Basin Event Observedfrom the North Atlantic Ocean, North Pacific Ocean and the SouthChina Sea AU: Laj, C et al. EM AB: The Iceland Basin event (IBE), which is named for a record from ODP Site 983 inthe North Atlantic Ocean (60.5øN), is a focus of growing interest in our community.This geomagnetic excursion is coeval with the marine oxygen isotope (MIS) stage 7/6boundary at about 190 ka according to the orbitally tuned SPECMAP time scale. Wehave detailed new records of this excursion at two new sites from the North Atlantic(core MD99-2247; lat. 59øN, long. 31øW and core MD99-2242; lat. 59øN, long. 47øW),at one site from the North Pacific (ODP Site 884; lat. 51.5øN, long. 168.3øE), and in twoothers from the South China Sea (ODP Site 1146; lat. 19.5øN, long. 116.3øE and ODPSite 1145; lat. 19.6øN; long. 117.6øE). For all five sites, the event is identified at the MIS7/6 boundary, which confirms its potential as a precise stratigraphic marker. The averagesedimentation rate for this portion of the cores is 7.5, 10 and 15 cm/kyr in NorthAtlantic, North Pacific and South China sea cores, respectively, which allows high-resolution studies in this time interval. The event is characterized by a marked minimumin the relative paleointensity (sometimes with a double feature) and by large swings ininclination and declination. The VGP latitudes reach 78øS and 45øS for ODP sites 1146and 1145, respectively, 37øS for ODP Site 884, and 74øS and 41øS for cores MD99-2247 and MD99-2242, respectively. The VGP paths for the four records from the NorthAtlantic and South China Sea cores are highly similar. For the most detailed of theserecords, the poles first pass over Africa, then they proceed to Antarctica and returnnorthward over Australia. The paths are less well resolved for ODP Site 1145 and coreMD99-2242, for which the poles cross the southern Indian Ocean rather than reachingAntarctica. The VGP paths for the two most detailed records (ODP Site 1146 and MD99-2247) are highly similar and are also similar to the path for ODP Site 983, which alsohas a high sedimentation rate and is precisely dated. In contrast, but in common withother published records of the IBE, the VGP path for ODP Site 884 loops in the oppositesense and passes from North to South America and then over the Pacific Ocean beforereturning to high northern latitudes. The striking similarities between multiple records fortwo observed sets of differing VGP paths for the IBE at locations spanning the northernhemisphere provides evidence for a non-dipolar, but relatively simple, HR:

08:15h AN: GP41B-02 TI: A 300 kyr Record of Geomagnetic Excursions andPaleointensity From the Irminger Basin: Candidates for MonoLake, Laschamp, Iceland Basin, Jamaica and Pringle Falls? AU: * Channell, J E EM AB: Sediments recovered at ODP Site 919, off east Greenland, record geomagneticdirectional excursions at 33 ka and 40 ka (Mono Lake and Laschamp), and at 187 ka(Iceland Basin), 208 ka (Jamaica?) and at 220 ka (Pringle Falls). U-channel records areaugmented by 1-cm discrete samples collected back-to-back alongside the u-channeltroughs. Deconvolution of the u-channel records yields records that can be closelymatched to the discrete sample data. The age-model based on planktic oxygen isotopedata (St. John et al., Marine Geology, in press) is consistent with the relativepaleointensity record and the recognition of Ash Layer 2 (55 ka). The results indicate thatthe Mono Lake and Laschamp excursions, and the Iceland Basin and Pringle Falls (andperhaps also Jamaica), are distinct excursions, rarely recorded together in individualstratigraphic sections. Why are they recorded at ODP Site 919? Mean sedimentation ratesare 22 cm/kyr in MIS 3 where Mono Lake/Laschamp are recorded, but sedimentationrates do not appear to be especially high in MIS 7 (13 cm/kyr) where candidates forIceland Basin/Jamaica/Pringle Falls are recorded. DE HR:

1340h AN: GP43B-0854 TI: Late Miocene-Recent Magnetic Polarity Stratigraphy andAstro-Chronology From ODP Sites 1207, 1208, 1209, 1210, 1211and 1212- Shatsky Rise AU: * Evans, H F et al. EM AB: ODP Leg 198 to Shatsky Rise recovered a total of ~768 meters of Late Miocene toRecent sediments from 6 Sites. Neogene sediments at the sites consisted mostly of lightgray to pale orange nannofossil oozes with varying amounts of clay, radiolarians anddiatoms. Site 1208 was drilled on the Central High and provided a Late Miocene toRecent sequence with sedimentation rates ~4-5 cm/kyr. Sites 1209, 1210, 1211 and 1212were drilled on the Southern High and yielded shorter sequences of Late Miocene toRecent sediments with sedimentation rates ~1-2 cm/kyr. Clearly interpretable magneticstratigraphies have been obtained from all six sites based on shipboard data. These resultshave been augmented using discrete sample cubes (7cc) collected shipboard andmeasured post-cruise. Astrochronologies for Sites 1207 to 1211 were based on cyclesseen in reflectance data from shipboard measurements. The reflectance data for thesecores were measured using a digital imaging track system equipped with a line-scancamera. ODP Leg 198 was the first cruise after installation of the track, and thesemeasurements provided a high-resolution stratigraphic record of color variations forvisible wavelengths. These data were placed on an initial age model by pattern fit of thepolarity zones to the geomagnetic polarity timescale (GPTS) of Cande and Kent (1995).Power spectra calculated using this initial age model often show concentration of powerat orbital frequencies, particularly around the 41 kyr obliquity cycle, although the orbitalpower is more pronounced in some parts of the section than in others. The reflectancerecord was tuned to the astronomical solution for obliquity from Laskar et al. (1993).Astronomically tuned ages were estimated for polarity reversals in the 1-9 Ma interval atSite 1207. At Sites 1208 and 1209 tuning was performed in the 1-7 Ma interval and atSites 1210 and 1211 in the 1-5 Ma interval. Cross spectral analysis on the tuned agemodel indicated significant coherence between the astronomic solution and thereflectance data. The tuned timescales are compared with other published ages for thispart of the GPTS and indicate that the Shackleton et al., (1995) ages from ODP Leg 138in the 8-9 Ma interval are too young by ~100 kyrs. The astronomical timescales are inbetter agreement with the timescale of Hilgen et al., (1995) in this interval. DE HR:

0800h AN: GP11D-0869 TI: Paleomagnetic and Rock Magnetic Investigation of Leg 210Cores, Newfoundland Basin AU: * Liu, Q et al. EM AB: Leg 210, the final leg of the ODP, was devoted to studying the history of rifting andpostrift sedimentation in the Newfoundland-Iberia rift. Two sites (Sites 1276 and 1277)were drilled in the central Newfoundland Basin that are along a transect exactlyconjugated to the ODP Leg 149/173 drilling sites on the Iberia margin. Site 1276 wascored from 800 to 1739 m below seafloor with excellent recovery of Albian-lowerOligocene sediments and sills (estimated to be 100-200 m above basement). Site 1277 islocated about 40 km southeast of Site 1276. Recovered cores from the upper part ofbasement at this site represent an assemblage of basalt flows, slivers of gabbro,serpentinized peridotite, and sediments. Below these rocks, basement is serpentinizedperidotite with veins of gabbro. Stable components of magnetization are revealed in theresults of detailed thermal and AF demagnetization on the sediments and diabase sillsfrom Site 1276 and serpentinized peridotites from Site 1277. Azimuths of the maximumanisotropy axis of magnetic susceptibility are used to evaluate the fidelity of the naturalmagnetic memory of the serpentinized peridotites. Combining the age informationavailable from other Leg 210 studies, we estimated paleolatitudes vs. time for theNewfoundland drill sites. Results from a series of rock magnetic measurements show that(titano)magnetites are present in the diabase sill and serpentinized peridotites, whereasmaghemite is mainly responsible for the magnetic signatures displayed in thesedimentary and volcanic succession at Site 1277. These results, in concert with previouspaleomagnetic characterization of serpentinized peridotite samples from ODP Legs 149and 173, provide an inter-basin correlation of the magnetic properties of the peridotiterocks. The magnetic signatures of the serpentinized peridotites recovered from both sidesof the Newfoundland-Iberia rift appear not to conflict with the notion that conjugatemargins will have generally similar crustal structure and evolution history. DE HR:

1340h AN: GP43B-0855 TI: 30 Myr of polarity stratigraphy and relative paleointensityfrom Equatorial Pacific sediments (ODP Sites 1218 and 1219, Leg199) AU: * Lanci, L et al. EM AB: ODP Sites 1218 and 1219 yielded an exceptional record of the direction and relativeintensity of the geomagnetic field during most of the Miocene and Oligocene. Thesedimentation rate in the Oligocene and the lower Miocene carbonate-rich pelagicsediments is > 10 m/Myr, and measurements on u-channel samples allowed a high-resolution magnetostratigraphy to be resolved. Moreover, the sediment has uniformmagnetic properties that made it suitable for relative paleointensity estimates. Relativepaleointensity was computed using the slope of thenatural remanent magnetization(NRM) versus anhysteretic (ARM) and isothermal remanent magnetizations (IRM)during AF demagnetization. ARM and IRM were AF demagnetized using the samealternating fields used for NRM demagnetization This high-resolution record of magneticpolarity and relative paleointensity has been used to determine whether small-scalemagnetic anomalies on the ocean floor (cryptochrons) represent short polarity subchrons,intensity fluctuations of the geomagnetic field, or both. DE: HR:

0800h AN: GP11D-0868 TI: Paleomagnetic and Rock Magnetic Signature of UpperOceanic Crust Generated by Superfast Seafloor Spreading:Results from ODP Leg 206 AU: * Acton, G and Wilson, D EM AB: During Ocean Drilling Program (ODP) Leg 206, Site 1256 ($6.736\deg$N,$91.934\deg$W) was cored deep into a 15-Ma section of oceanic crust that is part of theCocos Plate formed by superfast spreading ($>$200 mm/yr) at the East Pacific Rise.Three holes penetrated through 250 m of sediment and into igneous basement, with thetwo deepest holes, Holes 1256C and D, reaching 88.5 and 502 m sub-basement,respectively. The igneous section consists of an uppermost massive ponded flow that is$>$70 m thick, underlain by thin flows ($<$3 m thick), massive flows ($>$3 m thick;some of which may be dikes), pillows, and hyaloclastites. The uppermost units,particularly the massive ponded flow, record an anomalously steep paleomagneticdirection for this near equatorial site and commonly retain only a few percent of theirnatural remanent magnetization (NRM) after being demagnetized in peak alternatingfields (AF) of only 20 mT. The steep direction appears to be the characteristic remanentmagnetization (ChRM) as it can be separated from an even steeper drilling overprint.Units below this have shallow inclinations and retain 5% to 15% of their NRM after 20mT AF, both characteristics being more typical of what would be expected for nearequatorial oceanic basalts. Rock magnetic results based on hysteresis, FORC, andthermomagnetic measurements indicate that there are insignificant differences in thepaleomagnetic carriers for the units with steep and shallow inclinations. In both cases,pseudo-single domain titanomagnetite and titanomaghemite are the main carriers. Thissupports the interpretation that the uppermost basalts were extruded in a weak transitionalor excursional field. Given that the site was cored 5 km east of the transition zonebetween marine magnetic anomalies 5Bn.2n and 5Br, the massive ponded lava mostlikely recorded this transitional field after traveling ~5 km from the spreading axis. DE

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16:30h AN: GP34A-03 TI: Determination of Relative Contributions from Marine andTerrestrial Sediment Sources in the Cariaco Basin using aMagnetic Mixing Model AU: * Verosub, K L et al. E AB: The Cariaco Basin, an anoxic basin off the coast of Venezuela, acts as a depocenterfor sediments of both marine and terrestrial origin. Sedimentation rates for the upper 170m of sediment recovered during ODP Leg 165 at Site 1002 average 35 cm/k.y. and arefairly constant over the entire 600-k.y.-long interval cored. We have used a magneticmixing model to identify and quantify the contributions to the sediment at this site frommarine and terrestrial sources during the past 27,000 years. Our approach is based on abroad array of environmental magnetic parameters. Using the appropriate statisticalmethods, we first determine the extent to which different pairs of parameters areinterrelated. In the case of the Cariaco Basin, many of the parameters can be shown tovary coherently. We then use the extremal values of each particular magnetic parameterto determine the magnetic signature of two hypothetical source materials. A magneticmixing model is used to calculate the contribution at any point in the core from each ofthe sources. The magnetic signatures of the two hypothetical sources can be compared toactual source materials that have contributed sediment to the basin. For the Cariaco core,recent geochemical studies have shown that variations in Ti and Fe content correlate withprecipitation and that wetter intervals are associated with more riverine (terrigenous)input and higher Ti and Fe content while dryer intervals are associated with more marine(biogenic) input and lower Ti and Fe content. The relative contributions from our twohypothetical sources, as determined by the magnetic mixing model, show a goodcorrelation with variations between higher and lower Ti and Fe content. This suggeststhat we have successfully determined the magnetic signatures of the marine and terrestrialcomponents in the sediment. DE HR:

0800h AN: GP11B-0831 INVITED TI: Age Offsets of the Matuyama-Brunhes Polarity Transition inRecords From the Atlantic: Lock-in Depth Variations or SiteDependent Field Behavior? AU: * Clement, B M et al. EM AB: A number of high -resolution Matuyama-Brunhes transitions have recently beenobtained from deep-sea sediments in the Atlantic Ocean. Three of these transitionrecords were obtained from sites on the Blake-Bahama Outer Ridge and the BermudaRise as part of depth transect drilled during ODP Leg 172. The polarity transition recordsfrom these sites are remarkably similar, both during the reversal and in excursions thatoccurred prior to the reversal. Previous work has shown that in this region initialmagnetic susceptibility records provide a useful proxy for marine isotopic stages.However, using the shipboard susceptibility records as a correlation tool, it becomesapparent that while the transition records exhibit very similar features, these features areoffset relative to the susceptibility records at ODP Sites 1060, 1061 and 1063. Thedistance between Sites 1060 and 1061 is insignificant on a geomagnetic scale, implyingthat the differences are not likely due to time transgressive field behavior. Instead, theoffset of the magnetization record relative to the susceptibility record may result from adifference in the lock-in depths at these sites. A possible explanation is that the differentwater depths at the sites affect the amount of organic matter that is oxidized beforereaching the sea-floor. This in turn would lead to different depths of the redox boundarieswithin the sediment column. If the remanence lock-in zone is related to processesassociated with the redox boundary, the difference in water depths may explain theoffsets. To test this hypothesis, we compare the other Matuyama-Brunhes records fromthe Atlantic with the positions of the reversal relative to the marine isotopic stages,including the record from Site 1083, which was recorded in anoxic sediments. DE: HR:

16:10h AN: GP24A-01 TI: Hotspot motion, scales of mantle convection and the long-termhistory of the geodynamo AU: * Tarduno, J A EM AB: The Hawaiian-Emperor hotspot track has a prominent bend which has served as thebasis for the theory that the Hawaiian hotspot, fixed in the deep mantle, traced a changein plate motion. However recent data from ODP Leg 197 define an age-progressivepaleolatitude history, indicating that the Emperor seamount trend was principally formedby the rapid motion of the Hawaiian hotspot (81 to 47 Ma). Recognition of this motionaffects models of mantle convection and plate tectonics and our understanding ofterrestrial dynamics. For the future, the study demonstrates how paleomagnetism can beused to record large-scale mantle flow. Defining the nature of this flow is an importantprerequisite to our understanding of core-mantle boundary processes, and their ultimaterelationship with the geomagnetic field. While great progress has been madeunderstanding secular variation and reversal frequency, long-term paleointensity recordshave remained elusive. Studies of feldspars containing magnetic inclusions indicate thatthe mid-Cretaceous field was remarkably strong, stable and dipolar. Superchrons mayrepresent times when the nature of core-mantle heat flux allows the geodynamo tooperate at peak efficiency. On billion-year time scales, spanning initiation of inner coregrowth, the paleomagnetic record is sparse. The use of lasers to derive directions andpaleointensities from oriented silicate minerals holds significant promise forunderstanding the nature of the Archean geodynamo and its potential relationship withenvironmental conditions of the early Earth. UR HR:

14:55h AN: GP13A-05 TI: A Pilot Marine EM Study of Hydrate Ridge, Oregon. AU: * Weitemeyer, K et al. EM AB: It has long been proposed (e.g. Nigel Edwards, U.\ Toronto) that EM methods maybe able to detect and map gas hydrate, which is more resistive than host sediments andthus provides an electrical target. While the base of hydrates often produces a distinctiveseismic signature (the bottom-simulating reflector, or BSR), the gradational upper surfaceis less well imaged using seismology, and some hydrates are known to exist without aprominent BSR. In August of 2004 the Scripps Institution of Oceanography Marine EMLab collected magnetotelluric (MT), dipole-dipole controlled source electromagnetic(CSEM), and controlled source magnetotelluric (CSMT) data across Hydrate Ridge,about 70 km offshore Newport, Oregon. Three component electric field data and twocomponent magnetic field data were recorded at 25 evenly spaced sites along a 14.4 kmeast-west line that coincides with 2D and 3D seismic transects and ODP Leg 204 well-logdata. Forward calculations of models with conservative resistivity contrasts suggest thatradial mode CSEM electric fields at frequencies of 5 Hz (and up to the 7th square waveharmonic of 35 Hz) will give a measurable electric field response to shallow hydrates atsource-receiver ranges between 500 m to 2500 m. An important part of this experiment isto compare well log data with electrical conductivity estimates of hydrate {\it in situ},unmodified by either drilling or sample collection. We will present the CSEM and(CS)MT data from this new experiment along with preliminary interpretations. UR HR:

1340h AN: GP43B-0856 TI: Deep-tow Study of Magnetic Anomalies in the Pacific JurassicQuiet Zone AU: * Tominaga, M et al. EM AB: The Jurassic Quiet Zone (JQZ) is a region of low-amplitude, short-wavelength,difficult-to-correlate magnetic anomalies located on Jurassic seafloor and thought torepresent a time of decreased field strength and rapid reversals. We collected new deep-tow magnetic data over the Pacific JQZ that complement 2 deep-tow profiles reported inSager et al. (J. Geophys. Res., vol.103, p. 5269, 1998). Our primary goals were to extendthe correlation of deep-tow magnetic anomalies farther back in time, crossing ODP Site801 (where Jurassic ocean crust has been drilled and cored), to evaluate the correlation ofanomalies, and to refine the Jurassic geomagnetic polarity reversal time scale developedby Sager et al. (1998). These new data include: (1) closely spaced lines around M34 andSite 801, (2) two long lines extending from the previous survey, across Site 801 to thesoutheast, and (3) one line between the previous lines in the area of difficult-to-correlateanomalies. Systematic changes in anomaly amplitudes occur along the deep-tow lines,perhaps indicating changes in field strength. From northwest to southeast (i.e., increasingin age) anomaly amplitudes and wavelengths decrease, become nearly constant, and thenincrease slightly. The zone of smallest, shortest wavelength anomalies corresponds to aperiod of ~4 m.y. that appears to have an abrupt end. Comparing anomalies betweenlines, correlations were excellent on the closely-spaced profiles over M34 and aroundHole 801C. Correlation over supposedly older seafloor to the south of Site 801 was alsogood. However, anomaly correlation in the region between M34 and Site 801 wasdifficult. As with other studies of magnetic profiles, it is impossible to uniquelydetermine which anomalies are caused by reversals and which are not. Many of the largeranomalies are likely caused by changes in polarity, whereas smaller anomalies may beintensity fluctuations. The new deep-tow data, being closer to the source than theprevious lines, show more short-wavelength anomalies in some areas, particularly thearea where anomaly amplitudes are least. This observation suggests that many of theseshort-wavelength anomalies may result from intensity fluctuations. To construct areversal time scale, we limit short wavelengths by modeling magnetic profiles upwardcontinued to mid-water depth. DE HR:

0800h AN: GP11D-0867 TI: Paleomagnetic Paleolatitudes of the Ontong Java PlateauFrom 120 Ma to 55 Ma: Implications for the Apparent PolarWander Path of the Pacific Plate. AU: * Hall, S A et al. EM AB: Paleomagnetic analyses of Late Cretaceous- early Tertiary deep-water carbonatesobtained during ODP Leg 192 drilling have been used to document the latitudinal motionof the Ontong Java Plateau (OJP). Paleolatitude estimates were obtained for the followingperiods: magnetochrons 25n-25r (55.9-57.5 Ma), 27r-31n (61.3-68.7 Ma), 32n-32r (71.1-73.6 Ma) and 33n (73.6-79.1 Ma). The broad agreement between our new sedimentarypaleomagnetic data and those recently obtained from OJP basement rocks suggests thatpossible compaction-induced inclination shallowing in the studied sediments isnegligible. Anisotropy of anhysteretic remanent magnetization measurements furthersupport this argument, yielding magnetic fabrics that appear poorly correlated withindividual characteristic remanent magnetization inclinations. \ Our results whencombined with other OJP paleomagnetic data yield an internally consistent data set thatdescribes the northward motion of the plateau from its formation $\sim$120 Ma until 55Ma. Between 120 Ma and 76 Ma the plateau is located near $24\deg$S and is eitherstationary or exhibits a slow northward movement. From 76 Ma until 68 Ma the plateaumoves rapidly through approximately $10\deg$ of latitude to $\sim10\deg$S. From 68Ma until 56 Ma the plateau is again almost stationary before moving slowly northward.Our data therefore support previous suggestions for a Cretaceous "standstill" of thePacific plate and provide additional constraints upon proposed episodes of rapid platemovement. Our new OJP paleomagnetic paleolatitudes are generally lower than thosepredicted by indirect data from seamount magnetization studies and deskew analyses forchron 27r/31n but are higher than those predicted from deskew analyses for chrons 32and 33n. More direct paleomagnetic data are necessary to define Pacific plate motion,drift of hotspots, and possible true polar wander events. We suggest that deep-watercarbonates, if carefully analysed, can yield reliable paleomagnetic inclinations. DE: HR:

0800h AN: GP31B-0835 TI: Volcanic Influence on the Susceptibility Signal: a Case Studyin Indian Ocean AU: * Salome, A et al. EM AB: Magnetic susceptibility of sediments is now widely used as a climate proxy inpaleoclimatic and paleoceanographic studies. The correlation between the susceptibilityand the oxygen isotopic variations is either positive or negative and thus cannot be onlycaused by carbonate dilution. So far no convincing model has been proposed to entirelyexplain the dependency of the two signals. Many studies used the fact that the weatheringproducts, which are transported by rivers or by winds to the sea, keep the signature oftheir source. In order to evaluate the contribution of magnetic particles from differentorigins to the budget of susceptibility signal, we measured mass normalizedsusceptibilities for sands and suspended load from the world major rivers and from riversdraining volcanic lithologies. We found that weathering products transported by riverswhich drain volcanic terrains have a susceptibility signal which is 10 to 100 fold higherthan for granites. Taking into account the size of river basins, their lithology and the factthat the weathering rates of basalts are much higher than that of continental silicates, thecontribution of volcanic particles to the susceptibility of oceanic sediments is estimated tobe 100 to 1000 fold stronger than the contribution of particles eroded from granites. Thuswe infer that the susceptibility signal of oceanic sediments is mostly dominated bybasaltic inputs to the sea. With this assumption in mind, we can compare the carbonate-free susceptibility signals of several cores collected in the Arabian Sea [1,2], the SomaliBasin [3] and from the Ninety East Ridge (ODP Leg 121). The time-depth calibrationwas based on the oxygen isotopic variations measured in the same cores. In addition wemeasured the susceptibility of individual samples to improve and validate the calibrationbetween different cores with different material. Comparison of absolute values fromcarbonate-free sediments to our river sands data should allow us to estimate thecontribution of the volcanic input for each area. Ultimately this approach should lead usto retrace the amount of alteration of volcanic terrains through time. 1 P. DeMenocal, J.Bloemendal and J. King, 1991, Proc. Ocean Drilling Program Sci. Results 117, 389-401.2 M.W. Hounslow and B.A. Maher, 1999, J. Geophys. Res. 104, 5047-5061. 3 L.Meynadier, J.P. Valet and F.E. Grousset, 1995, Paleoceanography 10(3), 459-472. DE: HR:

0800h AN: GP31B-0840 TI: Rock Magnetic Properties Across Paleocene-EoceneBoundary Sediments from the North Atlantic, South Atlantic, andEastern Pacific AU: * Lippert, P C et al. EM AB: We present new rock magnetic data from Wilson Lake, NJ (N. Atlantic continentalshelf), ODP Site 1262, (Walvis Ridge, S. Atlantic), and Lodo, CA (continental shelf,coastal California) in an effort to evaluate the comet-impact trigger hypothesis (Kent etal., 2003) for the carbon isotope excursion (CEI) associated with the Paleocene-EoceneThermal Maximum (PETM). The comet-impact trigger hypothesis is based primarily onanomalous magnetic properties in outer shelf Paleocene-Eocene boundary sedimentsfrom the New Jersey continental margin; proponents of this hypothesis suggest thesemagnetic properties indicate the presence of extraterrestrial nanoparticles of magnetite.Our results suggest that these nanoparticles of magnetite may be terrestrial, not cosmic,in origin. Changes in magnetic hysteresis properties (e.g., Mr/Ms and Hc/Hcr) across theWilson Lake section are similar to those from other regional stratigraphic sections (re:Kent et al., 2003), but similar changes are not observed at S. Atlantic or coastalCalifornia sites; thus, there may be a regional rather than global source of magneticmaterial. Squareness plots (Tauxe et al., 2003) and Day plots (Day, 1977) of hysteresisdata suggest that Wilson Lake magnetite is single domain (SD flower structure to SDcubic), but the grain size of magnetite from the other two sites is mixed, possibly with asignificant component of pseudo-single domain grains. Weak-field high temperaturesusceptibility experiments suggest that the primary magnetic mineral in these sections ismagnetite. Low-temperature zero- and strong-field saturation isothermal remanentmagnetization (SIRM) experiments indicate that the fine-grained magnetite is partiallyoxidized, probably to maghemite. More significant, however, the low-temperatureexperiments suggest that the fine-grained magnetite from the CIE portion of the WilsonLake section may have a biogenic origin. Although it is clear that intact chains ofmagnetosomes are not preserved, the single-domain magnetite in the Wilson Lake sectionmay have a significant population of isolated magnetosomes or other biogenic magnetite.We present additional comparative studies of low-temperature data to better assess thecomponent of biogenic magnetite in the Wilson Lake section. We also presentgeochemical data to better understand the redox conditions that could favor or inhibit theproduction of biogenic magnetite at the three sampling sites. DE HR:

0800h AN: GP11D-0870 TI: Magnetic Properties and Paleointensity of a Mid-MioceneGabbro from the Costa Rica Accretionary Wedge, ODP Leg 170 AU: * Hawkins, L K et al. EM: AU AB: Samples of gabbro from cores recovered by the Ocean Drilling Program Leg 170have been analyzed for magnetic mineralogy and paleointensity using a Thellier-Thelliermethod. The cores are from the Costa Rica Accretionary Wedge, Site 1039, Hole C at aminimum depth of 423 meters below the sea floor. This gabbroic unit is younger than16.49 Ma based on nannofossils in the intruded oozes. This makes it ideal for apaleointensity study because few paleointensity data exist for this time period in thisregion. Rock magnetic investigations included continuous low field thermomagneticanalysis, alternating field (AF) demagnetization, optical microscopy, scanning electronmicroscopy (SEM), and element analysis. AF demagnetization paths are straight to theorigin on orthogonal vector endpoint diagrams suggesting that the magnetization is singlecomponent. Optical microscopy and SEM observations identified titanomagnetites as themost abundant magnetic mineral in the samples; occurring as either coarse- or fine-grainswith euhedral shape. Titanomagnetite composition, estimated from weight percentsprovided by element maps from the backscattered electrons, are both low and hightitanium, TM22 and TM74. Reversible susceptibility vs. temperature curves from lowfield thermomagnetic analysis to 710$\deg$C suggests that the minerals do not alter in anargon atmosphere. Curie temperatures below 200$\deg$C and above 400$\deg$Ccalculated from these curves are consistent with the SEM results. The modified Thelliertechnique used a 0.4 uT field and an argon atmosphere. Low temperaturedemagnetization before and after some temperature steps was used to look for differentbehavior of the large and small magnetite grains. Based on Thellier and thermalexperiments, most of the samples have about equal contributions from low and highCurie temperature titanomagnetite. Although alternating field demagnetization producedstraight line paths on demagnetization diagrams, thermal results show that the twomagnetites carry different components. We are currently exploring the reasons for thedifference, e.g., the contribution of drill string remanence, and whether either magnetitecan be used to determine the paleomagnetic field intensity. DE HR:

1340h AN: GP43B-0864 TI: Holocene relative paleointensity and paleosecular variationfrom the Southern Okinawa Trough (ODP Hole 1202B) AU: * Richter, C et al. EM AB: We investigated u-channels from the top 36 meters of Hole 1202B collected in theSouthern Okinawa Trough during Ocean Drilling Program Leg 195. Detailed rockmagnetic data demonstrate that the sediments preserve a high resolution record ofpaleosecular variation and a paleointensity signal spanning almost the entire Holocene.The sediments consist of homogenous, slightly calcareous, bioturbated clayey silt withisolated sandy intervals and fine sand laminae. An age-depth model was establishedthrough C-14 accelerator mass spectrometry dating of planktonic foraminfera. Thestudied section spans almost the entire Holocene (0-9.4 kyr) and exhibits sedimentationrates close to 400 cm/kyr. The magnetic properties are dominated by stable, pseudo-single domain low-titanium magnetite with a Curie temperature of about 540 deg C.High-field hysteresis data and the grain-size sensitive ratio of anhysteretic remanentmagnetization (ARM) to low field magnetic susceptibility indicate a narrow range ofgrain sizes and concentrations. Key magnetic parameters vary by less than a factor offour, thereby fulfilling the criteria for relative paleointensity determinations. The relativepaleointensity was extracted by normalizing the intensity of the natural remanentmagnetization (NRM) by the ARM and by the low field magnetic susceptibility. Bothnormalizations yield very similar results. Spectral analysis indicates that the record is notsignificantly affected by local environmental conditions. Comparison of this WesternPacific paleointensity curve with other curves suggests a geomagnetic origin for theobserved variations. Millennial-scale features in our record correlate with variations ofthe archeomagnetic dipole moment, which implies that the sediment from Hole 1202Brecorded changes of the geomagnetic field over the investigated time interval. DE: HR:

1340h AN: GP43B-0860 TI: Different magnetostratigraphic approaches: Lake Baikalsediments and the J/K boundary strata in the Tethyan realm AU: * Pruner, P et al. EM AB: Rock magnetic and paleomagnetic parameters were studied on two cores drilled inthe Academician Ridge, Lake Baikal, Russia. The rock magnetic parameters were used toidentify variations in the concentration, grain size and mineralogy of the magneticmaterial. Three intervals of deviating declinations and inclinations with steep totallyreversed inclinations are clearly present in the cores. The ChRM directions were clearlydominated by normal polarity indicating the Brunhes Chron age of the sediments. Theobserved excursions were interpreted as the Blake excursion, the Iceland Basin excursionand the Biwa II excursion. The reversal excursions fall within the intensity minima. Onthe basis of the identification of excursions we correlated the magnetostratigraphic results(relative paleointensity and polarity) from the Lake Baikal sediments to comparable datasets from ODP site 984. Data obtained from the cores indicate the age of deposits up to300 ka. Comparing the variations of the paleointensity records the mean sedimentationrate in the range of 3 - 4 cm/ka can be estimated. The result of magnetostratigraphic andmicropalaeontological investigations of the Jurassic/Cretaceous boundary strata in theTethyan realm (Brodno - Slovakia, the Bosso Valley - Italy, and Puerto Escano - Spain)can be reasonably intercorrelated. Reverse subzones proposed to be named "KysucaSubzone" in M20n and "Brodno Subzone" in M19n were precisely localized in all studiedprofiles. All the magnetozones and subzones can be related to the M-sequence of marinemagnetic anomalies. At the locality of Brodno, the interpreted duration of the transitionbetween N - R (R - N) polarity falls into the range of 5 - 10 ka. Stratigraphicallysignificant calpionellid events occupy an identical position in relation to magnetozonesand subzones derived in all the three sections. The base of the calpionellid zoneCrassicolaria coincides with the base of the "Kysuca Subzone". Appearance of thespecies Calpionella grandalpina represents a significant horizon; it lies immediatelybelow the base of the magnetozone M19r in all sections. The base of the standard zoneCalpionella was used for the definition of the J/K boundary in calpionellid stratigraphy. UR HR:

0800h AN: GP11A-0813 TI: Marine Controlled Source Electromagnetics for Gas HydrateEvaluation on the Cascadia Margin: Correlation BetweenResistivity Anomalies and Seismic Blank Zones AU: * Schwalenberg, K et al. EM AB: The gas hydrate deposits on the Cascadia Margin have been the focus of a vastnumber of projects and marine experiments to investigate the distribution andconcentration of this potential future energy resource. Gas hydrate or frozen gas consistsmainly of methane and water molecules. It is stable at low temperatures and highpressures and forms in pore space within the hydrate stability zone in marine sediments.Hydrate itself is electrical insulating and replaces conductive pore fluid, whichsubsequently increases the bulk resistivity of a hydrate formation. Accuratemeasurements of the seafloor resistivity can be a useful tool for hydrate estimation, whichis essential for resource and environmental hazard evaluation. The instrument - adevelopment of the University of Toronto - is basically an inline dipole-dipoleconfiguration dragged along the seafloor. It has been successfully applied in previousexperiments on the Cascadia Margin and on the Chilean Margin. Here we present apromising new data set collected in summer 2004. Measurements have been conductedalong three profiles. For the first time data have been collected with the marinecontrolled source electromagnetic method in water depths shallower than required forhydrate stability (i.e. below 500m). These data are important as a reference site forhydrate assessment. The second profile covers the bullseye, a vent site in vicinity of ODPsite 889B that correlates with a region of seismic blanking and recovered hydrateoutcrops. The 7km long profile also covers another series of seismically identified ventsites. The average amplitudes of the measured electric fields and thus the related apparentresistivities along the first profile (no hydrate) are smaller than along the second profile(vent sites). This is consistent with the idea of an increased resistivity in hydrate richzones. Two pronounced anomalies occur along the second profile in spatial agreementwith the bullseye and the other series of vent sites. The third profile intersects the secondprofile at the bullseye. However, beside of a careful lowering procedure, the array waslikely tangled on the seafloor for most parts of the deployment which complicates or eveninhibits the interpretation, but points out the importance of a careful coordination of shipsnavigation and instrument deployment as well as weather and sea conditions for asuccessful experiment. UR HR:

09:45h AN: GP41B-08 TI: A paleomagnetic record of the last 640 kyr from an easternMediterranean piston core and a review of geomagnetic excursionsin the Brunhes AU: * Oda, H et al. EM AB: Core KC01 (25.93 m long) was taken from a small ridge on the lower slope of thesouthern Calabrian Ridge (Pisano Plateau, 36deg15.25'N, 17deg44.34'E, 3643m waterdepth) during cruise MD69 of the French R/V Marion Dufresne in June-July 1991. Thesediment consists of hemipelagic sediments with intercalated sapropel and tephra layers.They form an alternation of grey, greenish, olive-coloured, yellowish, white and beigeshades. Sapropel layers are black to dark green. Paleomagnetic samples (6.4 cm3 cubes)were taken from the half split cores and measurements of the natural remanentmagnetization was conducted at Utrecht University with a DC SQUID magnetometer (2GEnterprises model 740-R). Stepwise alternating field demagnetization was done at 8-11steps up to 60-80 mT on each sample. Core KC01 (37.04 m long) was taken as acompanion core from core KC01B at the same locality, earlier subjected tomagnetostratigraphic work (Langereis et al., 1997). Langereis et al. (1997) established anage model based on the matching of (ghost-)sapropels with insolation minima. Theyapplied the 65degN summer insolation calculated from the astronomical solution La90(Laskar 1990; Laskar et al., 1993) as target curve and included a time lag of 3-kyr - basedon the age difference between the radiocarbon dated midpoint of S1 at 8.5 ka and theinsolation maximum at 11.5 ka following the method by Lourens et al. (1996). Lourens(2004) modified the astronomical chronology established by Langereis et al. (1997) andinvestigated the sapropel chronology on KC01B and KC01 based on high resolutioncolour correlation with ODP Site 964, which is 1 km away, and constructed an improvedage model, which gives a better estimate for these two cores. Langereis et al. (1997)reported four excursions (CR0, CR1, CR2, CR3) with ages of 261, 318, 515, and 573 kabased on the chronology of sapropels on Core KC01B. Lourens (2004) revised thechronology of Core KC01B and redated the excursions as 260, 319, 543, and 593 ka. Inthis study, these four excursion records were confirmed and dated as 258-263, 313-319,541-542, 592-594 ka based on the new chronology. Also Laschamp, Norwegian-Greenland Sea, Iceland Basin and Jamaica excursions were found at ages of 41-43, 77,193-194 and 212-213 ka. Finally, we conducted a review of published excursion recordsand identified a maximum of 23 excursions and a minimum of 16 excursions in theBrunhes.

HR: 13:40h AN: GC53A-01 INVITED TI: Late Quaternary Paleoenvironmental History of the Peru-Chile Current System and Adjacent Continental Chile AU: * Lamy, F et al. EM AB: A combined analysis of terrigenous and biogenic compounds in marine sedimentsfrom the Chilean continental margin allows detailed reconstructions of the paleoclimaticand paleoceanographic history of this region during the last ca. 120,000 years. Based onseveral sediment cores recovered during two German cruises and ODP Leg 202 (Site1233), we found evidence for changes both in continental rainfall, most likely induced bylatitudinal shifts of the Southern Westerlies, and marine productivity as well as seasurface temperature and salinity changes within the Peru-Chile Current system on timescales ranging from Milankovitch to centennial-scale. On Milankovitch time-scales, wefound strong evidence for precession-controlled shifts of the Southern Westerliesimplying for example generally more humid conditions during the LGM and a trendtowards more arid climates during the deglaciation culminating in the early Holocene.These shifts are paralleled by paleoceanographic changes indicating generally higherproductivity during the LGM mainly caused by increased advection of nutrients from thesouth through an enhanced Peru-Chile current. North of 33øS, these general productivitypatterns are complicated by additional impacts from the tropics resulting in maximumpaleoproductivity during the deglaciation and prior to the LGM. On shorter time-scales,extremely high resolution sediment cores from the southern Chilean margin provideevidence of significant short-term Holocene climate variability with bands of variabilitycentred at ca. 900 and 1500 years, periodicities also well known from NorthernHemisphere records. Recently drilled ODP Site 1233 allowed to prolong these recordsinto the last glacial. The available data show millennial-scale SST changes that closelyfollow the temperature pattern known from Antarctic ice-cores. Including other recordsfrom the Southern Hemisphere mid-latitudes, our data suggest a quasi-hemisphere-wideresponse that is consistent with the bipolar see-saw mechanism but may also imply amore prominent role of the Southern Hemisphere in the origin and transfer of millennial-scale climate variations during the last glacial. In addtion, Site 1233 offers the excellentopportunity to compare continental and marine paleoenvironmental signals within thesame well-dated archive suggesting a lagged response of the terrestrial signal most likelyrelated to climate inertia of the Patagonian ice-sheet. DE: HR:

0800h AN: GC51D-1078 TI: A Test for Extending the High-Resolution Global ClimateRecord in Santa Barbara Basin AU: * Hopkins, S E et al. EM AB: ODP Site 893 in Santa Barbara Basin recovered high-resolution global climate dataextending back to ~160 ka at 200 m sub-seafloor. Safety concerns though have preventeddeeper drilling at this site. Santa Barbara Basin is, however, tectonically active. As aresult, continuous late-Quaternary strata deposited in the deep paleo-bathymetric basinwere uplifted and folded across the Mid-Channel Trend, and strata as old as ~450 ka (OIS12) appear to be exposed at the seafloor where they are now accessible to piston coring.This project will test the accessibility along the anticline of these older stratigraphicsequences through detailed basin correlation of high-resolution seismic stratigraphy andsubsequent coring. In preparation for coring in summer 2005, grids of high-resolutionMMS analog, industry multichannel, and 2D USGS high-resolution seismic reflectiondata (collected in 2002) are being used to correlate dated reference horizons at ~120 ka,~160 ka and ~1 Ma along with several intervening seismic sequence boundaries acrossthe Mid-Channel Trend. Results provide the basis for modeling the structure andstratigraphy in 3D, and to precisely locate suitable sites for coring. Subsequent coreanalyses will be used to verify the predicted outcrop pattern and basin-wide sequencestratigraphic interpretation. Thus, in addition to its contributions to Quaternary climatehistory, this project will help document the nature and evolution of the Mid-Channelanticline, and the local interaction between tectonics, climate, and sea-level change. Todate, our results show that the Mid-Channel Trend has propagated from east to west aspreviously proposed. South of Santa Barbara harbor, folding on the anticline began about1 Ma, while 10 km farther west, folding began after ~450 ka. Furthermore, our resultsconfirm that older strata (extending back to inferred OIS 12) of the paleo-Santa BarbaraBasin have been folded, and are present at or near the seafloor.

HR: 15:25h AN: H53E-08 TI: Marine Sedimentary Record of Cenozoic Monsoon IntensityPreserved in the Asian Marginal Seas AU: * Clift, P D EM AB: Climate models predict that the intensity of the Asian monsoon is largely controlledby the elevation of the Tibetan Plateau. However, the elevation of Tibet and theerosional response to monsoon intensification is contentious. Compilation of seismicdata from the marginal seas of East Asia now shows that sedimentation rates sharplyincreased across the region, and especially in the Red River catchment after around 33Ma and continued to increase until around 11 Ma. The dating of potassic magmatism andstrike-slip faulting on the eastern flanks of the Tibetan Plateau starting at 35-30 Masuggests that this tectonism may accompany a period of accelerating surface uplift inTibet. At present few climate records exist for this time period, though the monsoonmight be expected to have strengthened in stages since that time. Most notably new datafrom ODP Site 1148 in the northern South China Sea show a sharp increase in clastic andcarbonate mass accumulation rates associated with a change in clay mineralogy to greaterillite dominance (physical weathering) starting around 17.2 Ma. I interpret this to reflect achange to a more erosive, more monsoonal climate starting at that time in southern China.Falling sedimentation rates at 11-8 Ma and lasting until 4 Ma indicate drier conditionsacross Asia at that time, also recorded by strong eolian sedimentation in the NorthPacific, slower sedimentation on the Indus and Bengal Fans, and change to a moresmectite dominated mineralogy on both these fans, indicating a less erosive environment.Only in the Mekong does erosion increase after 8 Ma, driven by local tectonic uplift inthe Vietnamese Highlands. Faster sedimentation and a return to an illite dominatedmineralogy after 4 Ma accompanies a series of proxies that indicate a stronger summermonsoon at that time, and a return to faster erosion driven by rains in East and SouthAsia. The evidence shows a broad positive correlation between monsoon strength anderosion over long periods of geological time. Pulses of sediment caused by faster erosiondo not appear to be strongly dampened over time scales >100 kyr by sequestering incontinental sedimentary basins, but mostly reach the continental margins of the SouthChina Sea. UR

0800h AN: MR11A-0916 TI: Calibration of Mobile NMR Instruments in Respect toPorosity and Pore Size Distribution of Drill Cores AU: * Arnold, J et al. EM AB: The focus of our research is set on the calibration of two different and newdeveloped light weight mobile NMR scanning systems: (1) the NMR-MOUSE and (2)the HALBACH device for measuring porosity and pore size distribution of different drillcores recovered from the International Ocean Drilling Program (IODP). Further goals areto adapt current NMR processing techniques, the development of new measurementroutines, and to evaluate precision and accuracy of this method. Transverse relaxation onwater-saturated drill cores were measured using a CPMG sequence. A regularizedLaplace transform analysis based on the UPEN program yields the distribution oftransverse relaxation times. The signal amplitudes and the integrals of distributioncorrelate directly to the core porosity. The main advantage of our mobile NMR scanningsystems compared to conventional methods is their small size and weight, which isparticularly attractive for the shipboard use and on any drilling platform envisioned forIODP. Both tools, the NMR-MOUSE and the HALBACH scanner are suitable for routinemeasurements of porosity and pore-size distribution of drill core sections. In contrast tothe NMR-MOUSE, the HALBACH tool has a sufficiently homogeneous magnetic fieldand is more sensitive. It can determine porosities as low as 3 %. While the NMR-MOUSE can be applied on core sections of any geometry, the Halbach tool is especiallydesigned for the size of standard drill cores recovered from the deep sea ocean floor bythe IODP. Combined with a mobile NMR spectrometer and special software for porosityand pore size distribution measurements, both light and mobile devices are particularlyattractive for the use on research vessels and logging platforms and thus alow todetermine prosity and permeability on very fresh material.

