Upload
nathaniel-susan
View
213
Download
0
Tags:
Embed Size (px)
Citation preview
K. H. James 07
Geology of the Caribbean PlateauGeology of the Caribbean PlateauKeith JamesKeith James
Institute of Geography & Earth Sciences, Institute of Geography & Earth Sciences, Aberystwyth, Wales, UK,Aberystwyth, Wales, UK,
[email protected]@aber.ac.uk
This model: the plate formed in place, This model: the plate formed in place, between N and S America.between N and S America.
--it is mostly extended continental crust.it is mostly extended continental crust.
Paradigm: Paradigm: -the Caribbean Plate is oceanic and -the Caribbean Plate is oceanic and came from the Pacific. came from the Pacific. -the Plateau formed over a mantle -the Plateau formed over a mantle plume.plume.
-the plateau consists of NE trending continental -the plateau consists of NE trending continental blocks, Palaeozoic and older, flanked by Triassic-blocks, Palaeozoic and older, flanked by Triassic-Jurassic seaward-dipping wedges and overlain by Jurassic seaward-dipping wedges and overlain by Cretaceous basalts.Cretaceous basalts.
5°
20°
35°
-85° -70° -55°
NORTH NORTH AMERICAAMERICA
SOUTH AMERICASOUTH AMERICA
U L
Atlantic PlateAtlantic Plate
Pacific PlatePacific Plate
““Middle America”Middle America”
LesserLesserAntillesAntilles
K. H. James 07
CaymanCaymanTroughTrough
CaymanCaymanRidgeRidge
Grenada Grenada BasinBasin
YucatánYucatánBasinBasin
Beata and Aves ridgesBeata and Aves ridges
MayaMayaBlockBlock
ChortisChortisBlockBlock
BahamasBahamas
GreaterGreater AntillesAntilles
Chorotega Chorotega BlockBlock
Chocó Chocó BlockBlock
Gulf of Gulf of MexicoMexico
Colombia Colombia BasinBasin
Venezuela Venezuela BasinBasin
““Accreted Accreted volcanic arc”volcanic arc”
Problems with Caribbean geologyProblems with Caribbean geology
Geology is spread over many different countries.Geology is spread over many different countries.
Some areas are poorly mapped (access, vegetation, weathering).Some areas are poorly mapped (access, vegetation, weathering).
There are no spreading ridges or magnetic anomalies in the There are no spreading ridges or magnetic anomalies in the whole of middle America, save for the central 300 km of whole of middle America, save for the central 300 km of thethe
Cayman Trough (Miocene - Recent).Cayman Trough (Miocene - Recent).
Most data are collected/interpreted under the assumptionMost data are collected/interpreted under the assumption
that the Caribbean Plate is oceanic and came from the Pacificthat the Caribbean Plate is oceanic and came from the Pacific..
K. H. James 07
Caribbean Plate crust in the western Venezuela Basin-BeataCaribbean Plate crust in the western Venezuela Basin-BeataRidge area is up to 20 km thick. This is the “original” Caribbean Plateau. Ridge area is up to 20 km thick. This is the “original” Caribbean Plateau. Five ODP/DSDP sites have penetrated Cretaceous basalts, dated 88 - 90 Five ODP/DSDP sites have penetrated Cretaceous basalts, dated 88 - 90 Ma, at the very top of the thick, uncalibrated section. Overlying Ma, at the very top of the thick, uncalibrated section. Overlying sediments are shallow marine carbonates.sediments are shallow marine carbonates.
Peripheral to thick Caribbean crust, supposed “original” oceanic crust is Peripheral to thick Caribbean crust, supposed “original” oceanic crust is thin, 3 km, not drilled, not dated.thin, 3 km, not drilled, not dated.
