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Geology of the Caribbean Plateau Keith James Institute of Geography & Earth Sciences, Aberystwyth, Wales, UK, This model: the plate formed.

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Presentation on theme: "Geology of the Caribbean Plateau Keith James Institute of Geography & Earth Sciences, Aberystwyth, Wales, UK, This model: the plate formed."— Presentation transcript:

1 Geology of the Caribbean Plateau Keith James Institute of Geography & Earth Sciences, Aberystwyth, Wales, UK, This model: the plate formed in place, between N and S America. Paradigm: -the Caribbean Plate is oceanic and came from the Pacific. -the Plateau formed over a mantle plume. -it is mostly extended continental crust. -the plateau consists of NE trending continental blocks, Palaeozoic and older, flanked by Triassic-Jurassic seaward-dipping wedges and overlain by Cretaceous basalts. K. H. James 07

2 “Middle America” Atlantic Plate NORTH AMERICA U L Pacific Plate
3 5 Cayman Ridge NORTH AMERICA SOUTH AMERICA “Accreted volcanic arc” Cayman Trough Bahamas Yucatán Basin Gulf of Mexico Greater Antilles Maya Block Grenada Basin 2 Chortis Block Lesser Antilles U Venezuela Basin L Beata and Aves ridges Chorotega Block Colombia Basin Chocó Block 5 Pacific Plate - 8 5 - 7 - 5 5 K. H. James 07

3 Problems with Caribbean geology
Geology is spread over many different countries. Some areas are poorly mapped (access, vegetation, weathering). There are no spreading ridges or magnetic anomalies in the whole of middle America, save for the central 300 km of the Cayman Trough (Miocene - Recent). Most data are collected/interpreted under the assumption that the Caribbean Plate is oceanic and came from the Pacific. K. H. James 07

4 The Caribbean Plateau Caribbean Plate crust in the western Venezuela Basin-Beata Ridge area is up to 20 km thick. This is the “original” Caribbean Plateau. Five ODP/DSDP sites have penetrated Cretaceous basalts, dated Ma, at the very top of the thick, uncalibrated section. Overlying sediments are shallow marine carbonates. Peripheral to thick Caribbean crust, supposed “original” oceanic crust is thin, 3 km, not drilled, not dated. Other parts of the Caribbean Plate interior (in the Colombia, Grenada and Yucatán basins) also are thick. Together with the “original” plateau and accreted rocks around the Caribbean and in Colombia, they are seen to comprise an oceanic plateau or large igneous province. Some of the accreted sections include palaeosols. Several oceanic plateaux (Ontong-Java, Iceland, Kerguelen, Vøring, Rockall) are known to have continental roots. Is this true of the Caribbean Plateau?

5 Popular model: The Caribbean Plate is oceanic and migrated from the Pacific (successive arc locations). Arc volcano Extinct MEoc 2 Mas LA Tur Brm MMio 5 CAP Popular model: The Caribbean Plateau formed above a mantle plume (Galapagos Hotspot). - 8 5 - 7 K. H. James 07

6 Caribbean Banda Scotia The plates are strikingly similar.
NORTH AMERICA SOUTH AMERICA ATLANTIC OCEAN SOUTHEAST ASIA Plate boundary 30° Continent margin Shoreline Volcanic arc Gulf of Mexico Bahamas 15° Philippines Hispaniola Yucatán Maya Puerto Rico PACIFIC OCEAN Basin BR 15° AR Lesser Chortis Sulawesi Antilles Borneo Sumatra Papua- New Guinea PACIFIC OCEAN Java INDIAN OCEAN Timor AUSTRALIA Scotia -100° -85° -70° 105° 120° 135° The plates are strikingly similar. SOUTH AMERICA ATLANTIC OCEAN -75° -45° -55° -30° Antarctic Peninsula Shackleton Fracture Zone N Scotia Ridge S. Scotia Ridge S Sandwich Islands Scotia and Banda formed in-place by back-arc spreading. PACIFIC OCEAN Scotia and Banda carry marginal and interior continental fragments. Is there continental material in the Caribbean? K. H. James 07

7 Indications of continent in the Caribbean
3 5 Cuban Cretaceous arc rocks Cayman Trough walls -carry Precambrian, Palaeozoic zircons, -continental grantitoids, red beds, greywackes, arkose. 2 Jamaica Southern Central America -crustal thickness 20 km, -crustal thickness km, -flysch from N.NE contains gneiss, schist, quartzite, slate, marble -gravity: continental density, -high silica ignimbrites, granulite xenoliths 5 -Albian and Miocene quartz sandstones. - 8 5 - 7 - 5 5 K. H. James 07

8 Indications of continent in the Caribbean
3 5 NE Caribbean: -crustal thickness 30 km -gravity: continental density -continental rocks on Hispaniola, Puerto Rico Trough, Cretaceous stratigraphic continuity with Bahamas -Silica content up to 76% 2 Siuna Cretaceous “oceanic terrane” Aves Ridge -conglomerates with abundant quartz, fragments of schist and quartzite -underlain by granitic rocks 5 - 8 5 - 7 - 5 5 K. H. James 07