HR: 1340h AN: OS43A-0526 TI: Global Distribution of Microbial Alteration of the OceanCrust AU: * Josef, J A et al. EM AB: Early evidence for a deep subsurface biosphere in ocean crust came from unusualalteration textures within petrographic thin sections. The textures are attributed tomicrobial activity within basalt minerals and glass. Microbial textures have now beenfound in DSDP and ODP holes and in sea floor surface basalt from around the globe.These samples revealed a variety of unique alteration textures, and our hypothesis is thatsimilar textures are the result of similar conditions in ocean crust environments. One-hundred and five petrographic thin sections from DSDP and ODP drill cores from thePacific, Atlantic, and Indian Oceans as well as the Mediterranean Sea were used to createa library of images of microbial alteration textures. Prevalent textures include straight,curving, segmented and angular twisting tunnels, mushroom shaped structures, andfungus-like groups of alteration. We are using Lossless Compression Analysis on ourlibrary of images to distinguish and classify the variety of alteration textures. Currentlywe are classifying textures both down-hole and across ocean basins and correlating theoccurrence of similar textures with measured drill-hole properties, including age, locationof the sample, water depth, basalt temperature, type and amount of sediment cover, depthwithin the basalt, and secondary minerals. DE: HR:

16:30h AN: OS34B-03 TI: Mechanism for free gas migration through South HydrateRidge hydrate system AU: * Liu, X and Flemings, P EM AB: At southern Hydrate Ridge, offshore Oregon, free gas vents through hydrate-bearingsediments where free gas coexists with gas hydrate and brine in shallow subsurface. Toestablish three-phase (liquid, hydrate and gas) equilibrium within the gas hydrate stabilityzone (GHSZ), salinity must increase from a baseline value of 3 wt.% at the base of theGHSZ to about 12 wt.% at the seafloor. This predicted salinity profile is similar to in situpore water salinity calculated at ODP Site 1249. We interpret that the upward increase insalinity is driven by rapid hydrate formation in the case of high methane flux frombelow. As hydrates form, dissolved ions are excluded and pore water salinity rises.Ultimately, salinity rises to the point where three-phase equilibrium is reached andadditional methane exists in free gas phase. By assuming that there is no transport ofwater or salt, we can estimate the hydrate amount from change in salinity relative to thebaseline. Hydrate volume faction would increase from 0 below the GHSZ to 70% at theseafloor. This predicted hydrate distribution is consistent with resistivity log- and PCS-derived hydrate occurrences at Hydrate Ridge. Thus, both observations and calculationsof three-phase equilibrium suggest that the formation of marine methane hydrate is a self-equilibrating process at locations where methane supply is abundant. This provides amechanism whereby free gas migrates through the GHSZ without being converted intohydrate. DE: HR:

1340h AN: OS33B-0587 TI: Sediment Accumulation Rates of Late Quaternary Deposits inSan Pedro Basin, the Gulf of Santa Catalina, and San DiegoTrough, Offshore Southern California AU: * Normark, W R et al. EM AB: A multiyear program of seismic-reflection profiling and sediment coring hasfocused on understanding the history of late Quaternary sedimentation within the innerbasins of the California Borderland. The objective of this study has been to develop ahigh-resolution seismic stratigraphy primarily for the Last Glacial Maximum and theHolocene that can be used to understand depositional processes, sediment budgets, anddeformation within the basins. The Santa Barbara and Santa Monica Basins in thenorthern Borderland are closed basins and both were cored during the Ocean DrillingProgram (ODP) in support of paleoclimatic studies. In contrast, the inner basins in thesouthern Borderland that are the focus of this report are open-ended basins that have notbeen the subject of scientific drilling. We present the preliminary results of sedimentcoring at 21 sites in San Pedro Basin, the Gulf of Santa Catalina, and San Diego Trough.Initial estimates of sediment-accumulation rates for these basins are based on 48previously unpublished radiocarbon dates. During the Holocene, average sediment-accumulation rates are generally less than 0.5 m/ky on the basin floors where turbiditedeposition locally continued at reduced rates from those of the OIS 2-lowstand interval.This rate is nearly an order of magnitude less than was documented for the Holocene byODP coring at Site 1015 in Santa Monica Basin reflecting, in part, the loss of sediment inthe non-closed basins. Background hemipelagic rates range from 0.01 to 0.1 m/ky, withthe lowest rates on mid-basin highs, e.g., Lasuen Knoll. More dating is currentlyunderway for some of the core sites to determine the rate of change in sedimentaccumulation during the Holocene. DE: HR:

1340h AN: OS33B-0583 TI: Relations Between Basement Tectonics, SedimentDeformation and Fluid Flow at the Eastern Juan de Fuca RidgeFlank: Results From Very High Resolution Seismic Data AU: * Zuehlsdorff, L and Spiess, V EM AB: In summer 2004, IODP Leg 301 was drilled on the eastern flank of the Juan de FucaRidge as a successor of ODP Leg 168 (1996). The main subject of the new leg was tostudy the properties of an active ridge flank hydrothermal system, which is for a big partisolated beneath a low permeable sediment cover. During the Leg 301 seismic pre-sitesurvey, which was carried out during R/V Sonne Cruise SO 149 (2000), this sedimentcover was imaged in a multi-frequency seismic data set at high and very high resolution.Folds, faults, and the layer structure were carefully mapped to show that forced folding isa dominant process affecting sediment physical properties and fluid flow. By comparingdata from areas of different basement age and integrating seismic and borehole data, theimportance of basement tectonics on sediment deformation and fluid flow, depending oncrustal age and sedimentation processes is investigated. Preliminary results show thatgrowth faults characterized by upwardly decreasing offsets reflect off-axis tectoniccrustal reorganization. Growth fault propagation at Second Ridge ceased about 0.28 Maago at the base of a major sediment transport channel, whereas tectonic activity at FirstRidge was more recent. Forced folding at First Ridge controls creation and maintenanceof a subsurface plumbing system for vertical fluid flow through the sediments.Indications for forced folding are also found at Second Ridge though vertical fluid flowlikely is much less affected. DE: HR:

0800h AN: OS41C-0492 TI: Estimation of Free Gas Saturation Using AVO Analysis on 3DSeismic Data at South Hydrate Ridge, Cascadia AccretionaryComplex AU: * Xun, H et al. EM AB: In 2000 we conducted a high-resolution 3D seismic survey of a 4x10 km2 region onsouth Hydrate Ridge on the Oregon continental margin. The objective of the survey is tocharacterize the regional pattern of fluid and gas migration and its relationship to hydrateaccumulations on Hydrate Ridge. These data were acquired with a high-resolutionseismic source with source-receiver offsets of up to 644 m, which results in incidenceangles of up to 20 degrees. In 2002 new 2D seismic data with source-receiver offsets ofup to 1500 m, producing incidence angles of up to 40 degrees, were collected during R/VEwing Cruise EW0208, which was coordinated with Ocean Drilling Program (ODP) Leg204. Prior to AVO analysis, we conducted true amplitude recovery by using the seismicrange equation, and true amplitude processing through prestack time migration. We alsocalibrated the 3D data by using the 2D data to remove unfavorable acquisition effects inthe 3D survey. On prestack-migrated gathers, we measured the seismic amplitude fromthe three surfaces associated with free gas accumulations: 1) the bottom simulatingreflection (BSR), 2) Horizon A, and 3) Horizon B'. Horizon A is a ~4-m-thick turbiditeinterval where it was drilled during ODP Leg 204 and it is identified as a primary conduitalong which free gas migrates from deep sources to the summit of Hydrate Ridge.Horizon A focuses gas hydrate formation and feeds gas vents near the southern summit ofHydrate Ridge. Horizon B' is a volcanic glass-rich horizon that is also a stratigraphicallydefined gas conduit. Intercept and slope are obtained from AVO fitting, and the Poisson'sratio is obtained by using intercept and slope with the constraints of well-log data. Gassaturation for the three surfaces is estimated by fluid substitution technique. Thedistribution of free gas inferred from AVO analysis shows that the highest free gasconcentrations lie directly beneath the highest gas hydrate concentrations estimated fromLeg 204 core data. For Horizon A, the gas saturation increases toward the summit asHorizon A shallows. Free gas within Horizon A is distributed in isolated pockets ratherthan in continuously connected veins. DE HR:

0800h AN: OS41C-0494 TI: Analysis of Sonic Velocity in an Active Gas Hydrate System,Hydrate Ridge, Offshore Oregon AU: * Guerin, G et al. EM AB: One of the best recognized and most intuitive influence of gas hydrate on its hostsediment is the change in its mechanical and elastic properties. This is identified throughan increase in acoustic velocity, which is partially responsible for one of the most distinctsignatures of gas hydrate presence, the Bottom Simulating Reflector (BSR). The unstablenature of gas hydrate makes the in situ recording of their properties by downhole loggingthe best way to identify and quantify its distribution. During ODP Leg 204 on HydrateRidge, offshore Oregon, acoustic logs were recorded in seven holes and vertical seismicprofiles (VSP) were acquired successfully in four holes. These data, recorded within awide range of frequency and scales provide a unique and extensive survey of the acousticproperties of a dynamic gas hydrate system. Because of the poorly consolidated nature ofthe Hydrate Ridge sediments, automatic picking of velocity was only partially successfuland a complete post cruise reprocessing of the sonic waveforms was necessary to drawaccurate compressional (Vp) and shear velocity (Vs) logs. Synthetic seismogramsgenerated with the Vp and density logs allow to confirm the nature of the main reflectorsidentified in a 3-D seismic survey of Hydrate Ridge, such as the BSR and various faultsunderlying the southern Hydrate Ridge system. Despite the highly heterogeneousdistribution of gas hydrate, the Vp logs and interval velocities calculated from the VSPclearly identify the presence of gas hydrate and the eventual presence of free gas directlyunderneath the hydrate stability zone or within the faults feeding the ridge system. Weuse various elastic models to try to estimate gas hydrate and free gas saturations fromsonic velocity and from bulk moduli. The best agreement with independent estimatesderived from resistivity logs and other methods indicate that gas hydrate interact with thehost sediment through cementation, which contributes also to a significant energy loss inthe recorded waveforms. DE: HR:

11:20h AN: OS22B-05 TI: Size and Age Characteristics for West Coast TsunamigenicLandslides AU: * Lee, H et al. EM AF: AB: Multibeam bathymetric imagery is now available for a number of well-definedsubmarine landslide deposits along the west coast of the United States. Several of theselandslides are known to have caused damaging tsunamis and others are of sufficient sizeto have generated tsunamis when they occurred, assuming that their motion was rapid.These failures are located off Palos Verdes Peninsula, California, and within SantaBarbara Channel, California, Commencement Bay, Washington, Resurrection Bay,Alaska, and Port Valdez, Alaska. For two of these failures, ages were determined byidentifying acoustic reflectors in the vicinity of the failed masses that either clearlypostdate or predate the landslide events. The ages of the reflectors are determined bytracing them to the locations of nearby ODP borings or to piston cores dated usingradiocarbon methods. Three of the landslides produced tsunamis during historic time(post 1750 AD) so the ages are well constrained. High-resolution subbottom reflectionprofiles also allow us to estimate the dimensions of the failed masses. Although theexamples selected clearly do not represent all scales of tsunamigenic west coastlandslides, this information is useful in providing input to statistically based models oflandslide-induced tsunamis. DE: HR:

0800h AN: OS21A-1204 TI: Authigenic Dolomite in Marine Marginal Sediments: AnIndicator of Fossil Microbial Activity AU: * Vasconcelos, C et al. EM AB: Dolomite formation under Earth surface conditions remains a long-standing enigmain Earth science. Although it is abundant in the rock record, dolomite does not commonlyform in modern marine sedimentary environments and attempts to precipitate dolomite inthe laboratory at Earth surface conditions have been largely unsuccessful. In recent years,however, microbial mediation of dolomite formation has been tested in culturalexperiments and in natural environments. A new microbial factor has been added to thelist of factors, which are thought to promote dolomite precipitation. This microbial modelfor dolomite formation has found wide acceptance and has been applied to explainmodern and ancient dolomite formation. In particular, deep-sea margin sediments providean ideal setting to apply the microbial dolomite model. With the discovery of dolomite inQuaternary deep-sea sediments in the late 1970's, e.g. during Deep Sea Drilling Program(DSDP) Legs 63 and 64 on the California Margin and in the Gulf of California, a newenvironment for dolomite formation was recognized. We have applied the microbialdolomite model in two different marine marginal settings and will present the results ofSEM, isotopic and mineralogical studies of the recovered dolomite. The discovery of afield of dolomite chimneys strewn on the Gulf of Cadiz seafloor provided an opportunityto study the fossil microbial activity, which had mediated dolomite formation in the flowpath of upward migrating methane on this tectonically active margin. In contrast, modernmicrobial activity was investigated in organic carbon-rich hemipelagic sedimentsrecovered in drill cores obtained from the Peru Margin during ODP Leg 201, which wasdedicated to the study of the deep biosphere. The microbial impact on the pore-watergeochemistry could be linked directly to the diagenetic processes occurring in thesediments, i.e. dolomite formation. Combining the results obtained from our two studyareas, we propose that dolomite formation in marine marginal settings is probablydirectly linked with microbial activity associated with the geochemical transitionbetween the zones of sulfate reduction and methanogenesis. DE HR:

1340h AN: OS33A-0578 TI: Holocene and Glacial Variability of the Hydrologic Cycle inthe Tropical Atlantic: Evidence from the Cariaco Basin AU: * Dulski, P et al. EM AB: Climate variability in the Central American tropics is largely forced by changes inthe intensity of the Hadley circulation and the strength and position of the IntertropicalConvergence Zone (ITCZ). The two most direct consequences of seasonal ITCZ motionfor Cariaco Basin and its sediments are the pronounced alternation between the upwellingthat occurs in the winter-spring and the increased river runoff that takes place in thesummer-fall. This seasonal contrast, coupled with the lack of bioturbation during anoxicphases of deposition in the basin, has produced a high deposition rate (ca. 30 to $>$150cm/kyr). Sediment sequence in most portions consisting of mm-scale, annually-pairedplankton-rich biogenic laminae and terrigenous detrital-rich laminae. The built-inseasonal clock that results from ITCZ movement has allowed development of annually-resolved chronologies over intervals where laminae are distinct enough to reliably countyielding nearly unparalleled temporal resolution for a marine sequence. In a series ofrecent papers, we have utilized measurements of sedimentary Ti and Fe contents asproxies for the total terrigenous fraction of Cariaco Basin sediments. Downcorevariations in Ti and Fe have been adopted as indices of past regional hydrologic change,with higher values interpreted to reflect increased rainfall, river discharge, andterrigenous sediment delivery to the basin. Bulk Ti and Fe and other major elementpatterns in sediment recovered from IMAGES core MD03-2621 and Ocean DrillingProgram (ODP) Hole 1002C were measured at a 50 to 500 um spacing, which reflects atemporal spacing of up to 10 measurements per varve, using a new profiling x-rayfluorescence scanner located at GFZ Potsdam. Here, we present a new data set spanningthe Holocene and parts of the last glacial period. DE

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16:15h AN: OS34B-02 TI: Structural Controls on Hydrate Distribution and Morphologyat Hydrate Ridge, Oregon AU: * Weinberger, J and Brown, K AB: Analysis of resistivity-at-the-bit (RAB) images from nine sites drilled during OceanDrilling Program (ODP) leg 204 to southern Hydrate Ridge reveals a complex pattern offracture orientations that correlate with the structural location of the borehole on theridge. Sites 1244 and1245 on the eastern and western flanks of the ridge, respectively,have concentrated zones of resistive fractures within the gas hydrate stability zone thatexhibit a preferred orientation orthogonal to the regional direction of plate convergenceand crustal shortening. The mean orientation of the identified fracture planes at Site 1244strikes N10W and dips $40\deg$E, and the mean fracture plane at Site 1245 strikesN15W and dips $33\deg$E. Higher on the eastern ridge flank, at site 1246, fractureplanes exhibit a transitional behavior from clustering on the flanks to a less wellorganized pattern at the ridge crest. Poles to structural planes at the ridge crest sites(1247-1250) are evenly distributed, though their typically shallow dips (i.e. steeplydipping planes $>$ $30\deg$) create a girdle pattern in stereographic projections. Thesteeply dipping planes at the ridge crest occur in zones of chaotic resistivity in the RABimages and correlate to zones of massive hydrate in the cores. Simple planar relationshipscan be obscured in these zones by hydrate growth patterns and morphology. Beddingplane dips were also measured and are consistently sub horizontal at all sites. Littlechange in bedding dip occurs with depth at sites on the ridge crest and flanks, though thebasin site shows bedding dips increase below $\sim$ 200 mbsf. As expected, few fractureplanes were documented in the basin site images where hemipelagic sedimentationdominates. Results of the RAB image analyses indicate that the orientation andmorphology of hydrate filled fractures is controlled by structural position on the ridge. Atthe ridge crest, undergoing extension, migrating aqueous fluid and free gas have thepotential to hydrofracture the sediment creating a network of steeply dipping, butrandomly oriented fractures with massive hydrate accumulations. Along the ridge flankswhere fluid flow is controlled primarily by lithology, hydrate filled fractures maintain apreferred orientation that parallels that of the uplifted sedimentary section and is orientedperpendicular to the regional maximum compressive stress. DE: HR:

09:30h AN: OS21E-07 TI: Slope Instability and Gas Hydrates in the Hudson CanyonRegion, U.S. Atlantic Continental Margin AU: * Rona, P et al. EM AB: The continental slope and the upper rise centered on Hudson Canyon offshore NewYork and New Jersey lie within a major gas-hydrate province. This region exhibits evidenceof gravitational mass movements and possible methane expulsion, as inferred from ourbathymetric and water-column surveys conducted in 2002 with support from NOAA/OE, andprior data. The bathymetric data cover our study area (200 km by 110 km; 37\deg40'N to39\deg50'N, 70\deg00'W to 72\deg30'W) from the inner edge of the continental slope (depth200 m) seaward to the middle rise (c.3500 m). The world's largest hub of submarinetelecommunications cables partially passes through this area. Evidence of gravitational massmovements and of probable gas release is extensive. Examples of the former include: (1)blocks of landward-dipping strata up to 2-km wide and 150-m high that lie at the base of thecontinental slope (water depth 2100-2200 m) seaward of an over-pressured zone beneath thecontinental slope (639 mbsf in ODP Hole 1073A; water depth 650 m; Dugan and Flemings,2000); (2) boulders of Eocene chalk that litter the lower slope and upper rise; (3) asemicircular, tabular glide block, about 20 km in diameter, which thickens to about 150 m atits seaward margin; the block is centered at 39\deg23.5'N, 71\deg10.0'W between 2450 and2600 m depth on the upper rise, about 15 km downslope from a congruent scarp at 2200 m onthe lower slope; (4) apparent penecontemporaneous faulting and gliding in strata inclinedsub-parallel to the seafloor along the upper rise; 5) apparent clogging of Hudson Canyon withhummocky sediment at a right-angle turn of the axis (depth 3368 m; 38\deg39.6'N,71\deg01.8'W); 6) changes in stratification from the upper to middle rise; uneven layeringbeneath the upper rise (seafloor mean inclination 0.75\deg down to 2700 m) is inferred toreflect disturbance by gravitational mass movements; even layering parallel to the seafloorbeneath the middle rise (inclination increase seaward from 0.25\deg to 0.76\deg) may reflectless disrupted hemipelagic sedimentation. Evidence of gas release includes: (1) a zone ofirregular pits, each up to 500-m in diameter and spaced kilometers apart, that extends alongthe upper rise (2600-2650 m); (2) a line of eight depressions each 50-70 m in diameter withseveral meters relief and spaced 100-120 m apart that trends NNW (2150 m; near 39\degN,71\deg52'W)and that may indicate gas or porewater escape along a local fault; 3) a plume ofsediment suspended in fluid that is discharging through the seafloor and rising about 1 m at2625 m depth on the SW margin of Hudson Canyon (38\deg52.4'N, 71\deg31.0'W) recordedon deep-towed video; and 4) three zones of regional, water-column, methane anomalies,which exceed background values, deeper than 2500-m depth, centered at 1200-m depth, andnear 200-m depth. These features indicate past and present dissociation of gas hydratesand/or venting of free gas. They also indicate that coherent gravitational mass movementsover low seafloor slopes (< 1\deg) have been facilitated by excess fluid (water and/or gas)pressures. The continental slope and rise in the Hudson Canyon region comprise a naturallaboratory in which to study slope instability in a gas hydrate province and to assess thehazards to telecommunications cables. Dugan, B. and P.B. Flemings (2000), Overpressureand fluid flow in the New Jersey continental slope: implications for slope failure and coldseeps, Science, 289, 288-291.

HR: 1340h AN: PP33B-0946 TI: High Resolution Calcareous Nannofossil Fluctuations Acrossthe Oligocene/Miocene Boundary, ODP Hole 1168A AU: * McGonigal, K L EM AB: Ocean Drilling Program (ODP) Leg 189 drilled five sites around Tasmania toinvestigate the timing and nature of the development of the Tasmanian Seaway. TheOligocene/Miocene interval at Site 1168, located on the western continental slope ofTasmania, was relatively expanded with an average linear sedimentation rate of 5 cm/k.y.A high resolution study of calcareous nannofossils was conducted at a 5 k.y. sampleinterval. Fluctuations in nannofossil assemblages, diversity, absolute abundance and fluxwere calculated across the Oligocene/Miocene interval at Site 1168. These data werecombined with physical property data to further elucidate changes across this interval.Multivariate statistical analysis was conducted on several time slices through the 2 m.y.interval of interest in an effort to identify paleoceanographic fluctuations. DE HR:

0800h AN: PP51F-1377 TI: Orbital and suborbital variability in Coccolithophoreassemblages in the eastern tropical and equatorial Pacific Ocean(7§N to17§S) for the last 500 ka (ODP Leg 202) AU: * Flores, J et al. EM AB: Ocean Drilling Program Leg 202 covered a South-North transect in the easternPacific Ocean, providing excellent material to reconstruct variations in surface andsubsurface water dynamics in selected time-slices. The main goal here is to investigatethe evolution of coastal and equatorial upwelling systems and their relationship to globaland/or regional climate processes such as El Nino or related features. Based on apreliminary age-model using calcareous nannofossil-calibrated datums, a quantitativeanalysis in the Coccolithophore assemblages was carried out to investigate orbitalvariations in surface water dynamics during the last 500 kys. Here we present data fromfour ODP sites: Site 1237 situated in the west South America upwelling system; Sites1240 and 1241 in the equatorial Pacific upwelling system, and Site 1242 close to theCosta Rica margin. The ratio between the shallow and deep coccolithophore dwellers isused to reconstruct fluctuations in the nutricline/thermocline position, and consequently,monitor variations in the upwelled waters. Our preliminary results show a orbitalperiodicity (ca. 100, ca. 40 and ca. 20 ka periodicity), together with an obvious millennialsignal in the above mentioned proxy. Moreover, other well-defined patterns areoverprinted in all sites, allowing us to differentiate three intervals without a clear orbitalrelationship. Periods of well defined upwelling alternate with other intervals wheresurface and subsurface waters appear better stratified. This model seems to respond toregional and almost synchronous variations linked to variations in like-El Nino-La Ninaperiods of orbital range. DE

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0800h AN: PP41A-0588 TI: Late Cenozoic reduction in Antarctic Circumpolar Currentflow from analyses of drift deposits along the Antarctic Peninsula,ODP Site 1095. AU: * Hassold, N et al. EM AB: All waters from the Earth's oceans flow into and are mixed in the AntarcticCircumpolar Current (ACC). Thus the ACC has a major effect on the transport of heat inthe oceans and the Earth's climate. Sediment drifts, which form along the AntarcticPeninsula under the influence of the ACC, record the history of this flow. We examinedsamples from cores drilled during Ocean Drilling Program (ODP) Leg 178 along theAntarctic Peninsula to determine paleocurrent strength changes. Both paleomagneticcubes and sediment samples were taken from cores from ODP Site 1095 ($66\deg$59'S,$78\deg$29'W, 3814m). Factor analysis using major element chemistry indicates a two-component system between terrigenous and biogenic opal. The terrigenous fraction of236 sediment samples was isolated and the grain size measured to determine theterrigenous mass accumulation rate (MAR), the median grain size ($\phi$50), the $>$63$\mu$m MAR and the biogenic opal MAR. Terrigenous mass accumulation rates reflectthe overall MAR's at the site, decreasing in a series of steps at 9 my, 5.5 my, and 2.5 my.Median grain size changes occur at 5.5 my (sharp decrease followed by a slight increase)and 2.7 my (decrease). The magnetic fabric, as determined for 324 samples byanisotropy of magnetic susceptibility (AMS), decreases sharply at 5.7 my and again at 2.7my. We interpret these step-like changes as indicating a decline in the current strengthover the last 6 my, with specific decreases occurring around 5.5 my and 2.5 my. DE: HR:

0800h AN: PP11A-0547 TI: New Insights into Inferring Climate Variability from Recordsof Planktonic Foraminiferal Mg/Ca, Oxygen Isotope and ShellWeight in the Southern Ocean AU: * Greaves, M et al. EM AB: Temperature is the dominant control on foraminiferal Mg/Ca, although other factorsare important and can bias paleoceanographic reconstructions. In order to investigate thecontrols on Mg/Ca, we compare records from two sites at different water depths locatednorth and south of the Subtropical Convergence in the Southern Ocean (ODP Site 1123and MD97-2120). Mg/Ca, d18O, and shell weight were obtained from two narrow sizefractions (250-300 and 300-355 um) of the planktonic foraminifer Globigerina bulloides.Combining these data allows us to investigate the effects of hydrography, dissolution andforaminiferal habitat as controls on Mg/Ca. Differences are observed between the recordsfrom these locations. Comparison of Mg/Ca records from both size fractions at MD97-2120 implies similar calcification temperatures. In contrast, Mg/Ca-derivedpaleotemperatures from the 250-300 um fraction at ODP Site 1123 are higher than in thelarger size fraction. Mg/Ca records from both size fractions at MD97-2120 are similaracross Termination 1 and imply a glacial-interglacial temperature change of 8 degrees C.The temperature record from the 250-300 um fraction from ODP Site 1123 shows aglacial-interglacial temperature change of 4 degrees across Termination 1, whereas in the300-355 um fraction no temperature change is observed. At ODP Site 1123, the contrastbetween size fractions in Mg/Ca-derived temperatures is even more striking acrossTermination 2. The differences in Mg/Ca records are associated with offsets in d18O andshell weight records from both size fractions. The larger fraction exhibits heavier d18Oand larger weight variability. Possible explanations for these observations includehydrographic differences between the two sites, foraminiferal habitat, dissolutionsusceptibility, and preservation history. DE: HR:

0800h AN: PP51F-1365 TI: Alkenone Sea-surface Temperature Variations in theSoutheast Pacific Ocean Inferred from a High-Resolution Recordof the past 200,000 Years (ODP Site 1234) AU: * Chen, M and Huang, C EM AB: High sedimentation rate records with millennial to centennial resolution wererecovered from ODP Site 1234 in the southeast Pacific. SST reconstructions by usingalkenone unsaturation indices measured from the sediments recovered from this siteallow assessment of climate variability pattern in the surface ocean of the southeasternPacific. Site 1234 SST records also provide opportunity to establish a high-resolutionrecord that is sensitive to eastern Pacific climate, and allow a comparison with a SSTrecord from a more southern (ODP Site 1233) near the glacial extension of PatagonianIce Sheet in southern Chile. The record from Site 1234 can be compare further with awestern Pacific record (MD972151) over the last two glacial-interglacial cycles and beused to identify any basin-scale type of climate variability pattern in the Pacific. In thisstudy, we present (~10cm mcd sampling intervals, ~200 years resolution) alkenone SSTreconstruction that covers the past ~200,000 years. Based on our preliminary results, theSST record from Site 1234 reveals large oscillations from ~17-11›FXC and patterns ofhigh frequency changes which open a room for further correlations with Greenland andAntarctic ice cores. Large amplitude oscillations in SSTs are also observed from the MIS5 interval of the record and appear to parallel to the variations of benthic oxygen isotopesmeasured from the same core. A long-term trend of alkenone concentration decreases isclearly observed from MIS 5 to the present, suggesting that at this site calcareousproductivity was decreased or siliceous productivity / terrestrial sediment supply wasincreased since MIS 5. Accurate chronological controls by using AMS 14C,paleomagnetic and oxygen isotope stratigraphies will provide opportunity to assess thetiming of these climatic events into a global framework. DE HR:

15:25h AN: PP43B-08 INVITED TI: Paleomagnetic Results From ODP Leg 202: The ChileanMargin Sites AU: * Stoner, J et al. EM AB: ODP Leg 202 sediments provided the unique opportunity to derive paleomagneticrecords that range from sub-centennial to tectonic timescales. Paleomagnetic studies areongoing with the most complete results to date from the Chilean Margin Sites (1233,1234 & 1235) and Site Survey cores. Shipboard data from these sites suggest that theycontain an unprecedented record of geomagnetic field behavior for the last 70 kyr.Progressive alternating field (AF) demagnetization of u-channel paleomagnetic samplesfrom the Holocene section of Site 1233 (41.0. S, 74.26W, water depth 838 m) indicatedthat these sediments preserve a strong (10-2 A/M), stable, well-defined, low coercivitymagnetization. Component directions show that inclinations vary around the expectedGAD values for the site latitude, declinations show variations consistent with PSV. Theu-channel results attest to the general robustness of the shipboard data. Comparisonsbetween ODP cores, multi cores and gravity cores demonstrate that Site 1233 preservesthe upper most sediment and records the distinct shallow inclination and eastwarddeclinations of the historical field off South America. By splicing u-channel andshipboard data and calibrating it to the historical record a long geomagnetic timeseries isreconstructed. Augmented by twenty-seven radiocarbon dates from Site 1233 and nearbycores show that the normalized intensity records capture millennial scale variability thatcan be correlated to the highest resolution relative paleintensity records globally. Wehave developed a composite chronostratigraphy for the last 75 kyr and will begin theexploration of the spatial coherence of the paleomagnetic secular variation record. Theseand other results will be discussed. DE HR:

0800h AN: PP11A-0545 TI: Changes in Deep Sea Temperature and Ice Volume Based onPaired Measurements of Benthic Foraminiferal Mg/Ca and$\delta$$^{18}$O: Evidence from ODP Site 849, Equatorial Pacificfor Marine Isotope Stages 1-3 AU: * Healey, S and Thunell, R EM AB: Most continuous records of sea level changes are based on benthic foraminiferalδ18O, which is a measure of both the δ18O of seawater and temperature. New calibrations[Martin et al., 2002; Lear et al., 2002] between temperature and Mg/Ca ratios in benthicforaminiferal calcite provide a means to differentiate the separate effects of temperatureand global ice volume on the benthic foraminiferal δ18O signal. We have measured theMg/Ca ratio of the benthic foraminifera species, Cibicidoides wuellerstorfi, throughoutMarine Isotope Stages (MIS) 1-3 (0-60 Ka) in sediments from Eastern Equatorial Pacific,ODP Site 849 (0$\deg$11'N, 110$\deg$ 31'W; 3851 m). Using published Mg/Ca -temperature relationships for this species, we estimate a 2.5$\deg$C increase in bottomwater temperature at this location over Termination 1. The change in benthicforaminiferal δ18O associated with this deglaciation is ~1.6$\permil$ [Mix et al., 1995].Using a conversion factor of 0.23 $\permil$ per 1$\deg$C [Kim and O'Neil, 1997], the$\delta$$^{18}$O change accounted for by a 2.5$\deg$C change in temperature isapproximately 0.58$\permil$, suggesting a residual 1.02$\permil$ change to beaccounted for by the change in global ice volume over Termination 1. This is consistentwith previous estimates of the global δ18O change of seawater due to melting ofcontinental ice sheets since the Last Glacial Maximum. DE: HR:

0800h AN: PP11B-0559 TI: New Data On The Distribution Of Calcareous NannofossilsDuring And After The Paleocene/Eocene Transition AU: * Raffi, I EM AB: Major changes occur among calcareous nannofossil assemblages at thetransition from Paleocene to Eocene. In most known P/E boundary sections withcomplete sediment records, the changes are associated to the brief, intensive interval ofglobal warming, the Paleocene-Eocene Thermal Maximum (PETM), and a concomitanthuge perturbation of the global carbon budget, the Carbon Isotope Excursion (CIE).Changes in nannofossil assemblages include: (A) occurrence of {\it Rhomboaster} spp. -{\it D. araneus} correlative with the CIE; (B) decrease in diversification of {\itFasciculithus} spp. at the CIE onset; (C) occurrence of {\it Zygrhablithus bijugatus} and{\it Fasciculithus} spp./ {\it Z. bijugatus} abundance cross-over within the upper part ofthe CIE-PETM interval; and (D) extiction of the Paleocene genus {\it Fasciculithus} justabove the CIE, an event that is closely followed by the further evolution of {\itRhomboaster - Tribrachiatus} plexus. The genus {\it Tribrachiatus} subsequently radiatesover the next $\sim$1 million years, a time interval showing further steps in theevolutionary history of calcareous nannofossils (speciations among discoasters andsphenoliths) during the Eocene. Quantitative analyses of selected calcareous nannofossilsin deep-sea sections recovered from the Atlantic (DSDP Site 550, ODP Site 929, andODP Sites 1262 and 1263 of Leg 208) and paleo-equatorial Pacific (ODP Sites 1215,1220, 1221 of Leg 199) provide new informations about calcareous nannofossils acrossthe Paleocene/Eocene transition interval. The distinctive {\it Rhomboaster} spp. - {\it D.araneus} association (RD) was previously considered to have a marked provincialism,restricted to the Atlantic Ocean and partially extending to the Tethys seaway andwesternmost Indian Ocean. Detailed study of Leg 199 sections (from equatorial Pacific)and preliminary analyses at the P/E boundary of ODP Site 929 (from Ceara Rise inwestern equatorial Atlantic) and ODP Sites 1262 and 1263 (from Walvis Ridge insouthern Atlantic) indicate some difference in the RD distribution. The suddenappearance and short co-existence of {\it R. calcitrapa} gr. and {\it D. araneus}, and thelowermost occurrence of {\it R. cuspis} at the onset of CIE clearly can be extended to theequatorial regions of the Atlantic as well as the Pacific Ocean. The genus {\itFasciculithus} undergoes a substantial decrease in diversification at the onset of CIE, andperish completely shortly afterwards. This significant turnover appears to represent aglobal event observed in all the known P/E boundary sections from different oceans andpaleo-latitudes. The abundance cross-over between Fasciculithus spp. and Z. bijugatushas been observed to occur within the the CIE-PETM interval in several deep-seasections. In the central paleo-equatorial Pacific Ocean, however, Z. bijugatus specimenswere not present at all, whereas a marked increase in abundance of {\it R. cuspis} wasobserved in conjunction with the final decline of {\it Fasciculithus} spp. Data from thewestern paleo-equatorial Atlantic Ocean (Site 929) shows only few {\it Z. bijugatus},implying that this particular early Eocene turnover is absent in these equatorial regions.{\it Thoracosphaera} spp. shows a short abundance peak immediately above thecarbonate barren interval at the P/E boundary, during the CIE, at paleo-equatorial PacificSite 1220, which probably reflects a stressed surface water environment.

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0800h AN: PP11B-0564 TI: Depth Dependant Variations in Benthic ForaminiferalAssemblages and Stable Isotopes Across the P-E Boundary, WalvisRidge (ODP Leg 208) AU: * McCarren, H et al. EM AB: The Paleocene-Eocene Thermal Maximum (PETM) ($\sim$55 Ma), wascharacterized by extreme global warming, a negative carbon isotope excursion,intensified carbonate dissolution, and a severe mass extinction of benthic foraminifera.The lack of continuous, undisturbed cores over a wide depth range has limited efforts toplace constraints on key aspects of the PETM event, such as changes in ocean redox andcarbon chemistry, and depth dependent patterns of the benthic extinction. The P-Eboundary was recovered in multiple holes at 5 sites from Walvis Ridge in thesoutheastern Atlantic (ODP Leg 208). We document changes in benthic assemblages andstable isotopes across the PETM at ODP Leg 208, and compare these with data fromother PE boundary sections, including DSDP Sites 525 and 527 previously drilled onWalvis Ridge. Faunal assemblage analyses show a distinct drop in diversity coincidentwith the base of the clay layer at all sites. There is a clear relationship between waterdepth and magnitude of the benthic foraminifera isotope excursion along the WalvisRidge depth transect. Site 1263 (2717m) records excursion values of -2.2$\delta$$^{13}$C and -2.5 $\delta$$^{18}$O; whereas Site 1262 (4759m) has values of-0.2 $\delta$$^{13}$C and -0.8 $\delta$$^{18}$O at the height of the excursion. Thisdifference implies truncation of the record at deeper sites by carbonate dissolution,possibly as well as a depth dependent difference in water mass chemistry and temperatureduring the PETM. Several benthic foraminiferal species such as {\it Nuttallidestruempyi} and various abyssaminid species that may indicate low nutrient availabilityincrease in abundance at the onset of the isotope excursion, while the percentage ofbiserial and triserial species, used as high food/low oxygen indicators, decreases. Thereare thus distinct changes in ocean chemistry over the 2.3 km paleodepth range of theWalvis Ridge transect during the PETM event. DE HR:

0800h AN: PP51F-1369 TI: A Reconstruction of Millennial-scale Changes in Sub-surfaceWatermasses Off of Central Chille AU: * Phipps, M and Mix, A EM AB: Here we examine millennial scale changes in subsurface watermasses off centralChile during the last ice age, based on stable carbon and oxygen isotopes from benthicforaminifera. ODP sites 1235: (489m water depth) and 1234 ( 985 m water depth) bracketthe modern extent of Antarctic Intermediate Water. The core top \delta 18O at 1235 and1234 are 2.7 \permil and 3.3 \permil respectively. This 0.6 \permil difference between thetwo cores corresponds to a modern 2.4 $^{\circ}$ C temperature offset between sites.Variations in \delta 18O from Site 1234 resemble similar high-resolution records from thedeep Atlantic, which suggests Southern Ocean linkage of deep ocean temperatures in thetwo ocean basins. High amplitude \delta 18O variations at Site 1234 indicate a largerchange in temperature in the intermediate Southeast Pacific than the deep North Atlantic,whereas Site 1235 varies with lower amplitudes. If glacial ice volume accounts for 1.1 -1.3 \permil of the observed change in benthic foraminiferal \delta 18O, Site 1235 mayhave experienced temperature changes of 2 - 3 $^{\circ}$ C and that Site 1234experienced changes of 3-4 $^{\circ}$ C. DE

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0800h AN: PP51D-1353 TI: The early Eocene in the Southern Ocean; an integrateddinocyst and geochemical analysis of ODP Leg 189 sites 1171 and1172, Tasman Sea. AU: Deltrap, R et al. EM AB: The early Eocene is known as the warmest and most extreme long-term greenhouseinterval of the Cenozoic. Superimposed on these conditions, short-lived 'hyperthermal'events, apparently caused by the fast input of carbon in the ocean-atmosphere system, areassociated with dramatic changes in ocean chemistry, the global hydrological cycle andbio-provincialism and evolution. The `Paleocene/Eocene Thermal Maximum' or PETMevent (55 Ma) is the most extreme hyperthermal event, but recently similar events withinthis time period have been identified. Many relatively complete late Paleocene throughearly Eocene sequences have by now been reported from around the world, but most arefrom ancient low- to mid-latitude sites. ODP Leg 189 in the Tasman Sea recovered thesouthernmost successions ever encountered from this critical phase in Earth's history atthe marginal marine Sites 1171 and 1172 (at 70\deg to 65\deg S paleolatitude). On thebasis of more detailed investigations of downhole and core logging data, in combinationwith bio- (dinocysts) magnetostratigraphy and organic stable isotope geochemistry, wehave identified the PETM, and possibly also the younger Elmo event (see Sluijs et al.,AGU fall meeting abstract volume 2004) and provide correlation and analysis of the latePaleocene through early Eocene in terms of completeness and paleoenvironment. DE HR:

0800h AN: PP51F-1366 TI: Alkenone and planktic foraminifer sea-surface temperaturereconstructions at ODP Site 1240: 500-900 kya AU: * Yu, P EM AB: One of the objectives of ODP Leg 202 is to retrieve high-resolution sediment coresfrom the eastern equatorial Pacific, an area in which modern interannual-scale climate aredynamically fluctuating. In this study we aimed to reconstruct paleoceanographic recordsfrom the ODP Site 1240 (0o1.311'N; 86o27.758'W; WD: 2921m) from the Leg 202. Oneof our objectives in the paleoceanographic reconstructions is to better understand howtropical oceans interact with global climate over orbital time scales, and focus on testinghypotheses of ENSO-like oscillation and of extra-tropical forcing prevailed in long-termclimate variations in the tropics. We are especially interested in examining an abnormally"warm and wet" climate in glacial MIS 14 shown in Chinese loess and South China Seamarine records and looking for any tropical origin of forcing or feedback for explainingthe abnormality. Site 1240 was chosen for this purpose as this site is ideal for monitoringupwelling and circulation changes in the eastern equatorial Pacific, and is likely verysensitive to if any ENSO-like oscillations occurred in this particular time interval. In thispreliminary study, the age model of cores from Site 1240 was constructed primarilybased upon 4 calcareous nannofossil datums at the top 80 meters composite depth (mcd)and the average sedimentation rate is ~10cm/kyr. We have also generated alkenone SSTsfrom an interval of 500-900 kya of the cores. Initial observations indicate that highalkenone concentrations are associated low SSTs and vice versa at this interval. AlkenoneSSTs calculated from Prahl's equation show an amplitude ~$4-5\deg$C variations overmajor glacial-interglacial periods in this interval and suggest a dynamic climate pattern inthe EEP. Comparison of the alkenone SSTs and relatively low-resolution plankticforaminifer fauna MAT-SSTs also indicates that these two estimates appear to be ofsimilar amplitudes, though the MAT-SSTs are apparently warmer than alkenone SSTs by~$1-2\deg$C. In the interval equivalent to MIS 13-15 based on our very initial agemodel, both SST proxies show large cooling (~$4\deg$C) which suggest a strongequatorial circulation at this time. DE: HR:

0800h AN: PP11B-0571 TI: Marine carbonate dissolution event across theEocene/Oligocene boundary: the Walvis Ridge transect, SouthAtlantic (ODP Leg 208) AU: * Liu, Z et al. EM AB: Sediments recording the response of South Atlantic to global cooling and marinecarbonate dissolution during the Eocene-Oligocene transition were recovered across abroad range of depths of five sites on the northeastern flank of Walvis Ridge during ODPLeg 208. Although the Eocene/Oligocene (E/O) boundary is not well preservedbiostratigraphically, especially at two deepest sites (Sites 1262 and 1267), oxygen andcarbon stable isotopes of benthic and/or planktonic foraminifers have determined theexact boundary position for most of sites. High-resolution carbonate content andforaminiferal grain size combined with coarse fraction and siliciclatic elementgeochemistry reveal that the strongest carbonate dissolution event occurred just above theE/O boundary, leading the global Earliest Oligocene Glacial Maximum (EOGM). Thiscarbonate dissolution event may take up abundant atmospheric CO2 into the deep oceanby the calcium carbonate pump system, and then induces the global cooling during theearliest Oligocene. The recovery of the foraminiferal preservation does not appear to beimmediate with rapid cooling; however, it lags behind about 500 kyr, implying that theshift in carbonate preservation was triggered by changes in climate. The carbonatedissolution event is associated with deepening of carbonate compensation depth (CCD)and falling of sea level. Moreover, the event has a close relationship with continentalweathering rates indicated by element geochemistry, implying the possible carbon cycle-forced global cooling event across the E/O boundary. DE: HR:

14:55h AN: PP13B-06 TI: Sea-surface and deep-sea temperatures and seawater d18O inthe Southern Ocean over the last 440,000 years AU: * Tripati, A et al. EM AB: The circulation of Antarctic Bottom Water is one of the controlling factors in theEarth's heat budget, and therefore Southern Ocean paleoceanography is critical tounderstanding glacial-interglacial climate change. Ocean Drilling Program (ODP) Site1123 (3290 m water depth) on Chatham Rise (41ø 47.15' S, 171ø 28.94' W) is locatedjust north of the present-day Subtropical Convergence, below the Pacific Deep WesternBoundary Current, within the depth range of Antarctic Bottom Water. The recoveredsedimentary sequence from ODP Site 1123 contains a record of Southern Ocea,hydrographic variations over several glacial-interglacial cycles: We present a 440,000year record of surface and deepwater hydrographic variability based measurements ofMg/Ca and stable isotope ratios in planktic and benthic foraminifera. Planktic Mg/Ca-based temperatures indicate a maximum glacial-interglacial temp. change of 7.5øC. Theplanktic record shares many features in common with a record from a shallower sitelocated just south of the Subtropical Convergence excepth that temp. changes acrossTermin. 1 and 2 aren't seen at Site 1123. Possible reasons for this include hydrographicdifferences between sites, foraminiferal habitat, and dissolution artifacts. Glacial-interglacial benthic Mg/Ca differences are variable through the record, with coldesttemperatures inferred for Stages 8 and 10. Deep-water temps. based on Mg/Ca indicateLGM values of -0.8øC (calibration of Martin et al. 2002) and a seawater d18O of 1.0 permil (VSMOW), similar to the porewater-based reconstruction at this site (Adkins et al.2002). DE HR:

1340h AN: PP23B-1408 TI: Pleistocene North Atlantic Deep Water Production; ASouthern Hemisphere Perspective AU: * Foote, J et al. EM AB: Faunal counts and stable isotopes of planktonic foraminifera are used to identifyglacial-interglacial and millennial scale change in Pleistocene Atlantic interhemispherictransport. The sampling site, ODP Site 1085, has a sedimentation rate of approximately 5cm/k.y. Samples were taken every 2 cm throughout the sections of the core representingthe last 200 k.y., giving the site a resolution of approximately 500 years, high enough toobserve glacial-interglacial variation, Dansgaard/Oeschger temperature cycles, andHeinrich events, within the Nyquist frequency. {\it Globigerina bulloides}, found in cold,nutrient-rich water, is used as a proxy for upwelling (Girardeau 1992). At Site 1085, {\itG. bulloides} peaks both during glacial and interglacial periods. The interglacial peakscovary with peaks of terrigenous sediment greater than 10 microns, an indicator ofaeolian transport (Stuut et al. 2002), indicating a link between upwelling and windstrength at that time. The glacial peaks broadly correlate to a low C/N ratio, indicating aprobable marine cause for the upwelling, such as an enhanced Benguela Current.Additionally, there is higher-frequency (sub-Milankovitch) variability through both theglacial and interglacial periods. DE: HR:

15:10h AN: PP43B-07 TI: Linking Global Climates Between Hemispheres and OceanBasins: Millennial-Scale Temperature and Isotopic Variability ofIntermediate and Mid-Depth Watermasses of the Equatorial andSoutheast Pacific. AU: * Mix, A et al. EM AB: Analysis of stable isotopes and trace metals in benthic foraminifera from rapidlyaccumulating sediments in the Equatorial and Southeast Pacific recovered on ODP Leg202, reveal remarkably high amplitude variations on millennial scales at water depths of$\sim$500-1500 m. Presence of climate signals that mimic variability in ice coresprovides a strategy for inter-hemispheric and interocean correlation. Surprisingly largevariability in subsurface watermass properties in this region mimics signals found in themid-depth Atlantic. This variability in the Pacific suggests a role for global-scale oceancirculation in interhemispheric and interocean linkage. DE

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1340h AN: PP23A-1396 TI: Early Onset and Origin of 100-kyr Cycles in a TropicalPleistocene SST Record AU: * Liu, Z and Herbert, T AB: The large 100-kyr cycles evident in most late-Pleistocene paleoclimatic records stilllack a satisfactory explanation. Many climatic records show that the period of Pleistoceneglacial cycles changed from 41-kyr, dictated by orbital obliquity, to 100-kyr during themid-Pleistocene transition (MPT). Careful documentation and consideration of how thistransition occurred may help resolve the puzzle of late Pleistocene 100-kyr cycles. Onehypothesis is that strengthened semi-precession cycles (about 10-kyr) originating in thetropics propagated to high latitudes around 1.5 Ma and triggered the sustained 100-kyrglacial cycles. A 2-Myr SST record from ODP Site 846 in the eastern equatorial Pacific(EEP) indicates that an early onset of 100-kyr cycles did occur in the tropics. However,the record also provides an alternative view of the MPT. Substantial spectral power nearthe 100-kyr period occurs in early Pleistocene tropical, but not extra-tropical SSTrecords. This spectral power is derived from the subharmonics (multiple integers, about120-kyr and 80-kyr) of obliquity cycles. In addition, as shown in evolutionary SSTspectra, the two subharmonics converge into the late-Pleistocene pseudo 100-kyr period.Therefore, we argue that the subharmonics of obliquity cycles in the early Pleistocenerepresent a _rprototype__ of the late Pleistocene 100-kyr cycles, and that the pseudo 100-kyr cycles are a nonlinear response to orbital obliquity forcing. This view can potentiallyresolve some existing Pleistocene climate puzzles: (1) the transition from 41-kyr to 100-kyr periodicity during the MPT, (2) the dominance of late-Pleistocene 100-kyr cycles,and (3) weakened late Pleistocene 41-kyr power in some climate records, despite theexpected ice-albedo amplification of high latitude insolation forcing. DE: HR:

0800h AN: PP51A-1328 TI: Duration of Pliocene Ice-Rafting Events Offshore of PrydzBay, Antarctica, Derived From Extraterrestrial Helium-3 AU: * McAuley, A et al. EM AB: The sediment record of ODP Site 1165, located 400 km offshore of Prydz Bay,Antarctica, contains layers rich in ice-rafted debris (IRD) dating from the Early Mioceneto the present. The IRD represents pulses of icebergs from the Lambert Glacier and theAntarctic coast west of the site. If the duration of the ice-rafting events is short, they arelikely to represent relatively rapid deglaciations of the continent. Alternatively, the IRDcould be concentrated in these layers by winnowing or a reduced sedimentation rate. Inorder to distinguish between these possibilities we have measured helium isotopes acrosstwo of the layers. Interplanetary dust particles (IDPs) are enriched in helium-3 comparedto terrestrial materials and they are deposited at a relatively constant rate, thus providinga means of determining the (relative) duration of the ice-rafting event. IDPs and helium-3 are diluted one of the Pliocene IRD-rich layers, indicating relatively fast deposition andincreased iceberg flux, probably during deglaciation.