Other parts of the Caribbean Plate interior (in the Colombia, Grenada and Other parts of the Caribbean Plate interior (in the Colombia, Grenada and Yucatán basins) also are thick. Together with the “original” plateau and Yucatán basins) also are thick. Together with the “original” plateau and accreted rocks around the Caribbean and in Colombia, they are seen to accreted rocks around the Caribbean and in Colombia, they are seen to comprise an oceanic plateau or large igneous province. Some of the comprise an oceanic plateau or large igneous province. Some of the accreted sections include palaeosols.accreted sections include palaeosols.
The Caribbean PlateauThe Caribbean Plateau
Several oceanic plateaux (Ontong-Java, Iceland, Kerguelen, Vøring, Several oceanic plateaux (Ontong-Java, Iceland, Kerguelen, Vøring, Rockall) are known to have continental roots. Rockall) are known to have continental roots. Is this true of the Caribbean Plateau?Is this true of the Caribbean Plateau?
5°
20°
-85° -70°
Arc volcano
Extinct
BrmTur
Mas
MEoc
MMio
LA
CAP
K. H. James 07
Popular model: The Caribbean Plate is oceanic and migrated Popular model: The Caribbean Plate is oceanic and migrated from the Pacific (successive arc locations).from the Pacific (successive arc locations).
Popular model: The Caribbean Plateau formed above a Popular model: The Caribbean Plateau formed above a mantle plume (Galapagos Hotspot).mantle plume (Galapagos Hotspot).
NORTH AMERICA
SOUTH AMERICA
ATLANTIC OCEAN
PACIFIC OCEAN
-70°-85°
15°
30°
-100°
Gulf of Mexico
YucatánBasinMaya
Chortis
HispaniolaPuerto Rico
LesserAntilles
Bahamas
BRAR
SOUTHAMERICA
ATLANTICOCEAN
-75° -45°
-55°
-30°
AntarcticPeninsula
ShackletonFracture Zone
N Scotia Ridge
S. Scotia Ridge
S SandwichIslands
PACIFICOCEAN
K. H. James 07
CaribbeanCaribbeanBandaBanda
ScotiaScotiaAUSTRALIA
120° 135°105°
0°
15°
Java
BorneoSulawesi
Timor
Papua-New Guinea
Philippines
Plate boundaryContinent marginShoreline
PACIFIC OCEAN
INDIAN OCEAN
Volcanic arc
SOUTHEAST ASIA
Sumatra
The plates are strikingly similar.The plates are strikingly similar.Scotia and Banda formed in-place by Scotia and Banda formed in-place by back-arc spreading.back-arc spreading.
Scotia and Banda carry marginal and Scotia and Banda carry marginal and interior continental fragments.interior continental fragments.
Is there continental material in the Is there continental material in the Caribbean?Caribbean?
5°
20°
35°
-85° -70° -55°
Indications of continent in the CaribbeanIndications of continent in the Caribbean
K. H. James 07
Southern Central AmericaSouthern Central America --crustal thickness 40 - 45 kmcrustal thickness 40 - 45 km,,
--high silica ignimbrites, high silica ignimbrites, granulite xenolithsgranulite xenoliths
--Albian and Miocene Albian and Miocene quartz sandstones.quartz sandstones.
-gravity: continental density-gravity: continental density,,
Cayman Trough wallsCayman Trough walls
JamaicaJamaica
Cuban Cretaceous arc rocksCuban Cretaceous arc rocks
--crustal thickness 20 kmcrustal thickness 20 km,,
--flysch from N.NE contains flysch from N.NE contains gneiss, schist, quartzite, slate, gneiss, schist, quartzite, slate, marblemarble
--continental grantitoids,continental grantitoids, red beds, red beds, greywackes, arkose.greywackes, arkose.
