Abstracts / Quaternary International 279-280 (2012) 346–461 389

we combine detailed glacial geomorphic maps and 10Be surface-exposuredating to document mountain-glacier moraines marking progressivelyless-extensive glacier expansions throughout the Holocene in the Cameronand Ashburton River valleys, and in a hanging valley beneath Mt. Lucia inthe Liebig Range, Southern Alps, New Zealand. Several prominentmoraines were constructed nearly every 1,000 yrs fromw11,500 yrs ago tow6,000 yrs ago. The last major glacier advance culminated by 600 yrs ago,after which time glaciers underwent oscillatory retreat. Thus, unlike thepattern documented from northern middle latitudes, the time during andsince the ‘classic' Little Ice Age represents the period of most withdrawnHolocene ice extent in New Zealand.

TIMING OF THE LAST MOUNTAIN-GLACIER MAXIMUM IN THEWESTERNUNITED STATES

Aaron Putnam. University of Maine, United StatesE-mail address: aaron.putnam@umit.maine.edu

The signature of mountain glacier behavior in the western cordillera of theUnited States during the last glacial maximum (LGM) and terminationremains unclear. Also unclear is whether LGM glaciers in different rangesof the cordillera registered a common climate signal, or whether localizedclimate influences overwhelmed broader drivers. Here, we present glacialgeomorphic maps and 10Be surface-exposure ages from a series ofexceptionally well-preserved moraine sets deposited during the last iceage by mountain glaciers in the Wind River Range, Wyoming, and theSierra Nevada, California. These moraine complexes occur east (down-wind) and west (upwind) of the Great Basin, which harbored extensivepluvial lakes during the LGM and termination; thus these glacier systemsare appropriately situated to assess the spatial nature of LGM climatevariability in the western U.S. Our chronologies, constructed from >180precise 10Be dates, exhibit matching patterns of mountain glaciationduring the LGM and termination in the Wind River Range and SierraNevada. Exposure ages also correspond closely with 14C-based recon-structions of the southern margin of the Laurentide Ice Sheet. Together,these results support a common, continental-scale climatic driver ofmountain glaciation in the western U.S. at the culmination of the last iceage.

COMPARISON OF THE SPATIO-TEMPORAL SEDIMENTATION PATTERNSOF DIFFERENT PROXIES IN LARGE SHALLOW LAKE

Liisa Puusepp. Institute of Ecology at Tallinn University, EstoniaE-mail address: liisa.puusepp@tlu.ee

Comparison of the spatio-temporal distribution of different proxies hasbeen a growing interest in paleo- and neolimnology. Lake Peipsi is a largeshallow lake (3,555 km2, average depth 7.1 m). Surface sediment samplesof the northernmost and largest part of the lake (Lake Peipsi sensu stricto)were studied. The bottom of the central area of the lake is covered by gyttja(up to 27% OM) with high fine-grained sediment content (silt, median 5.5–6.3 Ø units), where also the highest content of the P-tot fraction (0.64–1.1mg g-1 DW) and concentrations of diatoms (>100�106 g–1 DW) werefound. Coastal areas and southern part of the lake bottom are covered bycoarse-grained sediments (sand, median 0–3.7 Ø units) with a smallcontent of OM (average 1.7%), originating from coast abrasion. Northernand north-western part of the lake bottom is defined as mixed-grainsediment area covered by till and varved clay (median 3.5–7.6 Ø units). Inthese areas, covered by coarser material, concentrations of P-fractions anddiatoms are smaller (up to 0.73 mg g-1 DW and 3.3�106 g–1 DW respec-tively). However, the comparison of spatial distribution of proxies(lithology, grain-size, diatoms, phosphorous fractions and bulk geochem-istry) of L. Peipsi s.s. show rather different sedimentation patterns. Incertain boundary condition those patterns can be similar and probablyinfluenced by the same driving force (e.g. waterlevel, current systems andnear-bottom shear stress, formation of flocks). The flocculation of seston(OM, silt, clay, diatoms etc) in water column causes increase of specificgravity and quicker sedimentation of material. When in-lake conditionschange some proxies also show changes but others may remain the same.This study provides useful information about the similarities and

dissimilarities in spatial distribution of different proxies in surface sedi-ments in a large shallow lake, and how these findings could be beneficial topaleolimnological studies.