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0800h AN: PP51F-1371 TI: Sedimentary Characteristics through Glacial/InterglacialTransitions at ODP Site 1233 AU: * Joseph, L H EM AB: ODP Site 1233, located shoreward of the Chile Trench on the Chilean continentalslope ($\sim$38 km offshore; $41\deg$0.005'S, $74\deg$26.992'W, 838 mbsl),recovered a 136 mcd-thick continuous and extremely high-resolution sedimentarysequence that extends through 70 ka, providing the potential to significantly enhance ourknowledge of Southern Hemisphere climates. The sediment collected originates in anarea where the erosion and transport of sediment to the continental margin is enhanced byalpine glaciation and heavy rainfall. This study investigates glacial/interglacial sedimentvariations in through the use of magnetic fabric (anisotropy of magnetic susceptibility,AMS), terrigenous grain size, and flux calculations. Site 1233 consists primarily ofhomogenous nannofossil clay, nannofossil silty clay, and nannofossil-bearing silty clay.Ninety-one samples were taken at approximately 1.5-meter intervals from a compositesplice. On average, one sample was obtained for every $\sim$800 years. Bulk magneticsusceptibility values range from 3.4 x 10$^{-4}$ to 4.6 x 10$^{-3}$ SI with an averageof 3.0 x 10$^{-3}$ SI. Values of AMS parameter P' (the strength of the magnetic fabric)range from 1.005 through 1.058, with an average of 1.025 while T values (shape factor)fall almost exclusively within the oblate realm, especially when samples from notedintervals of diagenesis are disregarded. The depositional environment, as indicated by P'and T, plots within the field of low to mid-velocity currents, indicating some currentinfluence at this site. The strength of the magnetic fabric (P') varies through time, withmaxima present at $\sim$38 and 13 ka, and may represent fluctuations or changes in thesurrounding AAIW. Analyses of terrigenous grain size and flux are on-going and willfacilitate further interpretation of the magnetic fabric results. DE

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0800h AN: PP11B-0562 TI: Tracers of Productivity across the PETM, Walvis Ridge, ODPSites 1262 and 1263 AU: Quartini, J et al. EM AB: The rapid and extreme global warming across the Paleocene-Eocene ThermalMaximum (PETM) is unmatched in Earth's history. We are using sedimentaryphosphorus concentrations and geochemistry, along with barium and trace metals, toreconstruct nutrient burial, primary productivity, and paleoredox state across a depthtransect for Walvis Ridge. We have chosen Ocean Drilling Program (ODP) Sites 1262(4755 m water depth) and 1263 (2717 m water depth) at a sample resolution of $\sim$ 1-2 kyr for 5 Ma centered at 55 Ma. We are characterizing the nutrient burial historyduring the PETM by recording the associated short-term changes in ocean chemistry andcirculation. We have measured Ba excess, a good indicator of export productivity inmarine sediments underlying oxic conditions, for Site 1262 samples. Ba excessconcentrations range between $\sim$ 2-5 umol Ba/g prior to the warming event anddecrease to zero at the boundary (140.04 mcd). Ba excess gradually recovers but doesnot greatly exceed pre-event concentrations ($\sim$ 2-5 umol Ba/g). Uranium andmanganese enrichment factors (EF) were determined during this event for Site 1262. Uranges from 0.9 -1.1 relative to crustal averages pre-event, 0.7- 0.8 during the event, and0.9 -1.1 after the rapid warming. Uranium data shows consistent recovery with calciumcarbonate deposition over a depth range $\sim$ 0.5m. Mn EF values range between 3.7 -8.6 prior to the event, suggesting an oxygenated depositional environment. At theboundary, Mn EF values drop to 1.3, then gradually return to pre-event values with apeak at 139.76 mcd of 13.2. We will compare our geochemical results with Site 1263data. DE HR:

0800h AN: PP51F-1367 TI: Phosphorus and Barium Tracers of Productivity, Nazca RidgeODP Site 1237, Southeast Pacific Paleoceanographic Transects AU: * Chun, C and Delaney, M L EM AB: Phosphorus, biogenic barium, and trace metal concentrations have been measured insediments recovered from Ocean Drilling Program (ODP) Leg 202 Site 1237, NazcaRidge. Our work has been to understand how these tracers of productivity andsedimentary redox conditions may have responded to the tectonic and climatic evolutionof the Southeast Pacific. Changes in lithology as the site moves from a pelagic to hemi-pelagic depositional setting with past plate motion are important when applyingpaleoproductivity proxies. This unique record extends to 31 Ma over 360 mcd, with asampling resolution of $\sim$ 0.2 m.y. throughout the sequence. Reactive phosphorus, anindicator of nutrient burial, shows increasing concentrations toward the modern, peakingat 25.3 umol P/g at 15.34 mcd. Biogenic barite, a proxy for export productivity, peaks at36.90 mcd at a concentration of 3.8 umol Ba/g. Reactive P/Ba excess ratios display lowerthan expected values for the upper $\sim$ 180 mcd with a sharp increase to higher ratiosstarting at $\sim$ 270 mcd. Biogenic barite (determined by sequential extraction) definedas Ba barite, were performed on select samples to compare with Ba excessmeasurements. We found that estimates of biogenic barite from Ba excess are greaterthan those from barite extraction for these samples. Uranium and manganese enrichmentfactors (EF) were determined for the entire record. U EF all exceeds crustal values.Dramatic changes in Mn EF at $\sim$ 162 mcd and the observed color change fromgrayish white to a fairly homogeneous pale brown at this depth lead us to believe that achange in source material, not redox conditions caused this event. We will need animproved age model to generate accumulation rates and to test nutrient burial history atthis site. DE HR:

08:00h AN: PP31B-01 INVITED TI: Evidence For Deep-water Production In The North PacificDuring The Early Cenozoic AU: * Thomas, D J EM AB: The evolution of Cenozoic climate began with a long-term warming trendculminating in peak warmth during the Early Eocene. This was followed by intensecooling that ultimately led to the onset of the "icehouse" climate of the late Cenozoic.Changes in poleward heat transport via thermohaline circulation may have played a rolein the general evolution of Cenozoic climate. To investigate the relationship between theevolution of global climate and thermohaline circulation over the interval $\sim$70 to 30million years ago (Ma), I generated paleo-seawater neodymium isotopic records fromOcean Drilling Program (ODP) sites in the present-day northern Pacific Ocean. Fishdebris Nd isotope data from ODP Sites 1209 and 1211 (paleodepths $\sim$2300m and$\sim$2900m) indicate that $\epsilon$$_{Nd}$ values in the deep waters of the centralsubtropical Pacific were characterized by a composition of $\sim$-4.5 to -5 during thelatest Cretaceous and the Early Paleocene ($\sim$70 to 64 Ma). Beginning $\sim$64 Ma,the composition of Pacific deep waters became more radiogenic ($\sim$-3 to -3.5), andremained so for the next $\sim$20 million years. From $\sim$46 to 33 Ma, deep-water$\epsilon$$_{Nd}$ values subsequently became more nonradiogenic ($\sim$-4.5 to 5).The similarity in the overall $\epsilon$$_{Nd}$ trends at both sites indicates that theywere bathed by a common deep-water mass. Nd isotopic data from ODP Leg 199 Sites(1215, 1219, and 1221; north-central Pacific), which lie $\sim$6000 km to the west andsouth of Shatsky Rise, demonstrate a trend similar to the upper portion of the recordsfrom Shatsky Rise. Although the basal age of sediments from the Leg 199 Sites isyounger than 56 Ma, $\epsilon$$_{Nd}$ values from Sites 1215, 1219 and 1221demonstrate the shift from relatively radiogenic (North Pacific) values of -3.5 at 53.7 Mato more non-radiogenic (Southern Ocean) values of -4.9 by 44.8 Ma. The $\sim$1.5epsilon unit shifts toward more radiogenic values recorded at both sites reflect afundamental change in the source of deep waters bathing the northern Pacific sites from$\sim$65 to 45 Ma, involving a switch in deep-water production from the SouthernOcean to the North Pacific. Production of North Pacific deep waters lasted $\sim$20million years, and coincided with the warmest climatic interval of the Cenozoic Era. Thetiming of the deep-ocean circulation changes lagged changes in global temperaturesimplying that climate exerts long-term control over thermohaline circulation patterns.Thus Cenozoic thermohaline circulation patterns evolved in response to long-termchanges global climate, and were not the cause of extreme Cenozoic warmth. DE

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1340h AN: PP23B-1434 TI: Optical Dating of Marine Sediment From ODP Core 658B -An Intercomparison With an Independent AMS 14C Chronology AU: * Armitage, S et al. EM AB: We demonstrate the potential of optical dating of detrital quartz silt from marinesediments via a chronological intercomparison for samples from ODP Site 658, whichrange in age from 0 to 140ka. ODP Site 658 is located off Cap Blanc, Mauritania. It has ahigh sedimentation rate (18 cm/ka), due to high regional surface productivity and largeinputs of windblown Africa dust. This windblown dust provides both the substrate foroptical dating and a proxy for North African aridity. The AMS 14C chronology is basedon monospecific foraminiferal (Globigerinoides bulloides) samples. This is the firstlarge-scale, systematic application of optical dating to marine sediment, and demonstratesthat the technique has considerable potential for the age estimation of otherwiseundateable deep-sea material. Optical dating techniques measure the total ionisingradiation dose that a mineral grain has received since its last exposure to sunlight (i.e.during burial). The resulting optical age is essentially calibrated via a knowledge of theenvironmental dose rate, yielding the burial period. The environmental dose rate isderived from the decay of radioisotopes in the sediment (K, U and Th). In terrestrialsediments, the uranium and thorium decay chains can be assumed to be in equilibrium. Inthe marine realm this assumption is not valid, and unsupported uranium decay series existon deposition. Consequently, the environmental dose rate changes with sample age. Thisproblem was circumvented by quantifying U and Th decay series disequilibrium, usingan MC-ICP-MS. The evolution of the environmental dose rate during burial wasmodelled, and ages for each sample calculated. The 14C and optical ages are generally ingood agreement, indicating that the latter technique can provide equally robustchronologies for marine sediments. Although the maximum age attainable using opticaldating is sample specific, the dose rate and luminescence characteristics of the samplesanalysed in this study indicate that marine sediments ranging from 0-200ka should bedateable. Very precise (1-3%) burial doses and radioisotope concentrations wereobtained, although ultimately precision is limited to about 10% due to uncertainties in themoisture content, source calibrations and dose rate conversion factors. However, overthe timescales that optical dating is applicable, these overall errors are not inconsistentwith the rarely quoted precision accorded to orbitally tuned records. Optical datingshould provide a valuable geochronological tool for marine sediments extending wellbeyond the time range of 14C dating, and for dating marine sediments that contain nodateable carbon. DE: HR:

14:10h AN: PP43B-03 TI: Pliocene Shoaling of the Central American Seaway and itsEffect on Caribbean and Tropical East Pacific Upper OceanStratification AU: * Steph, S et al. EM AB: Multispecies planktonic \delta$^{18}$O records and Mg/Ca-temperaturereconstructions from ODP sites 999, 1000 and 1241 were used to assess changes inCaribbean and tropical East Pacific upper ocean stratification in response to theprogressive closure of the Central American Seaway. Our studies focus on the timeinterval from 5.5 to 2.5 million years. Previous studies suggested that the sill depth of thePanamanian Gateway shoaled to less than 50 m by about 4.6 Ma as indicated by anincrease in Caribbean sea surface salinity (SSS), reflecting the development of themodern Atlantic-Pacific SSS contrast. At site 1241, the general increase of\delta$^{18}$O and Mg/Ca temperature gradients between the mixed-layer dweller {\itG. sacculifer} and deeper dwelling foraminifers {\it N. dutertrei}, {\it G. limbata} and{\it G. tumida} suggests a shoaling of the tropical East Pacific thermoline from 5.5 Ma to3.3 Ma. At Caribbean sites 999 and 1000, both \delta$^{18}$O and Mg/Ca temperaturegradients indicate a warming of subsurface water masses after 4.4 Ma. The directcomparison of subsurface water signatures from Caribbean sites (999, 1000) and tropicalEast Pacific site 1241, however, points to a deeper leakage in the Central AmericanSeaway that persisted at least until 3.3 Ma, just before the onset of the NorthernHemisphere Glaciation. The increase in Caribbean SSS after 4.6-4.2 Ma is interpreted toreflect a diminished eastward volume transport of less saline Pacific water massesthrough the gateway, rather than a shoaling of the gateway to a water depth of less than50 m. Similar and stable Mg/Ca temperatures at sites 999 and 1241 paralleled by a\delta$^{18}$O increase at both sites display a salinity increase in Caribbean and tropicalE-Pacific subsurface waters from 4.4 Ma to 3.3 Ma, possibly indicating reversedthroughflow at greater water depths. DE:

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1340h AN: PP33A-0914 TI: An Excess $^{226}$Ra Geochronology for Saanich Inlet AU: * Grayson, R et al. EM AB: When examining past environmental and climatic change the ability to date bothfreshwater and marine sediments is essential. Numerous methods are currently available,however where present techniques fail, novel dating techniques are required to overcomethese obstacles. In particular the use of $^{14}$C to date sediments over the Holoceneperiod can be severely limited where there are significant hard-water and reservoir effectsand where reworking of organic matter occurs. The use of unsupported or excess$^{226}$Ra offers a potential dating tool in such depositional contexts over theHolocene time period as a result of its half-life of 1600 years. Indeed, the technique hasbeen applied to a number of environments since first being proposed by Koide et al.(1976). However, numerous question marks still surround the application of thetechnique, particularly with reference to the dating of sub-aqueous sediment deposits. Aspart of wider research into the applicability of excess $^{226}$Ra to date lakesedimentary environments, deep-sea samples from Saanich Inlet were obtained from theODP (Leg 169S) in order to validate the dating technique. Saanich Inlet is an anoxic fjordlocated on the coastline of Vancouver Island, British Colombia, the sediments of whichhave been shown to be comprised of lamina-scale alternations between diatom-rich anddiatom-poor clays and silts representing annual. Using digital sediment colour analysisNederbragt and Thurow (2001) constructed a varve chronology for the last 6000 years.Alpha-spectrometry was successfully used to measure $^{226}$Ra, $^{230}$Th and$^{234}$U in sediment samples collected from Saanich Inlet during ODP Leg 169S.These activities were used to determine an excess $^{226}$Ra geochronology forSaanich Inlet. This radiometric chronology compares well with dates obtained from thevarve record, and spans two different phases of sediment accumulation. DE HR:

08:45h AN: PP51G-04 TI: Nitrogen isotopic composition of ammonium released duringdiagenesis of organic matter under steady-state and non-steadystate conditions in marine anoxic sediments AU: * Prokopenko, M et al. EM AB: The d15N of organic matter in marine sediments has been successfully used as apaleoceanographic proxy. However, diagenesis may alter the original isotopic ratio. Oneapproach to evaluate the sign and magnitude of the diagenetic impact is to measure theisotopic composition of ammonium that is produced during the degradation ofnitrogenous organic matter (N-org). If diagenesis of organic matter is the only processaffecting ammonium concentration and its isotopic composition, the $\delta$15N ofammonium should reflect the isotopic ratio of the N-org plus fractionation, if any. Weevaluated the impact of diagenesis on $\delta$15N of N-org on a time scale of fewthousand years in two California Borderland Basins, Santa Barbara (SBB) and SanNicolas (SNB). We found ammonium to be about 2.5 \permil heavier than the bulk N-org. One interpretation is that N-org consists of multiple, isotopically distinct fractions oforganic matter with variable lability. The most labile fraction must be 2.5 \permil heavierthan the bulk N-org. The relatively large loss of N-org in SNB (50 %) should haveresulted in a 2 \permil shift in $\delta$15N of N-org downcore, while in SBB, higheraccumulation rates led to smaller loss of N-org (15%) and little change in its isotopiccomposition. Sediment from the Peru-Chile margin, collected during ODP Legs 201 and202, was used to evaluate the diagenetic impact on a time scale of millennia to millionsof years. In rapidly accumulating anoxic coastal sediments with constant $\delta$15N inthe N-org , we found diagenetic fractionation is less than 1 \permil. Several other ODPsites are also strongly influenced by non-steady state conditions, and the isotopiccomposition of pore water ammonium primarily reflects changes in $\delta$15N of thesource organic matter through time. Preliminary model results show that isotopicallyheavy ammonium released from organic matter deposited within the last 12-15 Kyr hasdiffused about 30 m into the sediments. This result underscores the importance ofrecognition and proper evaluation of non-steady state conditions. DE HR:

0800h AN: PP11B-0566 TI: The Composition and Flux of Terrigenous Material from thelate Paleocene to the early Eocene in the Indian Ocean AU: * Nicolo, M J EM AB: Stable isotope records of both marine and terrestrial origin constructed fromnumerous widespread locations show a characteristic sequence of large amplitudevariations in \delta $^{18}$O and \delta $^{13}$C between ca. 60 and 50 Ma, suggestingmajor changes in global climate and carbon cycling from the late Paleocene to the earlyEocene. Continental weathering and atmospheric circulatory systems should have variedin response to these global fluctuations. In this regard, the flux, composition and grain-size of both eolian and hemipelagic (terrigenous) components of oceanic sedimentsshould be affected by the intensity of atmospheric circulation and changes in terrestrialclimate and weathering respectively. Deep-Sea Drilling Project Site 215 (near Ninety-East Ridge), Ocean Drilling Program Site 752 (Broken Ridge), and Ocean DrillingProgram Site 762 (Exmouth Plateau) are located in the Indian Ocean, have well-datedearly Paleogene sections, and are applicable to these systems in different ways (e.g. arevaried by latitude and type of terrigenous material they likely received during the timeinterval of interest). Following early work at ODP Site 215 (Hovan and Rea, 1992), herewe present records of the terrigenous component at these sites, including massaccumulation rate (MAR), grain-size, and mineralogy (XRD). These records coupledwith future work in the southern Atlantic and southern Pacific oceans provide a basis forunderstanding early Paleogene climate changes in the Southern Hemisphere, as well asconstraints for future modeling. DE

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16:30h AN: PP44A-03 TI: Glacial ITCZ Shifts Recorded by Tropical SalinityReconstructions in the Pacific and Caribbean AU: * Spero, H et al. EM AB: A variety of data from terrestrial, marine and modeling studies indicate that thetropical Atlantic and Pacific ITCZ was shifted considerably south of its current positionduring the last glacial period. The effect of such a shift on the glacial ocean would be toincrease surface salinity (relative to today) in regions that are currently influenced by theITCZ and to decrease salinity in regions that are currently south of the modern ITCZ butwithin the influence of the glacial ITCZ. Here we compare a previously published 380 ka\delta$^{18}$O$_{sw}$ reconstruction (a proxy for salinity) for the western equatorialPacific (WEP) at ODP Site 806B ($0.33\deg$N, $159.34\deg$E) (Lea et al. 2000) with anew Caribbean \delta$^{18}$O$_{sw}$ reconstruction at ODP Site 999A($12.75\deg$N, $78.75\deg$W) that was derived from Mg/Ca (a proxy for SST) and\delta$^{18}$O data from a surface dwelling foraminifera, {\it Globigerinoides ruber}.These reconstructions indicate the WEP was considerably fresher during past glacialperiods with surface \delta$^{18}$O$_{sw}$ 0.3 to 0.4 \permil lower than today afterremoval of ice volume. Using modern \delta$^{18}$O$_{sw}$ vs salinity relationships,this geochemical change suggests glacial surface salinities in the WEP at Site 806B were~1-1.5 psu lower than today. In contrast, Caribbean surface waters were much saltierduring the last glacial period with \delta$^{18}$O$_{sw}$ 0.5 \permil higher thanmodern after removal of ice volume. This \delta$^{18}$O$_{sw}$ shift translates to aglacial surface salinity $>$2 psu higher than today (after the influence of ice volume wasremoved). Reconstruction of surface salinities across 3 glacial cycles back to 380 ka atthese two sites demonstrate that the Caribbean and WEP were antiphased with largesalinity differences during glacials and nominal differences during interglacials. Tropicalwestern Pacific sediment trap data indicate the maximum {\it G. ruber} flux is during thesummer months. Hence, we interpret these data to indicate that the glacial summer ITCZwas located over the equator in the WEP, considerably farther south than its currentposition at $8-10\deg$N. In contrast, the elevated Caribbean salinities support terrestrialand coastal Cariaco Basin data that indicate the ITCZ was situated over the over SouthAmerica during the summer months. We are optimistic that future\delta$^{18}$O$_{sw}$ records from adjacent tropical sites will permit us to reconstructthe continuous migration of the ITCZ through time. DE: HR:

1340h AN: PP33A-0911 TI: Differentiation of Cenozoic Eolian Dust Sources in theEastern Pacific by Nd-Sr-Pb Radiogenic Isotopes AU: * Stancin, A et al. EM AB: DSDP, ODP and piston core samples from the eastern Pacific provide a temporaland spatial context for mapping changing sources of eolian dust during the Cenozoic Era(65 Ma to present). We examined core sites from ODP Sites 469, 495, 853, 885/886,DSDP Sites 32, 319, 320, and piston core sites EW9709-01, 07 for Pb, Sr and Nd isotopicprovenance. Isotopic analyses were performed on the $<$63 micron extracted detritalcomponent following reductive cleaning to remove all authigenic and biogeniccomponents. Downcore comparison of continental margin sites with those dominated bypelagic clays from north and south of the equator was facilitated by factor analysis usingtwo programs. Multivariate factor analysis was performed with both CABFAC andMinitab. Three factors were identified and accounted for 98.4% of the variance. Factor 1(epsilon Nd and Pb 207/206) defines the dominant late Cenozoic Asian dust source andaccounts for 44.1% of the variance. Factor 2 identifies a South American dust sourcebased on $^{87}$Sr/$^{86}$Sr and Pb 206/204, 208/204 and 207/204 and accounts for36.5% of the variance. Factor 3 identifies a North American dust source($^{87}$Sr/$^{86}$Sr, Pb 208/206, and Pb 207/206) and accounts for 17.8% of thevariance. We conclude that in the eastern Pacific, late Cenozoic Asian dust sources canbe quantitatively differentiated from both North American and South Americancontinental sources. We are attempting to extend this record back to 65 Ma, with theultimate goal being to reconstruct long-term Cenozoic atmospheric circulation and windpatterns across major climate transitions. DE HR:

0800h AN: PP11A-0556 TI: The Nature of the $\delta$$^{13}$C of PeriplatformSediments: Implications for stratigraphy AU: * Swart, P et al. EM AB: The carbon isotopic composition ($\delta$$^{13}$C) of bulk carbonates, obtainedfrom a transect of sites drilled through platform and periplatform sediments of Holoceneto Early Miocene age, have been compared to ascertain whether changes in the$\delta$$^{13}$C can be correlated between sediments of equivalent ages and whethersuch changes can be related to global changes in the $\delta$$^{13}$C of the dissolvedinorganic carbon in the oceans over this time period. Five of the sites were drilled duringLeg 166 of the Ocean Drilling Project (1003-1007) in a transect ranging from five km to25 km away from the platform margin and penetrating sediments of Holocene toOligocene age that are contained in 17 depositional sequences (A-Q). Two shallow watersites, Clino and Unda were situated on a extension of the same transect on Great BahamaBank in a water depth of 10-15 m. With the exception of Unda and Clino, the$\delta$$^{13}$C of the carbonates range in isotopic composition from +5% in theyounger sequences to +1% in the Early Miocene. In each of the sites the$\delta$$^{13}$C is strongly positively correlated with the percentage of aragonite. As aconsequence the $\delta$$^{13}$C of sequences A through F is strongly correlated,reflecting the decreasing amount of aragonite with increasing depth. In the two platformsites, the $\delta$$^{13}$C is significantly more negative in the younger portions of thecores as a result of the influences of meteoric diagenesis during repeated exposure duringthe Pleistocene. Although the $\delta$$^{13}$C of the individual sequences can becorrelated in most instances between the ODP holes, the changes are not related to globalchanges in the d13C of the oceans which in contrast to the $\delta$$^{13}$C of theplatform sediments become isotopically more negative towards the present day. Insteadthe $\delta$$^{13}$C appears to be related to varying contributions from$\delta$$^{13}$C rich bank-top sediments. While the results from this study may not beuniversally applicable to all carbonates associated with shallow water platforms formedthroughout geological time, they certainly cast a note of caution that apparently relatedchanges in the carbon isotopic composition can be caused by mechanisms other thanglobal changes in the carbon cycle. DE HR:

0800h AN: PP11A-0550 TI: Orbitally Paced Climate Variability During the MiddleMiocene: High Resolution Stable Isotopes and Fe Records Fromthe Western and Southeastern Pacific AU: * Holbourn, A et al. EM AB: We present continuous high resolution middle Miocene benthic foraminiferalisotope ($\sim$ 4-ky) and XRF scanner Fe ($<$ 1-ky) records from two deep-sea cores inthe western and southeastern Pacific (ODP Sites 1146 and 1237). These records providenew insights into the pacing of climatic variability across the middle Miocene climatetransition. Spectral analyses of the $\delta$$^{13}$C records from Sites 1146 and 1237and the Fe record from Site 1237 reveal spectral power concentrated in the eccentricityband (400-ky, 100-ky) over the time interval from 13 to 17 Ma. In the $\delta$$^{18}$Orecords, a switch occurs at $\sim$ 14.9 Ma from predominant 100-ky eccentricity to 41-ky obliquity periodicity, suggesting a shift in the ocean-climate response to orbitalforcing from the low to the high latitudes. The $\delta$$^{18}$O obliquity signal, mainlyattributed to the waxing and waning of an expanded southern polar ice sheet, is pervasivein the $\delta$$^{18}$O records until $\sim$ 13.9 Ma, when a sharp increase in$\delta$$^{18}$O values indicates a further climatic transition (major expansion of EastAntarctic Ice Sheet). This critical step into the "icehouse-world" coincided with a furtherswitch in the $\delta$$^{18}$O records from the obliquity (41-ky) to the eccentricity(100-ky) band. DE HR:

1340h AN: PP23A-1397 TI: High Latitude and Tropical Climates Linked Prior to theOnset of Northern Hemisphere Glaciation: Evidence From theEastern Tropical Pacific AU: * Lawrence, K et al.

AB: The last major climatic transition in Earth's history occurred between the Plioceneand Pleistocene epochs. This transition witnessed a substantial increase in the variance ofEarth's climate in response to changes in orbital obliquity at $\sim$3 Ma, approximatelycoincident with the onset of Northern Hemisphere glaciation. A recent theory suggeststhat the start of this transition also marks a fundamental shift in the ocean's heat budgetfrom a state of local equilibrium prior to $\sim$3 Ma, to a state in which heat absorbed inlow latitude upwelling zones is balanced by heat removed at high latitudes after $\sim$3Ma. In this remotely balanced state, changes in the distribution of high latitude insolationdue to changes in orbital obliquity can be communicated from the high to low latitudesvia the thermocline. To evaluate this theory, we use the alkenone organic proxy onsediments from Ocean Drilling Program (ODP) Site 846 ($3\deg$S, $91\deg$§W) in theEastern Equatorial Pacific (EEP), documenting orbital scale variations in sea surfacetemperature (SST) and productivity in the largest upwelling zone on Earth over the past 5Myrs. Our U$^{k'}$$_{37}$ temperature record shows that SST decreased by$\sim$$1\deg$C/Myrs from a high of $28\deg$C in the early Pliocene to a low of$20\deg$C in the late Pleistocene. A dramatic increase in paleoproductivity occurred$\sim$3 Ma followed by a sharp decline $\sim$1.5 Ma. Evolutive spectral analysis of seasurface indices and benthic oxygen isotope data from ODP Site 846 show that before 1Ma all three proxies were dominated by obliquity variations and that these variationswere modulated by the 1.2 Myr obliquity envelope. Evolutionary cross-spectra furtherindicate that in the obliquity band, the phase relationships between these three climaticindices remain essential constant throughout the entire 5 Myr interval, with EEP SST andpaleoproductivity essentially in phase and both of these proxies leading benthic$\delta$$^{18}$O by $\sim$4 kyrs. The constancy of phase between SST,paleoproductivity, and ice volume implies that the physical mechanisms governing theclimate of the EEP have persisted for at least the past 5 Myrs and that the high latitudesand the tropics were linked at least 2 Myrs before the onset of Northern Hemisphereglaciation. These results do not rule out a major reorganization of the sources and sinks ofthe Earth's heat budget, but suggest that if it occurred, it took place prior to 5 Ma.However, the EEP was not entirely unaffected by the onset of Northern Hemisphereglaciation. The major increase in productivity and cooling of SST at $\sim$3 Ma suggesta dramatic strengthening of the EEP upwelling system at this time. DE: HR:

0800h AN: PP11B-0561 TI: Extreme Acidification of the Deep Sea at the Paleocene-Eocene Boundary: New Constraints From Ocean DrillingProgram Leg 208 AU: * Zachos, J et al. EM AB: A negative carbon isotope excursion and a rise in global temperature at thePaleocene-Eocene boundary have been attributed to the rapid release of as much as 2000Gt of methane. In theory, the subsequent oxidation and uptake of this carbon by the oceanshould have lowered deep-sea pH and carbonate ion content ([CO3]), thereby triggering arelatively rapid (~10-20 kyr) shoaling of the oceanic lysocline and calcite compensationdepth (CCD) followed by more gradual (~40 kyr) recovery via silicate weathering ofcontinental rocks. Here, we provide inorganic carbon, carbon isotope, and other physicalproperty and geochemical data from a vertical array of deep-sea cores that constrain thetiming and magnitude of CCD migration during the Paleocene-Eocene ThermalMaximum (PETM). The cores, Sites 1262, 1263, 1265, 1266, and 1267, were recoveredfrom between 2.7 and 4.8 km water depth on the flanks of Walvis Ridge in the SouthAtlantic during ODP Leg 208. In each section, the Paleocene-Eocene boundary is markedby an abrupt transition from carbonate-rich ($>$90%) chalk or ooze to a clay rich layer($<$1% CaCO3), the thickness of which increases (5-35 cm) from the shallowest todeepest core. With high-resolution carbon isotope and other records, we correlate thecarbon records to each other and to the carbon isotope record of ODP Site 690, one of themore expanded marine P-E boundary sections. The comparison shows that the CCDshoaling was relatively fast coinciding with the initial phase of the carbon isotopeexcursion, while the recovery of the CCD over the 2 km transect took between 30-50 kyr.The rapid shoaling and gradual descent support the hypothesis that an anomalously largemass of carbon was rapidly released at the Paleocene-Eocene boundary. We also positthat this extreme decline in oceanic carbonate saturation to paleodepths shallower than1.4 km contributed to the mass extinction of benthic foraminifera. UR

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14:25h AN: PP13B-04 INVITED TI: Calcareous Nannofossils and Orbitally TunedCyclostratigraphy in the Cenozoic AU: * Raffi, I EM AB: The well known reputation of calcareous nannofossils as powerful biostratigraphicand dating tools has been improved in the last two decades, with a decisive advancetowards consistently successful biostratigraphy. This has been obtained by improving thenannofossil database, following the pioneering paper of Backman and Shackleton (1983),with the application of a strategy that combines quantitative data-gathering techniqueswith high resolution sampling. The effort to optimize the analytical methodologies, in thestudy of an increasing numbers of suitable sedimentary successions, has generatedexcellent results for different intervals of geological time. The improvement of databaseis linked to improvements in the quality of sedimentary successions, as the high-qualitysediment cores recovered by the Ocean Drilling Program (ODP). It has been proved thathigh-quality biostratigraphic data provide the potential for high resolution calibrationbetween nannofossil biohorizons and the other records used for dating as, specifically,orbitally tuned cyclostratigraphy. In this way the accurate time resolution, whichdistinguishes this data sequence, is transferred to the biohorizons, and a precisebiochronology is obtained. On the other hand, detailed nannofossil biostratigraphy can beused to provide preliminary control points for the astronomical tuning ofcyclostratigraphic records. This rigorous approach in the study and use of calcareousnannofossils has been greatly stimulated by Nick Shackleton. The introduction oforbitally tuned time-scales has been crucial for the chronological precision of nannofossilbiohorizons, and has provided an accurate chronologic framework which is continuouslyimproved, in various intervals of the Cenozoic. Furthermore, an accurate database onancient nannofossil communities provides informations useful for clarifying theirpossible paleoceanographic meanings and their paleoecological affinities, and fordescribing the evolutionary "behaviour" of nannofossils during prominent climaticepisodes and climatic transitions. DE HR:

0800h AN: PP11B-0567 TI: Paleoceanographic changes in the western tropical Atlanticduring the late Paleocene (59-55 Ma): high-resolution stableisotope records from ODP Leg 207 Site 1258 AU: * Romano, M et al. EM AB: High-resolution isotopic records are being developed for the late Paleocene (59-55Ma) from cored materials from ODP Leg 207 Site 1258 to evaluate oceanographicchanges leading up to the Paleocene/ Eocene Thermal Maximum (PETM). Site 1258 islocated on the western slope of the Demerara Rise, $\sim$380 km north of Suriname. Itwas drilled in 3,192 meters of water and is the deepest water site of thepaleoceanographic transect drilled for Leg 207. Site 1258 contains an exceptionalsedimentary archive of late Paleocene oceanographic and climate changes based on highsedimentation rates and pristinely preserved benthic foraminifers, providing the requisitematerial to study deep-sea changes in the western equatorial Atlantic. The late Paleocene$\delta$$^{18}$O record at Site 1258 contains low values from 58 Ma until near thePETM at Site 1258, which are consistent with bottom water temperatures of up to10$\deg$ to 12$\deg$C. These low $\delta$$^{18}$O values result in a significantgradient (up to $\sim$1$\permil$) between the equatorial Atlantic and the southern ocean(e.g., Site 690) bottom waters. This suggests at least two bottom water sources existedduring this time, one originating from the southern ocean region and another from eitherthe Tethys Sea or somewhere near the equatorial Atlantic regions. A number of isotopicexcursions occur in both the $\delta$$^{13}$C and $\delta$$^{18}$O records between57 Ma and before the PETM. These are characterized by $\delta$$^{13}$C changes ofover 1$\permil$ and $\delta$$^{18}$O changes of up to $\sim$0.7$\deg$ (equivalent to$\sim$ 3$\deg$ C). Similar events were previously identified in records from the NorthPacific Ocean Site 577, which were interpreted to be restricted to the Pacific basin.Although limitations in age control cannot unequivocally show whether these eventswere synchronous at both sites, these results indicate that these brief abrupt deep-seawarming events occurred in both the Atlantic and Pacific basins, indicating that they wereglobal in nature. DE HR:

1340h AN: PP13A-0599 TI: Timing of Late Quaternary sea surface temperature change:Evidence from high-resolution {\it Globigerina bulloides} Mg/Carecords from the California Margin AU: * Pak, D et al. EM AB: The role of the Pacific Ocean in climate evolution remains a fundamental questionin paleoceanography of the late Quaternary. High-resolution sedimentary sections fromthe California margin provide a valuable opportunity to address the mechanisms of howheat is transmitted through the extra-tropical Pacific by closely examining the phasing ofsea surface temperature relative to ice volume changes in a region far removed from thedirect effects of continental ice sheets. We present high-resolution {\it Globigerinabulloides} Mg/Ca records from two sites on the central California Margin. ODP Site1017E (off Point Conception, California; 955 m) provides a millennial-scale sea surfacetemperature record to 60 kyr; MD2504 (Santa Barbara Basin; 440 m) provides acentennial-scale record through the Last Glacial Maximum. These records, together withoxygen isotopic data, provide a window into the timing of sea surface temperature changeon the deglacial as well as during short-term climate events in Marine Isotope Stage 3. AtSite 1017E temperature oscillations in MIS3 were synchronous with $\delta^{18}$O andhad an amplitude of as much as $6\deg$C, on average $2\deg$C larger than thoseinferred by $\delta^{18}$O. Comparison between the Mg/Ca records from the two sitesindicates that within the resolution of the age models, the amplitude and timing of SSTchanges were equivalent between Santa Barbara Basin and Point Conception, suggestingthat there was not a strong local overprint on temperature change along the Californiamargin. Mg/Ca records indicate that full glacial sea surface temperatures wereapproximately $8\deg$C. Both sites show a prominent pre-Bolling temperatureoscillation of 2-$3\deg$C, followed by an abrupt glacial-interglacial temperature changeof 7-$8\deg$C that occurred synchronously with $\delta^{18}$O. DE: HR:

0800h AN: PP51F-1373 TI: Surface and Thermocline Variability of the EasternEquatorial Pacific During the Last 80,000 yr: Results from ODPSite 1240 AU: * Cacho, I et al. EM AB: Recent hypothesis consider low latitudes as the source region for past global rapidclimatic changes. In this sense, the Eastern Equatorial Pacific (EEP) is an area with greatpotential to trigger global changes due to its active role in the El Ni€o-SouthernOscillation (ENSO). Here we present results obtained from ODP 1240 (Leg 202, 0§01.31'N, 86§ 27.76'W, 2921 mbsl) on paired stable isotopes (d18O, d13C) and traceelements (Mg/Ca) on planktonic foraminifera. Multiple species with different dwellingpreferential depths were studied to reconstruct both surface and thermoclinecharacteristics. Core-top Mg/Ca inferred temperatures are in good agreement with currentmean annual sea surface temperature (SST) and deep thermocline temperatures (DTT) asrecorded from available data from hydrographical stations. Our reconstruction covers thelast ~80 kyr, including the entire last glacial period, the glacial-interglacial transition andthe Holocene. Chronostratigraphy is currently in progress, but initial results evidencestrong changes in sedimentary rates. Higher accumulation rates are recorded during theglacial time and deglaciation, likely reflecting changes in the intensity of the upwellingsystem (cold tongue expansion). In general, sedimentation rates are relatively high for theregion (8-15 cm/kyr) which makes Site 1240 particularly valuable for the study of rapidclimatic variability. Results are still preliminary but several rapid oscillations of about 1-2C are observed during MIS 3 in both, SST (G. ruber) and DTT (N. dutertrei) records.Thermocline structure also changed in relation to these oscillations. Last deglaciation isseen as a SST (G. ruber) warming of about 4§C, while lower DTTs (N. dutertrei) increaseonly about 2§C. This early warming preceded the isotopic depletion of the lastdeglaciation. A middle deglaciation abrupt cooling event of about 3§C (SST) and 1§C(DTT) interrupted the gradual warming and nearly returning to full glacial conditions.During the Holocene two main periods are easily distinguishable in both d18O andMg/Ca records. Early Holocene is characterized by higher Mg/Ca and relatively highd18O values whereas Late Holocene presents lower Mg/Ca and lower d18O levels. DE HR:

0800h AN: PP11B-0558 TI: Decoupled Shelf-Ocean Phytoplankton ProductivityResponses Across the Paleocene-Eocene Thermal Maximum AU: * Gibbs, S et al. EM: AB: Significant transformations in the global biosphere accompanied dramatic globalwarming and profound perturbation of the carbon cycle during the Paleocene EoceneThermal Maximum (PETM, $\sim$55 Ma). These abrupt changes have been linked to amassive release of light carbon into the ocean-atmosphere system. Increasedphytoplankton productivity has been cited as a mechanism responsible for subsequentCO$_{2}$ draw-down. However, interpretations of geochemical and biotic data differ onwhere this increased productivity occurred. Here we constrain the loci of increasedproductivity using highly detailed nannofossil assemblage data. Calcareous nannofossilsprovide an excellent basis to monitor changes in primary production during the PETMgiven their sensitivity to surface water conditions, especially availability of nutrients. Wepresent nannofossil assemblage records from productivity end-member environments: acentral gyre setting (ODP Site 1209, Shatsky Rise, paleo-equatorial Pacific), a high-latitude, open-ocean setting (ODP Site 738, Indian Ocean sector of the Southern Ocean)and a neritic setting (USGS Wilson Lake drill hole, New Jersey). Nannofossilassemblages at all three sites display a pattern of continuous reorganization during thePETM. In particular, assemblage shifts at Shatsky Rise demonstrate a short-lived intervalof extremely low productivity coincident with the carbon isotope excursion. In contrast,assemblages at Wilson Lake suggest a transient shift to more mesotrophic conditions.Combined with published planktonic assemblage records, these data produce a globalpicture of productivity change across the PETM with shelf areas and the open oceanclearly decoupled regardless of latitude. Open ocean sites demonstrate a global buttransient increase in oligotrophy which may have resulted from a widespread deepeningof the thermocline. Shelf productivity increase is localized with mesotrophiccommunities spatially restricted to areas close to nutrient sources via increasedprecipitation and runoff. DE: HR:

1340h AN: PP23B-1432 TI: Fulfilling the Promise of the DSDP/ODP Legacy withMultiparameter Logging of Archive Cores AU: * Schultheiss, P et al. EM AB: Since 1968, the Deep-Sea Drilling Project (DSDP) and the Ocean Drilling Program(ODP) have been storing their recovered sediment and rock cores in purpose-built,refrigerated repositories. Approximately 300 km of core was recovered by DSDP andODP at an estimated average cost of $2,000,000/km. Half of every core recovered is keptas an archive half, normally only available for viewing (subsampling requires specialpermissions). Sound archiving policies and storage techniques over the years haveensured that these half cores have remained well preserved for analyses that were notmade, or were not technically possible, at the time of recovery. The archive half-cores arewell suited for automated non-destructive geophysical measurements ("core logging"),including many of those that provide essential data for reconstructing Earth's climatichistory, such as high-resolution magnetic susceptibility, natural gamma spectroscopy, andUV/VIS/IR spectrophotometry. Most of the cores have either not been logged for all therelevant parameters or have not been logged at the spatial intervals necessary for highresolution climatic studies. Consequently, a very large, untapped reservoir ofpaleoclimatic and other data awaits extraction from these well-preserved archive half-cores. Recently we used a new Geotek MSCL-XYZ core logger at the IODP West CoastRepository to log archive core halves recovered by D/V Glomar Challenger in 1983. Wewished to obtain a high-resolution paleoclimate record for DSDP Site 594, east of NewZealand, Southwest Pacific, to complement the record obtained more recently fromnearby ODP Site 1119, cored in 1998. The new MSCL-XYZ system is specificallydesigned to allow multiparameter, non-destructive geophysical data to be collected easilyat high spatial resolutions from archive core halves. Because the data acquisition fromarchive cores can be slow, either because of the measurement itself or the frequency atwhich the data is required, the system holds multiple 1.5 m-long core sections (currentlyup to 9) and can be left to run unattended for hours or days at a time. We obtainedcomplete data sets of natural gamma, magnetic susceptibility, spectral color and RGBdigital line scan images for the top 150m of the sediment column at Site 594 . No usefulcore log data was previously available for this site. The data set of primary interest wasnatural gamma, which will be compared with the downhole natural gamma record fromSite 1119. To our knowledge this is the first time that a high-resolution natural gammadata log has been recovered from an archive core half. Detailed magnetic susceptibilityrecords were also obtained despite low signal levels, using 10 sec sampling timethroughout. The excellent quality of the spectral color and RGB image data, despite thepartially ephemeral nature of these properties, is a testament to the core storagetechniques employed over 21 years. As core working halves become depleted, pressure ismounting to allow subsampling from the archive core-halves. The community now hasthe tools necessary to take advantage of what could be a final opportunity to collectcontinuous geophysical data on ocean cores drilled over the past three decades. DE HR:

0800h AN: PP51B-1333 TI: The Late Miocene Carbon Isotope Shift and MarineBiological Productivity. AU: * Diester-Haass, L et al. EM AB: The late Miocene global carbon isotope shift of approximately 1 per mil is not wellunderstood. Is it linked to ocean-related processes such as theAŸA›A›ƒ_sAªA.ƒ_oBiologic BloomAŸA›A›ƒ_sAª \(Farrell et al., 1995\), or to changesin type \(C3/C4 plants\) or cover of terrestrial vegetation? Here we examine the evolutionof marine biological productivity during the isotope shift at ODP Site 846 \(Pacificequatorial upwelling, where the AŸA›A›ƒ_sAªA.ƒ_oBiologic BloomAŸA›A›ƒ_sAª hasbeen first described, Farrell al, 1995\) and at Indian Ocean Site 721 \(monsoon-drivenupwelling\), and compare their productivity history with non upwelling locations in theAtlantic Ocean. The onset of the carbon isotope shift is accompanied at all locations byan increase in paleoproductivity derived from benthic foraminiferal accumulation rates\(expressed as gC/cm2 * ky; Huerguera, 2000\) and increased abundance of Uvigerinaspp.. At the equatorial upwelling sites the increase is comparable to half present-dayvalues to present-day values; in the Atlantic Ocean paleoproductivity increases frompresent-day up to 3 times present-day values. But the productivity maxima are notconcurrent. The carbon isotope shift is accompanied by severe carbonate dissolution andreduced ventilation of bottom waters, as reflected in the occurrence of pyrite and goodpreservation of cartilageous fish debris. Carbonate preservation is good since about 6 Madespite high productivity. We discuss changing deep water circulation patterns, increasedweathering and continental nutrient delivery, as well as erosion of terrestrial vegetation aspossible factors to explain our findings. DE:

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16:00h AN: PP44A-01 INVITED TI: Deep Ocean Temperature and Salinity at the Last GlacialMaximum AU: * Adkins, J and Schrag, D AB: Sediment pore fluids from the deep ocean contain a record of the bottom watersalinity and $\delta$$^{18}$O due to the last glaciation. Storage of water on land asglacial ice imparts a global signal of increased salinity and enriched oxygen isotopicvalues in the abyssal ocean and changes in deep circulation patterns can impart anadditional local signal. In the mean this signal was about 3.5% in salinity and about1.0\permil in $\delta$$^{18}$O, but has been diffusing and advecting away over the last20,000 years. Today, high resolution sampling (every 1.5 meters) coupled with highprecision geochemical analyses of pore fluids from a single core can be used, inconjunction with a 1-D pore fluid diffusion model, to reconstruct the Last GlacialMaximum (LGM) salinity and $\delta$$^{18}$O at that site. We have done this analysisfor several globally distributed Ocean Drilling Program (ODP) holes including some newunpublished data from the equatorial Pacific. In addition, benthic foraminiferalmeasurements of modern and LGM CaCO$_{3}$ $\delta$$^{18}$O, coupled with thewater $\delta$$^{18}$O reconstruction, can be used to constrain the deep-watertemperature change from LGM to today. Plotted as a T/S diagram for the LGM, our datashow that the entire deep ocean cooled to about $-$$1.0\deg$C potential temperature.This relative homogeneity in temperature is contrasted by much larger than modernsalinity gradients in the deep. Due to increased sea ice export, the Southern Ocean was byfar the saltiest water mass in the LGM, and as a result the modern salinity contrastbetween NADW and AABW was reversed. Stratification of the LGM deep ocean waslargely controlled by salinity (as opposed to temperature today) and this feature hasimportant implications for the stability of the LGM overturning circulation. With saltywaters filling the deep LGM Ocean, it is difficult for fresh water changes at the surface ofthe North Atlantic to alter the abyssal circulation. Before freshwater forcing can triggercirculation changes, some other forcing must first increase the buoyancy of the deepSouthern Source waters. In addition, the combination of our water $\delta$$^{18}$Odata and a global database of benthic $\delta$$^{18}$O imply that the deep Pacific waswarmer than the deep North Atlantic at the LGM. DE

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08:15h AN: PP31B-02 INVITED TI: Tracking Warm Saline Deep Water on Maud Rise Using NdIsotopes AU: * Martin, E et al. EM AB: Evidence for the production and export of Warm Saline Deep Water (WSDW) tothe southern high latitudes during the Paleogene is equivocal and widely debated. Thestrongest support for WSDW in the Southern Ocean are discrete intervals of benthic$\delta$$^1$$^8$O inversions between vertically offset sites on the Maud Rise, ODPsites 689 (2080m) and 690 (2914m), which were interpreted as temperature inversions.During these intervals a warm bottom water mass is believed to have occupied site 690.Nd isotopes in fossil fish teeth reflect water mass mixing and are unaffected by changesin temperature, salinity, nutrients, or productivity. We present Nd isotope records forsites 689 and 690 that cover the middle Eocene to the late Oligocene and which havebeen correlated by Sr isotope chemostratigraphy. The Nd isotope data support theincursion of a distinct water mass at depth in the middle Eocene and portions of theOligocene. During these intervals $\epsilon$$_N$$_d$ values at site 690 are 1$\epsilon$unit less radiogenic than those at site 689, reaching minimum values of -9.3 to -10. The$\epsilon$$_N$$_d$ minima at site 690 coincide with $\delta$$^1$$^8$O inversions. Inthe Paleogene, potential sources of deep water masses characterized by suchnonradiogenic $\epsilon$$_N$$_d$ values include the North Atlantic, Southern Ocean,and Tethys Sea. However, the North Atlantic is an unlikely source of such a strongsignature to the high latitude Southern Ocean and Paleogene $\epsilon$$_N$$_d$ valuesof Southern Ocean deep waters are too radiogenic to account for the Maud Rise Nd data.Further, we argue that a Southern Ocean water mass should influence both sites, and thedata clearly support instances when more than one water mass was present. The MaudRise Nd isotope data is best explained by the export of Tethys sourced WSDW to theSouthern Ocean. Authigenic shelf deposits from obducted Tethys margin sedimentsindicate that shallow Tethys seawater had $\epsilon$$_N$$_d$ values of -9.2 to -9.7,suggesting that deeper waters were less radiogenic. These values are also consistent withmodern Mediterranean outflow (-9.4). The pulsed export of WSDW to the SouthernOcean from a low latitude source accounts for the coincidence of $\epsilon$$_N$$_d$minima at site 690 with $\delta$$^1$$^8$O inversions between sites 689 and 690. DE

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1340h AN: PP13A-0601 TI: Primary Productivity Changes in the subtropical westernNorth Atlantic During Marine Isotope Stages 11-12: Inferencesfrom Benthic Foraminifera AU: * Poli, M et al. EM AB: The time interval referred to as Marine Isotope Stage 11 (MIS 11, ~423 to 362 ka)is characterized by a configuration of earth's orbit similar to that of the Holocene, and istherefore a good analog for our current interglacial. MIS 11 was probably the warmestand longest interglacial of the last 500 kyrs, characterized by sea level possibly 20mhigher than today and a maximum in NADW production. In contrast, during MIS 12, sealevel was about 140m below present, and the production of NADW was severelyreduced. We have examined benthic foraminiferal assemblages in sediments from ODPSite 1058 (Blake Outer Ridge, 3000m water depth), and Site 1063 (Bermuda Rise, 4584mwater depth) spanning the MIS 11-12 time interval at a time resolution of 500 to 3000years. At both sites the glacial-interglacial transition is accompanied by changes in faunalcomposition; however, bottom environmental conditions appear to have undergone themost dramatic change at Site 1058. Here, infaunal taxa indicative of organic carbon-richsediments dominate during glacial MIS 12, and are replaced during MIS 11 by epifaunalspecies indicative of oligotrophic environments. The beginning of the MIS 12 and MIS10 glaciation is characterized by large, rapid increases in the relative and absoluteabundances of {\it Epistominella exigua} both at Site 1058 and Site 1063. In the modernocean, this species inhabits seasonally deposited aggregates of phytodetritus producedduring spring plankton blooms, thus suggesting an increase in surface ocean primaryproductivity at these times. DE:

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1340h AN: PP13A-0600 TI: MILLENNIAL-SCALE CLIMATE VARIABILITY IN THESUBTROPICAL ATLANTIC DURING THE MIDDLEPLEISTOCENE AU: * Gibbons, F et al. EM AB: We are generating Globigerinoides ruber (white, ss) oxygen isotope and Mg/Carecords from ODP Site 1058 to assess relative climate stability in subtropicalnorthwestern Atlantic during the mid Pleistocene, Marine Isotope Stages (MIS) 11-22.Currently, our records span MIS 11 (a portion only) through MIS 15 with a temporalresolution of about 800-1000 years. The paired Mg/Ca and d18O records allow us toreconstruct fluctuations of sea surface temperatures (SST) and the regional oxygenisotopic composition of surface water on millennial time scales during one of the mostextreme glacial-interglacial transitions of the Pleistocene. Our ultimate goal is to test thehypothesis that relative climate stability is linked to the extent of continental glaciation(ice volume). The d18O record displays rapid, high amplitude variability during glacialMIS 12 and the MIS 12 to MIS 11 deglaciation. The Mg/Ca results show that the long-term trends in the temperature record follow the general glacial-interglacial patternimplying SST changes concurrent with large-scale climate change. Portions of the Mg/Carecord generated at higher resolution reveal SST variability similar in timing tovariability observed in the d18O record, particularly during MIS 13 and the MIS 13/12transition. The total amplitude of SST changes implied by the Mg/Ca data is ~6øC, withabsolute temperatures ranging from about 24 to 30øC. The current records show that thissite is sensitive to millennial-scale variability during the extreme glacial MIS 12 and theMIS 12/11 deglaciation, but not in the older portion of the oxygen is record (MIS 14)thus far generated. Ultimately, the entire record will show if other glacial extremes suchas MIS 16 contains similarly high variability, which would further support thehypothesis that ice sheet size plays an important role in determining the amplitude ofmillennial-scale climate change. DE:

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0800h AN: PP51F-1368 TI: Continental and Marine Climate Records from Chile and theSoutheast Pacific: Joint Pollen, Oxygen Isotope, and RadiolariaRecords from ODP Sites 1233 and 1234 AU: * Heusser, L et al.

AB: Rapidly-deposited sediments (1-3m/kyr) from ODP Site 1233 (41ø0.005'S,74ø26.992'W, 838m water depth) document millennial-scale changes in the response ofChilean plant communities to atmospheric circulation in the southeast Pacific over thepast 60ka. Pollen data from the upper 95m of Site 1234 (36ø13.153'S, 73ø40.902'W)replicate and extend the terrestrial record through the last glacial cycle (MIS 1-MIS5e),thus providing the first record of vegetation and climate from the last interglacial intemperate South America. Both Sites monitor a major discontinuity in Chilean climate -the transition between northern semi-arid, summer dry-winter wet climate and southernyear-round, rainy, cool temperate climate. Downcore changes in diagnostic pollen fromxeric and mesic vegetation (Lowland Deciduous Beech forest, Valdivian EvergreenForest, and Subantarctic Evergreen Forest and Parkland) reflect frequent latitudinal shiftsof the southern westerlies during MIS 2 and MIS 3. During most of the last glacial, cool,mesic rainforests composed of evergreen beech (Nothofagus dombeyi) and conifers, suchas the endangered Prumnopitys andina, characterized coastal Chile. Late Pleistocene,intervals of heavy rainfall and lower temperatures inferred from expansion ofSubantarctic Parkland correspond with regional glacial events, and the structure andvariability of southern Chilean vegetation and climate correspond with changes in marinesurface waters offshore and in Antarctic ice core data. In the last 140,000 years, onlyduring MIS 5e was vegetation of southern Chile similar to that of the Holocene. At theMIS 6/5e transition, coeval with the rapid shift to light isotopic values, glacial vegetationwas rapidly replaced by plant communities associated with Mediterranean climate. Anincreased prominence of halophytic vegetation suggests that MIS 5e was more arid andpossibly warmer than MIS 1. Lowland Deciduous Beech Forest (N. obliqua) extendedwell into the interval of ice growth of MIS 5d, thus interglacial conditions in southernChile were not synchronous with global ice volume. DE HR:

13:40h AN: PP43B-01 INVITED TI: Antarctic Timing of Surface Water Changes off Chile andPatagonian Ice-sheet Response Based on ODP Site 1233 AU: * Lamy, F et al. EM AB: ODP Site 1233 off southern Chile is situated in an ideal location to study SouthernHemisphere millennial-scale climate variations during the last glacial. We present recordsof surface ocean conditions in the southernmost Peru-Chile Current and associatedchanges in the extent of the Patagonian ice-sheet in adjacent southern Chile covering thelast ca. 70,000 years. Sedimentation rates at this continental margin site areextraordinarily high (in the order of 1-3 m/kyr) consistent with strong fluvial discharge inresponse to heavy continental rainfall in southern Chile and the proximity to thePatagonian ice-shield (PIS) that advanced towards the Chilean Lake District (directlyonshore Site 1233) during the last glacial providing terrigenous material via glacialerosion. This proximity to the ice-sheet provides the excellent opportunity to comparecontinental and marine paleoenvironmental signals within the same well-dated archive.Millennial-scale SST changes closely parallel the temperature changes recorded inAntarctic ice-cores. Including other records from the Southern Hemisphere mid-latitudes,our data suggest a quasi-hemisphere-wide response that is consistent with the bipolarsee-saw mechanism but may also imply a more prominent role of the SouthernHemisphere in the origin and transfer of millennial-scale climate variations during thelast glacial. Compositional changes in the terrigenous sediment input, interpreted toprimarily represent changes in the extent of the PIS, show a similar pattern as SSTchanges but reveal a lagged response of the terrestrial signal most likely related to climateinertia of the PIS. During the deglaciation, paleosalinity data suggest that meltwater inputfrom the ice-sheet started up to ca. 1000 years after the onset of deglacial warming.During early isotope stage 3. however, a lag between SST and PIS changes appears to beabsent. Spectral analyses suggest that both proxy records are characterized by highershort-term variability in this interval. Though the general pattern of the records is stillvery similar to the Antarctic records, we speculate that the short-term variability mayorigin from the tropics during warmer intervals of the last glaciation. DE HR:

0800h AN: PP31A-0887 TI: Planktonic Foraminifera Study at Site ODP 999A (CaribbeanSea): Insights into Oceanic Exchange and Paleocirculation Duringthe last 450 Kyrs. AU: Vautravers, M et al. EM AB: A recent micro-palaeontological study of a core from the South Atlantic (Peeters etal., Nature. 430, 661, 2004) stresses the importance of the Agulhas leakage intensity as akey control on North Atlantic Thermohaline operation. Planktonic foraminifera countswere conducted on the Colombian Basin core ODP 999A ($12\deg$N, $74\deg$W, 2878m); results are presented on a SPECMAP-based age model (Schmidt et al., in prep2004). At present both climate and surface circulation are driven by the motion of theIntertropical Convergence Zone (ITCZ), which governs dry/wet seasons and upwellingintensity. Caribbean surface water originates from both the south Atlantic, which re-circulates Indian Ocean water, and the north Atlantic subtropical gyre. Similarly thedeep-water is a mixture of AAIW and UNADW, originating in the southern and northernhemispheres respectively. A CaCO$_{3}$ preservation index, which is deduced fromplanktonic fragments and pteropod remains, is used to trace changes in the intermediatewater mixture. This study confirms that the sediments are better preserved during glacialtimes. Furthermore, it shows that the sediments of MIS11 are intensely dissolved,suggesting a maximal contribution of AAIW. Over the last 450 kyr, we observe adecreasing contribution of the AAIW during both interglacial and glacial times. Inaddition, the Holocene appears unusual, with a low AAIW to UNADW ratio incomparison to previous warm intervals. An examination of the percentages of the surfaceIndo-Pacific species {\it G. menardii} seems to confirm part this result, identifyingMIS11 as a time of maximal Indian-Atlantic exchange via the Agulhas 3valve_. It alsoconfirms that during MIS2, 3 and 4, Caribbean surface waters were unusuallyunfavourable for this species and/or that the Agulhas connection was absent. The % of{\it G. Hexagona}, another Indo-Pacific species, which lives in deeper thermoclinewaters, peaks during MIS11, MIS9e, MIS7c and MIS5e but is absent during theHolocene and MIS7e. This observation suggests a slightly different scenario for theintermediate water flowing through the 3valve_. This confirms the peculiarity of theHolocene as was found on the basis of benthic \delta$^{13}$C measurements in theNorth Atlantic (Raymo et al., Paleoceanography. 19, PA2008, 2004). Finally, on the basisof the species mentioned above in the Caribbean Sea we cannot find evidence ofenhanced exchange between the Indian and the Atlantic at the end of the past five glacialas found in the Agulhas area. This disagreement and the factors controlling the latereappearance of these species in the Caribbean Sea need further investigation. DE HR:

17:15h AN: PP44A-06 TI: Gulf Stream Salinity Variation During MIS 3 and its Link toD-O Cycles AU: * Schmidt, M et al. EM AB: Paleoclimate archives indicate that Marine Isotope Stage 3 (MIS 3) wascharacterized by a highly variable climate, expressed in the Greenland ice cores by theDansgaard-Oeschger (D-O) fluctuations associated with large temperature changes(Johnsen et al., 2001). However, the question remains as to the trigger for these abruptNorthern Hemisphere climate swings. A popular theory implicates thermohalinecirculation instability as a driver for D-O cycles, suggesting that salinity variability insurface waters delivered to the sub-polar North Atlantic via the Gulf Stream may haveplayed a role in driving millennial-scale oscillations in glacial thermohaline circulation(Broecker et al., 1990; Zaucker and Broecker, 1992). In order to investigate therelationship between Gulf Stream salinity variation and D-O cycles, we combine Mg/Cameasurements (a proxy for the temperature of calcification) with ($\delta$$^{18}$O)analyses of shells from the surface-dwelling foraminifera {\it Globigerinoides ruber}(white var.) from ODP site 1060 located beneath the Gulf Stream on the Blake OuterRidge (36.77$\deg$N, 74.47$\deg$W; 3480 m; 20-53 cm/kyr sed. rate) to produce ahigh-resolution record of $\delta$$^{18}$O$_{SEAWATER}$($\delta$$^{18}$O$_{SW}$) during MIS 3 (49.5- 59.2 kyr, corresponding to Interstadial13 to 16 on the SSO9sea time scale). The Mg/Ca-temperature (SST) record from 1060shows minimal variability ($\pm$3$\deg$C) between stadials and interstadials. Averageinterstadial Mg/Ca-SSTs (25.2$\deg$C) agree with faunal August SST reconstructions(Vautravers et al., 2004), but stadial Mg/Ca-SST reconstructions are warmer than faunalestimates. The calculated $\delta$$^{18}$O$_{SW}$ record co-varies with theGreenland ice core $\delta$$^{18}$O record (Johnsen et al., 2001), and indicates highstadial salinities, similar to MIS 3 Caribbean salinity reconstructions (Schmidt et al.,2004), followed by abrupt decreases in $\delta$$^{18}$O$_{SW}$ up to 0.9$\permil$occurring in less than 250 years on the transition to interstadials. We hypothesize that theinput of isotopically light freshwater from melting North American ice sheets duringinterstadials accounts for the rapid, large decrease in Gulf Stream$\delta$$^{18}$O$_{SW}$. Our $\delta$$^{18}$O$_{SW}$ reconstruction from ODP1060 therefore suggests that D-O cycles directly impact Gulf Stream salinity during MIS3, with elevated salinities occurring during stadials followed by a rapid decrease ofsalinity into interstadials in response to Northern Hemisphere warming. DE HR:

16:00h AN: PP54A-01 TI: Evidence for an Open Drake Passage in the Late MiddleEocene AU: * Scher, H and Martin, E E EM AB: Circulation of the Antarctic Circumpolar Current (ACC) appears to require anunimpeded circumpolar path, thus arguments for initiation of the ACC hinge on thetiming of tectonic gateway development in the Southern Ocean. However, timing of theonset of seawater exchange between the Pacific and Atlantic oceans through the DrakePassage is widely debated, with estimates ranging from the late Eocene to the earlyMiocene. Hiatuses and productivity increases in South Atlantic sediment records implythat ocean currents accelerated during the Eocene and Oligocene, though there is not yetindependent and unequivocal evidence for Pacific seawater entering the Atlantic Oceanduring the Paleogene. Nd isotopes in fossil fish teeth reflect water mass mixing and areunaffected by changes in temperature, salinity, nutrients, and productivity. We presentthe first Nd isotope record from the Atlantic sector of the Southern Ocean that covers theentire range of estimates for the opening of the Drake Passage; from ODP site 1090. Therecord indicates that a water mass with a Nd isotopic composition typical of Pacificseawater appeared in the Atlantic sector at 39 Ma, as illustrated by a rapid transition toradiogenic $\epsilon$$_N$$_d$ values ($\epsilon$$_N$$_d$ = -5.8). Pacific seawaterwas the only volumetrically significant water mass with such a radiogenic Nd signatureduring the Paleogene. A second transition to radiogenic $\epsilon$$_N$$_d$ valuesoccurs at 28.5 Ma. Pronounced peaks in productivity at site 1090 coincide with the$\epsilon$$_N$$_d$ transition at 39 Ma. The data support the opening of the DrakePassage to shallow depths at 39 Ma. Moreover, the association of productivity peaks withthis event implies that a shallow opening may have enabled a precursor to the modernACC. The data also support establishment of a deep-water connection at 28.5 Ma. Theinterpretations imply that tectonically induced changes in ocean circulation precededlarge shifts in global climate during the Paleogene. $\epsilon$$_N$$_d$ values duringthe late Oligocene to early Miocene covary with benthic $\delta$$^1$$^3$C values atthis site, confirming the capability of Nd isotopes as a tracer of past changes in oceancirculation. DE:

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0800h AN: PP51F-1375 TI: the Pliocene Evolution of E-Pacific and Caribbean SSTReveals the Final Phase of the Closure of the PanamanianGateway. AU: * Groeneveld, J et al. EM AB: We used samples from ODP Sites 999 ($12\deg$44N, $78\deg$44W, 2828mwaterdepth) and 1241($5\deg$50N, $86\deg$26W, 2027m waterdepth) to investigate thedevelopment of the sea surface temperature (SST) gradient between the East-Pacific andthe Caribbean for the Pliocene interval 2.2-4.8 Ma. For Site 1241 we constructed newbenthic and planktonic $\delta$$^{18}$O-records. The benthic $\delta$$^{18}$O-recordwas used to construct an orbitally tuned age model to which the age model of Site 999was tuned. SST was determined by applying Mg/Ca-analyses on the planktic foraminiferGlobigerinoides sacculifer. The spatial resolution for the SST-records averages 5 kyr, forthe $\delta$$^{18}$O-records 3 kyr. An open gateway, permitting the throughflow ofwater from the Pacific into the Caribbean, leads to equal SSTs on both sides of theIsthmus. When the gateway reached the final phase of the closure, the Caribbean startedto warm up and the E-Pacific cooled down, resulting in an increasing SST-gradient (E-Pacific-Caribbean SST difference). Before 4.6 Ma the Caribbean was slightly warmerthan the E-Pacific by about $1\deg$C, suggesting the inflow of Pacific water into theCaribbean. After 4.6 Ma, average SST at Site 999 decreased by about $2\deg$C, while atSite 1241 average SST remained the same. This implies that no longer the samewatermass is bathing both Sites, suggesting a cooler watermass, probably originatingfrom the Peru-Chile Current, to penetrate into the Caribbean. The final phase of theclosure is indicated by a change in Caribbean-Pacific SST relationships. Positivelycorrelated SST fluctuations persisted from 4.8Ma until about 3.2Ma, before larger-scalesea level fluctuations became important in response to the amplification of the northernhemisphere glaciation. After about 3.2Ma, glacial stages (indicative of sea level low-stand) are associated with Pacific minima in SST (Site 1241) and maxima in CaribbeanSST (Site 999). Thus, the cessation of the throughflow during glacials terminated theimprint of cooler Pacific surface waters in the Caribbean and allowed Caribbeantemperatures to increase. This documents the final phase of the closure of the CentralAmerican Isthmus, when sea level fluctuations on the order of 50-70 m start to controlthe Pacific water inflow into the Caribbean. DE HR:

1340h AN: PP23A-1395 TI: Do Tropical SST Changes Lead High Latitude ClimateChange, Or Are Our Proxies Misleading Us? AU: * Dekens, P et al. EM AB: Initial reconstruction of the last glacial maximum (LGM) sea surface temperature(SST) estimates showed little to no change in the world's tropical oceans. More recently,several studies have shown that the tropics were 1 to $6\deg$C cooler during the LGMand previous ice ages. These observations, as well as the timing of the SST changes, hasled some researchers to hypothesize that the tropical Pacific may have played animportant role in glacial/interglacial (G/IG) climate change during the late Quaternary.Uncertainty remains about the magnitude of the SST change, the spatial pattern of thechanges, and the timing of tropical SST changes relative to high latitude climatetransitions. For example, in the eastern equatorial Pacific (EEP) geochemical proxy dataindicate that during the LGM SST was only 1 to $2\deg$C cooler at the equator , but was2 to $3\deg$C cooler just north of the equator and in the central equatorial Pacificcompared to today. Additionally, the sites on the equator record a significantly larger leadin SST compared to ice volume than one site just north of the equator. These recordshave been reconstructed using different SST proxies however, leading us to question ifthe observed geographical differences in the magnitude and timing of SST changesduring recent glacial cycles could be explained by the different uncertainties inherent ineach of the proxies. The EEP is a critical region because SST in this region is sensitive tochanges in upwelling, and is therefore indicative of the state of the tropical Pacific, whichhas known air sea feedbacks that can affect global climate. A clear picture of the timingof SST changes and ice volume is needed if we are to understand the potential role of thetropical Pacific in G/IG climate change. We have generated high resolution ($\sim$2-4k.y.) SST records at ODP site 847 ($0\deg$12'N, $95\deg$19'W, 3346m water depth)using the U$^{k'}$$_{37}$ and Mg/Ca paleothermometers extending back 500 k.y. Thissite provides an excellent opportunity to compare Mg/Ca and alkenone records, as it islocated above the lysocline, thereby minimizing the effect of dissolution on Mg/Ca inforaminifera, and has relatively high organic matter content. The U$^{k'}$$_{37}$ SSTrecord shows a G/IG amplitude of $\sim$$2\deg$C through MIS 8, and a larger ($\sim$5-$6\deg$C) amplitude from MIS 9-12. SST leads ice volume changes at all glacial tointerglacial transitions, but the magnitude of the lead varies. Comparing the variability inthese two proxies at this site over the last ~500 k.y. will increase our understanding ofthe behavior of these two proxies in this region, and dramatically increase our confidencein our climatic interpretations. DE HR:

15:30h AN: PP53D-08 TI: A 10 Million Year, High-Resolution Record of C4 and C3Plant Evolution from Arabian Sea ODP Site 722 AU: * Huang, Y et al. EM AB: The Siwalik paleosol sequence in Pakistan and India and the Bengal Fan sedimentsindicate a major expansion of C4 plants during the late Miocene, approximately 8 to 5Ma. However, the depositional environments of paleosol sequences and deep-sea fansresult in uncertainties in chronology and sediment discontinuities. The paleosol isotopicdata are also local in nature. Here, we report new high-resolution carbon and hydrogenisotopic measurements of higher plant biomarkers from sediments in the Arabian Sea(ODP 722B). This site is situated at 2000 m water depth on the Owen Ridge, isolatedfrom turbidite deposition on the adjacent Indus Fan. Continuous deposition allows moreaccurate age control, based on oxygen isotope and nannofossil stratigraphy. The principalsource of terrestrial input to the site is from aeolian sources associated with monsooncirculation, which results in the transport of plant leaf waxes from adjacent continentalregions, especially the Arabian Peninsula, the Middle East, and the Indian subcontinent.Therefore, our data represent the first continuous integrated large scale records of C3 andC4 plants for these continental regions. We analyzed ca 200 samples over the last 10 My.Our results show that C4 plants were already present by 10 Ma. Assuming end memberd13C values for C3 (-34 %) and C4 (-20 %) plant leaf waxes, C4 plant percentage inputincreased from 25 to 45 percent from 10 to 7.5 Ma. Surprisingly, however, the C4 inputdecreased to 15 percent from 7.5 to 6.8 Ma. The major rise of C4 plant inputs occurredbetween 6.8 to 5 Ma, when the C4 percentage input increased from 15 to 65 percent. C4percentage continued to rise slowly from 5 Ma, reaching 75 percent at 0.7 Ma. A C4decrease from 57 percent took place from 0.7 Ma to present. Our hydrogen isotopic ratiosof leaf waxes suggest a major increase in continental aridity between 8 to 6 Ma, which isfollowed by a slower rate of aridity increases from 6 to 0.7 Ma. Both carbon andhydrogen isotopic ratios become more variable on shorter time scales after 6 Ma thanbefore 8 Ma. Notably, a decrease in C4 plants by ca. 15 percent, just prior to the majorexpansion of C4 plants, was also observed in published Siwalik paleosol carbonate d13Crecord. This pattern of C4/C3 plant evolution has not yet been observed in othercontinents, suggesting important regional climatic control, rather than a global change inatmospheric pCO2 may have played a key role on the rise of C4 plant during the lateMiocene. DE: HR:

14:10h AN: PP53D-03 INVITED TI: A Cenozoic terrestrial isotope record and the evolution ofC$_{4}$ photosynthesis AU: * Gr”cke, D et al. EM AB: Our understanding of C$_{4}$ plant evolution and expansion has predominantlyrelied on site-specific fossil teeth, paleosols, and pedogenic carbonates carbon-isotoperecords and suggests a global dominance between 15-6 Ma. However, more recenttechniques using bulk and compound-specific carbon-isotope ratios from terrestrialorganic matter and other biomarker evidence suggest C$_{4}$ plants may have evolvedmultiple times. Furthermore, C$_{4}$ plants may have been present in terrestrialenvironments much earlier than the late Miocene expansion, but owing to theirenvironmental preference and low preservation potential may not have been preserved inthe terrestrial sedimentary record, and/or such latitudinal sites have not been fullyexplored. An additional implication is that the carbon-isotope composition of CO$_{2}$(\delta $^{13}$C$_{CO2}$) has changed through time and paleoecologic reconstructionsbased on teeth and carbonate isotopic signatures may not reflect accurate floralcontributions. Thus, terrestrial and atmospheric carbon-isotope signatures must beintegrated in order to assess the Cenozoic history of C$_{4}$ photosynthesis. Presently,we are constructing a carbon-isotope record of long-chain {\it n}-alkanes with highcarbon preference indices (indicative of higher plant input) from a globally distributed setof oligotropic and marginal DSDP/ODP marine sediments. As mentioned above, anestimate of the C$_{4}$ plant proportion of total land-plant biomass requires anunderstanding of changes in \delta $^{13}$C$_{CO2}$ through time. Accordingly, wehave constrained this parameter by establishing the carbon-isotope composition ofC$_{3}$ plant organic matter from Paleogene-age shallow marine shelf and lagoonalsediments from the Isle of Wight, UK, by assuming constant carbon-isotopediscrimination between CO$_{2}$ and C$_{3}$ photosynthesis. Such \delta$^{13}$C$_{CO2}$ records can be directly compared with alkenone-based {\itp}CO$_{2}$ and {\it n}-alkane based floral contribution estimates. Using integratedisotopic proxies, our preliminary data suggest that the C$_{4}$ photosynthetic pathwayevolved prior to the late Miocene and was possibly driven by paleoenvironmentalpressures. DE HR:

11:20h AN: PP32A-05 TI: Structure of the Penultimate Deglaciation Along theCalifornia Margin and Implications for Milankovitch Theory AU: * Cannariato, K et al. EM AB: Several studies have suggested that the penultimate deglaciation occurred earlierthan Milankovitch theory predicts therefore calling into question the orbital theory of iceages. Furthermore, the detailed structure and timing of Termination II is insufficientlydefined yet critical for understanding mechanisms responsible for abrupt regional andglobal climate change. High-resolution climate records and a means to accurately datethem independent of orbital tuning are necessary to address these issues. Here we presentplanktonic and benthic foraminiferal oxygen isotope records at unprecedented resolutionencompassing late MIS 6 and Termination II ($\sim$150 to 120 ka) from Santa BarbaraBasin (ODP Site 893) supported by additional southern California margin records (Sites1017 and 1014), a region highly sensitive to global millennial-scale climate oscillationsduring the last deglaciation. These records reveal millennial- and centennial-scale climatevariability throughout the interval including a prominent interstadial immediatelypreceding the deglaciation, a brief warm event near the beginning of Termination II, anda B$\o$lling-$\AA$ller$\o$d/Younger Dryas-like climate oscillation midway through thedeglaciation. Previous work suggests the presence of millennial-scale variability overbroad regions during TII including climate instability during late MIS 6 and a pause orclimate oscillation during TII. Low-resolution Mg/Ca- and alkenone-derived temperaturerecords from these sites indicate the relative timing within the sequence of local salinityand global ice volume changes. Few options exist for dating marine records duringTermination II. They are typically tuned to orbital insolation, which precludes testingdeglacial mechanisms. However, the distinct millennial-scale features of TII documentedby the California margin records represent several widespread climate events thatpotentially could be correlated with well-dated high-resolution records elsewhere. Forexample, the $^{230}$Th-dated stalagmite oxygen isotope record from Dongge Cave,China appears to exhibit the same millennial-scale climate events as the Californiamargin records during late MIS 6 and Termination II. This allows the adoption of thestalagmite radiometric chronology to the California margin records. This chronologysupports the Milankovitch theory of deglaciation. The suborbital history of climatevariability during Termination II may account for records of early deglaciation. DE: HR:

16:15h AN: PP54A-02 INVITED TI: Exploring the Carbonate Production/Dissolution Paradox inthe Mid-Bruhnes of the Southern Ocean Using Coupled Records ofBiological and Chemical Dynamics AU: * Flores, J et al. EM AB: The Mid-Brunhes event, an interval including MIS 9 to 11, is considered one of thewarmest during the Pleistocene. This interval is also characterized by generally highcarbonate concentrations (and presumably high productivity) with punctuated intervals ofhigh dissolution in the deep ocean. The paradox of high carbonate production and highdissolution in certain intervals might be linked to nutrient available, ocean geochemistry,and upwelling. To explore this situation in the Southern Ocean, we examined calcareousnannofossil and geochemical proxies in order to estimate the degree of dissolution in thecalcareous nannofossil assemblages, and examine primary production of these organismsand their relationship with surface water dynamics. In ODP Site 1089 (Cape Basin,Atlantic Ocean) the MIS 9 to 11 is characterized, as in the whole ocean, by thedominance of Gephyrocapsa caribbeanica (a small but robust and well-calcifiedplacolith). Although the record of calcareous nannofossil is continuous, we observedfluctuations in the degree of preservation in the calcareous nannofossil assemblages,particularly periods of high to moderate dissolution during interglacial periods.Conversely, glacials are characterized by moderate to good calcareous nannofossilpreservation. During Terminations IV and V we observed maxima in calcareousnannofossil accumulation, but with moderate preservation, indicating that maxima incalcareous nannofossil production occur during Terminations. One potential explanationis related to ocean geochemical mass balances and upwelling dynamics. The geochemicaldata from this site show that the P/Ti ratio, a paleoproductivity and P mass balance proxy,and Sr concentrations, a nannofossil production proxy, also show peaks duringTerminations IV and V-thus, high production from nutrients coincides with highcarbonate dissolution. In a coupled biological, chemical, and oceanographic model, lowsea levels during glacials result in a basin dominance of the shelf-basin fractionation,with generally high nutrient delivery to the deep sea and increased carbonate production.During termination, the shelf reservoir of nutrients and carbonates begins to increase, butperhaps ocean stratification is diminished with higher upwelling causing greaterproductivity, with high dissolution the result of a switch in alkalinity with thetermination. Basin production then decreases with the increase of nutrient apportionmentto the shelves during higher interglacial sea levels. DE HR:

16:50h AN: PP54B-04 TI: From Greenhouse to Icehouse: Evidence for Late EarlyEocene Concomitant Cooling of Southern Ocean Surface Watersand Global Deep Waters From Dinoflagellate Endemism AU: * Brinkhuis, H et al. EM AB: ODP Leg 189 drilling around Tasmania retrieved continuous Eocene records fromthe Southern Ocean - Antarctic Margin. The shallow marine, pro-deltaic successions ofSites 1170, 1171 and 1172 include the interval representing the onset (55 Ma) andtermination (50 Ma) of the Early Eocene Climatic Optimum (EECO). The end of theEECO is globally reflected in the oceans by the onset of increasingly cooler deep-watertemperatures, and marks the onset of the trend towards the Icehouse world. Here we showthat a strong increase of endemic Antarctic dinoflagellates precisely matches thetermination of the EECO in the Southern (Pacific) Ocean. The record of these surface-dwelling organisms thus indicates that changes of surface water parameters, notablytemperature, occurred near simultaneously with global deep-water temperature changes.Moreover, the signal coincides with the return to heavier d13C-values, and atmosphericCO2 decline. Comparison of the field data with predictions from fully coupled climatemodel simulations, and a new basic understanding of Eocene Southern Ocean circulation,suggests that changes in carbon burial was driving changes in atmospheric greenhousegasses, and the apparently coupled surface- and deep-water temperature signals. DE: HR:

14:40h AN: PP13B-05 TI: Oxygen Isotopic Stratigraphy and Geomagnetic FieldIntensity AU: Meynadier, L and Valet, J EM AB: Nick Shackleton intellectual leadership in isotope stratigraphy had profoundimplications for paleoclimatology and paleoceanography. What is not so well enoughknown is that Nick contributed also to significant advances in studies of variations of theEarth's magnetic field. The first link between the two disciplines was certainly the paperthat he produced with Neil Opdyke in 1973. About twenty years later Nick Shackletonobtained a very detailed isotope stratigraphy after analyzing the oxygen isotopes of bulksediment of two cores from the Somali basin characterized by high resolution records ofrelative paleointensity for the past 140 kyr. This stratigraphy allowed us to correlatethese two records with other independent data from the Mediterranean sea and topropose that the signal which was recorded at the two locations was global and thus ofgeomagnetic origin. The fast growing database made possible a stacking of the results forthe past 200 ka and then for the past 800 kyr. The resulting curve was constructed from33 paleointensity records and Shackleton's isotopic records were essential in many cases.Indeed without high resolution stratigraphy much information could not be retrieved dueto uncertainties in correlating different records. The results revealed the very variablecharacter of the field with large 20 to 60 kyr oscillations and changes in amplitude thatcan exceed a factor of five, but no apparent periodicity. Short periods of very lowintensity occur at more or less regular intervals (roughly every 100 kyr) and correspondwith geomagnetic excursions. The next step was to obtain a much longer record thatwould document the field changes across reversals and during entire polarity intervals.The opportunity was met during ODP Leg 138 with the recovery of beautifullymagnetized sequences that covered at least 4 Myr of geomagnetic history. Nick wasresponsible for correlating sedimentary columns taken at each site. He performed atremendeous task by orbitally tuning the density variations for thousands of meters ofsediment. This allowed us to correlate the paleointensity signals from several holes and toproduce the first long dataset with a very accurate time-depth control. Very recently theaccumulation of data made it possible to stack records from different oceans for the past2 Myr and to extract features of field intensity which add significant constraints to themodelling of the geodynamo. Alternatively this curve can be used as a stratigraphicreference, similarly to isotopes records. DE: HR:

0800h AN: PP51F-1370 TI: Metal Deposition Along the Peru Margin Since the LastGlacial Maximum: Evidence For Regime Change at \sim 6ka AU: * Tierney, J et al. AF AB: The Peru Margin upwelling zone plays a key role in regulating marinebiogeochemical cycles, particularly the fate of nitrate. High biological productivity andlow oxygen waters fed into the oxygen minimum zone result in intense denitrification inthe modern system, the consequences of which are global in nature. It has been verydifficult, however, to study the paleoclimatic history of this region because of the poorpreservation of carbonate in Peru Margin sediments. Here we present records of tracemetal accumulation from two cores located in the heart of the suboxic zone off the centralPeru coast. Chronology comes from multiple AMS $^{14}$C dates on the alkenonefraction of the sediment, as well as correlation using major features of the \delta$^{15}$N record in each core. ODP Site 1228 provides a high resolution, continuoussediment record from the Recent to about 14ka, while gravity core W7706-41k extendsthe record to the Last Glacial Maximum. Both cores were sampled at a 100 yr resolution,then analyzed for % N, \delta $^{15}$N, alkenones, and trace metal concentration.Analysis of redox-sensitive metals (Mo and V) alongside metals associated with changesin productivity (Ni and Zn) provides perspective on the evolution of the upwelling systemand distinguishes the two major factors controlling the intensity of the oxygen minimumzone. The trace metal record exhibits a notable increase in the intensity and variability oflow oxygen waters and productivity beginning around 6ka and extending to the present.Within this most recent 6ka interval, the data suggest fluctuations in oxygenation andproductivity occur on 1000 yr timescales. Our core records, therefore, suggest that thePeru Margin upwelling system strengthened significantly during the mid to lateHolocene. DE HR:

0800h AN: PP51D-1355 TI: Eocene-Oligocene Southern Ocean Paleo-bathymetry mapsgenerated with geophysical, sedimentological and microfossil data. AU: * Brown, B et al. EM AB: The Eocene-Oligocene transition is characterized by the cooling of the SouthernOcean region and growth of the Antarctic ice-sheet. Through this transition, changes inspatial distribution and topography of land masses and ocean basins have played a role.Our objective is to produce a set of enhanced paleo-bathymetry maps based on both platereconstruction models for the Southern Ocean and sedimentological and microfossil data.We used paleo-age grids to create a series of paleoceanic basement-depth grids, based ona thermal boundary layer depth-age model. We further constrained these paleo-bathymetry grids, especially for continental margins, with sedimentological andmicrofossil data (diatoms, foraminifera, nannofossils, organic walled dinoflagellates,pollen & spores and radiolarians); derived from new and published data from land basedsections and DSDP/ODP (and other) cores. In particular, we aim to map the opening ofoceanic gateways (Tasmanian Gateway and Drake Passage) and changing oceantopography through Eocene-Oligocene times. It is known that the evolution of circumAntarctic current systems were strongly dependent on bottom topography, particularlythe deepening of oceanic gateways and the mid-ocean ridge system. It is hoped that thiswork will offer a more realistic/resolved starting input for ocean basin configuration(paleo-geographic model) and topography (paleo-bathymetry model). It would be avaluable tool to assess boundary conditions for oceanographic circulation models andnext generation CCM's; in particular it would help assess deep-water circulation andrelated climate change further back in geological time. DE HR:

0800h AN: PP51F-1379 TI: Continental and marine climate records from the SoutheastPacific as inferred from Radiolaria and pollen records from 0 to90ka at ODP Site 1233 AU: Pisias, N et al. EM AB: Site 1233 drilled during Leg 202 of the Ocean Drilling Program provides a detailedrecord of oceanographic and continental climate change in the Southeast Pacific andSouth American continent. Splits from over 500 samples from Site 1233 were used fordetailed radiolarian and pollen species population analysis. Samples were taken at 20cminterval equivalent to temporal resolution of 200 to 400 years. In each sample splits usedfor pollen analysis abundances of 25 species were determined while in the splits used forradiolarian studies abundances of 41 species were evaluated. Age control is provided by25 AMS 14C dates (Lamy et al., 2004). From detailed multivariate analysis of these datasets we state the following conclusions: 1) During the past 75kyr the region of thesouthern Chile coast is not directly influenced by polar water from the Antarctic region.2) Changes in ocean conditions during this time interval reflect small north-south shifts inthe south Pacific transition zone and its impact on the coastal waters of Chile. 3) Theocean and terrestrial climate records extracted from Site 1233 show remarkablesimilarities to each other as well as to temperature records from the Antarctic. Theserecords suggest that climate variability during the past 75kyr in the Southeast Pacific istightly coupled at periods longer than 3000 years and not linked directly to changes in theNorthern Hemisphere and; 4) the marine and terrestrial climate records from Site 1233studied here, show no phase shift in response suggesting that ocean/continentalvegetation is much more tightly coupled with regional atmospheric changes as indicatedby the Antarctic temperature proxy record while the results of Lamy et al., (2004) show atime lag between ocean responses and the Patagonian Ice Sheet suggesting possiblyreflecting the long response time of ice versus continental vegetation and oceanicsystems. DE: HR:

16:55h AN: PP54A-04 TI: Two Highly-Resolved Geochemical Records of HoloceneVariability: A Comparison Between West and East Antarctica AU: * Kryc, K et al. EM AB: Based on results from ODP Site 1098 in the Palmer Deep, we have a highlyresolved record of West Antarctic Holocene climate evolution as traced by terrigenousprovenance and accumulation, nutrient utilization, and surface and export production. Todate, there are few comparable records from East Antarctica despite its critical role indeep ocean circulation. Here we compare results from a 25 m core recovered fromIceberg Alley on the MacRobertson Shelf of East Antarctica with the results from thePalmer Deep (PD), West Antarctica. Both cores are characterized by laminateddiatomaceous muds comprising a two-component system of biogenic opal andterrigenous material. Both of these sedimentary sequences span the Holocene and capturethe termination of the deglaciation event at 10kyr. The geochemical parameters we usedinclude XRF scanned and discrete ICP-ES major and trace element analyses, biogenicopal, and carbon and nitrogen isotopes. The PD geochemical records are stronglydelineated between the Holocene Climate Optimum (HCO) and the Neoglacial. Bothsurface and export production are elevated through the HCO, which is indicative if awarmer period. Additionally, the terrigenous provenance record of Al/Ti shows that thesource of sediment during the HCO was different than during the Neoglacial. This islikely the result of water mass reorganization as a function of Westerly wind strength.The major events seen in the PD record have also been observed worldwide. In contrast,the Iceberg Alley record does not show a difference between the HCO and theNeoglacial. Rather, there are high-frequency changes that appear to vary over anunchanged average throughout the Holocene. There is, however, a large change in boththe absolute values and the amplitude of the signal at 10kyr that signifies the terminationof the deglaciation event. Why the Iceberg Alley records do not reflect the same structureexhibited in the PD records remains to be determined. As a first approximation, it appearsthat the climatic conditions differed between these two sites during the Holocene. DE HR:

17:10h AN: PP54A-05 TI: Paleoceanography and Paleoclimatology of the SouthernOcean: A Synthesis of Three Decades of Scientific Ocean Drilling AU: Warnke, D et al. EM AB: A Workshop on " Paleoceanography and Paleoclimatology of the Southern Ocean:A Synthesis of Three Decades of Scientific Ocean Drilling" Jan. 21-23, 2005 Boulder,CO Co-Convenors: D. Warnke, G. Filippelli, J.-A. Flores, T. Marchitto One of thegreatest successes of the Ocean Drilling Program has been the concerted drilling effortsand exciting results recovered from the Southern Ocean (SO), which has been the focusof ten DSDP/ODP drilling legs. The SO is a critical component in the development andpersistence of Antarctic glaciation, is a sensitive mixing pool of global water masses, alocus of high biological sedimentation, and contains high resolution records of climateforcing and response. As such, it is one of the most important oceanographic regions inthe world. It is now an important time to mine the rich results from scientific oceandrilling over the past several decades and develop a scientific framework for future oceandrilling in this region. The focus of this Synthesis Workshop will be on thebiogeochemical history of the SO, including: ú Productivity proxies, rates, records,variations, and role of climate ú Sedimentary records of organic carbon, calcium, silica,nutrients, and biogenic proxies: The role of the SO as a biogeochemical sink úDevelopment and dynamics of the APFZ ú Thermal structure and evolution of the SO úThe role of limiting nutrients The overall goal to integrate the various proxies into acoherent paleoceanographic picture. Such a goal will help to synthesize several decadesof scientific ocean drilling in the SO, and will likely bring to the forefront the as-yet-unanswered questions about the biogeochemical history of this important oceanic system.With this goal in mind, workshop participants will submit of a short (~250 word) abstractas the Workshop application, commit to presenting a poster at the workshop based onthis abstract, and contribute to one or more manuscripts that will be published after theworkshop, likely as a Geological Society of America Monograph. The workshop is opento both U.S. and international scientists. Individuals interested in participating shouldapply by emailing a brief statement of interest and attaching an abstract (sent as a worddocument) of the research to be presented to gfilippe@iupui.edu. Although the deadlinefor submitting abstracts will have passed at the time of the meeting, interested personsshould contact gfilippe@iupui.edu immediately to see whether space is still available.Participation will be limited to optimize workshop goals. DE: HR:

0800h AN: PP51D-1351 TI: Radiolarian and Sedimentologic Evidence for Late EoceneOrigin of Southern Ocean Environments AU: * Lazarus, D et al. EM AB: Benthic foram $\delta$$^{18}$O and Mg/Ca records indicate that the deep oceancooled by 5-$10\deg$C between the early Eocene and earliest Oligocene, although thetiming, magnitude and dominant style of change (continuous vs. steps) is still debated.The largest change occurs at the Eocene/Oligocene boundary (33.5 Ma), associated withthe first major Antarctic glaciation. Current debate concerns whether this glaciation was athreshold event related to long-term decline in CO$_{2}$ or was caused by opening ofthe Tasmanian Gateway, with thermal isolation of Antarctica and development ofcircumpolar circulation. The Southern Ocean, characterised by circumpolar current flowsand bounded by the Polar Front, has contained since the mid Paleogene a distinctAntarctic radiolarian biota consisting of endemic forms and bipolar high-latitude taxaadapted to seasonal high productivity environments. It is also characterised by commonbiogenic silica in pelagic sediments. Past changes in the abundance and geographicdistribution of these faunas and sediments provide qualitative proxies for the origin anddevelopment of this environment. We examine trends in radiolarian evolution,biogeography and biosiliceous facies development from the mid-Eocene to earlyOligocene. We calculate diversity, speciation and extinction rates; track the origin anddispersal patterns of Antarctic radiolarian biota (percent Antarctic species at each site);and map sedimentary facies distribution changes through a series of time slices from thelate Middle Eocene to the middle Early Oligocene. Data comes from numerous DSDPand ODP sites drawn from the Pacific, Indian and Atlantic sectors of the Southern Ocean.Results show maxima in rates of evolutionary change, increases in Antarctic species, andappearance of biosiliceous components in sediments in the late Middle to middle LateEocene interval. There is little evidence for major change in, or expansion of theAntarctic radiolarian fauna; or increase of biosiliceous sediment at the time of theopening of the Tasmanian Gateway and Eocene-Oligocene glaciation. We conclude thatthe Antarctic environment largely developed prior to the Eocene-Oligocene boundary. DE: HR:

14:40h AN: PP43B-05 TI: Regime Shifts in Climate Forcing of Peru Denitrification AU: * Altabet, M et al. EM AB: Water column denitrification occurs in suboxic intermediate waters when bacteriatransform nitrate to N2 gas, thereby removing it from the ocean's combined N inventory.Combined N availability is an important controlling factor for organic C productionacross much of the ocean, such that past variations in oceanic denitrification likely hadrepercussions for marine productivity and perhaps, at appropriate time scales,atmospheric CO2. Prior studies in the Arabian Sea and E. Tropical N. Pacific havedemonstrated climatically-forced oscillations in denitrification on orbital to millennialtime scales. Here we examine the Peru denitrification zone, the last of major watercolumn denitrification zones to be studied and the only one in the S. Hemisphere. It isalso the most likely to be influenced by ENSO variability. We have examined a series ofhigh resolution cores from the upper Peru margin and developed a chronostratigraphycovering the last 60 kyr overcoming difficulties of common hiatuses and little or nopreserved foraminifera. We have also examined ODP Site 1237 and associated sitesurvey cores located in deep waters near the margin on the Nazca Ridge. A multi-proxyapproach is taken including N isotopic composition to record denitrification intensity;major and minor elemental composition for sediment provenance, water column redoxstate, and productivity; alkenone UK37 for SST. Denitrification intensity is observed tovary at a variety of time scales. The lower resolution, 2 Ma record from site 1237 showslarge orbital-scale shifts with the dominant mode shifting at the MPT. The high resolutionrecords from the margin elucidate the nature of important forcings. The last deglaciationexperienced a sharp and early rise in Peru denitrification that preceded by 2 kyr anymajor changes in local productivity. Forcing appears to be remote from the Peruupwelling zone, likely due to changes in either the ventilation of source intermediatewaters in the Subantarctic and/or changes in the relative isolation of the `shadow zone'from the subtropical gyre circulation. The Holocene is also marked by large excursions indenitrification that are only centennial scale in duration that are unique to this region. Aregime shift appears to have occurred in which local, productivity-driven forcing appearsto dominate. UR HR:

1340h AN: PP53B-1395 TI: $^{15}$N depleted nitrogen isotope values in Cretaceousblack shales: paleoceanographic event or diagenesis. AU: * Junium, C and Arthur, M AB: Nitrogen isotopic values of bulk sediment samples in black shales are almostexclusively near 0 $\permil$ and C/N ratios are high (20-35). Sequential extraction ofexchangeable and non-exchangeable N fractions demonstrates that the inorganic Nfraction is negligible and bulk sediment data reflect the organic N fraction. The trend in\delta$$^{15}$N and C/N has been observed in numerous localities and depositionalenvironments in the mid-Cretaceous (Demarara Rise, DSDP Sites 367, 603B and 530, theCretaceous Western Interior Seaway, Wunstorf, Germany, and Bahloul, Tunisia) as wellas the Toarcian of England and in Quaternary Mediterranean Sapropels. Threeexplanations are considered: 1) That primary production during black shale depositionwas dominated by a unique community composed of nitrogen-fixing cyanobacteria; or 2)utilization of a $^{15}$N depleted ammonium source by another set of biota; or 3) thatthe values are the result of diagenetic loss of N prevailing in C$_{org}$-rich strata with alow capacity for N adsorption. The depleted nitrogen isotopic values suggest thatnitrogen fixation or utilization of a depleted nitrogen source (e.g. ammonium) may havebeen important which is plausible in consideration of nitrogen deficiencies that mightcharacterize widespread deep-water anoxia. Secular variations in nitrogen isotope valuesacross the Cenomanian-Turonian Boundary of ODP Site 1261, Demarara Rise, show ashift from -1 to -3$\permil$. One interpretation of the origin of the excursion could bethat a fraction of the organic matter was produced utilizing a $^{15}$N depletedammonium source, assuming that the nitrogen isotopic composition of fixed oceanicnitrogen does not change. However, it should be noted that large (greater than1$\permil$) variations in nitrogen isotope values are observed above and below theCenomanian-Turonian Boundary Event and have no known paleoceanographic forcing.The variations in nitrogen isotope values are matched by antithetic variations in C/Nindicating diagenetic N-loss that could be interpreted as the primary control on thenitrogen isotope variations. The high C/N ratios probably result from selective removalof N-enriched compounds in the water column and during burial diagenesis. Clay-poor,C$_{org}$-rich sediments have a low sorptive capacity, allowing diffusion of dissolvedN out of the C$_{org}$-rich sediments resulting in higher C/N ratios. Pore waterammonium concentrations are mM, indicating low sorption and high rates of diffusioninto overlying strata. Coupled C/N and N-isotope variations occur by the removal of a$^{15}N$ enriched fraction. Protein degradation has been suggested to result in negativeisotopic shifts but would not result in large increases in C/N and the isotopic shifts arelimited by the protein richness of the primary organic matter and the internal isotopicheterogeneity of the organic matter pools. Although we favor an explanation thatinvolves a primary signature, diagenesis cannot be excluded in low $\delta$$^{15}$Nvalues. DE: HR:

1340h AN: PP53B-1396 TI: Evaluation of Geochemical Proxies Preserved in the SapropelRecord from the Eastern Mediterranean Within the Pliocene-Holocene Time Interval AU: * Gallego-Torres, D et al. EM AB: Considerable research has been devoted during the last decade to productivity andoxygenation proxies of sapropel deposition in the Mediterranean. Pliocene-Holocenesapropel layers from Mediterranean basins are considered to be an important key toassess the role of productivity vs. anoxia in organic matter (OM) accumulation.Evaluation of proxy preservation within these sediments is therefore crucial to furtherinvestigate forcing mechanism for OM deposition. With this aim, diverse layers fromPliocene, Pleistocene and Holocene sediments recovered at ODP Site 964 in the easternMediterranean have been analyzed. Ba excess is recognized as a reliable proxy forenhanced productivity because it derives from barite crystals originated in the watercolumn. Additionally, their S isotope composition revealed that barite is an authigenicphase (Paytan et al., 2004). This proxy also revealed of exceptional importance inMediterranean basins because some sapropels have been partially or totally oxidized.Assessment of productivity variations cannot be based therefore on the OM record whichis strongly subjected to diagenetic preservation. Certain redox-sensitive elements as Mnwere also subjected to remobilization during oxidation precipitating upon encounteringthe oxidation front. However some well preserved trace-element ratios, used asoxygenation proxies, are still recognized. These consistently point to a relatively oxicenvironment during the deposition of Quaternary sapropels while Pliocene sapropelstend to be characterized by lower oxygen conditions. Ba excess also indicates that bariteaccumulation rates within sapropels decreased through time, being considerable higherduring the Pliocene. Thus, elevated primary export production could have enhancedoxygen consumption leading to lower oxygen levels at this time. Paytan, A., F. Martinez-Ruiz, M. Eagle, A. Ivy, and S.D. Wankel (2004) Using sulfur isotopes in barite toelucidate the origin of high organic matter accumulation events in marine sediments.Sulfur Biogeochemistry, GSA Special Paper, 379, 151-160. DE: HR:

0800h AN: PP51D-1352 TI: Evolution of North Atlantic Thermohaline Circulation: Fromthe Greenhouse to the Icehouse AU: Via, R and Thomas, AB: A growing body of data indicates that the pattern of oceanic thermohalinecirculation has varied through the geologic past. At any given time, tectonic and climaticboundary conditions will tend to dictate the operating pattern of thermohaline circulation.For example, in the Early Cenozoic prior to the opening of the northern North Atlanticbasins, the Southern Ocean was the dominant source region for deep water formation. Asglobal climate cooled and tectonic gateways changed through the Cenozoic, this modegradually evolved into the Late Cenozoic mode, characterized by Southern Ocean andNorth Atlantic sources of deep water formation. To better understand how the evolutionof Cenozoic thermohaline circulation related to changes in global climate and ocean basinconfiguration, we generated Nd isotope records from a depth transect of Ocean DrillingProgram sites in the southeastern Atlantic to track deep water mass composition throughtime. We used fossil fish debris from ODP sites 1262-1264 (Leg 208), which spanpresent-day water depths of 2500 m to 4750 m, to reconstruct the isotopic signature ofdeep waters over the past 55 Ma. The data indicate an initial transition from relativelynon-radiogenic values ($\sim$-10 $\epsilon$$_{Nd}$ units) at 55 Ma to more radiogenicvalues ($\sim$-8.5) at 32 Ma. From 32 Ma to 3.85 Ma, the Nd signal becomes more non-radiogenic, approximately -12.3 at the top of our record. Comparison of our data with Ndisotopic records derived from a North Atlantic Fe-Mn crust show similar non-radiogenicvalues ($\sim$-10.5) in the 50 - 32 Ma interval and a trend toward more non-radiogenicvalues beginning at approximately 20 Ma. The data likely reflect an overall shift from aSouthern Ocean deep water source to the ultimate incursion of deep waters from theNorth Atlantic. The non-radiogenic values at the base of the record reflect a SouthernOcean source of deep water. The shift toward more radiogenic values indicates anincreased contribution of Pacific waters to the Southern Ocean source as the DrakePassage began to open to deep flow at $\sim$33 Ma. Though the subsequent trend towardmore non-radiogenic Nd isotope values does not directly correlate to any major tectonicevent, it is approximately coincident with the increase of benthic foraminiferal$\delta$$^{18}$O values, based on comparison with the Zachos et al (2001) globalcompilation. Thus the build-up of continental ice on Antarctica and global cooling mayhave altered the character of Southern Ocean deep waters during the early Oligocene. DE: HR:

0800h AN: PP11A-0541 TI: Middle Eocene to early Oligocene paleoceanography of theSouthern Ocean from foraminiferal stable isotope and Mg/Carecords AU: * Bohaty, S et al. EM: AB: The middle Eocene to early Oligocene is a critical phase of Cenozoic climaticevolution, characterized by long-term cooling of deep waters and the first appearance oflarge Antarctic ice sheets. The Southern Ocean is a key area for monitoring Eocene-Oligocene climatic variability, and development of high-resolution paleoceanographicrecords from this region is crucial to evaluating possible mechanisms of long-termclimate change. These records will ultimately help constrain the timing and nature ofmiddle-to-late Eocene cooling and ice buildup on Antarctica in relation to the timing ofmajor paleogeographic changes, especially the opening of Southern Ocean gateways, andindependent records of {\it p}CO2 variability. We have generated high-resolution stableisotope records from ODP Sites 689, 702, 738, and 748 in the Atlantic and Indian sectorsof the Southern Ocean. These sites are separated by considerable distances, but therecords display coherent trends with several unique features. These features enabledetailed site-to-site correlation and indicate that a common paleoceanographic history isshared by all study sites. The late middle Eocene records are punctuated by a strong,transient warming event at $\sim$41 Ma. This event is followed by an increase in$\delta$$^{18}$O values that culminates at $\sim$37 Ma, indicative of long-termcooling and/or growth of small ice sheets. This is followed by an inferred brief warmingin the early late Eocene ($\sim$36.5-36.0 Ma), and a slight cooling step at ($\sim$35.5Ma). A period of relative stability in the latest Eocene precedes the well-documented$\sim$1.4$\permil$ increase in $\delta$$^{18}$O (the Oi-1 event) in the earliestOligocene. In addition to the stable isotope records, we are developing high-resolutionplanktonic foraminiferal Mg/Ca records. The primary goal of this work is to separate theice-volume and temperature contributions to the Eocene-Oligocene $\delta$$^{18}$Osignal. Our initial focus is on the early Oligocene Oi-1 event, which is thought torepresent the first major Cenozoic buildup of large ice sheets in East Antarctica. At Site748, Mg/Ca data from the thermocline-dweller Subbotina angiporoides indicate asignificant decrease in temperature in the earliest Oligocene. These data are interpreted torepresent a 2-3$\deg$C cooling at the Oi-1 transition. Removal of this temperaturecomponent from the oxygen isotope signal retains a significant ice volume signature. Aminimum of 60% modern ice volume is estimated during peak Oi-1 glaciation. DE: HR:

1340h AN: PP53B-1393 TI: Implications of Mn-Mg-rich Contaminant Phases for Mg/CaPast Temperature Reconstructions AU: * Pena, L et al. EM AB: In recent years, many paleoceanographic studies have employed the foraminiferalelemental composition as a proxy of sea water paleoenvironmental conditions. Inparticular, the foraminiferal Mg/Ca ratio has been widely used as a sea waterpaleotemperature estimator. Nevertheless, this technique is still in development andspecial attention needs to be focussed on those factors which can introduce potentialbiases in the Mg/Ca ratio and therefore leading to inaccurate reconstructions of past-oceanographic scenarios. This study aims to solve or reduce overestimations of past seawater temperatures derived from a contaminant Mg-rich phase associated to Mn-enrichments. We address this problem using samples from ODP 1240 (0§01.311'N,86§27.758'W, 2921m water depth) from the Panama basin which is a Mn-enriched basin.By means of the LA-ICP-MS capabilities at the Research School of Earth Sciences(Australia) we have documented and identified the presence of Mn-Mg-rich contaminantphases at the inner part of the foraminifera walls. In order to asses the efficiency of theclassical Mg/Ca cleaning protocols when dealing with the presence of thesecontaminants, we have selected a set of samples with different contents in Mn andcleaned them with both the oxidative and the full reductive methods. LA-ICP-MS andbulk ICP-MS results show that the reductive cleaning successfully removes the Mn-Mgrich layers from the samples whereas the oxidative cleaning does not effectivelyeliminate the contaminant phases from the selected samples. In order to test the efficiencyof the different cleaning steps we have analyzed (ICP-MS) the residual fractions fromeach cleaning step using two sample sub-sets. The order in the reductive and oxidativestep was reversed for each sub-set. Results suggest that the Mn-enrichment occurs in twodifferent phases, one which is eliminated by either the oxidative or the reductive step buta second one which only is removed by the reductive step. This second one is alsoassociated to Mg-enrichments. As a consequence of this contamination phase,temperature reconstructions can provide overestimations in the range of 0.5-4§C. Inaddition, our results clearly demonstrate that there are no significant differences in theMg/Ca ratio when the order between reductive and oxidative steps is altered. A furtherinsight on the nature of these Mn-Mg-rich contaminant phases has been obtained bymeans of complementary analytical techniques (XRD, SEM, EDX). The results obtaineddemonstrate that the contaminant phase is mainly a Mn-Mg carbonate known asKutnahorite. This mineral has been previously identified in Mn-rich crusts of marinesediments but this study has been able to identify it for the first time within foraminiferaltests. DE HR:

1340h AN: PP23A-1393 TI: Detrital Sediment Supply And Late QuaternaryEnvironmental Changes Off Taiwan, ODP Site 1202 AU: Hofmann, J et al. EM AB: During Leg 195 of the Ocean Drilling Program, Site 1202 was drilled in thesubtropical northwestern Pacific Ocean beneath the Kuroshio ("Black Current") betweennorthern Taiwan and the Ryukyu Island Arc on the northern flank of the Ilan Ridge at1275 m water depth. The ridge separates the southwestern end of the Okinawa Troughfrom the basins of the Philippine Sea. The upper 120 m of the Site 1202 section,composed of dark grey calcareous silty clay, provide a high-resolution record of the last30 kyr, deposited at high sedimentation rates between 3.0 and 5.0 m/kyr and peak valuesof 9,0 m /kyr between 15.5 and 11 ka. Variations in the modes and sources of detritalsediment input, as inferred from sediment granulometry, mineralogy, and element-scanner data, reflect complex changes in environmental boundary conditions related topostglacial sea-level rise, monsoon climate, tectonics, and Kuroshio variability. Between30 and 11 ka, low portions of sortable silt show that the Kuroshio did not enter theOkinawa Trough because of low sea level. Clay-mineral tracers point to increasedsediment supply from mainland China by the discharge of Yangtze sediments directlyacross the East China Shelf edge into the Okinawa Trough. Consistent with maximumsedimentaion rates, Yangtze discharge reached a maximum between 15.5 and 11.0 ka.High fluvial sediment supply apparently was triggered by both postglacial sea-level riseand strengthened summer monsoon in response to precessional forcing of insolation. TheHolocene was dominated by sediment supply from Taiwan since 11 ka, as indicated byclay-mineral tracers and geochemistry. High proportions of sortable silt point to strongbottom currents, mediated by sea-level rise and enhanced Kuroshio activity at Site 1202.Element-scanner data reveal the presence of 200-yr cycles, possibly related to short-termclimate perturbations. DE: HR:

0800h AN: PP51F-1372 TI: High-Resolution Accumulation Rate and Authigenic UVariations On The Nazca Rise , Peru Margin, Over the last 25ka AU: * Higgins, S et al. EM AB: As part of a larger regional study into ocean circulation changes along the PeruMargin over the last 25 ka, we have a developed an excess Th-230 (xsTh-230) record ofsediment mass accumulation rates (MAR) and authigenic U (Uauth) at an offshore site(140km off margin) on the Nazca Rise. Over an interval between 7 and 25 ka, theseprofiles consists of 50 xsTh-230 and U measurements for an average resolution of ~350yr/sample. This has allowed us to evaluate concerns about sediment redistributionaffecting interpretations of other proxies, like $\delta$N-15, as well as make more directcomparisons with shallower marginal sites. The Site RR9702A-69TC (3.2 km waterdepth) is located at $16\deg$S $76\deg$W and has an average sedimentation rate of 5.4cm/ka based on AMS C-14 dates and correlation to nearby locations. The xsTh-230profile combined with estimates of dry bulk density and sedimentation rates indicates thatsediment focusing (a surplus of Th-bearing sediments) is about 1.5 to 2x the expectedthroughout the record. Th-230 data and %CaCO$_{3}$ analyses enabled us to producedetailed records of carbonate and non-carbonate MAR. The Th-normalized detrital MAR(primarily eolian) decreases by a factor of two (1.2 to 0.6 g/cm$^{2}$/ka) across thedeglacial (15 to 12 ka). In contrast, Th-normalized CaCO$_{3}$ MAR shows valuesincreasing slowly through the LGM (0.1 to 0.15 g/cm$^{2}$/ka) then decreasing frommaximum at 15ka to no Holocene accumulation by 11 ka. In addition to xsTh-230,measurements of Th-232 and Uauth (often interpreted as a total organic carbon (TOC)proxy provide us independent measures of detrital flux and productivity variations,respectively. The Th-232 derived detrital flux is consistent with estimates of eolianaccumulation from nearby site ODP Site 1237 and is relatively constant through the LastGlacial Maximum (LGM). Uauth varies from 4 to 10 ppm during the LGM, decreasingthrough the deglacial to Holocene values of 1 to 2 ppm. However, the Th-232 detritalflux does not co-vary with Uauth concentrations (R$^{2}$ =0.2) . Instead, there is amuch better correlation between CaCO$_{3}$ flux and Uauth (R$^{2}$=0.5). Thisindicates that the variability (factor of 4-5x) observed in Uauth was not caused primarilyby dilution by terrigenous inputs. DE: HR:

16:45h AN: PP14A-04 TI: Revisiting ODP Site 690 to Assess the Responses of MarineCarbonate Chemistry to the Paleocene-Eocene Thermal Maximum AU: * Kelly, D et al. EM AB: The close of the Paleocene epoch (ca. 55 Ma) is punctuated by a transient ($<$100kyr) global warming event referred to as the Paleocene-Eocene Thermal Maximum(PETM). In the marine realm, hallmark signatures of the PETM are a negative carbonisotope excursion (CIE) on the order of 3 per mil, widespread carbonate dissolution, anda benthic foraminiferal mass extinction. The rapid onset and anomalous magnitude of theCIE has been attributed to a sudden release of some 2000 Gt of methane into earth'ssurficial carbon reservoir. Presumably, oxidation of this methane elevated pCO2 levels inthe atmosphere/ocean system, fueling global greenhouse warmth and carbonatedissolution. Here we revisit what is arguably the most complete deep-sea record of thePETM recovered from ODP Site 690 to explore the dynamic coupling betweenatmospheric CO2 levels, marine carbonate chemistry, continental weathering and globalclimate. The abrupt onset of the CIE is accompanied by a sharp decline in wt.%carbonate, yet wt.% coarse-fraction ($>$63 microns, foraminiferal shells) values remainfairly constant. These sedimentological shifts collectively point toward the selectiveremoval of fine-fraction ($<$63 microns) carbonate produced by calcareousnannoplankton during peak oceanic warmth. We believe this selective pattern of"dissolution" actually reflects, in part, reduced calcification among some calcareousnannofossil taxa. An important corollary of this interpretation is that rising pCO2 levelsattained a critical threshold that inhibited nannoplankton calcification. Decreased surface-ocean carbonate production triggered a shoaling of the local lysocline and concomitantlyenhanced the ocean's carbon-storage capacity providing an important sink foratmospheric CO2. The character of carbonate sedimentation is reversed during the later,recovery stages of the CIE. It is within this stratigraphically expanded portion of the CIEthat wt.% carbonate values and the relative proportion of wt.% fine-fraction increasemarkedly. This secondary shift coincides with a 5 degrees C cooling of intermediatewaters and a sharp influx of kaolinite. Concurrent cooling of sea-surface temperatures isalso suggested by the disappearance of warm-water microplankton. We believe thesechanges to be interrelated. The kaolinite spike likely reflects intensified silicateweathering on Antarctica as well as increased continental runoff. Thus, enhanced silicateweathering reactions (CaSiCO3 + CO2 -$>$ SiO2 + CaCO3) may have served as anadded sink for atmospheric CO2 and a source of oceanic Ca2+ and HCO3- that drove analkalinity overshoot thereby fostering increased carbonate sedimentation within theWeddell Sea region. The remarkable sequence of oceanic changes preserved in the Site690 PETM record is consistent with the hypothesis that both marine carbonate chemistryand continental weathering acted as negative feedbacks to curb PETM warmth. DE HR:

1340h AN: PP33A-0917 TI: High Resolution Record of Seawater Osmium Isotopes Overthe Last 100,000 Years AU: * Zylberberg, D et al. AF AB: We present a high-resolution record of the osmium isotopic composition of oceansover the past 100,000 years. The main intent of this study is to investigate the claims thatthe Os isotopic composition of the deep oceans varies on a glacial-interglacial timescaleand consequently the mean residence time of Os in the oceans is between 8 and 10 ka(Oxburgh, 1998; 2001), about a factor of four to five less than that estimated from massbalance calculations (Sharma et al., 1997, 1999; Levasseur et al., 1999; Peucker-Ehrenbrink, 2002). At present, it is commonly believed that Os in seawater is derivedfrom continents (rivers), submarine alteration (abyssal peridotites?), and micrometeorites.A shorter residence time would require the need to search for a yet another substantialsource of Os to the deep ocean. We have measured Os isotopes in Fe-Mn fraction of coreTNO57-21, which is a piston core recovered from ODP site #1089, located in the CapeBasin on the Agullhas drift ($41\deg$S, $7\deg$ E, depth = 4825 m). This site is uniquein that it experienced extremely high sedimentation rates with little input of continentaldust or volcanic ash. Therefore, the sediment is composed entirely of authigenic claysand carbonates. Osmium sequestered in the Fe-Mn portion of the core should yield the$^{187}$Os/$^{188}$Os ratio of ambient seawater. If Os has a residence time of 8-10ka, we would expect to observe glacial-interglacial variations in our record reflective ofvariations in the intensity of continental weathering. If, on the other hand, the residencetime is ~40 ka, as predicted by mass-balance equations, then the Os isotopic compositionshould remain essentially constant throughout the past glacial-interglacial cycle. Our datafor the TNO57-21 show substantial variation during the past 100 Ka extending into theHolocene. Intriguingly, during MIS 4 and MIS 2 the isotopic composition of the oceanswas more radiogenic than during much of MIS 3. Our record is relatively stable with$^{187}$Os/$^{188}$Os ratio of ~1.04 during MIS 5, 4 and 2, but shows significantvariability during MIS 3: at 56 ka the $^{187}$Os/$^{188}$Os rises from 1.04 to themodern seawater composition of 1.06. It drops to a ratio of 1.0 at 40 ka and then rises to1.04 at 36 ka. We also observe a rise in the Os isotopic composition from ~1.04 in MIS2to ~1.06 in the most recent Holocene samples, a magnitude of change consistent with thatobserved by Oxburgh (1998). However, our record shows a much more recent transitionto the modern seawater composition, a transition continuing into the present. It furthersuggests that Os is not in steady state and may be subjected to climate forcing. Indeed,Lomb-Scargle Spectrum analysis of the record shows the presence of 27 ka and 18 kawavelengths, which have normalized spectral powers of 4 and 3.5, respectively. Furtheranalyses are underway to understand the cause of this variation and to obtain a morecomplete record for the Holocene. DE HR:

14:55h AN: PP43B-06 TI: Paleoproductivity and Paleoclimate off Southern Chile Duringthe last Deglaciation. Diatom and Phytoliths Records from Site1233 AU: * Abrantes, F et al. EM AB: Diatom and Phytolith Accumulation Rates (DAR and PhAR) and diatomassemblage composition were determined between 23 and 8 Cal kyr B.P. for Site 1233recovered off Southern Chile (41$^{§}$S, 74.45$^{§}$W, 837 m) during ODP Leg 202.At present, the site is located in an area where the surface forcing is dominated by strongpoleward winds and heavy precipitation that generates a tongue of low-salinity water thatspreads northward from the fjord region (43$^{§}$S). Oceanic circulation is dominatedby the spliting of the West Wind Drift (WWD) into the Peru Current (PC) and the CapeHorn Current (CHC). Primary productivity in the region increases in winter/springpossibly associated to river input of nutrients and/or micronutrients. During the 22-8 Calkyr B.P.time interval, both diatoms and phytoliths abundance show centennial tomillennial variability. Marine Diatom AR increases as alkenone SST decreases and\delta$^{18}$O becomes heavier. Highest AR (10$^{8}$ valves/cm$^{2}$ kyr) occursbetween 20 and 22 Cal kyr BP. The diatom assemblage is dominated by the genusChaetoceros, which may be interpreted to reflect an intensification of the PC. A newaverage increase in DAR (to values 8*10$^{7}$ valves/cm$^{2}$ kyr) is noted from 11to 9 Cal kyr B.Pfollowed by a sharp decrease to a minimum centered at about 8.4 Cal kyrB.P. This second maximum is accompanied by an increase in Thalassiosira spp indicatingan increase in river induced productivity, and consequently stronger precipitation oversouthern Chile. Oceanic warm water forms reach maximum AR between 10 and 9 Calkyr B.P. indicating a possible strong southward penetration of relatively warmsubtropical waters or the poleward flowing undercurrent in the earliest Holocene.Increased PhAR occurs between 17 and 12 Cal kyr B.P. In general good agreement witha decrease in isotopic and alkenone derived salinity, this data points to an increase ingrass source and continental input. Past sea-surface temperatures and productivity will beestimated on the basis of tranfer functions generated from a multivariate analysis of 232SE Pacific surface sediment samples. DE HR:

13:55h AN: PP53D-02 INVITED TI: The evolution of atmospheric carbon dioxide since the middleEocene: a biomarker perspective AU: * Pagani, M et al. EM AB: The carbon isotopic fractionation that occurs during marine photosynthetic carbonfixation ($\epsilon$$_{p}$) is primarily a function of surface-water [CO$_{2aq}$],growth rate, and cell geometry. Therefore, if temporal variations in growth rate and cellgeometry are minimal or constrained, $\epsilon$$_{p}$ values provide the potential toevaluate paleo-pCO$_{2}$ concentrations and trends. Alkenone-based $\epsilon$$_{p}$($\epsilon$$_{p}$$_{37:2}$) records have been used to estimate atmospheric carbondioxide concentrations during the Miocene ($\sim$24-5 Ma). These records provideevidence that pCO$_{2}$ was substantially lower than previously anticipated andsuggest that changes in CO$_{2}$ played a secondary role in forcing global climatechange during the Neogene. Alkenone $\delta$$^{13}$C values ($\delta$$_{37:2}$) forthe middle Eocene to the late Oligocene were measured from six ocean locationsencompassing a range of growth environments (DSDP sites 511, 513, 516, 612, and ODPsite 803). Data from sites 511, 513, and 803 are limited but overlap other records. Site516 (Southwest Atlantic Ocean) represents the most continuous record ranging from themiddle Miocene to the earliest Oligocene. The Eocene portion of the record is derivedlargely from site 612 (Northwest Atlantic Ocean). Our results reveal a clear secular trendin $\delta$$_{37:2}$ from the early Miocene to the latest Eocene ($\sim$45 Ma), with$\delta$$_{37:2}$ values leveling off to $\sim$-32 to -33.4$\permil$ by the latestEocene. By $\sim$25-30 Ma and older, $\delta$$_{37:2}$ values are more negative thanthe lowest values recorded from similar environments in the modern ocean.$\epsilon$$_{p}$$_{37:2}$ values were calculated using the $\delta$$^{13}$C valuesof aqueous CO$_{2}$ estimated from the $\delta$$^{13}$C of coeval planktonicforaminifera or modeled from the isotopic composition of the $<$60 um fraction. Surfacetemperatures were estimated from the $\delta$$^{18}$O compositions of shallow-dwelling foraminifera and/or modeled from the isotopic composition of the $<$60 umfraction. All carbonates were assumed to be influenced by secondary carbonate and thusestimated temperatures were increased by $3\deg$ to $6\deg$C to account for diagenesis.In general, $\epsilon$$_{p}$$_{37:2}$ values track $\delta$$_{37:2}$ reachingmaximum values of $\sim$23$\permil$ by the late Eocene. Atmospheric carbon dioxideconcentrations can be estimated if we apply the modern calibration for$\epsilon$$_{p}$$_{37:2}$ as a function of surface-water [PO$_{4}$$^{3-}$] and[CO$_{2aq}$] and assume that the range of paleo-[PO$_{4}$$^{3-}$] for each site wassimilar to modern distributions. These criteria lead to minimum estimates of pCO$_{2}$that are highly dependent on our assumed ocean temperatures. Our results suggest thatmiddle Eocene atmospheric carbon dioxide concentrations were $\sim$1000 to 1500ppmv. Atmospheric carbon dioxide concentrations appear to rapidly decline followingthe Eocene/Oligocene boundary reaching modern values near the end of the Oligocene. DE: HR:

0800h AN: PP11A-0557 TI: Cenozoic variations in the South Atlantic carbonatesaturation profile: Insights from the Walvis depth-transect (ODPLeg 208) AU: * Schellenberg, S and Nielsen, J

AB: Ocean Drilling Program Leg 208 Science Party (D. Kroon, J. C. Zachos, P. Blum, J.Bowles, P. Gaillot, T. Hasegawa, E. C. Hawthorne, D. A. Hodell, D. C. Kelly, J. Jung, S.M. Keller, Y. Lee, D. C. Leuschner, Z. Liu, K. C. Lohmann, L. Lourens, S. Monechi, M.Nicolo, I. Raffi, C. Riesselman, U. R”hl, D. Schmidt, A. Sluijs, D. Thomas, E. Thomas,H. Vallius) Carbonate saturation profiles are complex and dynamic products of processesoperating on temporospatial scales from the "short-term local" (e.g. carbonate exportproduction) to the "long-term global" (e.g. carbonate-silicate weathering, shelf:basincarbonate partitioning). Established, if admittedly crude, proxies for reconstructingcarbonate saturation from sediments include wt% carbonate, where values of 0-20% aretypically attributed to deposition below the carbonate compensation depth (CCD), andplanktonic foraminifer fragmentation, where enhanced fragmentation is typicallyattributed to deposition below the lysocline. Ocean Drilling Program Leg 208successfully drilled a six-site Walvis Ridge depth-transect spanning modern water depthsfrom 2,717 to 4,755 m. Exceptional core recovery, well-constrainedbiomagnetostratigraphy, and standard crustal subsidence corrections provide a workingage-depth framework for contouring ship-board wt% carbonate determinations andidentifying the following first-order features of the regional CCD: (1) $>$3.5 km positionfrom 60-48 Ma punctuated by a major transient shoaling to $<$2 km during thePaleocene-Eocene Thermal Maximum at $\sim$55 Ma; (2) shoaling to $\sim$2.75 kmfrom 48 to 44 Ma; (3) subsequent deepening to $>$4.25 km from 37 to 28 Ma; (4)marked high amplitude fluctuations from 28 to 20 Ma followed by deepening to $>$4.75km; (5) transient shoaling to $\sim$4 km around 15 Ma followed by deepening to$>$4.75 km by $\sim$12 Ma. These first-order features are broadly congruent withclassic Atlantic CCD reconstructions by van Andel (1975) and Berger and Roth (1975).A wealth of higher frequency variation in carbonate saturation is clearly preserved withinthe Leg 208 depth-transect. Ongoing shore-based analyses aim to transform cm-scalevariations in core physical properties (i.e. magnetic susceptibility, color reflectance) intosynthetic records of wt% carbonate. These data, combined with other proxies (e.g.,planktonic foraminifer fragmentation, stable isotopes) and placed within the evolvingpost-cruise biomagnetostratigraphic and cyclostratigraphic age-model, will providevaluable constraints on cyclic and secular fluctuations in the South Atlantic carbonatesaturation profile and their relation to other major components of the earth system (e.g.pCO$_{2}$, eustacy). DE HR:

0800h AN: PP51E-1360 TI: Solar vs. Tidal Forcing of Centennial to Decadal ScaleVariability in Marine Sedimentary Records from the WesternAntarctic Peninsula AU: * Kirkwood, G et al. EM AB: Prior studies on Holocene marine sediments from the Antarctic Peninsula, includingODP Site 1098 and USAP N. B. Palmer jumbo piston cores have revealed pronouncedmulti-century scale variations within a number of paleoenvironmental proxies. In order tofully understand the exact timing of this signal an ultra-high resolution jumbo piston corefrom the Schollaert Drift was correlated with the well-known Palmer Deep record. Aprecise and accurate radiocarbon chronology is now available from the former site thatutilizes in-situ mollusks, rather than bulk organic matter. The resulting time series spansthe last 5000 years over the 20 m length of core NBP99-03 JPC28 and the surfacestratigraphy of kasten core NBP01-07 KC8. The corrected and calibrated ages (with anapplied reservoir correction of 1170 years) of 10 mollusks dated by the National OceanSciences Accelerator Mass Spectrometry Facility and the University of Arizona TAMSfacility were used to construct an age-depth profile for JPC28 and KC8. A linear trend(R$^{2}$ value of 0.993) of the age-depth profile was used to extrapolate the constanttime interval between magnetic susceptibility measurements, which were analyzed every1 cm. Dominant periods in the upper 10 m of the time series were identified using theArand Spectral Analysis Package (Howell, 2001). This analysis revealed a singlepronounced maxima at 160 years, which is inconsistent with the dominant periods foundin time series of climate proxies from other sites on the western side of the AntarcticPeninsula. In particular, periods of 200 and 400 years, which are dominant in the PalmerDeep site (Warner and Domack, 2002), are not present in the Schollaert Drift. Thespectral peaks derived from the two records are significantly different at the 95%confidence level. The cycles in the Palmer Deep record have been associated with solarvariability, where as the 160 year cycle in the Schollaert Drift is close to a 180 year cyclein tidal forces (Keeling and Whorf, 2000). We discuss these alternative forcingmechanisms with respect to: contrasts in regional processes of glacial marinesedimentation, the mechanism whereby the tidal or solar signal is transferred to thesediment column and possible cryptic stratigraphy of the Palmer Deep record (ie. missingtime, Nederbragt and Thurow, 2002). Resolution of the correct forcing factor is critical toour ability to hind cast the last 100 years of paleoenvironmental data within these coresand hence to our attempts at recognizing an anthropogenic climate signal in the AntarcticPeninsula region. Howell, P. (2001), ARAND time series and spectral analysis packagefor the Macintosh, Brown University, IGBP PAGES/World Data Center forPaleoclimatology Data Contribution Series #2001-044, NOAA/NGDC PaleoclimatologyProgram, Boulder, Colo. Keeling, Charles D., and Timothy P. Whorf (2000), The 1,800-year oceanic tidal cycle: A possible cause of rapid climate change, {\it Proc. Natl. Acad.Sci., 97} (8), 3814-3819. Nederbragt, A. J., and Thurow, J. (2002) Sediment colorvariation and annual accumulation rates in laminated Holocene sediments, Site 1098,Palmer Deep. In Barker, P. F., Camerlenghi, A., Acton, G. D., and Ramsay, A.T.S. (eds),Proc. ODP Sci. Results, 178: College Station TX (Ocean Drilling Program). Warner,

Nathaniel R., and E. Domack (2002), Millennial-to decadal-scale paleoenvironmentalchange during the Holocene in the Palmer Deep, Antarctica, as recorded by particle sizeanalysis, {\it Paleoceanography, 17} (3), 8004, doi:10.1029/2000PA000602. DE HR:

16:15h AN: PP14A-02 TI: Multiple Early Eocene Thermal Maximums AU: * Roehl, U et al. EM AB: Periodic dissolution horizons signifying abrupt shoaling of the lysocline and CCDare characteristic features of deep-sea sections and often attributed to Milankovitchforcing via their diagnostic frequencies. Prominent dissolution horizons also correspondto abrupt climate events, such as the Paleocene-Eocene thermal maximum (PETM), as aresult of input of significant CH$_{4}$ - CO$_{2}$ into the ocean-atmosphere system.The question arises whether other significant dissolution horizons identified in sedimentsof late Paleocene and early Eocene age similar to the recently identified ELMO (Lourenset al., 2004) were formed as a result of greenhouse gas input, or whether they wererelated to cumulative effects of periodic changes in ocean chemistry and circulation. Herewe report the discovery of a 3$^{rd}$ thermal maximum in early Eocene (about 52 Ma)sediments recovered from the South Atlantic during ODP Leg 208. The prominent claylayer was named the "X" event and was identified within planktonic foraminifer zone P7and calcareous nannofossil zone CP10 at four Walvis Ridge Transect sites with a waterdepth range of 2000 m (Sites 1262 to 1267). Benthics assemblages are composed of smallindividuals, have low diversity and high dominance. Dominant taxa are {\it Nuttallidestruempyi} and various abyssaminids, resembling the post PETM extinction assemblages.High-resolution bulk carbonate \delta$^{13}$C measurements of one of the moreshallow Sites 1265 reveal a rapid about 0.6 per mill drop in \delta$^{13}$C and\delta$^{18}$O followed by an exponential recovery to pre-excursion \delta$^{13}$Cvalues well known for the PETM and also observed for the ELMO. The planktonicforaminiferal \delta$^{13}$C records of {\it Morozovella subbotina} and {\it Acaraninasoldadoensis} in the deepest Site 1262 show a 0.8 to 0.9 per mill drop, whereas the\delta$^{13}$C drop of benthic foraminifera {\it Nuttallides truempyi} is slightly larger(about 1 per mill). We are evaluating mechanisms for the widespread change in deep-water chemistry, its connection to the surface-water response, and the relationship of theevent, as well as the PETM and ELMO, with current astronomical solutions (Laskar etal., 2004; Varadi et al., 2003). References 1. Lourens, L.J., Sluijs, A., Kroon, D., Zachos,J.C., Thomas, E., Roehl, U., and the ODP Leg 208 Shipboard Scientific Party, 2004. Anearly Eocene transient warming (~53 Ma): Implications for astronomically-paced earlyEocene hyperthermal events.- Abstract, 8th International Conference onPaleoceanography (ICP), 5-10 September 2004, Biarritz, France. 2. F. Varadi, B.Bunnegar, M. Ghil, Astrophysical J. 592, 620-630 (2003). 3. J. Laskar et al., Astronomyand Astrophysics (2004). DE: HR:

0800h AN: PP51D-1354 TI: Orbital forced sea level fluctuations during the Middle Eocene(ODP site 1172, East Tasman Plateau) AU: * Warnaar, J et al. EM AB: Ocean Drilling Program leg 189 was undertaken to test and refine the hypothesis(by Kennett et al., 1975), that the reconfiguration of continents around Antarctica (e.g.:the opening of the Tasmanian Gateway and Drake passage) led to the onset of theAntarctic Circumpolar Current that, in turn, would cause thermal isolation and hencecooling of Antarctica. This would possibly even cause global cooling, as suggested bythe 33.3 Ma Oi1 event. The cores of leg 189, site 1172 on the eastern side of theTasmanian Gateway provided a nearly complete succession of Eocene and Oligocenesediments. Cyclostratigraphic analysis based on XRF derived Ca and Fe records indicatesdistinct Milankovitch cyclicity between 40 and 36 Ma. (R”hl et al, in press). In the core-section representing magnetochron 18n-1n, the Ca record shows precession cycles incombination with obliquity, suggested to reflect sea level fluctuations (R”hl et al, inpress). New datasets include microfossil data (organic-walled dinoflagellate cysts,pollen/spores and diatoms), loss-on-ignition measurements, magnetic data(environmental magnetics - ARM). Here, we aim to further investigate the proposedrelationship between astronomical forcing and sea-level fluctuations. Additionally, weaim to obtain insight in the palaeoecology of the distinct endemic circum-Antarctic lateMiddle to Late Eocene dinoflagellate cyst assemblages. Results corroborate the conceptthat the cyclicity recorded by Ca and Fe measurements is the result of sea-levelfluctuations. This implies that during late Middle Eocene times, astronomical forcing hasmodulated sea level - most likely through Antarctic ice buildup and meltdown. In turn,this would indicate the presence of significant, though probably modest, ice massesalready ~40 Ma ago, well before the onset of the Antarctic Circumpolar Current. Kennett,J. P., R. E. Houtz, et al. (1975). Development of the circum-Antarctic current. Science186: 144-147. R”hl, U.; H. Brinkhuis, C.E. Stickley, M. Fuller, S.A. Schellenberg, G.Wefer, G. Williams, Cyclostratigraphy of Middle and Late Eocene sediments from theEast Tasman Plateau (site 1172), in press. DE HR:

16:20h AN: PP54B-02 TI: Timing and Nature of the Deepening of the Tasmanian Gateway AU: * Stickley, C et al. EM AB: In the late Paleogene, Australia separated from Antarctica and continued to driftnorthwards allowing the eventual development of the Antarctic Circumpolar Current(ACC). The exact timing and nature of the opening of this gateway during the Eocene-Oligocene (E/O) transition is of interest in respect to its apparent synchroneity withclimate deterioration on continental Antarctica. The recovery of a continuous marinesedimentary record across the E/O transition at 4 sites within the Tasmanian Gateway(TG) during ODP 189, allows detailed paleoenvironmental changes to be documented athigh resolution in this region. The critical sedimentary units are barren of calcareousmicrofossils yet siliceous and organic-walled microfossils (notably diatoms anddinocysts) are abundant and excellently preserved, allowing an integrated and detailedpaleoeonvironmental analysis of the E/O transition. We present results from Site 1172and report on the timing and nature of several step-wise deepening events andpaleooceanographic changes across the E/O transition in the TG. We use integrateddiatom, dinocyst, geochemical, lithological and physical property data to show that theTG deepened at 35.5 Ma, preceding the E/O Antarctic glaciation event by 2 Ma.Importantly our microfossil data indicate a pre-deepening shallow-water pro-deltaicsetting characterized by highly endemic biota influenced by a cool clockwise rotating`proto-Ross Sea gyre', to a post-deepening pelagic setting in the earliest Oligocenecharacterized by cosmopolitan biota. Interestingly these findings indicate a warming inthe TG at the exact time when, according to previous hypotheses, a cool-ACC should beinfluencing the region. These conclusions are corroborated independently by themodeling results of Huber et al., (in press, Palaeoceanography). DE HR:

08:15h AN: PP11C-02 TI: Late Quaternary Biosiliceous Laminated Marine SedimentsFrom Antarctica: Seasonality During a Period of Rapid ClimateChange AU: Pike, J et al. EM AB: The Antarctic ice sheet plays a key role in global oceanic and atmosphere systems.One of the most dynamic regions of the continent is the Antarctic Peninsula (AP) whereecological and cryospheric systems respond rapidly to climate change, such as the lastdeglaciation ($\sim$12-13 kyr BP). Here, deglacial laminated diatom-rich marinesediments are well known, e.g., Palmer Deep (64$\deg$S 64$\deg$W; ODP Hole 1098A)comprising a distinctive 3 m thick sequence of deglacial `couplet' laminations. The EastAntarctic margin (EAM), however, has received less attention than the West Antarcticmargin (WAM) in palaeoceanographic studies yet its role in deep ocean circulation and,therefore, the global ocean system is significant. Recent sediment cores recovered fromEAM sites during NSF Polar Programs-funded cruise NBP0101 in February and March2001 (e.g. Mertz Drift \{66$\deg$S 143$\deg$E\}, Svenner Channel \{69$\deg$S77$\deg$E\} in Prydz Bay, Nielsen Basin \{67$\deg$S 66$\deg$E\} and Iceberg Alley\{67$\deg$S 63$\deg$E\}), reveal that a similar sedimentary facies was deposited alongthe EAM, in similar geomorphological settings to Palmer Deep, during the sametimeframe. These rich sediment archives reveal clues about circum-Antarcticpalaeoceanographic change during the last deglaciation, a time of both high silica fluxand rapid climate change. Microfabrics and diatom assemblages from scanning electronmicroscope backscattered and secondary electron imagery analysis of coeval deglacialvarves from Palmer Deep (WAM), Mertz-Ninnis Trough and Iceberg Alley (EAM) arepresented and compared. The varves from these localities are characterised by laminae tothin beds of orange-brown diatom ooze up to $\sim$8cm thick alternating with blue-greydiatom-bearing terrigenous sediments up to $\sim$4cm thick. The orange-brown oozesare dominated by resting spores and vegetative valves of {\itHyalochaete Chaetoceros}spp., resulting from spring sedimentation associated with stratified surface waterspromoting exceptionally high primary productivity. The blue-grey terrigenous sedimentscontain mixed open-water Antarctic diatoms resulting from summer/autumnsedimentation associated with increased terrigenous input and the annual trend to moreoligotrophic conditions. The significance of these biogenic seasonal and annualcyclicities will be discussed in terms of interannual palaeoclimate oscillations. Sub-seasonality and a related deglacial trend are apparent within the spring lamine from theEAM and in the summer/autumn laminae from the WAM. This circum-Antarcticasymmetry indicates differences in the nature and timing of oceanographic andcryospheric systems operating around the Antarctic continent at this time. DE

HR: 0800h AN: S51B-0148 TI: Permeability Measurements of Ocean Drilling ProgramSamples Collected From the Costa Rican Subduction Zone AU: * Hays, T et al. EM AB: Permeability is a key component in evaluating pore pressures and consolidationhistory in sediments. Core samples collected from the Costa Rican subduction zone weretested to determine their vertical permeabilities. The samples are from Ocean DrillingProgram (ODP) Leg 205 Sites 1253, 1254, and 1255 and ODP Leg 170 Site 1040. TheCosta Rican subduction zone has been shown to currently be a nonaccreting margin, andall samples are from within the underthrust sediments. The measurements were madeusing a constant head test by inducing a pressure gradient across the sample.Measurements were taken for three different consolidation pressures with five differentpressure gradients induced across the sample in each consolidation. Two types of sampleswere tested; light colored, fine grained pelagic carbonates and dark colored, fine grainedhemipelagic clays. Our results show two groupings of permeabilities, with the pelagiccarbonates approximately two orders of magnitude higher than the hemipelagic clays.These results are consistent with permeabilities found by previous researchers. DE: HR:

0800h AN: S51B-0163 TI: Along strike changes in basement topography and sedimentthickness in the northern Shikoku Basin: Variable inputs to theNankai Trough Seismogenic Zone AU: * Ike, T et al. EM AB: The very thick terrigenous sediments in the Nankai Trough and the northernShikoku Basin mask significant basement irregularities that will soon be subducted intothe Nankai seismogenic zone. We present a new seismic reflection data set across thenorthern Shikoku Basin that images remarkable variations in basement relief andcorresponding variations in sediment thickness and type. The basement relief has awavelength of ~5-15 km, with the amplitude of the peaks and troughs generally ~300-400m. Two significant troughs exist south of Shikoku that are each ~ 12 -15 km wide and1900 m deep. These troughs strike NW-SE and are at least 40 km long. They are mostlyfilled with high amplitude continuous reflections that onlap the trough margins. Wecorrelate these reflections with the mid-Miocene lower Shikoku Basin turbidite sequencedrilled at ODP site 1177. Along strike approximately 125 km to the NE, off the KiiPeninsula, there is a significant basement high that is just entering the trench ~ 15 kmfrom the base of the inner trench slope. It is roughly oval with a diameter of ~50kmparallel to the trench axis and ~20 km perpendicular to the trench, with a peak that is1400 m higher than the adjacent crust. This basement high (seamount) is covered by thehemipelagic Shikoku Basin sediments that thin from 900 m on the SW flank to 200 m atthe summit. The Shikoku Basin turbidite section that fills the troughs to the SW is absenton the seamount and its flanks. Because of the variations in sediment thickness aroundthis seamount, its bathymetric summit is only 800 m above the adjacent seafloor whilethe basement relief is 1400m. Between the seamount and Zenisu Ridge (~ 60 km NE), thebasement deepens by 500 m and has subdued relief (compared to that SW of theseamount). Basement is overlain by the Shikoku Basin hemipelagic sequence andonlapped by young trench turbidites. These significant along strike variations in basementtopography (1400m high seamounts and 1900m deep troughs), sediment thickness (200-2000m) and sediment type (hemipelagics vs turbidites) will soon be input to the Nankaiseismogenic zone and are representative of the kinds of irregularities that have been inputin the geologic past. Such variations must contribute to along-strike differences inseismogenic behavior. DE HR:

0800h AN: S51B-0151 TI: Pore-Water Freshening in the Nankai Trough, Japan:Implications for Lateral Fluid Flow AU: * McKiernan, A and Saffer, AB: Pore-water freshening has been observed in ocean sediments cored along theMuroto Transect in the Nankai Trough, offshore Japan during ODP Legs 190/196.Chloride concentrations up to $\sim$11% below normal seawater values ([Cl-] $\sim$555mM) were documented at drill site 1173, 13 km seaward of the trench. Updip, lateralfluid flow from depth, and in situ clay dehydration have been proposed as fresheningsources. Placing realistic bounds on the relative contributions of these potential sourceshas importance for quantifying fluid and chemical fluxes in subduction zones. Here, weevaluate the hypothesis that freshening is due solely to in situ clay dehydration. Wesimulate the general shape and magnitude of the down hole [Cl-] anomaly observed atsite 1173 using a one-dimensional model which combines sedimentation, thermal history,clay dehydration, and Cl- diffusion. Sediment accumulation during arcward transport andhigh heat flow for the area ($\sim$180 mW/m2), result in temperatures sufficient totransform smectite to illite + H20. The volume of released water scales with initialsmectite abundance (here we assume 50% by weight based on mineralogy at site 1177,where heat flow is low and clays are less reacted). In the model, released water is addedat each time step creating unstable [Cl-] profiles. Chloride diffusion is modeled implicitlyin a reference frame fixed to the interstitial water column, through which consolidatingsediment nodes move. Basal boundary conditions used in the model are: constant [Cl-],no-flow, and the inclusion of oceanic crust in diffusion. Simulated reaction progressmatches observed clay mineralogy for site 1173. Minimum simulated [Cl-] scales withinitial smectite content, ranging from 4% freshening for 20% initial smectite, to 14%freshening for 70% initial smectite. Simulated [Cl-] profiles for all boundary conditionsmimic the general [Cl-] profile for site 1173, but no single boundary matches observeddata exactly. A no-flow basal boundary reaches a minimum [Cl-] of $\sim$500 mM (10%freshening) but does so at the sediment-oceanic crust interface, $\sim$100 m below theobserved minimum. Constant-concentration basal conditions show a return to normal [Cl-] near the base of the section, but lack [Cl-] minima and maxima comparable to thoseobserved. Oceanic crust is included in some models to simulate communication betweenbasement and sediment. These models show similar behavior to no-flow and constant-concentration boundaries, differing mainly in magnitude.

HR: 11:20h AN: T42B-05 TI: Stratigraphic Control on Excess Pore Pressure at the PlateBoundary Fault of Nankai Trough AU: * Underwood, M B et al. EM AB: One of the unresolved issues regarding the subduction front of Nankai Trough is thecontrol over stratigraphic position of the decollement. The Muroto Transect area (ODPSites 808, 1173, 1174) is atypical of the regional system because hemipelagic stratawithin the lower Shikoku Basin accumulated above a basement high formed by back-arcspreading and late-stage seamount volcanism. The Ashizuri Transect area (ODP Site1177) is more characteristic of the system as a whole. Seismic reflection and coring provethat sandy turbidites are common within the lower Shikoku Basin facies, except along theMuroto Transect. Consolidation tests demonstrate that the stratigraphic equivalent of thedecollement at Site 1173 is slightly overconsolidated, whereas strata below thedecollement horizon are heavily overconsolidated. Samples from Site 1177, in contrast,are slightly to heavily underconsolidated within and immediately below the stratigraphicequivalent of the decollement. Mudstones within the underlying Shikoku Basin turbiditefacies show moderate to strong overconsolidation. Evidently, the turbidite facies drainsvery effectively through a process of compaction-driven fluid flow. There is a 40-minterval of mudstone above the turbidites, however, which acts as an aquitard.Stratigraphic compartments of overpressure build up long before the subducting stratareach the deformation front, especially where the uncemented sand packets pinch out.Tectonic consolidation and up-dip fluid flow beneath the decollement exacerbate theoverpressured condition. The unusually high fluid pressures reduce effective stress andprovide the optimal location for propagation of the plate boundary fault. DE HR:

0800h AN: T41E-1273 TI: Distribution of Post-Rift Sills on the NewfoundlandNonvolcanic Margin Around the ODP Leg 210 Transect FromWaveform Inversions and Synthetic Seismograms AU: * Shillington, D et al. EM AB: Nonvolcanic rifted margins commonly include a section of crust of uncertainaffinity between normal oceanic crust and extended continental crust. The origin of thisportion of the margin, often called the transition zone, is essential to establishing thesymmetry of rifted margins and developing models for margin evolution. TheNewfoundland-Iberia rifted margin pair is among the best-studied nonvolcanic conjugatemargin pairs in the world. Drilling on the Newfoundland nonvolcanic margin duringODP Leg 210 at Site 1276 did not reach enigmatic transitional basement, but did revealthe presence of interlayered sills and sediments immediately above the inferred top oftransitional crust. The presence of sills has implications for the appearance of underlyingtransitional basement in seismic reflection sections, the signature of this section of themargin in shiptrack magnetic data and late-stage margin evolution. Sills are estimated tobe approximately 100 m.y., while rifting likely occurred ~125 Ma. Shipboard worksuggests that sills encountered at Site 1276 correspond to bright reflections in thelowermost sedimentary section overlying transitional crust that are observed in coincidentseismic reflection profiles collected during the SCREECH (Studies of Continental Riftingand Extension on the Eastern Canadian SHelf) experiment during 2000. These profilesalso show that basement in the transition zone is essentially featureless in seismicreflection data except where it rises above these bright reflections, implying either thatimpedance contrasts in the deep section prevent signal transmission or that there is littlecontrast between interlayered sills and sediments and the underlying basement. Here, westrengthen the link between seismic reflection data and drilling data by creating syntheticseismograms from physical properties measurements made at sea aboard ODP Leg 210.Physical properties data were used in lieu of logging data, which could not be collecteddue to poor hole conditions. To extend the results from Site 1276 to rest of the grid ofseismic lines in this region, waveform inversions were also carried out on selectsupergathers around the SCREECH Line 2 survey and compared with waveforminversions of data near Site 1276. This work reveals significant variability in the velocitycontrasts required by deep reflections thought to be associated with sills in the transitionzone, implying similar variability in the distribution of sills. Furthermore, a distinctdifference is observed between bright reflections overlying transitional crust andreflections at similar depths further seaward over unambiguous oceanic crust. DE

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0800h AN: T41A-1160 TI: Enriched MORB in the Northeastern Pacific, Petrological andGeochemical Features of igneous Basement at Site 1224, ODPLeg200 AU: * Haraguchi, S and Ishii, T EM AB: During Ocean Drilling Program (ODP) Leg 200, 45-Ma igneous basement wascored in the northeastern Pacific at Site 1224. The basement surface was assumed to be28 m below seafloor (mbsf). Basement lithology down to 170 mbsf is divided into threeunits: Unit 1 massive flow, Unit 2 pillow breccia, and Unit 3 massive flow. Theshallowest Unit 1 shows massive structure with some altered layers and vein deposits,and core recovery was 30%-50%. This unit is divided into two thick lava flows based ongrain size stratigraphy and alteration layers. Intermediate-depth Unit 2 shows differentcharacteristics than Unit 1. Core recovery was so low (<10%), and many of the smallpieces retain almost circumferential alteration. Some calcite-cemented hyaloclastitelayers were found. The difference in induration between the two units was so great thatthe drill bit broke at the Unit 1/Unit 2 boundary. The deepest Unit 3 shows featuressimilar to Unit 1. Portions of at least two cooling units were recovered, and possiblymore. Recovery in Unit 3 was lower than that in Unit 1 but higher than that in Unit 2(20%~30%). Bulk compositions of Site 1224 rocks show interesting characteristics, themost important of which is high high-field-strength element (HFSE) content compared totypical normal and enriched mid-ocean-ridge basalts (MORB) (Sun and McDonough,1989). Chemical stratigraphy (chemostratigraphy) differences among the three units atthis site are clear. Unit 3 rocks are fractionated, and Unit 2 rocks have relatively primitiveFeO/MgO ratios. Large-ion-lithophile element (LILE) content is higher Unit 2 than inUnits 1 and 3. The high LILE content of Unit 2 is thought to be caused by hydrothermalalteration rather than a petrographic feature. HFSE content patterns are similar to those ofFeO/MgO ratios. Unit 1 is separated into upper and lower subunits, which correspond toflow units, on the basis of HFSE content. Unit 2 has lower HFSE content and higher Y/Zrratios, thought to result from a magma generation environment that was different fromother units. The parent mantle of Unit 2 basalt was probably of a different, depletedcomposition compared to Units 1 and 3. Perhaps the most interesting result from this siteis isotope characterization. The Sr and Nd isotope ratios are more enriched than typicalPacific MORB (Hickey-Vargas et al., 1995). These characteristics are attributed tomantle enrichment, and this enriched component is thought to still exist in the Pacificmantle. Many drill sites in the eastern Pacific show compositions similar to N-MORB(Sun and McDonough, 1989) (i.e. ODP Leg148; Brewer et al., 1996). Brewer et al.(1996) studied chemostratigraphy of the basement at from Holes 896A and 504B. Theyconcluded that variations in chemostratigraohy were mainly caused by differentiation.When the Leg148 sites and Site 1224 results, are compared, Site 1224 basement showsmore than twice the HFSE content than Sites 896 and 504, and the compositional changesis noted at Sites 896 and 504 differ from those of Site 1224. It is thought that the mid-ocean-ridge volcanism at Site 1224 was produced from more enriched mantle than that ofthe recent Eastern Pacific Rise and that these activities were associated with differentmantle sources simultaneously. Chemostratigraphic and lithologic differences between

the basement units correlate to differences in physical properties between the three units.Each lithologic unit displays different P-wave velocity, bulk density, and other physicalproperties. Physical properties are thought to be associated with petrological features. DE

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16:50h AN: T14C-04 TI: Analysis of the Growth of Active Detachment Folds Applyingthe new Thickness Relief Method, With Examples From the Tien-Shan and Nankai Trough AU: * Gonzalez-Mieres, R and Suppe, J EM: AB: Active folds develop distinctive stratigraphic geometries resulting from theinteractions of sedimentation and deformation, which provides a quantitative record ofdeformation history. Modern seismic with excellent images of growth deposits, allow usto extract this record of deformation in a detailed and quantitative way applying the newthickness-relief method. We apply the thickness relief method to growth strata of twoactives detachment folds, one in Yakeng anticline of the southern Tien-Shan China andanother at the front of the Nankai Trough Japan (ODP legs 190, 196). The methodinvolves determination of areas of structural relief as a function of height based onthickness variations of all imaged horizons. This yields a high-resolution profile ofshortening, as a function of height since shortening is the derivative of the area-heightcurve. The thickness-relief method has been successfully applied to pre-growthsequences in a number of structures. Here we extend the method to growth strata. Theonset of growth is represented in the area-height plot as an upward decrease rate ofgrowth of fold area, which is most easily analyzed through modeling. A wide variety ofdistinctive behaviors are expected for various ratios of sedimentation to deformation rate,depending also on the depth to detachment. Amplitude obtaining valuable informationabout the shortening and how this is accommodated into detachment folds. The slope ofbest-fit line represents shortening or displacement in the area relief graph. So, asdeformation and sedimentation starts to interact the geometry of deposits change andarea-relief, height, and shortening relationship is affected. Deviation from the lineartrend, negative or a decrease in slope, are signatures of the growth in area relief graph,however data are restricted and theoretical models are necessary to understand thebehavior of the graph. We use these models to fit real data on growth strata of Nankai andYakeng detachment folds, which show substantially different behavior. We found that thevery young and rapidly growing Nankai fold at a fast-moving plate boundary displays asedimentation rate that is no more than 25 to 30 % of shortening rate. In contrast theYakeng anticline in the more slowly deforming Tien-Shan of central Asia shows asedimentation rate that is 167 % the shortening rate. We make use of available agecontrol to transform these observations into sedimentation and deformation rates. DE HR:

1340h AN: T13B-1357 TI: Structure of the Upper Crust Exposed at Endeavor Deep:Implications for Crustal Accretion at Ultra-Fast Spreading Rates AU: * Popham, C et al. EM AB: Endeavor Deep lies at the tip of the propagating spreading center defining the JuanFernandez/Nazca plate boundary. This 3 km-deep, amagmatic basin,which rifted intoultra-fast spread 3Myr old Nazca Plate crust, was recently surveyed and sampled withSimrad EM300, DSL-120 and ROV Jason II. Over 140 structural orientations measuredfrom Jason II video of the south rift wall show that flows in extrusive layer 2a strikenorth-south and dip shallowly to the west, while dikes in intrusive layer 2b strike east-west and dip steeply to the south. Using a general model for crustal accretion in whichdikes are emplaced vertically and extrusives horizontally, a rotational history isdetermined for the 3 Myr old crust exposed in the walls of the deep. Multiple rotationsare necessary with two-fold intent, first to return structure to the original off-axisorientation prior to tectonic reorganization; second to account for rotations involved inthe process of accretion. Tectonic events are first addressed with a 10-25 degree rotationabout a horizontal rift parallel axis to account for flexural uplift. Next a 65-degreerotation applied about a vertical axis to return magnetic lineation 2a to its proposed paleo-off axis orientation. After rotation, intrusive and extrusive populations are strike parallel(N5E). In this orientation, dikes average 65-degree dip away from and extrusives 25-degree dip towards the ridge axis. This generally conforms to observations at Hess deep,Blanco FZ, and ODP hole 801C. The second goal of rotation is to account for off axisadjustments during crustal accretion; a 25-degree rotation about a ridge parallel,horizontal axis returns the average dike inclination to vertical and the extrusive dip tohorizontal. DE:

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0800h AN: T41C-1241 TI: Varying Rates and Modes of Subduction Erosion Along thePeruvian Margin AU: * Kukowski, N et al. EM: AB: At least half of the world's active margin length now is attributed to the erosive typewith regard to their mass transfer modes. However, the mechanisms, loci and rates ofsubduction erosion still are not fully understood. Among factors contributing tosubduction erosion, subduction of asperities, roughness of the downgoing plate, andrheological properties of the overriding plate are thought to be of major importance indetermining its styles and amounts. The Peruvian margin, the southern portion of whichhas experienced collision of the Nazca Ridge, is an exceptionally suitable location tostudy subduction erosion. Here it is possible to compare portions of a margin that haveeither been affected or not affected, respectively, by the subduction of major asperities.Swath bathymetry data acquired during RV Sonne cruise SO146 reveals high, butregionally different roughness of the almost sediment free Nazca plate. RMS roughness,local dip, curvedness, and void volume, i.e. the volume between peaks and valleyspotentially filled with eroded material, decrease from north to south. Recently acquiredwide angle data now together with information on long-term subsidence from ODP Leg112 Site 683 enable to estimate the rates of subduction erosion across the Peruvianmargin at 9\deg S, a region which was not affected by ridge subduction. Rates are 24 to30 km$^{3}$ km$^{-1}$ myr$^{-1}$ since the middle Miocene, 15 km$^{3}$km$^{1}$ myr$^{-1}$ since about 40 Ma and 6.5 km$^{3}$ km$^{1}$ myr$^{-1}$ forthe interval 40 to 13 Ma. These rates are considerably smaller than published long-termrates (since 40 Ma) estimated further to the south (12\deg S) or short-term (since thePliocene) erosion rates estimated further north at about 7\deg S. However, at 9\deg S, thevoid volume is not much less than the eroded volume, whereas at 12\deg S, the erodedvolume is about 3 times the void volume. This comparison reveals that differentmechanisms of subduction erosion, which are suggested to be attributed to differences inthe rheology and strength of the overriding South American plate, take place along thePeruvian margin. DE

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0800h AN: T41A-1170 TI: Atlantis Bank as a Key to Understanding the Nature of theMoho and Crust-Mantle Boundary AU: * Matsumoto, T et al. EM AB: Atlantis Bank on the Southwest Indian Ridge is a key site for the study of theoceanic lower crust and mantle. It exposes an eroded oceanic core complex lying alongthe western flank of the Atlantis II transform. The complex exposes of huge 400+ km2gabbroic massif that is at least 1500-m thick at ODP Site 735. Mantle peridotites areexposed on the lower slopes of the transform wall that flanks the core complex, wherethey locally appear to underlie the gabbro body. During the SHINKAI 6500 cruises in1998 and 2002, seafloor gravimetry was carried out at 16 stations on the Bank to detectits precise density structure. The average density of the basement rocks on the westernslope of the bank was estimated as 3.0 g/cc (lower part), 3.8 g/cc (middle part) and 3.1g/cc (upper part), corresponding to mantle peridotite, oxide Fe-Ti gabbro andperidotite/oxide olivine gabbro collected at these sites respectively. Average density ofbasement rock on the eastern slope was estimated as 3.1 g/cc (lower part) and 2.6 g/cc(middle part). The southwestern slope of the bank is characterised by exposure ofunaltered layered gabbro underlain by serpentinized peridotite according to observationsand sampling during the 2002 survey. Average bedrock density at this site is 2.5g/cc,extremely low considering the exposure of lower crust and upper mantle rocks there.According to the seismic survey crossing the bank (Muller, et al., 1997, 2000), adiscontinuity at 4 km below seafloor at the foot of the bank and at 6 km bsf at the summitwas identified. P wave velocity contrast indicates that the boundary is equivalent toMoho. Their result also shows that the southwestern slope corresponds to the Layer-2(Layer-1 is missing), and the estimated P wave velocity of 3.6 km/s is in good agreementwith the basement rock density derived from seafloor gravimetry. The Moho is notnecessarily identical to the petrological crust-mantle boundary and it is possible that it isthe boundary between serpentinized and non-serpentinized peridotite as shown in 'Hessmodel', and as also suggested by Muller, et al. (1997). This hypothesis will be tested inthe future IODP riser drilling. DE: HR:

0800h AN: T41E-1256 TI: Opal diagenesis and sediment properties in the NankaiTrough, Japan AU: * Spinelli, G et al. EM AB: We have measured the opal content and modeled opal diagenesis for sediment fromOcean Drilling Program (ODP) Sites 1173, 1174, and 1177 in the Nankai Trough, Japan.The porosity of the Upper Shikoku Basin facies at 1173 is nearly constant with depthfrom $\sim$102 to 344 mbsf. There is a step decrease in porosity across the UpperShikoku Basin / Lower Shikoku Basin facies boundary at Site 1173; porosity decreaseswith depth normally in the Lower Shikoku Basin facies. Sediment physical propertiessuggest that the cementing of grain contacts within the Upper Shikoku Basin faciesinhibits sediment consolidation, however, the nature of the cement has not beenpreviously identified. In addition, it has been suggested that the Upper Shikoku Basin /Lower Shikoku Basin facies boundary is at least partially a diagenetic boundary. Opalcomprises $<$2 wt% of the sediment at all of the sites. At Site 1173, the Upper ShikokuBasin sediment contains $\sim$1.25 wt% opal. The opal content drops abruptly to $<$0.5wt% across the Upper Shikoku Basin / Lower Shikoku Basin facies boundary -corresponding with the drop in porosity and the return to normal consolidation behaviorin the Lower Shikoku Basin facies. Secondary and back-scattered electron image analysisof sediments at this site reveals a low density, Si-rich phase that is probably opal. Thismaterial occurs as a pore-filling cement, coating grains and grain-to-grain contacts. Itappears to be more common in the Upper Shikoku Basin facies than in the Lower facies.SEM analyses suggest the presence of authigenic clays in the Lower Shikoku Basinfacies. We model sediment accumulation and the thermal evolution of the sedimentcolumns for the sites. Then, we use the thermal history of the sediment and laboratoryderived kinetics for the opal-to-quartz diagenetic reaction to model the opal content in thesediment column. Modeled opal content at Site 1173 decreases rapidly below 250 mbsf,where temperatures exceed 50$^\circ$C. The model results indicate that the reaction runsto completion (i.e. the last of the opal is removed) approximately at the Upper ShikokuBasin / Lower Shikoku Basin facies boundary. The model results are in good agreementwith the opal measurements and suggest that opal cement may be holding open the porespace in the Upper Shikoku Basin section. It appears that during opal diagenesis thestrength of the cement is lost and the pore space collapses. This apparent loss of strengthis consistent with previously described loss of shear rigidity reflected in anomalousseismic velocities measured across this zone. Both this loss of strength and high dissolvedsilica content in sediment pore water in the Upper Shikoku Basin facies may result fromthe loss of opal without immediate conversion into quartz. A sharp decrease in dissolvedsilica across the facies bounadry may be related to the uptake of silica into authigenicclays in the Lower Shikoku Basin facies. D

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0800h AN: T21C-0538 INVITED TI: Long-Term Observations of Active Hydrothermal Processeson the Gorda Ridge: The Sea Cliff Hydrothermal Field andEscanaba Trough AU: * Von Damm, K et al. EM AB: The two known sites of high temperature hydrothermal venting on the Gorda Ridgeare the northerly Sea Cliff hydrothermal field and the southerly Escanaba Trough.Indications that the Sea Cliff field (GR-14) existed were first obtained from hydrographicwork in 1985, and confirmed by the discovery of the site in 1988. Our cruise at the site in2000 was the first time fluids were sampled, and we subsequently also collected fluids in2002. One reason the Sea Cliff field is of interest is its location $\sim$3km east of theaxis of spreading. It was suggested that the site might therefore be relatively 'old,' or atleast located on 'older crust' at the 5.5cm/yr spreading rate. All of the hydrothermal fluidsfrom Sea Cliff are low chlorinity, or vapor phase, contrary to its previous interpretation asan older hydrothermal system which are generally interpreted to vent fluids with chloridecontents greater than seawater. Our other chemical data also support our interpretationthat this system is not tapping highly altered crust. In spite of the $>$$300\deg$Cmeasured temperatures of the vent fluids, they are strikingly clear, and have Fe contents$\sim30$ umoles/kg, about 2 orders of magnitude less than typical. The low Fe, and othertransition metals, are likely a result of the slightly elevated pH (4.5 at $25\deg$C) ofthese fluids. Possible causes of the elevated pH include: incorporation of buried organicmatter, dissolution of fracture-filling calcite, supercritical phase separation phenomena,and other reactions that may impact the proton balance in the fluids, as there is nosediment cover at this site, and no (chemical) evidence for buried sediments. The verylow metal contents are in agreement with the water column signals observed in 1985,suggesting the fluids have not changed in $\sim20$ years, and that the site was notimpacted by the seismic activity on the Gorda Ridge in 1996 and 2001. Hydrothermalfluids were first collected from Escanaba Trough (NESCA) in 1988, and this site wassubsequently drilled by ODP in 1996. Our fluid samples collected in 2000 and 2002 havethe same compositions as those collected in 1988. All of the fluids we collected ventingfrom this site are high chlorinity (brines), while ODP also encountered low chlorinityvapors subsurface. We propose a model to explain why the brines are ventingpreferentially to the vapor phase at this site. Chemical stability in hydrothermal systems,as in these two cases from the Gorda Ridge, are in stark contrast to observations ofvariability elsewhere on the global mid-ocean ridge system. The time scales andexplanations for the fundamental causes of these differences remain poorly understood. DE:

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12:05h AN: T12B-08 TI: Holocene Turbidite Recurrence Frequency off NorthernCalifornia: Insights for San Andreas Fault Paleoseismicity AU: * Nelson, H et a. EM AB: Numerous turbidites along the northern California continental margin are influencedby the northern San Andreas Fault (SAF). The fault parallels the coast near SanFrancisco Bay and further north underlies the California margin. Multiple tributary slopecanyons and proximal channels join downstream into large channels, and all systems aredominated by the deposition of turbidite silt and sand beds. Our research aims to: 1) testthe hypothesis that synchronous turbidites along the margin result from turbidity currentstriggered by great earthquakes on the SAF and 2) thus define a paleoseismic record. Mostimportant, we want to outline the recurrence history of paleoseismic events. Several linesof evidence suggest that there is synchronous SAF triggering of turbidites. Channelsbelow tributary confluences are characterized by many single-event turbidite beds withmultiple coarse-grained sediment pulses that contain different mineralogy from tributarysource canyons. The rate of turbidite bed deposition (number/m) above and belowchannel tributary confluences typically is the same and not additive in downstreamchannels. Geotek log signatures of turbidites from different channel systems correlatealong the margin and our present limited number of 14C ages suggest correlative events.The most complete and reliable turbidite record is found in Noyo Channel where thecanyon head source of turbidites is directly underlain by the SAF. The five youngestturbidite 14C ages of Noyo show general agreement with the SAF paleoseismic record onland.This apparent correlation suggests that Noyo Channel may provide a much longerpaleoseismic record for 24 events on the SAF during the past 6,000 yr. We utilizemultiple cores with 24 correlative turbidite events from the channel to define eventrecurrence time between turbidites. We base this time on two independent methods: 1)hemipelagic sediment thickness (H) between two consecutive turbidites (i.e.H/sedimentation rate =recurrence time)(24 events), and 2) 14C ages (i.e. difference inages between two consecutive turbidites= recurrence time)( 8 events). The averagerecurrence time we find between events is 210 yr (H method) and 180 yr (14C agemethod). Both methods show a minimum recurrence time of 140 yr and a maximum timeof 275 yr with 75 percent of the recurrence times between 150 to 225 years. With twomajor assumptions that 1) Noyo Channel turbidites represent great earthquakes on theSAF and 2) the Noyo recurrence pattern continues into the future, the Noyo recurrencedata suggests that we are not yet in a window for another great earthquake on thenorthernmost SAF. This statement is based on present evidence indicating that in theNoyo Channel area: 1) an earthquake greater than 7.2 magnitude is necessary to trigger aturbidity current, 2) minimum recurrence times are140 yr, and 3) the great earthquake in1906 triggered the youngest turbidite. DE: HR:

0800h AN: T41C-1235 TI: Structural vergence variation and clockwise block rotation inthe Cascadia accretionary wedge, offshore central Oregon AU: * Johnson, J et al. EM AB: Along the Cascadia margin offshore Oregon, the structural vergence at the toe of theaccretionary wedge varies from landward vergent offshore northern Oregon to seawardvergent across the southern Oregon margin. A transition zone between these vergencedomains occurs along the central Oregon portion of the wedge, centered on the HydrateRidge region. We examine the past variability in structural vergence across the HydrateRidge region through detailed structural mapping using multichannel seismic reflectiondata and gridded bathymetry. These data are coupled to biostratigraphic age constraintsobtained from ODP drilling to constrain the timing of accretionary wedge growth sincethe early Pleistocene (<1.7 Ma). Our results indicate that the wedge in the Hydrate Ridgeregion was accreted in three structural phases: an early Pleistocene seaward vergent phase(~1.7-1.2 Ma), an early to middle Pleistocene (~1.2-0.3 Ma) landward vergent phase, anda late Pleistocene-Holocene (~0.3-0.25 Ma to present) seaward vergent phase. Ageconstraints on the timing of landward vergent deformation suggest coincidence with thetiming of the deposition of the Astoria fan. High pore fluid pressures due to rapid fandeposition have been suggested as the likely cause of landward vergence for the northernOregon and Washington margins. The large bathymetric expression of northern HydrateRidge is likely due to its history of continued seaward vergence, which permitted somesediment subduction, likely underplating and observed thrust duplexing, all resulting inan increase in the thickness of the accretionary wedge (more uplift) beneath this region.Superimposed on the accretionary wedge growth in the Hydrate Ridge region, twobasement involved transverse strike-slip faults have affected the wedge development.Evidence of clockwise block rotation of the Hydrate Ridge tectonic block between thetwo transverse strike-slip faults appears most pronounced in the older portion of thewedge, and decreases toward the west. Constraints on the timing of propagation of thebasement strike-slip faults into the abyssal plain section near the deformation frontindicate that the early-middle Pleistocene landward vergent phase (~1.2-0.3 Ma) mayhave been terminated by this faulting. We speculate that the propagation of the strike-slipfaults into the upper plate may have reduced pore fluid pressures and increased couplingalong the decollement, triggering the change from landward to seaward vergence at thedeformation front. DE HR:

10:50h AN: T12B-03 INVITED TI: Cascadia Great Earthquake Recurrence: CorrelationEvidence for Repeated Margin Wide Rupture AU: * Goldfinger, C et al. EM AB: We are now testing correlation between turbidite event records at widely separatedsites in Cascadia with radiocarbon ages and physical properties of the core sediments. Wefocus here on physical property correlations between sites to test for connections betweensites independent of radiocarbon ages. Gamma density, magnetic susceptibility, and P-wave velocity data were routinely collected for all cores at a 2 cm interval. We find that agood stratigraphic correlation can be made between Juan de Fuca Channel (JDF, atributary of Cascadia Channel) and Cascadia Channel based on individual eventsignatures, and upon the sequence of unique signatures through the Holocene record of18 events. 16 individual event density-magnetic signatures between JDF and CascadiaChannel have correlation coefficients of 0.6-0.9, with two scores (0.16 and 0.32) forevents with similar, but out of phase characteristics. Non correlated events have lowercoefficients in most cases. The event sequence includes a mix of many unique signaturesand some events that are similar to others. The unique sequence of these signatures limitsthe possibility of miscorrelation because rarely do similar events occur adjacent in time.These correlations further support the temporal correlation to great earthquake records inWillapa Bay (this session), as well as extend the record to ~ 9800 years. We find thatmany events can be correlated in this way between JDF, Cascadia, Hydrate Ridge(central Oregon margin), and Rogue (southern Oregon margin) core sites. The signaturesvary more between sites that are not directly connected, but many robust features arepreserved, including in many cases, the relative volume of the turbidite, and the numberof coarse pulses in the turbidite. These features allow direct correlation between sitesindependent of other methods. That we are able to correlate physical property "wiggle"plots along channel systems is intriguing, given the expected chaotic nature of depositioncontrolled by turbid flow. However, the inter-site correlations between turbidite channelsthat are not connected, implies that the deposition process is influenced by more thanlong distance transport of event characteristics. We suggest that such correlation impliesthat something of the earthquake shaking signal may be contained in these records. Whilenot all sites can be correlated on the basis of physical properties, we find that key eventsin the event sequence have characteristics observable at most if not all sites. Events T6,T8, and T16 are large triplets at all sites, T4 and T9 are single events, T10, T12 are smallevents at all sites, and T11 is a massive doublet event at all sites. These observationsstrengthen the correlation, and thus the inference of earthquake origin for these events.The correlations further support the un-segmented nature of most Cascadia ruptures,since direct correlation effectively eliminates this option. Currently, not all events can becorrelated margin wide, leaving open the possibility of several segmented ruptures.Strengthened correlations further support a repeating pattern of Great Earthquakes inCascadia. The pattern appears to have repeated at least four times, with the most recentAD 1700 event being the third of three events following a long interval between eventsT4 and T5. DE: HR:

0800h AN: T41C-1212 TI: Metamorphic Tectonites and Differential Exhumation Reveal3D Nature of Extension and Lower Crustal Flow in the ActiveWoodlark Rift, Papua New Guinea AU: * Little, T et al. EM AB: The D'Entrecasteaux Islands metamorphic core complexes (MCCs) occur in theWoodlark rift, a continental region where $\sim$200 km of extension since $\sim$6 Mahas been focused into a relatively small number of normal faults, some dipping at $<$30º.Flow of a low viscosity lower crust on a time scale of $<$4 m.y. is evidenced by thenarrow width of the rift zone, and the apparent large magnitude of extension (Beta ~5) ,as contrasted by observed relief on the Moho ($<=$10 km). Gneisses in the footwalls ofMCCs, including retrogressed eclogites, have been exhumed from depths of $\sim$30 kmsince ~ Ma. Our structural and thermochronometric data covers parts of theD'Entrecasteaux MCCs, including Normanby Island. These are mantled by serpentinizedultramafic rocks of the Papuan ophiolite. Remnants of this upper plate are preservedalong the margins of the MCCs. In underlying mylonites, exhumation-related fabrics,microstructures and quartz lattice preferred orientations reveal a regional pattern oflineations and top-north shear inconsistent with diapir tectonics. The gently dippingmylonites were later warped by uplift of the $\sim$30 km-wide domes, perhaps inresponse to magmatic underplating during intrusion of dolerite dikes and granodiorites at$\sim$2 Ma. Southward across Fergusson Island, muscovite Ar/Ar ages, increase by ~2m.y. along the detachment, suggesting footwall exhumation by top-to-the-north slip at$>$12 mm/yr. To the east, an MCC on eastern Normanby Island has top-north footwallmylonites that dip gently SW and that were exhumed during the Pliocene as part of anorthward progression of normal faulting that did not arrive at the offshore MoresbySeamount until ~1.2 Ma (ODP Leg 180 site), relationships that suggest a rolling-hingestyle uplift. Importantly, its detachment exposes no rocks deeper than blueschist-facies.Ductile deformation fabrics in the MCCs reveal patterns of lower crustal motion that canbe evaluated against seafloor spreading-derived plate motions. Shear fabrics in MCCsclosest to the Woodlark spreading ridges, including Normanby and Misima Islands areparallel to the NNE direction of 0.5-3.6 Ma Solomon Sea-Australia spreading. Fartherwest, lineations in the lower plates of the D'Entrecasteaux MCCs locally deflect ~40-50ºclockwise from this direction. This obliquity is interpreted to reflect inhomogeneouslower crustal extension to the west of the Woodlark spreading ridges. A rift corridorextending $\sim$100 km to the north of Goodenough and Fergusson Islands is defined byactive normal faulting and subsidence of the Trobriand margin. We infer that a previouslysubducted, locally eclogite-bearing, slab of thinned Australian lower crust to the north ofthe islands is being pulled out from beneath this zone as it is being sinistrally shearedalong its eastern edge. Today the rift zone steps ~70 km south towards the PapuanPeninsula to define a right-step, an asymmetry that is enhanced by seafloor spreading eastof ~151.4ºE. Published focal mechanisms suggest that N-S sinistral shear along thenorthern Woodlark rift is continuing. In central Normanby Island, ~2 Ma andesites mayhave erupted along a transverse fault bounding the deeply exhumed D'Entrecasteauxcorridor. Its offshore extension trends N along a major embayment in the Woodlark Rise.

HR: 1340h AN: V23B-0625 TI: Magnetization Of Gabbroic Rocks and Peridotites RecoveredFrom Mid Atlantic Ridge 14N - 16N, ODP Leg 209 AU: * Kikawa, E et al. EM AB: ODP Leg 209 was performed from May to July, 2004 at Mid Atlantic Ridge 14N -16N. The precruise site survey studies performed by Alvine and Shinkai 6500submersibles indicated the existence of fresh mantle peridotites for the drilling sites.However, the recovered rocks were basalts, gabbroic rocks and peridotites few of whichwere unaltered. Natural remanent magnetization (NRM) intensities calculated from ODPLeg 209 gabbroic rocks and peridotites indicated very large variations from 0.001 A/m to50 A/m. Many of the rocks recovered were observed to have drilling-induced remanentmagnetizations (DIRM). The DIRM was in general easily removed by alternating field(AF) demagnetization up to 20mT, so for most of the rocks recovered, it was possible todetermine stable characteristic remanent magnetization vector directions. The DIRMwhich was unstable against AF demagnetization showed nearly vertical direction(downward). In many cases, the DIRMs possess more than 90 percent of NRMs of therocks recovered. The existence of the DIRM in the rocks recovered made it difficult toobtain original natunal remanent magnetization intensities not altered by drilling. So caremust be taken in considering in-situ magnetization of ODP Leg 209 gabbroic rocks andperidotites before recovered from the sea-floor, specially as remanent magnetizationsource for overlying sea-floor spreading magnetic anomalies, though some of the ODPLeg 209 gabbroic rocks and peridotites that were not affected by DIRM indicatedreasonably high magnetization of 1 - 2 A/m to contribute to lineated marine magneticanomalies . Similar DIRMs have been found to exist among gabbroic rocks andperidotites recovered during Legs 118, 147, and 176. Non-magnetic drilling toolsincluding drill pipes, core barrels, BHA and so on would be essential to further studiesfor magnetizations for deep ocean crustal rcoks and mantle peridotites that containrelatively coarse grain magnetites easily affected by DIRM of essentially isothermalremanent magnetization (IRM) origin. DE: HR:

10:55h AN: V22A-03 INVITED TI: An ocean floor prospecting: Implications from thepetrological insights of the abyssal chromitites from ODP Leg 209,MAR 15 20 N FZ AU: * Abe, N EM AB: ODP Leg 209 performed to drill mantle peridotites and associated gabbroic rocks(at 8 Sites, 19 holes) along the Mid- Atlantic Ridge (MAR) from 14 to 16 N, both sides of15 20 N FZ. Several podiform chromitites were recovered at Site 1271, both Hole 1271Aand B, south of 15 20 N FZ during the cruise. These chromitites are the first sampledfrom the Mid-Atlantic Ridge. The primary chromites in the chromitites have moderatelyhigh-Cr# (0.52 and 0.48 for Hole 1271A and 1272B, respectively) and chromian spinelsin the surrounding chromitites have similar composition. It is considered that podiformchromitite is formed by two kind of melt (melt-mantle interaction, therefore there shouldbe plenty volume of melt in the mantle beneath this area. Abundant of gabbro and dunitewere recovered from this area suggest that main volume of melt body were consumed inthe upper mantle by melt-wallrock interaction. On the other hand, chromite grains havethick rims of Cr-magnetite or completely replaced by magnetite without chromite core.Cr content elevation in the Cr-magnetite rim occurred with Fe-enrichment. Thesechemical modifications suggest that the chromitite from Site 1271 were metamorphosedat amphibolite facies because significant Al-missing from chromite cores is taken placeabove 550 degree Celsius. DE

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08:50h AN: V21C-04 TI: Tephrochronology of North Pacific Volcanic Arcs - data fromODP Leg 145 AU: * Prueher, L

AB: Volcanic ash layers in deep-sea sediment from the North Pacific provide a record ofvolcanism in North Pacific Island Arcs. 450 ash layers were counted in deep-sea coresfrom the Ocean Drilling Project Sites 882, 883, and 887, in order to determine frequencyof eruption, ash thickness, episodes of regional volcanism, and the impact of multipleeruptions on the intensification of Northern Hemisphere Glaciation. Episodes ofexplosive volcanism occurred approximately at 0.2-0.5, 1.5-1.7, and 2.5-2.65 Ma in theKamchatka-Kurile volcanic arc, and 0.15-.4, 1.5-1.7, and 2.55-2.65 Ma in the easternAleutian volcanic arc. Aeolian mineral grains and volcanic glass were removed from thedeep-sea sediments using a method developed at the University of Michigan. A newmethod of heavy-liquid separation was developed to separate volcanic glass fromterrestrial mineral grains. The glass was isolated in order to calculate the flux of volcanicglass in order to quantify the climatic impact of the eruptions. The amount of volcanicglass in the sediments between visible ash layers was measured and used as a proxy forsulfate aerosols in the atmosphere. Eruption ages were determined by magnetic reversalstratigraphy. Argon-argon geochronology will be used to compare the ages and to furthertest the usefulness of the argon-argon method for determining the age of volcanic glass. DE HR:

08:20h AN: V21C-02 TI: Terrestrial-marine Correlation of the 24 kyr BP DawsonTephra: Implications for Dispersal and Preservation of AlaskanTephra Deposits AU: * Beget, J et al. EM AB: The Dawson tephra, radiocarbon-dated to ca. 24,000 yr BP, is as much as 50 cmthick in Pleistocene sediments in Yukon Territory of Canada, but is not found in nearbyparts of Alaska. Nonetheless, the geochemical characteristics of the tephra suggestedderivation from an Aleutian arc volcano (Westgate et al., 2000). Its source was unknownuntil proximal deposits were recognized at Emmons Lake Volcanic Center (ELVC) onthe Alaska Peninsula (Mangan et al., 2003). We have identified Dawson tephra in ODPcore 880B, collected in the Northeast Pacific Ocean. The Dawson tephra also occurs indiscontinuous small pods in two new localities near Fairbanks in central Alaska. Our datasuggest the Dawson tephra was dispersed from the ELVC principally to the southeastover the North Pacific , and then carried to the northeast by high altitude winds.Reconstructions of the volume and distribution of individual tephras or of arc-wideexplosive volcanism in Alaska must incorporate data from proximal and distal terrestriallocalities, as well as marine cores.