--carry Precambrian, Palaeozoic carry Precambrian, Palaeozoic
zirconszircons,,
5°
20°
35°
-85° -70° -55°
Indications of continent in the CaribbeanIndications of continent in the Caribbean
K. H. James 07
NE Caribbean:NE Caribbean:
Aves RidgeAves Ridge
-crustal thickness 30 km-crustal thickness 30 km
-continental rocks on Hispaniola,-continental rocks on Hispaniola,Puerto Rico Trough, Cretaceous Puerto Rico Trough, Cretaceous stratigraphic continuity with Bahamasstratigraphic continuity with Bahamas
-Silica content up to 76%-Silica content up to 76%
-gravity: continental density-gravity: continental density
--underlain by granitic rocksunderlain by granitic rocks
Siuna Cretaceous “oceanic Siuna Cretaceous “oceanic
terrane”terrane” -conglomerates with abundant -conglomerates with abundant quartz, fragments of schist quartz, fragments of schist and quartziteand quartzite
NORTH AMERICA
shelf edge
plate boundary
5°
20°
35°
-55°-100°
SOUTH AMERICA
ATLANTIC
PACIFIC
thick crust
.
"accreted plateau"
DSDP locationsridge
K. H. James 07
The Caribbean “plateau”The Caribbean “plateau”
has NE structural has NE structural grain (not the radial grain (not the radial pattern expected of a pattern expected of a plume)plume)
The original The original “plateau”“plateau”
.
5°
35°
-100°
K. H. James 07
Next slide
It conforms with the regional tectonic patternIt conforms with the regional tectonic pattern
N35°E Palaeozoic structural N35°E Palaeozoic structural trendtrend
This extends along the Atlantic seaboard of N. America into the N. This extends along the Atlantic seaboard of N. America into the N. AtlanticAtlantic
K. H. James 07
WedgeRidge“Seamount”
Seismic line 1293Seismic line 1293 (after Diebold & Driscoll, 1999)(after Diebold & Driscoll, 1999)
Seaward-dipping wedgesSeaward-dipping wedges are commonare common
features of continental margins (e.g. N. Atlantic, after Parson et al.)features of continental margins (e.g. N. Atlantic, after Parson et al.) Jan Jan MayanMayan
IcelandIceland
GreenlandGreenland
RockallRockallPlateauPlateau
Vøring Vøring PlateauPlateau
Seismic lineSeismic line
FaroeFaroe
Wales, Wales, etc.etc.Rockall: 5 km sedimentary section,Rockall: 5 km sedimentary section,
including 1.5 km basalt, on ~13 km including 1.5 km basalt, on ~13 km highly stretched continental crust.highly stretched continental crust.
Rockall and Vøring: Rockall and Vøring: subaerial-shallow marine subaerial-shallow marine basalts.basalts.
Vøring: andesite-dacite at Vøring: andesite-dacite at (ODP Site 642) shows (ODP Site 642) shows continental input.continental input.
Jan Mayan and Jan Mayan and Iceland:Iceland:continental roots.continental roots.
NW SE
SENW
smooth B"
convex-up reflections
A
B C
C
Seaward-dipping wedges, Seaward-dipping wedges, Caribbean and Vøring plateauxCaribbean and Vøring plateaux
Caribbean Caribbean
“plateau“plateau””
Vøring Vøring marginmargin
Convex up reflectionsConvex up reflections BasaltBasalt
300 300 KmKm
Eastern N AmericaEastern N America (after Manspeizer, 1988) (after Manspeizer, 1988)..
Next slideNext slide
Onshore: Triassic clastic basins
Offshore:Triassic - Jurassic basinswith salt
5
10
15
20
Shore lineCOST
Pre-Mesozoicbasement
Riftbasin
Wedge
Mid. JJ -Early KK
Neogene
NW SE SW NE
Post riftunconformity
U Cret - PalKm
100 Km
V/E x10
Seaward-dipping wedges:Seaward-dipping wedges: offshore N America; note offshore N America; note presence of salt (after Benson & Doyle, 1988).presence of salt (after Benson & Doyle, 1988).
