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,

khj@aber.ac.ukkhj@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°

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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?

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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?

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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,,

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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

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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”

.

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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

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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).

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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

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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

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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

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Pangean reconstructionPangean reconstruction

Palaeozoic Palaeozoic suturesuture

FloridaFlorida

BahamasBahamasCubaCuba

S. AmericaS. America

MayaMaya

ChortisChortis

AppalachiansAppalachians

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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.