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11:40h AN: V22A-06 TI: Upper Mantle Geochemistry at Peridotites of Site 1274 (ODPLeg 209): Relation to Melt-Rock Reaction and Processes at theBase of the Lithosphere AU: * Suhr, G and Paulick, H EM AB: ODP Leg 209, Site 1274, has penetrated 156 m of upper mantle rocks plus minorgabbro intrusives north of 15\deg20' N Fracture Zone at the Mid Atlantic Ridge. Thecore has an unusually high amount of dunite (21%) and contains an unusual suite of opx-depleted harzburgites and dunites between 70 and 90 m depth. Between 0 and 70 mdepth, harzburgites are chemically highly depleted (Cr\# in spinel 37 to 52, TiO2 in cpx$<$ 0.07% with negative correlation to Cr\#). The chemistry of these harzburgitesappears to preserve evidence for progressive melt extraction. A section of 3 m duniteoccurring within this interval largely shares the depleted chemical signature, thoughTiO2, Na2O and REE in cpx are somewhat elevated relative to the local host rocks. In theinterval between 70 and 90 m depth, Cr\# are 45-57 and cpx is enriched in TiO2 (0.09 to0.24%) and Na2O (up to 1%). Microstructural evidence for melt-rock reaction (e.g. cpxrims on opx) is pervasive throughout the core. The pristine preservation of thesemicrostructures argues for efficient freezing during a rapid uplift. The percolating meltsappear derived relatively locally because chemical indicators for foreign melts are weak.In the interval between 70 and 90 m, melt infiltration from a more remote source issuggested by the presence of strong reactive tendencies (opx depleted peridotites anddunites) and a more enriched chemical signature in all rocks. Probably, the opx-depletedrocks formed when focused melt channels failed near the lithosphere-asthenosphereboundary. In the upper part of the core, the depleted chemical signature of the dunite isinterpreted as derived by melt extraction from the host into the dunite at a late stage,perhaps triggered by a fracture in the overlying lithosphere. Since locally generated meltsare only weakly reactive towards opx, the formation of the dunite itself (by dissolution ofopx from harzburgite) cannot be explained by locally generated melt. Instead, the earlypassage of more reactive melts derived from larger depth seems likely. Chemical clues tothe former passage of different melts in this dunite are the occurrence of an enriched cpxinclusion in spinel in dunite and preliminary data suggesting that the internal part of thedunite may record the passage of a melt with a more radiogenic Os signatures than thehighly unradiogenic harzburgites and marginal dunites. It thus appears that meltinfiltration and extraction can occur in close proximity, depending on the local physicalproperties of the lithosphere-asthenosphere boundary. DE

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1340h AN: V13B-1480 TI: The Hf-Nd isotopic diversity of subducting oceanic sediments AU: * Vervoort, J et al. EM AB: We report Lu-Hf and Sm-Nd isotopic data for sediments from several DSDP andODP sites from the Atlantic (South Sandwich, ODP 801), Indian (Nicobar Fan, DSDP211) and Pacific Oceans (Aleutian site 183; W. Alaskan abyssal plain, DSDP 178;Astoria Fan, DSDP 174; Central America, DSDP 495, ODP 844; S. American, DSDP321; Tonga, 595/6; Marianas, DSDP 801; Phillippines/Ryuku, DSDP 291, 294/295).These sediments span the compositional variation that exists in the ocean basins and thatare actively being transported to subduction zones on the present-day Earth. Thecompositions of these sediments lie between three end-member groups. One group ofsediments (Central America; Aleutians) has radiogenic Hf and Nd isotopic compositions($\epsilon$$_{Hf}$ =$^{+}$10; $\epsilon$$_{Nd}$ =$^{+}$5) that are largelycontrolled by ash inputs from proximal volcanic arcs. A second group of sediments(Astoria and Nicobar fans) has very unradiogenic Hf and Nd isotopic compositions($\epsilon$$_{Hf}$ =$^{-}$20; $\epsilon$$_{Nd}$ =$^{-}$15) that reflect theirderivation from mature continental crust. Both these end-members, and intermediatecompositions between them, lie within the crust-mantle Hf-Nd array and have Lu/Hf andSm/Nd ratios typical of crustal rocks. This variation in isotopic composition mirrors to alarge extent the range that exists in continental sediments. The third end-member groupof sediments, composed of slowly accumulating metalliferous clays, is highly anomalousin terms of both its trace element and isotopic composition. These pelagic clays are thedominant components of the Tonga and Ryuku sites and are also important in thePhilippine site and, locally, the Marianas site. The clays are highly enriched in REEs(many with Nd concentrations 100 to 400 ppm), but have average concentrations of Hf.This results in extremely high, superchondritic Lu/Hf ratios ($^{176}$Lu/$^{177}$Hf upto 0.18), but Sm/Nd ratios that are typically subchondritic. In addition, nearly all of thesesediments have anomalously radiogenic Hf compared to Nd ($\epsilon$$_{Hf}$=$^{+}$10 to $^{+}$15; $\epsilon$$_{Nd}$ =$^{-}$5), which causes them to plotdistinctly above the crust-mantle array. In summary, there is a wide range of isotopiccompositions being delivered to subduction zones that is a function of the diversity ofsediment types in the world's oceans. Although the REE rich pelagic clays have uniqueHf-Nd isotopic compositions, their restricted global distribution will limit theirwidespread application as an isotopic tracer. DE

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11:25h AN: V22A-05 TI: Geochemical Study of Mid Atlantic Ridge Peridotites From15\deg N: Preliminary Results From ODP Sites 1272 and 1274 AU: * Godard, M et al. EM AB: During ODP Leg 209, eight sites were drilled along the Mid-Atlantic Ridge from14\deg43 to 15\deg44 N, allowing recovery of ca. 354 meters of residual mantleperidotite intruded by gabbroic rocks (up to 25% of recovered samples). We present herethe results of a whole rock major and trace element study of 28 peridotites selectedamong the less altered samples (those which preserved enough primary features to allowdetailed petrographic and mineralogical studies), at Site 1272 and Site 1274 (respectivelyS and N of the 15\deg20 fault zone). Site 1272 and Site 1274 peridotites are mainlyharzburgites (cpx $<$ 5%) with a few dunites. Harzburgites are characterized by highlyvariable opx contents (10-30 vol.%). Some samples show evidence of trapped melt (up to3-5%). A few samples at Site 1274 show textural evidence of abundant cpxcrystallization, resulting in the formation of lherzolites. All studied peridotites have beenmodified by alteration ($>$70% serpentinisation), leading to the addition of significantamounts of volatiles (loss on ignition $>$10 wt%). Nevertheless, except for alkali-earthelements and U, major and trace element compositions show no evidence of additionalcompositional changes during alteration. Site 1272 and Site 1274 peridotites arecharacterized by high Mg# (100 x molar Mg/[Mg + Fe]) (90.3- 92.2) and lowAl$_{2}$O$_{3}$ contents ($<$0.3 wt% in dunites and ranging from 0.6 to 0.9% inharzburgites). Site 1272 and Site 1274 peridotites display flat to light Rare Earth Element(REE) depleted patterns (harzburgites : Ce$_{N}$$<$0.015; Yb$_{N}$$<$0.26 - dunites: Ce$_{N}$$<$0.001; Yb$_{N}$$<$0.04-0.08- $_{N}$: chondrite normalised). Themost depleted harzburgites are observed at the southernmost Site 1272(Ce$_{N}$$<$0.003; Yb$_{N}$: 0.045-0.1). REE allow to distinguish two harzburgitesgroups at Site 1274. The first one shows patterns similar to those of Site 1272 peridotitesyet with slightly higher REE content (Ce$_{N}$: 0.0015-0.015; Yb$_{N}$: 0.14-0.26).The second displays on average lower heavy REE contents (Yb$_{N}$: 0.1-0.18) andmore variable light REE contents (Ce$_{N}$: $<$0.002-0.05). These samples are foundat the bottom of Hole 1274A where cpx display the highest Na- and Ti contents amongthe studied peridotite suite. Site 1272 and Site 1274 peridotites composition is similar tothat of the most depleted peridotites sampled in ophiolites (e.g., Oman, Cuba) and inoceans (e.g., Izu-Bonin-Marianna). They represent the most refractory peridotites yetsampled at a slow-spreading ridge. DE AN:

V31B-1435 TI: Gabbro fracturing and elemental analysis in the Costa Ricamargin (ODP Leg 205): Core-log integrated high-resolution study AU: * Thu, M et al. EM AB: Costa Rica margin is an important area for studies of the seismogenic zone andsubduction factory. Building on Ocean Drilling Program (ODP) Leg 170 coring andlogging while drilling (LWD) at the same sites, Leg 205 drilled three sites to determinethe igneous and alteration history of the upper most part of the down going plate, tocharacterize the hydrological regime above and within the decollement, and successfullyinstalled long-term borehole observatories to monitor downhole pressure and temperatureand sample fluids and gases. Among the several highlights from the results, coring andlogging of thick gabbro zone at Site 1253 was significant to detail the fracturedistribution, structure and nature of oceanic crust through core-log data integration. Eventhought logging runs in the sediment section was failed due to the hole conditions, triplecombination and FMS-sonic tool strings made successful measurements. Post-cruiseresearch work included quality control on several wireline logs and processing ofFormation MicroScanner (FMS), and interpreting these logging data and core sampleanalysis results in integrated manner. Among several downhole logging results, FMSimages are used to characterize structure and fabric in the igneous units. As the holeconditions were good in most of the igneous intervals, the textural and structural variationis clear between the sections and also shows differences within the section itself.Moreover, mineralogic results from the recovered cores are combined with logging datathrough level-by-level multi-mineral evaluation with an optimized simultaneous equationsolver and model combining method. Due to the good logging results and simple mineralcomposition of the single rock type, the results from the process filled mineral percentageof the no core recovery depths as well. High-resolution core-log integration in this studyenhanced the understanding of structural process and nature of the oceanic crust of thisparticular region. DE: HR:

1340h AN: V13B-1471 TI: Characterizing Sedimentary Carbon and NitrogenSubduction Fluxes in the Central America Convergent Margin(ODP Legs 170, 205) AU: * Li, L and Bebout, G E EM AB: We present new data regarding the C and N contents and isotope ratios of thesubducting calcareous sediments from the lower section (U3) of Site 1039 and the siltysediments from the accreted section sampled by Sites 1040, 1254, and 1255. Sediments inthe calcareous section contain 62 to 866 ppm N with $\delta$$^{15}$N$_{Air}$ of 2.4to 8.5 per mil and 0.09 to 0.73 wt.% TOC with $\delta$$^{13}$C$_{PDB}$ of -25.4 to -21.4 per mil. Integrating the upper diatomaceous ooze section (U1) and the silty claysection (U2) [Li et al., 2003], the subducting sediments along the 1100-km CentralAmerican convergent margin could carry inventories of 1.3\times10$^{10}$ g/yr N withaverage $\delta$$^{15}$N$_{Air}$ of 5.7 per mil, 1.4\times10$^{11}$ g/yr TOC withaverage $\delta$$^{13}$C$_{PDB}$ of -22.0 per mil and 1.5\times10$^{12}$ g/yroxidized C with average $\delta$$^{13}$C$_{PDB}$ of 1.9 per mil. Sediments at Sites1040, 1254 and 1255 contain 832 to 2398 ppm N with $\delta$$^{15}$N$_{Air}$ of 3.6to 6.6 per mil, 0.85 to 3.06 wt.% TOC with $\delta$$^{13}$C$_{PDB}$ of -26.6 to -21.1 per mil, and $<$4 wt.% CaCO$_{3}$ with $\delta$$^{13}$C$_{PDB}$ of -26.1 to4.1 per mil and $\delta$$^{18}$O$_{VSMOW}$ of 30.0 to 36.4 per mil. No obviouschanges in N, TOC and carbonate contents and isotope concentrations are observed insediments in and near the fault zones and the d\'{e}collement, indicating that fluid flow inthe Central American convergent margin had a minimal effect on the TOC and Nconcentrations and isotopic compositions of the sediments. However, the impact of fluidprocesses on the sediment geochemistry could be indicated by extreme $^{13}$C-depletion in minor carbonate in the sediments; this depletion could have been producedbiogenetically by incorporation of methane C. Regarding the mass-balance across theCentral American subduction zone, if the C and N loss in sediments due to fluidprocesses and early devolatilization is not significant, the large amount of subducting Cand N (even without considering the potentially comparable C and N inputs in alteredoceanic crust and tectonically eroded material), relative to the smaller output fluxes in arcvolcanic gases, indicates significant transfer to the deep earth, likely affecting the C andN isotopic characteristics of the mantle. DE

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17:30h AN: V54B-07 TI: Deep Marine Sediment Diagenesis of Germanium, Silica,Lithium and Lithium Isotopes in ODP-177: The "Missing OceanicGe Sink" AU: * Froelich, P and King, S L EM AB: Understanding sediment diagenetic alterations of the crustal Ge/Si ratio is importantas a clue to identifying the phases and processes responsible for burying the "missing"portion of the input Ge-flux (rivers and MOR vents) that can not be ascribed to diatomGe/Si burial. In the ocean, in diatoms, and in most low-temperature biogeochemicalprocesses, Ge behaves much like a trace cogenor of Si, substituting for Si and displayingGe/Si ratios that don't deviate much from crustal (10-6 mol/mol). Significantfractionation of the ratio is now recognized for continental weathering processes andhydrothermal basalt reactions. During early diagenesis in the shallow suboxic zone ofmarine sediments, where non-silicate phases may dominate Ge-cycling (e.g., FeOOH),pore water [Ge] also reflects uptake into authigenic phases but seldom exceeds severalhundred picomolar (10-12 Molar). In this paper we present the first deep pore water Gedata from Sub-Antarctic South Atlantic Sites drilled during ODP Leg 177 across theSouthern Ocean biosiliceous ooze belt. In all sites (ODP 1088-1094), pore water Gedisplays steep gradients and maxima and minima that are unrelated to opal diagenesis.Deep maxima Ge-concentrations approach 120 nM, 1000-fold higher than seawater (0.1nM). The shapes of these profiles require local diagenetic sources and sinks for Ge thatare very large, and both upward and downward fluxes that far exceed those estimated forlocal Ge-burial in diatomaceous opal. Thus there must be other non-biosiliceous phasesthat carry Ge to the seafloor that are activated during deep burial diagenesis. Temperaturedoes not seem to be a factor: deep borehole temperatures do not exceed 46-deg C. So farwe have been unable to identify these reactive phases, although we suspect somecombination of chert formation and clay alteration as likely culprits. In contrast, Siprofiles are featureless, exhibiting near-zero Si gradients over most intervals, with Sitypical of opal saturation (1-2 mM) diluted by opal/detrital sediment ratio. Pore waterlithium [Li] and del-7Li display both uptake and release profiles related toaluminosilicate clay formation and destruction. Del-7Li varies from +5 to minus 25 permil (ref seawater), while [Li] varies from sligtly below seawater values (25 uM) to about250 uM. The downcore data are consistent with release of Li from clay minerals carryinglight (7Li depleted) cations. These Li and Li-isotope data are internally consistent, but donot shed any light on the diagenetic processes affecting deep Ge diagenesis. DE HR:

17:45h AN: V34B-08 INVITED TI: Hawaiian Hotspot - Spreading Ridge Interaction in the LateCretaceous: A Fair and Balanced Look at the Evidence AU: * Keller, R EM AB: As is so often the case in years divisible by 4, reality turns out to be quite differentfrom reputation. The Hawaiian hotspot, often righteously promoted as the hotspot that therest should strive to emulate, was not as stable nor as free from interactions with plateboundaries as some supporters suggest. Mounting geochemical and geophysical evidenceshows that in its youth the hotspot not only inhaled, but probably snorted and did shots aswell. The purpose of this presentation is to summarize what we know about the LateCretaceous interaction between a spreading ridge and the Hawaiian hotspot from recentwork on the Emperor Seamount chain. At the time of this writing, facts are a commodityto be fabricated, deleted, spun, denied, and denied-that-you-denied; but by the time ofthis presentation, we (hopefully) will be looking toward the future: can the Hawaiianhotspot's checkered past be treated as a bonus rather than a burden? Plate reconstructionsof the Late Cretaceous northwest Pacific place a seafloor spreading center very close to,or even directly on top of, the Hawaiian hotspot. The geochemical effects of this hotspot-ridge interaction are now well documented by work on Ocean Drilling Program samplesfrom Detroit Seamount, the next-to-oldest remaining Emperor Seamount. Basaltsrecovered from ODP Site 883 partway up the east side of Detroit Seamount have traceelement and isotopic characteristics more akin to MORB than to Hawaiian Islandsbasalts. Basalts from ODP Site 884 at the eastern foot of the seamount are highlydepleted tholeiites unlike anything else found so far in the Hawaiian-Emperor chain(Keller et al. 2000, {\it Nature}). Their trace element and radiogenic isotope values areessentially indistinguishable from MORB values (Keller et al. 2000), although triple-spike Pb isotope data are distinct from modern EPR MORB data (Regelous et al. 2003,{\it J. Pet.}). These characteristics were the result of the hotspot melting a greaterproportion of a depleted mantle component, whether entrained from the surroundingupper mantle (Keller et al. 2000) or intrinsic to the plume (Regelous et al. 2003), while itwas close to the spreading center. The Site 884 basalts are surprisingly old (81 Ma; Kelleret al. 1995, {\it Leg 145 Sci. Results}) in comparison to recent results for Site 1203basalts from near Site 883 (76 Ma; Duncan and Keller 2004, {\it G-cubed}). The uniquecomposition and surprisingly old age of the Site 884 basalts could be due to the fact thatwe have not drilled a similar location deep on the flank of another Hawaiian hotspotisland or seamount. However, my preferred explanation is that the temporal and spatialdistribution of hotspot volcanism was also influenced by the nearby spreading center. Amodern analog for Detroit Seamount may be a complex seamount platform similar to theGal\`{a}pagos hotspot-ridge system. DE HR:

14:55h AN: V53B-06 TI: Thallium Isotope Constraints on Hydrothermal Water Fluxesat Mid-Ocean Ridge Axes and Flanks AU: * Rehkamper, M et al. EM AB: The hydrothermal circulation that occurs at mid-ocean ridge axes and flanks hasprofound effects on the chemical budgets of the oceans but our understanding of therelevant fluxes is incomplete. Here, we use new thallium (Tl) isotope and concentrationdata for hydrothermal fluids and rocks from ODP Hole 504B to obtain independentestimates of the high- and low-temperature (T) hydrothermal water fluxes at spreadingaxes and ridge flanks. Seawater is characterized by relatively uniform Tl isotopecompositions and concentrations of $\epsilon^{205}Tl$ = -6 and 65 pmol/kg,respectively ($\epsilon^{205}Tl$ represents the deviation of the $^{205}Tl/^{203}Tl$ratio of a sample from the standard in parts per 10,000). In contrast, high-T hydrothermalfluids from ridges axes display $\epsilon^{205}Tl = -2\pm1$, indistinguishable fromunaltered mantle rocks. The correlation of Tl and Cl abundances indicates an average Tlcontent of 10-25 nmol/kg for high-T endmember fluids. The low-T alteration of the uppervolcanic zone of ODP Hole 504B is associated with Tl-uptake from seawater. Theisotope fractionation that occurs during the uptake generates Tl-rich rocks that have$\epsilon^{205}Tl$ as low as -16. The sheeted dike complex displays low Tl contentsdue to leaching of the rocks by high-T hydrothermal fluids. Taken together, theseobservations indicate that high-T vent fluids do not acquire significant Tl from the alteredTl-rich rocks of the volcanic section. With this constraint, the high-T axial water flux canbe calculated, assuming that Tl is leached with an efficiency of $60-95%$ from 1.0-1.4km of sheeted dikes and upper gabbros, which have a Tl concentration of $3\pm1$ ppb.These parameters yield a high-T water flux of 0.2-2.5 x $10^{13}$ kg/yr, equivalent to aheat flux of 0.1 to 1.2 TW. This result is in excellent agreement with other geochemicalestimates of high-T water fluxes, e.g., those based on Li isotopes (Chan et al., 2002) orthe Sr isotope profile of ODP Hole 504B (Teagle et al., 2003). If the total axialhydrothermal power output is about 2 TW, the geochemical data indicate that at leastsome heat loss at mid-ocean ridges is due to diffuse low-T fluid flow. The Tl dataacquired for off-axis fluids and the volcanic zone rocks are in accord with significant($30-80%$) losses of Tl from circulating seawater. If it is assumed that 15-35 ppb of Tlare added to the top 600 m of ocean crust, the low-T water flux of ridge flanks can becalculated as 1-5 x $10^{16}$ kg/yr, which is equivalent to an average fluid exittemperature of about $3-10\deg$C. This result is in accord with a recent Mg-basedestimate (Mottl, 2003), which indicates that about $90-98%$ of the ridge flank poweroutput occurs at cool sites with fluid temperatures of less than $20\deg$C. DE HR:

1340h AN: V23B-0626 TI: Lithium and strontium isotope compositions of serpentinite-hosted carbonate veins from the MAR (ODP Leg 209): Records ofdifferent stages of seafloor metamorphism AU: * Rosner, M et al. EM AB: Geochemical investigations of carbonate veins hosted in serpentinized peridotitesdrilled from the Mid-Atlantic Ridge 14$\deg$-16$\deg$N (ODP Leg 209) wereconducted to gain insights into temperature and composition of the alteration fluids fromwhich carbonates were precipitated. We have examined carbonate veins that can begrouped into low-T ($<$20$\deg$C) aragonite veins hosted in serpentinite, low-T calciteveins hosted in troctolitic rocks, and high-T (90-220$\deg$C) calcite veins hosted in talc-serpentine schists. The geochemical and radiometric characteristics of these veins ispresented in a companion paper (Bach, Paulick, and Rosner) in this session. Here wereport on Li and Sr isotope compositions and their relations to age, temperature, and traceelement composition. Strontium isotope compositions are similar to, or slightly lowerthan that of modern seawater. This is consistent with young radiocarbon ages ($<$55kyrs) and limited Sr exchange between circulating seawater and basement at lowtemperatures.$\delta$$^{7}$Li values (relative to L-SVEC) of the majority of aragonitesamples range between 14 and 20 $\permil$. At sites 1271 and 1274 on rift valley wallsof inside corner highs north and south of the 15$\deg$20N fracture zone, the$\delta$$^{7}$Li values of aragonites increase systematically with depth. At site 1274.$\delta$$^{7}$Li shows a weak positive correlation with 14-C formation ages. Ourpreliminary interpretation of the Li isotope data is a decrease in the Li isotopefractionation factor as temperatures increase with increasing basement depth. Thisinterpretation would require a fractionation factor at 2$\deg$C of about 1.016 -significantly larger than $\alpha$ =1.011 proposed for biogenic aragonite formation at25$\deg$C. The large fractionation observed in the upper part of the drilled cores couldbe due to lower temperature, different precipitation kinetics, variations in fluid chemistry(e.g., strongly variable Mg/Ca), or combination of these effects. Calcite veins from Sites1271 and 1275 display at least two compositional groups. Low T calcites range$\delta$$^{7}$Li from 22 to 27 $\permil$ and precipitated at T$<$20$\deg$C from afluid with seawater-like Sr isotope composition. Three high-T calcite veins record anearlier and deeper stage of metamorphism associated with detachment faulting.$\delta$$^{7}$Li values between 3 and 8 $\permil$ correlate with Sr isotope ratios (aslow as 87Sr/86Sr=0.70385) and indicate a prominent contribution of Li and Sr leachedfrom the peridotite basement. DE HR:

1340h AN: V23B-0627 TI: Extensional Faulting at 15\deg North on the Mid-AtlanticRidge, ODP Leg 209 AU: * Schroeder, T et al. EM AB: At slow spreading ridges, oceanic mantle can be uplifted and brought to the seafloorby extensional faulting, but the style of faulting and mechanisms by which this occursremain poorly understood. We present data from faults observed in mantle peridotite andgabbro intrusions drilled at six sites on the Mid-Atlantic Ridge near the 15\deg20'Fracture Zone during ODP Leg 209. The data reveal that faulting and significant tectonicrotation can take place either via long-lived (detachment?) faults that are active throughductile and brittle regimes, or via successive series of short-lived (domino) faults. Werecognize three styles of faults: a) High-temperature, mylonitic shear zones at Sites 1268,1272 and 1274 that are overprinted by dominantly static greenschist facies alteration.These textures indicate that ductile faults were active at depth and later became inactiveduring denudation and are cut by brittle faults at shallow lithospheric levels. b) Brittleand semi-brittle faults that do not directly overprint ductile shear zones. These includepartially- to non-cohesive serpentine mud fault gouge in zones ranging from 10 cm toseveral meters thick (Sites 1268, 1272 and 1274), and cohesive cataclasites andtalc/tremolite schists (Site 1275). c) Ductile to brittle faults in peridotites from Sites 1270and 1271. Strain in the peridotites at both sites appears to have been initially localizedinto gabbroic veins and dikes at granulite facies, and remained localized in these zones tosub-greenschist facies during long-lived faulting and denudation of peridotite. There is noapparent correlation between the faulting style and seafloor bathymetry. For example,bathymetry of Sites 1270 and 1275 indicate the presence of a detachment fault (oceaniccore complex), yet 1270 displays type c faults and 1275 displays type b faults. Peridotiteand gabbro from all six sites experienced significant tectonic rotation (50ø to 90ø) asinterpreted from the inclination of the remnant magnetization vector (assuming horizontalaxis rotations). This result is consistent with both rotation via long-lived (detachment)faulting, and/or multiple short-lived fault bounded domino systems. Variability infaulting styles and seafloor morphology along with significant tectonic rotations indicatethat highly complex faulting may be typical at slow-spreading ridges. DE: HR:

16:15h AN: V54A-02 TI: Pb and Other Trace Elements in Melt Inclusions FromModern Seafloor Tectonic Settings AU: * Beaudoin, Y et al. EM AB: Evidence for the contribution of magmatic metal-bearing fluids to modern seafloorhydrothermal systems has been presented for key ore metals such as Cu, Zn, Au and Agbut not for Pb. The source of Pb in these systems can be attributed to leaching of hostrocks by hydrothermal fluids and/or potentially by direct degassing of magma. Wepresent data from 103 melt inclusions mainly in plagioclase crystals hosted in basaltic torhyolitic lavas from 9 modern seafloor tectonic settings: oceanic back-arcs (Manus Basinincluding an ODP Leg 193 drill hole, Bransfield Straits), continental back-arc (OkinawaTrough), mid-ocean ridges (Explorer, MAR), seamounts (Foundation, Axial, Pito), and atransform (Garrett). Most sites host active hydrothermal systems that are producingpolymetallic sulfides. Inclusions were analyzed for Pb and other trace elements by LA-ICP-MS at ETH Zurich. Although inclusion trace element compositions vary betweentectonic settings, for a given setting variability between different volcanic sequences islow and follows a general mafic to felsic fractionation trend. N-MORB compositionsdominate most inclusion populations with exceptions seen at Explorer (plume-ridgeinteraction), Garrett (near-ultramafic source) and in some Foundation samples(seamounts affected by ridge interaction). Results show high Pb concentrations ininclusions from oceanic back arc and continental back-arc settings coinciding withevolved volcanic chemistries and related in the latter to contamination from sediments orcontinental crust. Sulfide deposits in these back-arcs are also Pb-rich. Inclusions fromprimitive basalt and near-ultramafic hosted samples from MOR, intraplate seamounts andtransforms have low Pb abundances. In the most Pb abundant settings, melt inclusionshave Pb concentrations 1-3 times higher than that of the bulk rock or volcanic glassindicating possible Pb removal from the magma prior to eruption. This loss may beexplained by direct degassing of the magma into the hydrothermal circulation. Exceptionsto the behavior of Pb in the studied settings include: elevated Pb in inclusions hosted inprimitive basalts TAG (MAR) and some samples from the Okinawa Trough showinglow Pb with respect to bulk rock. DE HR:

16:30h AN: V34B-03 TI: Plume-Ridge Interaction on the Cocos Plate (ODP Leg 205,Costa Rica): Implication for Fluid Circulation AU: * Chavagnac, V et al. EM: AB: At subduction zone, the permeability and hydrology of the down-going igneoussection play a key role on the behaviour of the seismogenic zone, which producesearthquake and tsunamis. We present, here, evidence of fluid circulation pathways in theigneous section being subducted at the Central American convergent margin (Site 1253ODP Leg 205, Costa Rica). The geological evolution of the Cocos plate over the last 25Ma is complicated as a result of plate boundaries re-arrangement (Silver et al., 1998).The Cocos-Nazca spreading centre (CNS) interacted with the Galapagos hotspot, whichsimultaneously deposited volcanic material on both side of the CNS, on the Cocos andNazca plates. The oceanic crust of the Cocos and Nazca plates was formed along fourspreading centres (Meschede et al., 1998) and the East Pacific Rise (EPR). The EPRoceanic crust has the featureless morphology and low-amplitude magnetic anomaliescommon to fast spreading ridge (Wilson & Hey, 1995) while the CNS oceanic crustpresents a rough topography and high-amplitude magnetic anomalies (Wilson & Hey,1995). We wish to focus on the ODP 1253 Site drilled in the Cocos plate because itsamples the igneous input (rock, heat and fluid) to the Central American subduction zone.Coring at Site 1253 penetrated two separate igneous Units of which the upper one is a sill(Unit 4A) separated from the lower Unit (Unit 4B) by sediment. Both Unit 4A and 4Bpresent similar texture, structure and mineralogy apart from the thin basaltic interval at513 mbsf, below which Unit 4B becomes more glass-rich and altered. Unit 4B is either asill complex with multiple intrusions related to the Galapagos volcanic activity or a seriesof thick slowly cooled lava flows formed at the EPR. Some of these characteristics ofUnit 4B are similar to those seen in horizons recovered at Site 1256, which intersectedthick-ponded lava flows. Analyses of marine magnetic anomalies indicate that the crust atSite 1253 was formed at EPR 25 Ma ago. However, its thermal gradients andconductivity yield surface heat flow anomalies of 10-40 mW\/m$^{2}$, which is$\sim$70% lower than normal cooling lithosphere of that age (Fisher et al., 2003). Off-axis magmatic and tectonic activity associated with the formation of the Cocos Ridgemay have increased fluid circulation pathways within the basement structure. Mobiletrace element (Ba, Sr) and Sr isotope variations in conjunction with petrographicobservation help identify horizons of fluid/rock interaction, e.g. fluid circulationpathways within Unit 4A and 4B. Based on veins, fractures, and void occurrences, theUnit 4A and 4B were subdivided into two and seven subunits respectively. Along thecore-depth profile, mobile element concentrations and $^{87}$Sr/$^{86}$Sr ratios varymainly in a narrow range (0.703245 and 0.703503) but are still higher than those of EPRor the Galapagos hotspot ($<$0.703). At sub-unit interface, we observe drastic increasesin Ba and Sr content and more radiogenic Sr isotope signature (up to 0.705106),especially above the thin basaltic horizon. This reflects exchange of Sr with seawater orhydrothermal fluids during alteration. Further work will determine fluid flux estimate atSite 1253. The origin, nature and structure of the oceanic crust at Site 1253 will bepresented in two additional abstracts (see Dreyer and Moe, this session).

DE: Subducting Crust Offshore Costa Rica: Constraints From Major,Trace Element, and Isotopic Data From ODP Legs 170 and 205

* Dreyer, B et al.

Enriched gabbro sills ($\sim$30m) intruded into post-16Ma sediments and deepermedium-grained gabbros to cryptocrystalline basalts ($>$150m) were cored on ODPLegs 170 and 205 (9\deg39$\prime$N, 86\deg11$\prime$W) on the Cocos plate nearCosta Rica. Magnetic anomalies indicate that the basement is EPR lithosphere(Barckhausen et al, 2001). The units studied here may be related to overprinting by theGalapagos hotspot, consistent with the site's paleolocation. The rocks are low- tomedium-K (K$_{2}$0 $<$0.44wt$%$) subalkaline tholeiities with SiO$_{2}$ 46-50wt$%$ and Mg$\#$ 0.44-0.60, similar to Leg 206. Major and minor element variationsare consistent with previous fractional crystallization of olivine, plagioclase, Fe-Tioxides, $\pm$augite; discrete alteration is 1-5vol$%$. The small ranges in major andcompatible elements largely reflect phase equilibria control, rather than sourcedifferences. However variations in incompatible trace element ratios are best interpretedin terms of two distinct magma batches with slightly different mantle sources. On a plotof Sr-Nd isotopes, Leg 205 samples ($^{143}$Nd/$^{144}$Nd= 0.512937-0.513020$\pm$8, $^{87}$Sr/$^{86}$Sr= 0.703245-0.705106 $\pm$10) overlap the range ofGalapagos Island basalts rather than EPR, except when $^{87}$Sr/$^{86}$Sr$>$0.70400. Elevated $^{87}$Sr/$^{86}$Sr is likely a result of alteration, althoughleachates have not yet been analyzed. The Nd-isotopic ratios cluster near 0.512950 (onevalue extends to 0.513020) and good correlation between the Sr-Nd isotopes of less-altered samples suggests mixing between mantle domains of variable enrichment. Rocksfrom Leg 205 record enrichment within EPR-generated lithosphere and may be the mostnortherly expressions of the Galapagos hotspot. REE patterns for Leg 170 samples form 2distinct groups, both overlapping ranges of the Galapagos Islands and regional spreadingcenters (EPR and Cocos-Nazca spreading (CNS) center). The two groups (Grp 1 LREE~60$\times$ chondrites; Grp 2 ~32$\times$, both with HREE ~16$\times$ chondrites)may correlate with depth, but their differences cannot be explained by fractionalcrystallization alone. Consideration of HFSE systematics and REE abundances suggestthat mixing between heterogeneous sources and differing degrees of partial melting arerequired to generate these two groups. On a plot of Hf/Ta vs. (La/Sm)$_{N}$, CNS andEPR lavas (Hf/Ta $>$10, (La/Sm)$_{N}$ $\sim$0.5-1.5) are well separated fromGalapagos lavas (Hf/Ta $<$5 and (La/Sm)$_{N}$ $\sim$1-2.5). Leg 170 rocks arewithin the Galapagos field, as are samples from the 14Ma Fisher Seamount SW of theODP sites. The origin of igneous units from Leg 170, and by association Leg 205, is bestexplained as 10-20$%$ degree partial melting from a mantle source $<$30$%$ enrichedcompared to regional depleted mantle. Mantle mixing between the Galapagos hotspot andthe nearby EPR and CNS ridges is recorded in off-axis volcanism offshore Costa Rica.Trace element and isotope results suggest that the spatial and geochemical influence ofthe Galapagos hotspot is more extensive than previously recognized, and may form asignificant part of the oceanic section subducting off Costa Rica, a NSF-MARGINSfocus site for studies of crustal recycling at convergent margins.

HR: 0800h AN: V31A-1418 TI: Evidence for Extremely Large Lava Flows on Ontong JavaPlateau from High Precision Measurements of Volatiles andMajor Elements in Natural Glasses AU: * Michael, P J EM AB: Magmas of Ontong Java Plateau (OJP) display little geochemical variation, havingonly a few widely dispersed magma types (Mahoney et al. , 1993). (Here we definemagma type as all lavas that have evolved by similar extents of melting of a similarmantle source, and have undergone similar polybaric fractionation histories). In thisstudy, we use high precision microprobe measurements of Cl, K, S, H2O, CO2 and majorelements in glasses to show that magmas from widespread locations on OJP are identicalin composition and are probably from the same eruption and quite possibly from the sameseries of lava flows. By same eruption, we mean the quasi-continuous issuance of magmafrom a continuous chamber over a time period that is insufficient for furtherdifferentiation or assimilation. By same lava flow, we mean lavas that have issued fromthe same or nearby vents and were part of a sequence that that was continuously moltenat the surface or beneath a crust. Cl concentrations are controlled by assimilation thattakes place fairly late at shallow levels in the magma chamber. The amount ofassimilation and Cl content of assimilated material control Cl contents of magmas, andare expected to be highly variable in this stochastic process. It is inconceivable thatmagmas erupted at different times would have precisely the same Cl content, even if theyhave the same major element chemistry from identical cotectic evolution. The clearestcase of distant lavas being from the same eruption is the Kroenke-type lavas from ODPholes 1187A and 1185B, about 140 km apart. The lavas form roughly 150 flow units ofabout 1 meter average thickness, which we feel are multiple surges of lava from a quasi-continuous eruption. Glass compositions (major elements and volatiles) do not vary morethan analytical uncertainties within each hole. Differences between the two holes are alsoless than analytical uncertainties. Averages of 4 samples from each of the two holes are:Cl 750 vs 732 ppm; s.d.=15 ppm. S 988 vs 969 ppm; s.d.=5 ppm. K 616 vs 608 ppm;s.d.=22 ppm. Counting precision is ñ15 ppm (2 sigma) for each element in each singleglass analysis. Precision is better than accuracy. Similar CO2 contents in the glasses ofthe separate holes (Roberge et al., 2004), despite several hundred meters difference intheir current reconstructed basement depth suggests that the lavas were erupted from thesame vents and flowed for long distances: that they are not merely separate flows of alarge eruptive episode that issued from a single magma chamber that had many vents.This observation does not mean that dissolved CO2 contents cannot be used to estimatepaleoeruption depths, but that caution is required. The volume of the eruption exceedsthat of any known submarine eruption by a great deal. If its lateral dimensions are similarto the length between the holes, then its area would be >200 km2 and its volume wouldbe >3000 km3. That such widely separated lavas have identical chemistry means thatthere was virtually no cooling over 10s of km of flow. This requires an insulating layerabove a rapidly flowing magma (Gregg and Fornari, 1998). We are currently evaluating

whether other widely separated recoveries on OJP are also from single lava flows.Possible matches include 1185B (lower) and 1186A, which are about 150-200 km apart.They would indicate even larger eruptive volumes. It is possible that certain glasses from807C are the same as a thin layer in 1185B. References: Gregg and Fornari, JGR 103,27517. Mahoney et al. Proc. ODP: Sci Results 130, 3-22, 1993. Roberge et al. Geol. Soc.Lond. Spec. Pub 229, 239-257, 2004. DE HR:

1340h AN: V33E-1500 TI: Trace Element and Isotopic (Re-Os, O) Systematics of RobertsVictor Eclogites: Evidence for 3 Ga Subduction-Incorporation ofArchean Oceanic Lithosphere into the South African KaapvaalCraton Keel AU: * Shirey, S et al. EM AB: Eclogite xenoliths from the 125 Ma old, Group II, Roberts Victor kimberlite have longbeen of interest in studies of Kaapvaal craton evolution because of their diversity, abundance,availability in large size, occurrence with peridotite and their sometimes highcarbon/diamond content. From among the coesite, corundum, kyanite, Ca-, Mg-, and Fe- richeclogites available, we have chosen to work on those that can be classified as Group I, GroupII or diamondiferous with the goal to better understand their petrogenesis, the evolution ofthe Kaapvaal craton keel, the role of eclogites in diamond formation and the behavior of theRe-Os system. Group I vs Group II eclogites can be distinguished by texture (isolated gt in acpx matrix vs subhedral, interlocking gt-cpx) and mineral chemistry (higher Na$_{2}$O in gtand K$_{2}$O in cpx for GI vs lower for GII). Such differences have been thought to resultfrom higher vs lower pressures of equilibration. Recent laser fluorination oxygen isotopes(δ18O) on gt (GI = 5.8 to 6.9; GII = 2.1 to 5.1), ion-probe trace elements (e.g. Ce chondritenormalized) on gt (G1 = 0.2 to 0.5; GII = 0.002 to 0.07) and cpx (G1 = 7 to 20; GII = 0.2 to2) and whole-rock Re-Os (G1 Re = 0.19 to 3.41 ppb; GII Re = 0.006 to 0.38 ppb) highlighteven more distinct differences between Groups I and II. These differences are likely a pre-metamorphic signature of their original protoliths and not just due to pressure differences ormagmagenesis during emplacement into the lithosphere. Using the stratigraphic variation ofO isotopic composition and trace element content of ophiolites and drill core fromDSDP/ODP holes 735B and 504B as a guide, Group I eclogites might represent the volcanicrocks of Layer 2 of Archean oceanic crust whereas Group II might represent the cumulate,intrusive rocks of Layer 3. This idea is supported by the presence, only in Group II eclogites,of positive Eu anomalies in reconstructed ion-probe whole rock rare earth element patterns.The Re-Os sytematics of the oceanic lithosphere is poorly known, especially in the Archean,but Roberts Victor eclogite Re-Os and trace element abundances and major elementcompositions suggest a basaltic komatiitic protolith as might typify slightly hotter oceanridges in the Archean. A U-Pb age of 3.061$\pm$0.006 Ga on zircon grains separated from aGroup I Roberts Victor eclogite and a same-age but scattered whole-rock Re-Os isotope arraycontaining the diamondiferous and some Group I eclogites (including the zircon-bearingeclogite), firmly date the eclogite protoliths as Meso-Archean. The direct covariation of Recontent (and hence 187Re/188Os) with O isotopic composition allows the low-T alterationprocess occurring on the seafloor to be firmly dated at that time. For Kaapvaal cratonevolution, this age is interesting because it predates by about 100 Ma the terrane collision thatsutured the Kimberley block to the Eastern Kaapvaal along the Colesburg magneticlineament, the stabilization of a thickened lithospheric mantle keel, and the generation of awidely distributed suite of eclogitic diamonds. Incorporation of these eclogites in thelithosphere is further evidence for Meso-Archean plate tectonics and the role of subduction incratonization and diamond genesis.