SaltSalt
K. H. James 07
Interpretation of plateauInterpretation of plateau (after Diebold & Driscoll, (after Diebold & Driscoll,
1999)1999)
““Seamount”Seamount”
ve = 25
A - Early volcanic thickeningvolcanic mounds with dipping flanks
Mantle
B - Extension - final volcanics
depleted source
additional depletion
10 km
SENW
SW
NE
1 km
SW
5 km
Diapirs: - Gulf of Mexico and CaribbeanDiapirs: - Gulf of Mexico and Caribbean
Caribbean:Caribbean:Line 1293, after Diebold & Line 1293, after Diebold & Driscoll, 1999Driscoll, 1999
Gulf of Mexico: Gulf of Mexico: Sigsbee Knolls, after Burk Sigsbee Knolls, after Burk et al., 1969et al., 1969
Challenger Knoll: Challenger Knoll: drilled - salt diapirdrilled - salt diapir
Not a seamount but a Not a seamount but a diapir (salt, shale, diapir (salt, shale, serpentinite?)serpentinite?)
NW SE
Diapir - ?salt
Triassic-Pz basement
oceanized crust
U TrL Jur
U-Jur -L - Cret
M - U Cret
U - E0 - Mio
Mio - Rec
1000 CDP 5000 10000 15000 20000 25000
6 s/twt
8
10
9
Moho
?
?
SB" A"
RB"
Sea floor
?CVFZ
11
K. H. James 07
Seismic line 1293:Seismic line 1293: interpretationinterpretation - this study (James- this study (James 2007)2007)
““Ski jump”? = marginal Ski jump”? = marginal reef/moundreef/mound
NE-trending continental blocks, seaward-NE-trending continental blocks, seaward-dipping wedges, salt, covered by subaerial dipping wedges, salt, covered by subaerial Cretaceous basalts - SB smooth Horizon B”. Cretaceous basalts - SB smooth Horizon B”. RB - rough Horizon B” - serpentinized mantle RB - rough Horizon B” - serpentinized mantle (“oceanic” crust).(“oceanic” crust).
K. H. James 07
Atlantic spreadingAtlantic spreading
JJJJKKKK
N60°W drift, Late Jurassic - Early N60°W drift, Late Jurassic - Early Cretaceous, of N America from Cretaceous, of N America from Gondwana involved Middle America Gondwana involved Middle America
extensionextension
*
NorthAmerica
SouthAmerica
K. H. James 07
Middle America:Middle America: mostly extended continental mostly extended continental
crust. Greatest extension produced serpentinized mantlecrust. Greatest extension produced serpentinized mantle ..
CZCZ
Extended continent: thick Extended continent: thick Cretaceous carbonatesCretaceous carbonates
Extreme extension: Extreme extension: serpentinized mantle serpentinized mantle (Jurassic and Cretaceous)(Jurassic and Cretaceous)
Highly extended Highly extended continent: NE-trending continent: NE-trending continental blocks, continental blocks, seaward-dipping wedges seaward-dipping wedges (Tr-JJ), Cretaceous (Tr-JJ), Cretaceous basaltsbasalts
JJJJ KKKK
The only trueThe only trueoceanic crust (spreading oceanic crust (spreading ridge, magnetic anomalies)ridge, magnetic anomalies)
Continental crust
Extendedcontinental crust
Oceanized crust
Shelf edge
Oceanic crust
Accreted ocean/arc
K. H. James 07
Caribbean crustal typesCaribbean crustal types
Restoration:Restoration: removal of extensionremoval of extension
K. H. James 07
300 km300 kmoffsetoffset
Jurassic Jurassic riftrift Seaward-Seaward-
dipping wedgedipping wedge
K. H. James 07
Pangean reconstructionPangean reconstruction
Palaeozoic Palaeozoic suturesuture
FloridaFlorida
BahamasBahamasCubaCuba
S. AmericaS. America
MayaMaya
ChortisChortis
AppalachiansAppalachians
K. H. James 07
Triassic-Jurassic rift/driftTriassic-Jurassic rift/drift
Regional tectonic fabric is inherited from Palaeozoic and older Regional tectonic fabric is inherited from Palaeozoic and older structures (e. g. Appalachian suture).structures (e. g. Appalachian suture).