9 The Caribbean “plateau”
shelf edge 3 5 NORTH AMERICA plate boundary thick crust "accreted plateau" DSDP locations ridge The original “plateau” ATLANTIC 2 has NE structural grain (not the radial pattern expected of a plume) 5 . PACIFIC SOUTH AMERICA - 1 - 5 5 K. H. James 07

10 It conforms with the regional tectonic pattern
. N35°E Palaeozoic structural trend 3 5 Next slide 5 - 1 This extends along the Atlantic seaboard of N. America into the N. Atlantic K. H. James 07

11 Seismic line 1293 (after Diebold & Driscoll, 1999)
“Seamount” Ridge Wedge K. H. James 07

12 Seaward-dipping wedges are common features of continental margins (e.g. N. Atlantic, after Parson et al.) Jan Mayan Greenland Jan Mayan and Iceland: continental roots. Vøring Plateau Seismic line Iceland Rockall and Vøring: subaerial-shallow marine basalts. Faroe Vøring: andesite-dacite at (ODP Site 642) shows continental input. Rockall Plateau Wales, etc. Rockall: 5 km sedimentary section, including 1.5 km basalt, on ~13 km highly stretched continental crust.

13 Seaward-dipping wedges, Caribbean and Vøring plateaux
NW convex-up reflections SE smooth B" Basalt Convex up reflections Caribbean “plateau” C B C NW SE Vøring margin

14 Eastern N America (after Manspeizer, 1988).
Next slide 300 Km Offshore: Triassic - Jurassic basins with salt Onshore: Triassic clastic basins

15 Seaward-dipping wedges: offshore N America; note presence of salt (after Benson & Doyle, 1988).
NW SE SW NE Shore line COST Neogene U Cret - Pal Km Mid. JJ - 5 Early KK Pre-Mesozoic basement 10 Post rift Salt 15 unconformity Rift basin 100 Km 20 V/E x10 Wedge

16 Interpretation of plateau (after Diebold & Driscoll, 1999)
A - Early volcanic thickening volcanic mounds with dipping flanks depleted source Mantle ve = 25 “Seamount” B - Extension - final volcanics additional depletion K. H. James 07

17 Diapirs: - Gulf of Mexico and Caribbean
NW SE Caribbean: Line 1293, after Diebold & Driscoll, 1999 Not a seamount but a diapir (salt, shale, serpentinite?) 10 km SW NE 1 km 5 km Gulf of Mexico: Sigsbee Knolls, after Burk et al., 1969 Challenger Knoll: drilled - salt diapir

18 Seismic line 1293: interpretation - this study (James 2007)
NW SE Diapir - ?salt Triassic- Pz basement oceanized crust U Tr L 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 ? 11 “Ski jump”? = marginal reef/mound Sea floor SB" A" RB" CVFZ ? NE-trending continental blocks, seaward-dipping wedges, salt, covered by subaerial Cretaceous basalts - SB smooth Horizon B”. RB - rough Horizon B” - serpentinized mantle (“oceanic” crust). K. H. James 07

19 Atlantic spreading JJ KK
N60°W drift, Late Jurassic - Early Cretaceous, of N America from Gondwana involved Middle America extension KK K. H. James 07

20 Middle America: mostly extended continental crust
Middle America: mostly extended continental crust. Greatest extension produced serpentinized mantle. The only true oceanic crust (spreading ridge, magnetic anomalies) Extended continent: thick Cretaceous carbonates North JJ America KK Highly extended continent: NE-trending continental blocks, seaward-dipping wedges (Tr-JJ), Cretaceous basalts CZ Extreme extension: serpentinized mantle (Jurassic and Cretaceous) * South America K. H. James 07

21 Caribbean crustal types
Continental crust Extended continental crust Oceanized crust Accreted ocean/arc Oceanic crust Shelf edge K. H. James 07

22 Restoration: removal of extension
300 km offset Seaward-dipping wedge Jurassic rift K. H. James 07

23 Pangean reconstruction
Appalachians Palaeozoic suture Florida Maya Cuba Bahamas Chortis S. America K. H. James 07

24 Triassic-Jurassic rift/drift
Seaward-dipping wedges with salt - Baltimore Canyon, Carolina Trough, Blake Plateau, Gulf of Mexico, Caribbean, (?Yucatán and Colombian Basins). Rifts Regional tectonic fabric is inherited from Palaeozoic and older structures (e. g. Appalachian suture). K. H. James 07

25 SUMMARY The Caribbean Plate formed in place during American drift.
It consists mainly of extended continental crust. The Caribbean “plateau” is built of NE trending Palaeozoic/older blocks, flanked by basins with Triassic - Jurassic seaward dipping wedges, Jurassic - Cretaceous shales/salt, covered by Cretaceous igneous flows. K. H. James 07

26 Last thought: if Scotia, Banda and the Caribbean are so alike, why is there an LIP in the Caribbean alone? Caribbean Plate. Caribbean Plateau - was an impact involved? K. H. James 07

27 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 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 Manspeizer, W., 1988, Triassic-Jurassic rifting and opening of the Atlantic: An Overview: In: Manzpeizer, W. (Ed.), Triassic-Jurassic Rifting, Part A, Elsevier, p 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 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 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.

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