HR: 1340h AN: V13A-1457 TI: Along Strike Hf-Nd Isotopic Composition of Aleutian ArcLavas AU: * Gerseny, M G et al. EM AB: The Aleutian Arc provides an ideal tectonic setting to study Hf-Nd systematics dueto its along-strike tectonic and geochemical variation. Sediment load and subduction ratedecrease westward along the arc with an increasingly oblique subduction angle, causing aprogressive decrease westward in the flux of sediment into the subduction zone. A suiteof samples collected across the length of the arc were analyzed for Hf and Nd isotopiccomposition. A coupled decrease in both Hf and Nd isotopic composition was observedfrom east to west along the arc. Piip seamount samples at 193\deg W have the highest$\epsilon$$_{Hf}$20.3 and $\epsilon$$_{Nd}$10.4. Lavas from Great Sitkin (176\degW) and Korovin (174\deg W) have intermediate compositions of 7.4-7.9$\epsilon$$_{Nd}$and 13.6-14.4 $\epsilon$$_{Hf}$. The lowest $\epsilon$$_{Hf}$values obtained (12.2-13.0) were from the Cold Bay Volcanic Complex (163\deg W).Various ashes of the DSDP site 178 of the Alaskan abyssal plain have approximately thesame Hf and Nd isotopic composition as Cold Bay. Clay and turbidite sequences fromsite 178 have lower $\epsilon$$_{Hf}$0.8-7.8 and $\epsilon$$_{Nd}$2.8-0.82 values.The change in Hf and Nd isotopic composition along the arc is consistent with a decreasein sediment flux westward. A sediment melt component in the east could mobilize Hf andNd into the mantle wedge. Fluxing of the subducting sediment could also incorporate Ndinto the melting mantle. Both these processes would lower the radiogenic signature of thesource region. DE:

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0800h AN: PP51B-1336 TI: Radiolarian and Sedimentologic Paleoproductivity ProxyRecord From the Benguela Upwelling System, DSDP Site 532, 0-6Ma AU: Bittniok, B et al. EM: beatrice.bittniok@museum.hu-berlin.de AF AB: The Neogene history of the Benguela upwelling system is fundamental to betterunderstand both regional climate change and how the global ocean cycles nutrients,including carbon. We examined the 0-6 my record of the system at ca. 400 kyr spacingfrom Walvis Ridge DSDP Leg 75 Site 532. More than 70 radiolarian taxa were countedand two indices computed: a water depth ratio index reflecting mid water exportproductivity, and the URI index of species that are biogeographically restricted to tropicalupwelling regions. Both proxies have been applied so far only to the late Pleistocene.Other proxies measured on the samples include BFAR, TOC, % and MAR carbonate,bulk opal and radiolarian presevation (semiquantitative), foraminiferal dissolutionindices, and stable isotopes of oxygen and carbon. The radiolarian water depth index, andto a lesser degree the URI, show gradually increasing productivity in the early Plioceneand high productivity through the late Pleistocene. This general productivity pattern forthe region has been established by numerous prior studies. The radiolarian water depthindex is strongly correlated to TOC, and importantly is not affected by low opalconcentration and poor radiolarian preservation in the basal Pliocene and late Pleistocene.Carbonate, and carbonate microfossil based indices such as BFAR by contrast showlargely inverse trends to radiolarians and TOC, but are interpreted as beingpredominantly dissolution controlled, as indicated by the carbonate dissolution proxies.Our results show that radiolarian faunas yield useful productivity proxies in theseupwelling sediments as far back as the latest Miocene. Further, radiolarian basedproductivity proxies are relatively robust to preservation or the supply of silica to surfacewaters, which is thought to affect bulk opal based measures of productivity in the region. DE HR:

10:55h AN: OS52A-03 INVITED TI: Jack Dymond's "Fingerprints" on Sediment Chemistry,Biogeochemical Fluxes, and my Career AU: * Leinen, M

AB: I first met Jack Dymond as a graduate student at Oregon State University. He wasn'tmy thesis advisor. He wasn't even on my committee. But his ever so gentle counsel andhis low key advice did much to shape my career, as a student, as a scientist, and later asan administrator of science. At the time, Jack was wading through the analysis of a verylarge number of surface sediment samples from the Nazca Plate as part of an IDOEproject. The number and density of sampling was extraordinary for the time and his workshowed that the geochemistry of the sediments could be deconvolved to understand thecontributions of sediment sources over the entire plate. I had been planning to analyzeDSDP samples from the equatorial Pacific to understand the history of siliceoussedimentation in that region and I began to talk with Jack about how I could usegeochemical signatures to estimate the non-biogenic fraction of the sediment. WhenJack's Nazca Plate paper came out, Debra Stakes and I decided to analyze all of mysample residues for the same elements that Jack had studied. In the only piece of badadvice that he ever gave me, Jack told me that it was a waste of time because therewouldn't be high enough concentrations of transition metals in the calcareous andsiliceous sediments to measure. We insisted and Jack, in typical fashion, agreed to payfor reagents and give us instrument time without charge anyway. The larger thanexpected concentrations, and the even more surprising match between the accumulationrates of some the metals and the accumulation rates of biogenic sediment were the subjectof many discussions, all of which ended in the need for more information on thecomposition, fluxes and transformations of biogenic sediment in the water column and inrecent sediments. This, of course, became another of Jack's specialties: his designs forsediment traps were important contributions to the evolution of this important samplingdevice. His studies of fluxes in a wide variety of environments - from hydrothermal ventfields to Crater Lake --were critical to the development of modern biogeochemicalcycling experiments and thinking. And this, of course, was only one of the fields inwhich he made major contributions. DE

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1340h AN: PP23B-1413 TI: High resolution paleoceanography of the central Gulf ofCalifornia during the past 15,000 years AU: * Barron, J et al. EM AB: A high resolution paleoceanographic history of the central Gulf of California duringthe past 15,000 years has been assembled using microfossil (diatom and silicoflagellate)and geochemical proxy data from a composite section of gravity core GGC55 and giantpiston core JPC56 in the western Guaymas Basin (27.5 deg. N, 112.1 deg. W, waterdepth 818 m) and from DSDP Site 480 (27.9 deg. N, 111.7 deg. W, 655 m water depth)in the eastern Guaymas Basin. These data argue for abrupt, basin-wide changes duringthe Bolling-Allerod, Younger Dryas, and earliest part of the Holocene that mirrorchanges documented in cores from the Pacific margins of both Baja and Alta California.Between about 10 ka and 6 ka, these central Gulf of California records became moreregionally distinctive, as surface and intermediate waters resembling those of the modern-day northern Gulf became dominant and virtually no calcium carbonate or tropicalmicrofossils were preserved in the underlying sediments. Beginning at about 6 ka,tropical microfossils returned to the central Gulf, possibly signaling enhanced El Nino-like conditions. Proxy data suggest that late winter-early spring coastal upwelling wasabruptly strengthened on the mainland (eastern) side at about 5.4 ka and again at about3.0 ka, whereas sediments from the western side of the central Gulf became increasinglydiatom poor and calcium carbonate rich. An intensification of northwest winds during thelate winter to early spring likely occurred in the central Gulf at about 5.4 ka.Interestingly, this proposed wind shift in the Gulf of California coincides with an abrupt5.4 ka change to drier conditions in the Cariaco Basin off Venezuela that has beenproposed to reflect a southward shift in the mean position of the IntertropicalConvergence Zone in response to increasing El Nino-like conditions. DE HR:

0800h AN: V51A-0513 TI: Variations in the marine Ca cycle and implications for paleo-CO$_2$ levels over the past 24 Ma AU: * Fantle, M et al. EM AB: A detailed record of the calcium isotopic composition of bulk nannofossil ooze fromDSDP Site 590, based on 40 samples measured multiple times, shows variations of$\delta^{44}$Ca over the past 24 million years between --0.2 and --0.9$\permil$, relativeto bulk Earth Ca (--1.15 to --1.85$\permil$, relative to seawater). These isotopicvariations are inferred to reflect changes in $\delta^{44}$Ca of seawater between +1.1and +0.4$\permil$. Fluctuations in $\delta^{44}$Ca, which occur in 1 to 4 Ma cycleswith varying amplitude, are interpreted as resulting from imbalances between the input ofCa to the oceans by weathering processes and the biogenic removal of Ca. Using a modelfor oceanic inputs and outputs of Ca, we reconstruct past weathering fluxes and marineCa concentrations. Combining this information with paleo-pH of the ocean, as estimatedfrom B isotopes, we derive a record of atmospheric $pCO_2$ levels over the past 24 Ma.The concentration of Ca in the ocean was at a minimum at $\sim$20 Ma, during theNeogene climate optimum, increased until 6 Ma, and then decreased toward the present.Maxima in the record occur at 6.4 and 4 Ma, corresponding to a generally-recognizedperiod of enhanced marine productivity and high mass accumulation rates at Site 590.Peaks in the inferred weathering flux occur at 18, 14, 8, 5, and 1 Ma. Our derived$pCO_2$ record indicates that the highest $CO_2$ levels during the 24 Ma period underconsideration occurred at 20--24 Ma and were no more than about twice the present-day(pre-industrial) levels. The maximum in the $CO_2$ record occurs during the warmingthat accompanied the Neogene climate optimum. The $pCO_2$ minimum occurs at 6--4Ma, during a period of enhanced marine productivity. The calculated marine paleo-Caand paleo-$pCO_2$ values are sensitive to the assumed $\delta^{44}$Ca value for theweathering flux, but the shapes of the derived curves do not change greatly over the rangeof likely input values. The reconstructed $pCO_2$ curves depend significantly on pH,but the assumption of constant pH (which only barely violates the available constraintsfrom B isotopes) yields substantially the same result. Although the paleo-$pCO_2$ curveis likely to be revised when more data are available, the present results do not show asimple linear relationship between $pCO_2$ and high-latitude temperature as reflected inthe benthic oxygen isotope records. DE HR:

1340h AN: T13B-1356 TI: Magnetic Properties of Ocean Crust from the Walls ofEndeavor Deep: Implications for the Source Layers of MarineMagnetic Anomalies AU: * Richmond, R et al. EM AB: The presence of lineated marine magnetic anomalies in the ocean basins is thefoundation for plate tectonics and global plate reconstructions. The relative importanceof the source layers of these anomalies, however, is still poorly constrained. Identifyingthe source layer(s) of the magnetic anomalies is important for present-day models ofcrustal accretion that require crustal rotations of up to 20-30 degrees. These rotations mayresult in anomalously skewed seafloor magnetic anomalies, which could significantlyalter global plate reconstructions. To address the question of the magnetic sources atultra-fast spreading rates, we have measured the magnetic properties of 135 preciselylocated rock samples collected with JASON II from the walls of Endeavor Deep.Endeavor Deep is the tip of a propagating rift on the Nazca/Juan Fernandez plateboundary. It exposes a 70 km-long, 40 km-wide, and 3 km-deep section of ~3 Myr oldupper oceanic crust (layers 2A and 2B) created at the ultra-fast spreading (~150 km/myr)East Pacific Rise. Measurements of natural remanent magnetization, magneticsusceptibility, and median destructive field define three "stratigraphic" units and arecharacterized relative to similar measurements by Pariso and Johnson (1991) on samplesfrom DSDP Hole 504B. The upper 200 m of extrusives were likely altered by lowtemperature oxidation, and carry a relatively low magnetization (0.4 A/m). Theunderlying 300 m of extrusives carry a relatively high magnetization (2.1 A/m), whichlikely contributes significantly to the amplitude of the magnetic anomaly signal. Thetransition zone from extrusive layer 2A to intrusive layer 2B (pillow basalts to dykes) andpossibly the upper portion of layer 2B carries an unexpectedly high magnetization (1.6A/m) and likely contributes to the magnetic source layer as well. A dramatic increase insusceptibility is present below the base of layer 2A that has not been previously observed. DE:

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1340h AN: T53A-0471 TI: Extremely Rapid and Localized Erosion in the HimalayaRecorded in Sediments of the Bengal Fan AU: * Stewart, R and Hallet, B EM AB: Vigorous erosion during mountain building is now recognized as a significant factorfor integrated climate-tectonics-erosion studies in Earth system science. In this context,the ages of detrital grains in sediments both define the depositional age and provide directevidence for the tempo of erosion. In the eastern syntaxis of the Himalaya, the youngestpeak identified by BINOMFIT in detrital zircons from fluvial sediments of the modernBrahmaputra River is 0.6 Ma, and significantly, it includes 47% of the entire sand-sizedzircon population. The youngest grains are ~ 0.1 Ma, and a significant subset has a peakage of 0.4 Ma. The youngest peak in apatite fission-track ages from the same samples is0.4 Ma and includes 39% of the grains. These ages are astonishingly similar to bedrockcooling dates from their source in the Tsangpo gorge, where the Yarlung-BrahmaputraRiver slices through the Namche Barwa-Gyala Peri massif in southeast Tibet. TheTsangpo gorge is particularly significant because it is a region with exceptionally youngbedrock ages, including zircon fission-track dates (0.2 Ma), biotite 40Ar/39Ar coolingages (1.0 Ma), zircon [(U-Th)/He] cooling ages (0.3 Ma), and migmatite crystallizationages ($<$3.0 Ma). These data are all compatible with an estimated exhumation rate ofabout 7 mm/yr in the Tsangpo gorge, and provide an actualistic model for interpreting thedistribution of grain ages in older sediments; clustering of grain ages from differentgeothermometers about the time of deposition is an indicator of exceptional exhumationrates, and, if sustained in the longterm, accompanying rapid uplift. The Bengal Fan is arepository for debris eroded from the Himalaya. Grains of K-feldspar, muscovite, andapatite are abundant in sediments of the Bengal Fan. Fission-track and 40Ar/39Ar dateson apatite, K-feldspar and muscovite recovered from DSDP Sites 717 and 718 constraindeposition on the outer fan to about the past 12 m.y. With 2 exceptions, duplicatedeterminations of the age of the youngest grain from identical depositional horizonswithin the fan are essentially concordant. This remarkable synchronicity in 40Ar/39Arand fission-track ages requires erosion and transport from the outcrop to the fan in anastonishingly short time. It requires deposition of first-cycle material with essentially theidentical age at the time of deposition, despite the significantly different cooling historiesthat each of these systems records. This concurrence requires exceptional erosion in asetting that exposes grains of essentially "zero-age," and provides in-situ evidence thatextremely rapid and localized erosion, such as that now occurring in the vicinity of theNamche Barwa-Gyala Peri massif and the Tsangpo gorge, has been a factor inexhumation of the Himalaya for at least the past 12 m.y. DE:

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0800h AN: T11A-1238 TI: Evidence That Early to Middle Miocene ice Streams FromWest Antarctica cut Into Southeastern Ross Sea Continental Shelf AU: * Sorlien, C et al. EM AB: The extent of the West Antarctic ice sheet during mid-Cenozoic time iscontroversial and important to climate models. High-resolution multichannel seismicreflection data were acquired using the RVIB Palmer along the edge of the Ross Ice Shelfacross the Eastern Basin of Ross Sea, in an area where calving of the ice shelf hasexposed seafloor that has not been accessible to marine geophysics in several decades. Asub-basin in the far southeast corner of Ross Sea contains a succession of sediment-filledtroughs, each capped by an unconformity. These troughs range between 5 and 20 kmacross, and are 100 to 150 m-deep. They are cut into a sequence correlated to slightlypredate ~24 Ma. The shallowest of these unconformities (named "Red" here) can betentatively projected across the northern plunge of a basement ridge located north ofRoosevelt Island (named "Roosevelt Ridge" here), and is a regional unconformity in theEastern Basin. Reflections just below Red can be correlated to DSDP 272, where they aredated at ~14 Ma. Red is flat and level in the south, adjacent to the ice shelf edge. Oldersequence boundaries beneath Red merge with it across a 70 km extent between the deepEastern Basin and Roosevelt Ridge. Much of the late-Early Miocene and early-MiddleMiocene section is missing and appears to be removed by erosion associated with the Redunconformity. There is no evidence for broad glacial troughs that predate Red west ofRoosevelt Ridge. If our correlations are correct, the succession of glacial troughs must beMiddle Miocene and older, and we cannot rule out the oldest being Late Oligocenewithout additional data. Because we do not believe that a glacier or grounded ice sheetcould erode a thick interval of sedimentary rocks and still produce a smooth and levelunconformity, our preferred hypothesis is that Red is a wavecut surface that has sincesubsided to its present 700 m depth. The fill of one 20 km-wide trough is exposed at theseafloor and accessible to Shaldrill coring to test our hypothesis. The Ross Ice Shelf isadvancing over the surveyed troughs and future drilling from the ice shelf will also bepossible. Finally, it may be possible to correlate the fill of the troughs to DSDPstratigraphy with acquisition of carefully-positioned seismic reflection profiles. Thesetroughs are consistent with erosion by ice streams or glaciers fed from an ice cap over atleast part of western Marie Byrd Land. An Early Miocene ice cap contrasts with the LateMiocene age for the earliest widely accepted time for grounded ice in West Antarctica. DE

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0800h AN: V51B-0544 TI: Critical Evaluation of Radiometric Ages Used for TrackingHotspots in the Pacific Ocean AU: * Baksi, A EM AB: One of the pillars supporting the plume hypothesis, is the progression of ages fornumerous hotspot tracks in oceans. These ages should be based on radiometricmeasurements. The argon dating methods have been the tool most commonly used. Sincemost of the rocks selected for dating have suffered (considerable) alteration, K-Ar datesshould not be used as accurate measures of the age of crystallization. 40Ar/39Ar totalfusion ages, though better than K-Ar dates in general, do not pinpoint samples that (a)contain excess argon or (b) have suffered partial loss of 40Ar* due to alteration. Hence40Ar/39Ar incremental heating studies remain as the (only) tool of choice. From suchexperiments, at a minimum, ages must be based on plateau and/or isochron sections thatmeet the necessary statistical requirements to be considered crystallization ages. Earlier(Baksi, 1999, Jour. Geol.) it has been shown that almost all the purported crystallizationages for hotspot tracks in the Atlantic and Indian Oceans, are invalid (see alsowww.mantleplumes.org/ArAr.html). Herein, I apply the tests outlined therein, to evaluateages available in the literature for hotspot tracks in the Pacific Ocean. These can bedivided into five main groups. (1) Those with reliable age data (e.g. Dalrymple andGarcia,1980; Dalrymple et al., 1980, DSDP 55, Hawaiian-Emperor Chain); the authorsuse care in selecting valid ages from their data sets. (2) Others (e.g. Pringle, 1993, AGUMonograph 77, Musicians Seamounts), most ages are statistically valid, though some failthe requisite test. In addition, many samples show high levels of atmospheric argon,suggesting the samples are (quite) altered; this could lead to incorrect plateau ages. (3)The next set (e.g. Winterer et al., 1993, AGU Monograph 77, Cretaceous guyots in theNorthwest Pacific; Ozima et al., 1977, JGRAS, Western Pacific guyots; Saito and Ozima,1977, EPSL, Western Pacific area) have few, if any, valid ages. Most plateaux/isochronsclearly fail the statistical test of reliability; many steps show high levels of atmosphericargon - the samples are (badly) altered. (4) A set of papers (e.g. Gripp and Gordon, 2002,Geophys. J. Int., young hotspot tracks; Duncan, 1985 - New Hebrides-Samoa lineament)make use of K-Ar dates, wholly or in the main. These dates should be treated asminimum estimates of the crystallization age. (5) A final set of papers (Sager et al., 1993,AGU Monograph 77, Japanese and Marcus-Wake Seamounts; Lincoln et al., 1993, AGUMonograph 77, Marshall Islands), quote ages without listing the relevant analytical data.These results are to be treated as suspect, and not used for quantitative tracking of hotspottrails. In conclusion, the purported progression of ages for numerous hotspot tracks in thePacific Ocean does not withstand critical scrutiny. DE

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0800h AN: T11A-1244 TI: Ice shelf drill sites proposed to study Pre-Late Oligoceneclimate and tectonic history, Coulman High, Southwestern RossSea, Antarctica. AU: * Decesari, R et al. EM New geophysical data were collected in front of the Ross Ice Shelf using the RVIBNathaniel B. Palmer in January of 2003. The primary goal was to collect detailed gridsof seismic data to select drill sites to investigate the climate and tectonic history of theRoss Sea region. The survey sites were located where large sections of the ice shelf havebroken off, exposing previously inaccessible seafloor. A site survey at the C-19 icebergcalving site, located in 800-900 m of water adjacent to Ross Island and 120 km NE fromMcMurdo Station, was conducted under the premise that the ice sheet, advancing north at~1 km/year, will in time cover the survey thereby allowing drilling into the seabed fromthe ice sheet. We propose an E-W transect of drill sites along the ice shelf front designedto target section where pre-Late Oligocene strata dips east allowing successively deeperstratigraphic sampling with a series of holes across strike. Cores from here may recordthe transition from warm climate in Eocene time to the cooler Oligocene and will test ourhypothesis that extension between East and West Antarctica is recorded in sediments inthis sector of the Ross Sea. Rifting in Cretaceous time resulted in widespread extensionof the Ross Sea amounting to several hundred kilometers. Adare Trough seafloorspreading in Eocene-Oligocene time adjacent to the Ross Sea continental shelf resulted inabout 180 km of spreading, and may project into the western Ross Sea. Syn-riftsediments of these ages may be present. The C-19 site on Coulman High is characterizedby N-S trending basement half grabens filled with syn-rift sediments of unknown agetruncated by an angular unconformity, and overlain by undeformed Late Oligocene andyounger strata that we correlated to DSDP and Cape Roberts drill sites. We have dividedthe pre-Oligocene units into an upper (Early Oligocene?-Eocene?; ~ 680-1000 m belowsea floor (bsf)) unit and lower (Eocene?-Late Cretaceous?; >1000 m bsf) unit, separatedby an unconformity, all resting on top of acoustic basement at ~1400m bsf. We suggestthat the pre-Oligocene strata are syn-rift units deposited and deformed during both LateCretaceous and Early Eocene extension.

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0800h AN: V51B-0570 TI: Widespread Synchronous Volcanism Reveals a BroadGalapagos Hotspot Melting Anomaly AU: * O'Connor, J et al. EM AB: The massive aseismic ridges and associated seamounts dominating the morphologyof the Panama Basin, eastern Central Pacific, have long been attributed to a Galapagoshotspot melting anomaly linked to a deep-seated mantle plume. Although these structurescan provide information about the origin of hotspots and existence, or otherwise, ofmantle plumes very little is known about their volcanic histories due to a lack of directage and geochemical information. We report here 74 whole rock and 2 plagioclase$^{40}$Ar/$^{39}$Ar ages for rocks dredged from 53 locations during the firstsystematic sampling of the Cocos, Carnegie, Coiba and Malpelo aseismic ridges andassociated seamounts (F.S. SONNE PAGANINI expedition). In addition we also reportages for DSDP drill sites on Cocos, Carnegie and Coiba ridges and 7 Cocos Islandsubaerial samples. The distribution of new, and published ages for the GalapagosArchipelago-platform and NE end of the Cocos Ridge, show a general trend of increasingage with distance from the Galapagos Archipelago. A more dominant trend however isone of aseismic ridge-seamount formation in a progression of broad zones ofsynchronous, often overlapping volcanism created at discrete intervals. Broad zones ofcoeval Cocos and Carnegie volcanism once formed much larger regions of synchronousvolcanism that have been split apart by the complex history of seafloor spreadingassociated with the Cocos-Nazca spreading center. We link these broad regions ofsynchronous volcanism to a correspondingly large hotspot melting anomaly. The presentday, as yet unfragmented, zone of synchronous volcanism associated with this proposedbroad hotspot is marked by the extensive region of recent volcanism extending across theNazca and Cocos plates encompassing the Galapagos Archipelago-Platform and theCocos Ridge as far north as Cocos Island. The complex tectonic history of the Cocos-Nazca spreading-center has controlled how the broad zones of synchronous, oftenoverlapping volcanism created by the broad Galapagos melting anomaly have beenfragmented between the Cocos and Nazca plates. However, interplay between the broadGalapagos melting anomaly and the Cocos-Nazca spreading center is a second-orderprocess compared to a fundamental underlying mantle process responsible for a broadGalapagos hotspot melting anomaly exhibiting long-lived characteristics (size, time-progression, episodicity) which, on a first-order, are independent of local tectonics andlithospheric architecture. Evidence for a broad Galapagos hotspot melting anomaly andthe possibility of detecting long-lived underlying mantle processes has implications forhow oceanic hotspot volcanism is sampled for purposes of rigorously testing the mantleplume paradigm. A major question posed by our results is whether individual Pacificseamount chains are in fact the product of tectonic plate drift over narrow hotspots? Ifnot, then inferring the existence and behavior of a mantle plume on the basis of ageprogression of volcanism produced by a narrow seamount chain could well prove to bemisleading. Thus, although great leaps are being made in the theory and numericalmodeling - often on a global scale - of hypothesized deep plumes, significantly morehigh-quality age and geochemical data are needed for oceanic hotspot volcanism that

gave birth to the mantle plume hypothesis in the first place. DE: HR:

1340h AN: V33E-1500 TI: Trace Element and Isotopic (Re-Os, O) Systematics of RobertsVictor Eclogites: Evidence for 3 Ga Subduction-Incorporation ofArchean Oceanic Lithosphere into the South African KaapvaalCraton Keel AU: * Shirey, S et al. EM AB: Eclogite xenoliths from the 125 Ma old, Group II, Roberts Victor kimberlite havelong been of interest in studies of Kaapvaal craton evolution because of their diversity,abundance, availability in large size, occurrence with peridotite and their sometimes highcarbon/diamond content. From among the coesite, corundum, kyanite, Ca-, Mg-, and Fe-rich eclogites available, we have chosen to work on those that can be classified as GroupI, Group II or diamondiferous with the goal to better understand their petrogenesis, theevolution of the Kaapvaal craton keel, the role of eclogites in diamond formation and thebehavior of the Re-Os system. Group I vs Group II eclogites can be distinguished bytexture (isolated gt in a cpx matrix vs subhedral, interlocking gt-cpx) and mineralchemistry (higher Na$_{2}$O in gt and K$_{2}$O in cpx for GI vs lower for GII). Suchdifferences have been thought to result from higher vs lower pressures of equilibration.Recent laser fluorination oxygen isotopes ($\delta^{18}$O) on gt (GI = 5.8 to 6.9; GII =2.1 to 5.1), ion-probe trace elements (e.g. Ce chondrite normalized) on gt (G1 = 0.2 to0.5; GII = 0.002 to 0.07) and cpx (G1 = 7 to 20; GII = 0.2 to 2) and whole-rock Re-Os(G1 Re = 0.19 to 3.41 ppb; GII Re = 0.006 to 0.38 ppb) highlight even more distinctdifferences between Groups I and II. These differences are likely a pre-metamorphicsignature of their original protoliths and not just due to pressure differences ormagmagenesis during emplacement into the lithosphere. Using the stratigraphic variationof O isotopic composition and trace element content of ophiolites and drill core fromDSDP/ODP holes 735B and 504B as a guide, Group I eclogites might represent thevolcanic rocks of Layer 2 of Archean oceanic crust whereas Group II might represent thecumulate, intrusive rocks of Layer 3. This idea is supported by the presence, only inGroup II eclogites, of positive Eu anomalies in reconstructed ion-probe whole rock rareearth element patterns. The Re-Os sytematics of the oceanic lithosphere is poorly known,especially in the Archean, but Roberts Victor eclogite Re-Os and trace elementabundances and major element compositions suggest a basaltic komatiitic protolith asmight typify slightly hotter ocean ridges in the Archean. A U-Pb age of 3.061$\pm$0.006Ga on zircon grains separated from a Group I Roberts Victor eclogite and a same-age butscattered whole-rock Re-Os isotope array containing the diamondiferous and some GroupI eclogites (including the zircon-bearing eclogite), firmly date the eclogite protoliths asMeso-Archean. The direct covariation of Re content (and hence$^{187}$Re/$^{188}$Os) with O isotopic composition allows the low-T alterationprocess occurring on the seafloor to be firmly dated at that time. For Kaapvaal cratonevolution, this age is interesting because it predates by about 100 Ma the terrane collisionthat sutured the Kimberley block to the Eastern Kaapvaal along the Colesburg magneticlineament, the stabilization of a thickened lithospheric mantle keel, and the generation ofa widely distributed suite of eclogitic diamonds. Incorporation of these eclogites in thelithosphere is further evidence for Meso-Archean plate tectonics and the role of

subduction in cratonization and diamond genesis.

HR: 1340h AN: ED13E-0755 TI: Teaching Biostratigraphy Using Real Cores and IODP Data:The use of Information Technology on Spatial Visualization Skills,Motivation and Transfer of Undergraduate Science Majors AU: * Hilding-Kronforst, S et al. EM: AB: We have developed a problem-solving lab exercise using real IODP data andgraphic correlation to address planktonic community change at the Eocene-Oligoceneboundary. This stratigraphic interval represents a time of dramatic global cooling, but thechange is expressed in different ways and to different degrees at different locations in theworld's oceans. The question the students are asked to address is whether observedchanges in taxonomic composition across the Eocene-Oligocene boundary are global orlocal responses to changes in oceanic and atmospheric circulation. First, students wereintroduced to graphic correlation, a quantitative biostratigraphic technique thatincorporates data from many local sections into a composite reference section. Second,students were taken to the core repository of the Integrated Ocean Drilling Program onthe campus of Texas A&M University to examine the Eocene-Oligocene boundary in aseries of cores from the Indian and Pacific Oceans. Some cores show virtually nolithological change at the boundary, whereas others show dramatic changes in rock type.Finally, students were asked to download biostratigraphic data from the IODP on-lineJanus database from the same cores that they had measured and use them to create acomposite global reference section. Using their own observations of the cores, the resultsof their graphic correlation of the real data, and additional information they wereprovided by IODP scientists during their field trip to the repository, students addressedthe global versus local nature of biotic change at the Eocene-Oligocene boundary.Evaluation of spatial skills and motivation were performed pre and post lab. Anadditional post lab exercise measured student ability to transfer conceptual knowledge.Evaluations from students will assess the effectiveness of this exercise and reflect thevalue of integrating technology in geoscience curriculum. DE: HR:

1340h AN: T13A-1348 TI: Airborne Gravity Gradiometer Survey Over the San AndreasFault AU: * Talwani, M EM: AB: An airborne gravity gradiometer survey is being conducted over the San AndreasFault drill site. The survey is over a 10km x 10km area. Forty lines will be flown in adirection parallel to the strike of topography; the lines, 250 meters apart, will each be10km in length. Ten lines 1km apart will be flown in a perpendicular direction. The lineswill be flown on a drape surface at a nominal ground clearance of 200 meters, althoughthe ground clearance will be substantially greater in many parts of the survey because ofthe presence of steep topography. The principal objective of the survey is to detectdensity inhomogeneties associated with the San Andreas Fault which lie at a shallowdepth (less than 1km). Terrain corrections are very large in the area of the survey andcorrect application of the corrections is essential for detection of sub-surface densityvariations. The survey will be carried out by Bell Geospace using its six componentairborne gravity gradiometer. We expect to be able to present some preliminary results atthis meeting. DE HR:

0800h AN: ED51C-0030 TI: USIO-IODP Developing a New Fellowship for HBCUStudents AU: * Castner, et al. EM AB: The U.S. Implementing Organization for the Integrated Ocean Drilling Program hasdeveloped a new Fellowship for students enrolled at Historically Black Colleges andUniversities. In this pilot year, the Fellowship is being offered to students enrolled atHBCUs that are in proximity to the JOI Alliance institutions: the Joint OceanographicInstitutions in Washington, DC; Texas A&M University in College Station, TX; and theLamont-Doherty Earth Observatory of Columbia University in Palisades, NY. SelectedFellows will work closely with Alliance mentors on projects related to scientific oceandrilling in the areas of science and engineering, education and public affairs, andscientific program management. Future plans include expanding the Fellowship toinclude students from all HBCUs. DE: HR:

0800h AN: ED31C-0751 TI: Learning Activities Developed at The University of Texas atAustin Institute for Geophysics Using Ocean Drilling Science,Technology and Data AU: * Bailey, D et al. EM AB: NSF GK-12 Fellows at The University of Texas at Austin Institute for Geophysics(UTIG) actively contribute to K-12 education by linking K-12 students and teachers toresearch scientists and recent discoveries, and by developing hands-on learning activitiesdesigned primarily for secondary school learning environments. The excitement of thenew Integrated Ocean Drilling Program (IODP), an international research program thatexplores the history and structure of the Earth by studying the sediments and rocksbeneath the seafloor, has provided UTIG's GK-12 Fellows with an incentive to developnew, and revise existing, inquiry-based learning activities based on the science,technology and/or data of scientific ocean drilling. These activities, grouped into acurriculum module, address the mechanics of collecting cores, fossil identification andage relationships within a core, and the interpretation of geophysical logs. They exposeteachers and students to the exciting science and advanced technology of the IODP andthe achievements of the Ocean Drilling Program, which preceded IODP. UTIG scientistsactive in the IODP guided the development of the module's science content. The moduleactivities are aligned with U.S. educational standards, but could be adapted for use inother countries that participate in the IODP. Where this isn't possible, they can serve asan example of educational curriculum materials that underscore the vital nature ofinternational collaboration. UR

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0800h AN: ED21C-0077 TI: Experiences and Results from the Integrated Ocean DrillingProgram (IODP) Teacher at Sea Program, Expedition 301 AU: * Rice, J et al. EM AB: The IODP US implementing organization began a Teacher at Sea Program (TASP)during Expedition 301 to the eastern flank of the Juan de Fuca Ridge. The mainscientific objectives of this expedition were to establish borehole observatories as part ofa series of multidisciplinary experiments that will help evaluate the hydrogeologicproperties of the oceanic crust, including the distribution of fluid pathways within anactive hydrothermal system as well as the linkages between fluid circulation, alteration,and microbiological processes. The goals of the U.S. sponsored IODP TASP were toprovide the participant with seagoing research experiences, working side-by-side withscientists, using current state-of-the-art approaches to solve scientific problems pertinentto this expedition, and gaining first-hand knowledge of the results of seagoing science. Inaddition, the participating teacher will use these experiences for translating scientificresults into useful teaching resources, such as expedition information materials and helpdisseminating these resources into classrooms across the country. During IODPExpedition 301, the participating teacher spent 2 months working with shipboardscientists in processing core data and learning the different techniques used for theshipboard laboratory analyses. Several laboratory briefs targeted for middle to highschool student audiences were developed during the cruise including the microbiology,chemistry, paleomagnetics, and physical properties laboratories and educationalclassroom activities are currently being developed. In addition, other laboratory briefsand educational activities for the underway geophysics, core, downhole measurements,and paleontology laboratories are being developed as part of the post-expeditioncurriculum development initiatives. The teacher also kept a daily journal detailing life atsea experiences as well as all the science and operational developments that took placeduring the expedition. The journal entries can be found athttp://iodp.ldeo.columbia.edu/EDU/TAS/. Interaction with other middle school and highschool educators while at sea was successful via a conference call where experiences andgeneral daily operations were shared. DE:

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0800h AN: MR11A-0916 TI: Calibration of Mobile NMR Instruments in Respect toPorosity and Pore Size Distribution of Drill Cores AU: * Arnold, J et al. EM AB: The focus of our research is set on the calibration of two different and newdeveloped light weight mobile NMR scanning systems: (1) the NMR-MOUSE and (2)the HALBACH device for measuring porosity and pore size distribution of different drillcores recovered from the International Ocean Drilling Program (IODP). Further goals areto adapt current NMR processing techniques, the development of new measurementroutines, and to evaluate precision and accuracy of this method. Transverse relaxation onwater-saturated drill cores were measured using a CPMG sequence. A regularizedLaplace transform analysis based on the UPEN program yields the distribution oftransverse relaxation times. The signal amplitudes and the integrals of distributioncorrelate directly to the core porosity. The main advantage of our mobile NMR scanningsystems compared to conventional methods is their small size and weight, which isparticularly attractive for the shipboard use and on any drilling platform envisioned forIODP. Both tools, the NMR-MOUSE and the HALBACH scanner are suitable for routinemeasurements of porosity and pore-size distribution of drill core sections. In contrast tothe NMR-MOUSE, the HALBACH tool has a sufficiently homogeneous magnetic fieldand is more sensitive. It can determine porosities as low as 3 %. While the NMR-MOUSE can be applied on core sections of any geometry, the Halbach tool is especiallydesigned for the size of standard drill cores recovered from the deep sea ocean floor bythe IODP. Combined with a mobile NMR spectrometer and special software for porosityand pore size distribution measurements, both light and mobile devices are particularlyattractive for the use on research vessels and logging platforms and thus alow todetermine prosity and permeability on very fresh material. DE:

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0800h AN: GC51D-1084 TI: Data Modeling, Development, Installation and Operation ofthe ACEX Offshore Drilling Information System for the MissionSpecific Platform Expedition to the Lomonosov Ridge, ArcticOcean. AU: * Conze, R et al. EM AB: During August/September 2004, the Arctic Coring Expedition (ACEX) was used totrial a new Offshore Drilling Information System (OffshoreDIS). ACEX was the firstMission Specific Platform (MSP) expedition of the Integrated Ocean Drilling Programme(IODP), funded by the European Consortium for Ocean Research Drilling (ECORD). TheBritish Geological Survey in conjunction with the University of Bremen and theEuropean Petrophysics Consortium were the ECORD Science Operator (ESO) forACEX. IODP MSP expeditions have very similar data management requirements andoperate in similar working environments to the lake drilling projects conducted by theInternational Continental Scientific Drilling Program (ICDP), for example, theGLAD800, which has very restricted space on board and operates in difficult conditions.Both organizations require data capture and management systems that are mobile,flexible and that can be deployed quickly on small- to medium-sized drilling platformsfor the initial gathering of data, and that can also be deployed onshore in laboratorieswhere the bulk of the scientific work is conducted. ESO, therefore, decided that anadapted version of the existing Drilling Information System (DIS) used by ICDP projectswould satisfy its requirements. Based on the existing DIS, an OffshoreDIS has beendeveloped for MSP expeditions. The underlying data model is compatible withIODP(JANUS), the Bremen Core Repository, WDC-MARE/PANGAEA and theLacCore in Minneapolis. According to the specific expedition platform configuration andon-board workflow requirements for the Arctic, this data model, data pumps and userinterfaces were adapted for the ACEX-OffshoreDIS. On the drill ship Vidar Viking thecores were catalogued and petrophysically logged using a GeoTek Multi-Sensor CoreLogger System, while further initial measurements, lithological descriptions andbiostratigraphic investigations were undertaken on the Oden, which provided laboratoryfacilities for the expedition. Onboard samples were registered in a corresponding samplearchive on both vessels. The ACEX-OffshoreDIS used a local area network covering thetwo ships of the three icebreaker fleet by wireless LAN between the ships and partlywired LAN on the ships. A DIS-server was installed on each ship. These weresynchronized by database replication and linked to a total of 10 client systems and labelprinters across both ships. The ACEX-OffshoreDIS will also be used for the scientificmeasurement and analysis phase of the expedition during the post-field operations `shore-party' in November 2004 at the Bremen Core Repository (BCR). The data managementsystem employed in the Arctic will be reconfigured and deployed at the BCR. Inaddition, an eXtended DIS (XDIS) Web interface will be available. This will allowcontrolled sample distribution (core curation, sub-sampling) as well as sharing of data(registration, upload and download) with other laboratories which will be undertakingadditional sampling and analyses. The OffshoreDIS data management system will be oflong-term benefit to both IODP and ICDP, being deployed in forthcoming MSP offshore

projects, ICDP lake projects and joint IODP-ICDP projects such as the New JerseyCoastal Plain Drilling Project. UR

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1340h AN: V23B-0628 TI: New insights into serpentinization at Atlantis Massif, 30$\deg$N Mid-Atlantic Ridge, using wide-angle seismic method AU: * Singh, S et al. EM AB: The Atlantis Massif is an ultramafic core complex that was formed in the last 1.5-2.0 Myr at the intersection of the Atlantis Fracture Zone and the Mid-Atlantic Ridge near30ø N by tectonic extension along a long-lived oceanic detachment fault. Theexhumation of deep crustal and upper mantle rocks in the footwall of the fault providesan excellent tectonic window into the oceanic lithosphere. The Atlantis Massif will bethe subject of a deep-drilling investigation for upcoming IODP Legs 304 and 305(November 2004 - February 2005). Near-offset seismic reflection data (offset up to 3 km)across the core complex imaged a reflection at 0.2-0.25 s below the seafloor, which hasbeen interpreted as an older detachment fault [Canales et al., Earth Planet. Sci. Lett., 222,543-560, 2004]. The application of a non-conventional multichannel seismic (MCS)imaging technique allows us to include wide-angle seismic reflection data (offset up to 6km) in the imaging process. We find that this reflection is continuous along most of theprofiles and is present beneath the exposed detachment surface over an area larger thanpreviously estimated from the near-offset MCS sections. Complementary data from on-bottom shots and ocean bottom seismometers constrain both P and S-wave velocitiesdown to 0.5-0.6 km below the seafloor, at approximately the depth of the widespreadreflection. The combined seismic data suggest that the interval between the seafloor andthe reflection contains serpentinized peridotite. We quantify the amount and distributionof alteration in this layer by using an effective medium theory, and we interpret theresults to shed new light on serpentinization processes at Atlantis Massif. IODP drillingresults this winter will allow us to compare our interpretation to ground-truthmeasurements. DE

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1340h AN: OS43B-0547 TI: A Three-Dimensional Subseafloor Observatory Network forCross-Hole, Hydrogeologic Experiments Established in theNortheast Pacific Ocean AU: * Fisher, A et al. EM AB: The upper oceanic crust, composed mainly of basalt, comprises the largest aquiferon Earth. Global fluid fluxes through the upper oceanic crust are at least as large as theannual riverine flux to the ocean, and influence a diverse array of processes andproperties, including the thermal state and evolution of oceanic plates; alteration of thelithosphere and the chemistry of flowing fluids; establishment and maintenance of vastsubseafloor microbial ecosystems; and diagenetic, seismic, and magmatic activity alongplate-boundary faults. Active experiments are needed in the oceanic crust to determinehydrogeologic properties at a crustal scale, and to quantify linkages between thermal,fluid, solute, and biological processes. The first expedition of the Integrated OceanDrilling Program established two new subseafloor observatories within 3.5 Ma crust inthe northeast Pacific Ocean, and replaced a previously-deployed observatory, inanticipation of planned cross-hole tests and related experiments. The new holes extend upto 320 m into basement and isolate distinct depth intervals. All of the new observatoriesare instrumented with autonomous temperature loggers, osmotic fluid samplers, andmicrobiological incubation substrate. Future experiments will include hydrogeologic teststo determine fluid transmission and storage properties, at cross-hole distances of 35 to2200 m, tracer tests to quantify rates and modes of solute transport, and seismicexperiments to elucidate relations between velocity and hydrogeologic anisotropy. DE:

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09:00h AN: ED41C-05 TI: Undergraduate Student Research with the Integrated OceanDrilling Program on Expedition 301 AU: * Hawkins, L et al. EM AB: I was invited to participate as a shipboard scientist on board the JOIDES Resolutionduring Expedition 301 of the Integrated Ocean Drilling Program (IODP). The scientificobjectives of this expedition were to establish borehole observatories to evaluate thehydrogeologic properties within oceanic crust, determine how fluid pathways aredistributed within an active hydrothermal system, establish linkages between fluidcirculation, alteration, and geomicrobial processes and determine relations betweenseismic and hydrologic anisotropy. I worked as a paleomagnetics shipboard scientist withWilliam Sager from Texas A&M University. My primary responsibility was to producethe initial paleomagnetic data through alternating field and thermal demagnetization forthe sediments and basement rocks recovered during the expedition. The magnetic dataobtained from samples recovered from the 220 m basaltic section that was drilled showsome consistency with expected normal polarity acquired at high-mid latitudes and somereversed polarity or low inclination values which may be related to alteration.Additionally, I assisted in core curation and processing, the underway geophysics lab,and with core description. I was included in the scientific meetings discussing samplehandling, preliminary results, on-going developments, and post-cruise research. My post-cruise project, under the direction of William Sager and Bernard Housen of WesternWashington University, investigates magnetic properties of the basaltic rock from theupper oceanic crust. The primary goal of this work will be to refine our understanding ofthe magnetization process and geomagnetic field geometry recorded by young ($<$ 3.5Ma) oceanic crust. This experience was invaluable to me as an aspiring scientist. I wasparticipating in cutting edge research with renowned scientists who were working onsubjects of global interest and I was not reading chapters out of a textbook. The scientistsshowed me a glimpse of what the future may be for me, including some of the challengesas well as benefits. I also received guidance for post-baccalaureate study, made contactwith professors, post-docs, and graduate students outside my university, and formed life-long friendships. I cherished this opportunity and I look forward to sharing more of myundergraduate research experiences with others. DE

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0800h AN: G21A-0139 TI: An Experiment on GPS/A Seafloor Positioning in the CentralPart of Kumano-nada, Central Japan AU: * Fujimoto, H et al. EM AB: Kumano-nada, northeast of Kii Peninsula in the central part of Japan, is aseismogenic zone of the M-8 class Tonankai earthquakes that occurred repeatedly at aninterval of about 100 years. The MEXT (Ministry of Education, Culture, Sports, Scienceand Technology, Japan) initiated a 5-year program in 2003 for seafloor observations inand around Kumano-nada. Nagoya and Tohoku Universities initiated experiments onGPS/A seafloor positioning to monitor crustal deformation in the subduction zone with afocus on investigation of the effect of sound velocity structure in the ocean on seafloorpositioning (e.g., Tadokoro et al., this meeting). Tohoku group deployed five precisionacoustic transponders (PXPs) jointly developed with Scripps Institution of Oceanographyin the central part of Kumano-nada at depths of about 2,000m. The deployed PXPs A, B,C, and D form a diamond on the seafloor, and PXPs C, D, and E form a triangle.Although three typhoons were in the way of our 12-day cruise in August this year, wecarried out GPS/A observation for several days. After an observation for locating theprecise position of each PXP, we tried to keep the buoy near the center of the diamond orthe triangle. The vessel held the position within 20-30m from the center, and the buoy_fsposition was kept with 100m from the center. Kinematic GPS positioning is now underprocessing with GEONET data observed in Kii Peninsula. We also tried monitoring thesound velocity structure with 3 sets of inverted echo sounders (IESs) deployed near thePXPs C, D, and E. The IESs can monitor temporal and spatial variation in the soundvelocity structure in the triangle array of PXPs. We plan to carry out the second GPS/Aobservation in November. The result is worthy of notice. Strange earthquakes ofmagnitude 6.9, 7.4, and 6.4 occurred on the nearest Nankai Trough axis on September 5-7, 2004. Co-seismic crustal deformation observed by the GEONET was about 4 cm nearthe coast of Kii Peninsula. The seismogenic zone is in the list ocean drilling under theIODP (Integrated Ocean Drilling Program). DE

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11:35h AN: OS42A-06 TI: Medusa-Isosampler: A modular, network-based observatorysystem for combined physical, chemical and microbiologicalmonitoring, sampling and incubation of hydrothermal and coldseep fluids AU: * Schultz, A et al. EM: AB: The study of life in extreme environments provides an important context fromwhich we can undertake the search for extraterrestrial life, and through which we canbetter understand biogeochemical feedback in terrestrial hydrothermal and cold seepsystems. The Medusa-Isosampler project is aimed at fundamental research intounderstanding the potential for, and limits to, chemolithoautotrophic life, i.e. primaryproduction without photosynthesis. One environment that might foster such life isassociated with the high thermal and chemical gradient environment of hydrothermalvent structures. Another is associated with the lower thermal and chemical gradientenvironment of continental margin cold seeps. Under NERC, NASA and industrialsupport, we have designed a flexible instrumentation system, operating as networked,autonomous modules on a local area network, that will make possible simultaneousphysical and chemical sampling and monitoring of hydrothermal and cold seep fluids,and the in situ and laboratory incubation of chemosynthetic microbes under highpressure, isobaric conditions. The system has been designed with long-term observatoryoperations in mind, and may be reconfigured dynamically as the requirements of theobservatory installation change. The modular design will also accommodate new in situchemical and biosensor technologies, provided by third parties. The system may beconfigured for seafloor use, and can be adapted to use in IODP boreholes. Our overallproject goals are provide an instrumentation system capable of probing both high andlow-gradient water-rock systems for chemolithoautotrophic biospheres, to identify thephysical and chemical conditions that define these microhabitats and explore the detailsof the biogeochemical feedback loops that mediate these microhabitats, and to attempt toculture and identify chemolithoautotrophic microbial communities that might exist there.The Medusa-Isosampler system has been produced and is now undergoing initialdeployments at sea. DE HR:

1340h AN: OS43B-0574 TI: Geology of Smooth Ridge: MARS-IODP Cabled ObservatorySite AU: * Jordahl, K et al. EM AB: We document the geologic environment of Smooth Ridge, off shore CentralCalifornia, where the deep-water node associated with the MARS (MontereyAccelerated Research Site) scientific research cable is to be deployed. The MARS cablewill provide internet connections and electric power at a node in 890 m of water insupport of scientific observatory development and experiments. IODP boreholes areproposed which will be connected to the MARS cable. The deeply incised channels ofMonterey and Soquel Canyons flank Smooth Ridge to the SW and NE and the SanGregorio faults marks its NW and upslope boundary. However, the top of Smooth Ridge,as its name implies, only has subdued bathymetric features. These include a subtledownslope channel and one distinct slump scar. A patch of acoustically reflectiveseafloor on the west side of the ridge, over 5 km from the MARS site, is associated withthe only known large-scale biological community on the crest of Smooth Ridge. Areflection seismic survey conducted in 2003 with a high-resolution electrical sparkersource reveals the stratigraphy of the Smooth Ridge in unprecedented detail. Inconjunction with previously collected widely-spaced multichannnel seismic data,observations and samples obtained using remotely-operated vehicle (ROV) dives, andpiston cores, this new survey reveals the erosional and depositional history of SmoothRidge. The continuity of seismic reflections indicates nearly undisturbed depositionoccurred until at least the mid-Miocene. Since that time, and especially since the upperPliocene, the record is marked by unconformities and infill due to shifting channels, largeslumps and landslides, and sediment waves. Several crossing seismic lines provide aquasi-three-dimensional view of a distinct slump scar's structure, and reveal a history ofmultiple headwall failures. Other subsurface structures, including a much larger, andolder, slump feature, have no bathymetric expression at all. 14C dated piston cores, andROV observations and sampling reveal that sediments have not been accumulating in theHolocene. Exposure of Plio-Pleistocene strata on the surface of Smooth Ridge in waterdepths of less than 1 km indicates that this is an area of active seafloor erosion.Measurements of sulfate gradients in piston cores indicate sulfate depletion occursbetween 3 to 5 m below the seafloor, which is unusually shallow for continental marginsediments and suggests enhanced biogeochemical/microbiological activity occurs in thesubsurface under Smooth Ridge.