RiftsRifts
Seaward-dipping Seaward-dipping wedges with salt - wedges with salt - Baltimore Canyon, Baltimore Canyon, Carolina Trough, Blake Carolina Trough, Blake Plateau, Gulf of Mexico, Plateau, Gulf of Mexico, Caribbean, (?YucatánCaribbean, (?Yucatánand Colombian Basins).and Colombian Basins).
K. H. James 07
The Caribbean Plate formed in place during The Caribbean Plate formed in place during American drift.American drift.
It consists mainly of extended continental crustIt consists mainly of extended continental crust ..
The Caribbean “plateau” is built of NE trending The Caribbean “plateau” is built of NE trending Palaeozoic/older blocks, flanked by basins with Triassic Palaeozoic/older blocks, flanked by basins with Triassic - Jurassic seaward dipping wedges, Jurassic - - Jurassic seaward dipping wedges, Jurassic - Cretaceous shales/salt, covered by Cretaceous igneous Cretaceous shales/salt, covered by Cretaceous igneous
flowsflows. .
SSUMMARYUMMARY
Last thoughtLast thought: : if Scotia, Banda and the Caribbean are so alike, why is there an LIP in the if Scotia, Banda and the Caribbean are so alike, why is there an LIP in the Caribbean alone?Caribbean alone?
K. H. James 07
Caribbean Plate.Caribbean Plate.
Caribbean Plateau -Caribbean Plateau -was an impact involved?was an impact involved?
References:Diebold, J., N. Driscoll, and the EW-9501 Science Team, 1999, New Insights on the Formation of the Caribbean Basalt Province Revealed by Multichannel Seismic Images of Volcanic Structures in the Venezuela Basin: IN: Mann, P. (ed.), Caribbean Sedimentary Basins, Sedimentary Basins of the World, Elsevier, p. 561-589. Parson, L.M. & the ODP Leg 104 Scientific Party: Dipping reflector styles in the NE Atlantic Ocean: In: Morton, A. C., and L.M.Parson, Early Tertiary Volcanism and the Opening of the NE Atlantic: GSL Special Publication No. 39, p. 57-68. Manspeizer, W., 1988, Triassic-Jurassic rifting and opening of the Atlantic: An Overview: In: Manzpeizer, W. (Ed.), Triassic-Jurassic Rifting, Part A, Elsevier, p. 41-79. Benson, R. N. and R. G. Doyle, 1988, Early Mesozoic rift basins and the development of the United States middle Atlantic continental margin: In: Manzpeizer, W. (Ed.), Triassic-Jurassic Rifting, Part A, Elsevier, p. 99-127. Burk, C. A., M. Ewing, J. L. Worzel, A. O. Beall, W. A. Berggren, D. Bukry, A. G. Fisher and E. A. Pessagno, 1969, Deep-Sea Drilling into the Challenger Knoll, Central Gulf of Mexico: AAPG Bull., v. 53, p. 1338-1347.
Diebold et al. (1999) discuss seaward-dipping wedges, the Vøring Plateau, unusually thin oceanic crust and serpentinization. However, their interpretation (shown in this presentation) of the Caribbean Plateau is that it formed by two phases of volcanic extrusion on extended oceanic crust. They remark that their “volcanic mounds” have magnetic signature, so the diapirs discussed in this presentation could be igneous/serpentinitic. However, the magnetic data could record old intrusions and structural relief along basement faults. Salt diapirism is often focussed along fault zones. Diebold et al. (1999) note that their volcanic mounds trend NE or E-W. Sigsbee Knoll and NE Mexican salt diapirs in the Gulf of Mexico trend NE, following the regional fabric highlighted by this presentation.