THE TAPHONOMY OF LAST GLACIAL–INTERGLACIAL TRANSITION (LGIT)DISTAL VOLCANIC ASH IN SMALL SCOTTISH LAKES

Sean Pyne-O'Donnell. University of Bergen, NorwayE-mail address: sean.pyne-odonnell@geo.uib.no

An extensive micro-tephrostratigraphic survey of three small lakes in theScottish Inner Hebrides was conducted encompassing the Last Glacial–Interglacial Transition (LGIT). The lakes are highly contrasting in terms oflake area to catchment ratio, the presence or absence of stream inletsdraining the catchment, and in the complexity of the catchment drainagenetwork. A suite of distal Icelandic volcanic ashes was consistentlydetected in all three lakes, with three: Penifiler Tephra, Vedde Ash andAshik Tephra, being common to all the lakes. These ashes were chosen toexamine the taphonomic intercomparability of ash location and concen-tration among the lakes. Findings reveal that the part played by catchmentinlets in determining ash concentration and within-basin location appliesto microtephra layers as much as it does in studies of macrotephra layerthickness. The position of ash concentration maxima is also shown to varysignificantly for different LGIT periods and may be a consequence of lake-level changes, especially during the early Holocene. High-resolutionstratigraphic analysis through the Vedde Ash visible macrotephra at LochAshik reveals a high degree of complexity in taphonomic behaviourbetween the different geochemical components, with possible implica-tions for the correct interpretation of isochron position. The detection ofmultiple intact ash isochrons and the taphonomic processes responsiblefor their deposition should prove useful in future tephrostratigraphicsurveys, as well as having applications within other palaeolimnologicaldisciplines.

TOWARDS A HOLOCENE DISTAL TEPHROCHRONOLOGY FOR NORTH-EASTERN NORTH AMERICA

Sean Pyne-O'Donnell. University of Bergen, NorwayE-mail address: sean.pyne-odonnell@geo.uib.no

PRECIP (palaeo-reconstructions of ocean-atmosphere coupling in peat) isa multi-proxy project examining the influences of Gulf Stream and Lab-rador Current variations on Holocene raised bogs along the AtlanticSeaboard of North America (cf. M. Amesbury, Session 13). The project aimsto reconstruct the influences of such currents at multi-decadal timescalesthus enabling hypotheses testing of ocean-atmosphere coupling betweenTHC variability and terrestrial responses (e.g. the timings and causes of the‘8.2 ka’ event). A valuable geochronological tool for this task is teph-rochronology, which utilises far-travelled volcanic ash (microtephra)layers as precise parallel time horizons between depositional archives. OnePRECIP site at Nordan's Pond Bog in Newfoundland has been found topotentially contain up to 12 rhyolitic microtephra layers throughouta continuous 8700-year profile. This number exceeded expectations,especially as the site is located ca. 2500 km upwind of Icelandic and JanMayan source volcanoes. Additionally, ultra-distal inputs may derive viaWesterlies from North American sources such as Alaska or the PacificMountain System (ca. 5000+ km). Two layers of particularly high shardconcentration (>600 shards/cm3) are estimated by the age model to occurat ca. 7500 14C yrs BP and ca. 1200 14C yrs BP (ca. AD 800), and probablyrepresent large magnitude eruptions. Candidates of comparable age arethe Mazama Ash (Crater Lake) (7627 Greenland GISP2 ice core yrs BP) andPopocatepetl AD 823 (GISP2) eruptions respectively. The tephrochrono-logical potential of other PRECIP sites in the region is anticipated to be justas prolific, and should therefore provide a new Holocene tephrostratig-raphy for north-eastern North America enabling highly precise correla-tions with equivalent tephrostratigraphic records such as the Greenlandice cores. The sites may also provide a bridge linking North American,North Atlantic and European tephrostratigraphic frameworks.