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Evolution of Middle America and the in Situ Caribbean Plate Model

Evolution of Middle America and the in Situ Caribbean Plate Model

Evolution of Middle America and the in situ Plate model

KEITH H. JAMES Institute of Geography and Sciences, Aberystwyth, Wales, UK and Consultant Geologist, Plaza de la Cebada 3, 09346 Covarrubias, Burgos, Spain (e-mail: [email protected])

Abstract: Regional geological data and global analogues suggest Caribbean Plate geology con- tinues that seen along the margin of eastern in a more extensional setting, between the diverging . From west to east there are continental masses with Triassic , proximal continental blocks with kilometres-thick Mesozoic carbonates, more distal areas of Palaeozoic horsts flanked by Triassic–Jurassic dipping wedges of sediments, including salt and overlain by Cretaceous basalts, and most distal areas of serpentinized upper mantle. Plate history began along with the Late Triassic formation of the Central Atlantic Magmatic Province and involved Triassic–Jurassic rifting, Jurassic–Early Cenozoic extension and Oligocene– Recent strike–slip. Great extension promoted volcanism, foundering, eastward growth of the plate by backarc spreading and distribution of continental fragments on the plate interior and along its margins. Hydrocarbons probably are present. Caribbean geology has important implica- tions for understanding of oceanic plateaus, intra-oceanic volcanic arcs, the ‘andesite problem’ and genesis of ‘’ HP/LT metamorphic rocks. The model can be tested by re-examination of existing samples and seismic data and by deep sea drilling.

Middle America – crustal makeup as Triassic–Jurassic rifts with dextral component of movement; (b) generated N608E extensional Based upon data discussed in a sister article this faults such as the Hess and NW Campeche escarp- paper suggests an in situ evolution of the Caribbean ments; and (c) generated the Florida Arch. Curved Plate between North and . The data faults in northern reflect oroclinal indicate that Middle America is built mainly of bending and shortening during Cenozoic sinistral extended/distributed continental crust and smaller reactivation of N358E trends (James 2007). areas of pseudo- (serpentinized mantle) The following sketches suggest a Pangaean recon- (the only recognized spreading crust, with magnetic struction and the evolution of Middle America. anomalies, lies in the centre of the ; They do not pretend to be quantitative. Fig. 1). The geology continues that along the eastern margin of North America but in a more extensional Pangaean reconstruction setting between the diverging Americas. Rifted and extended with thick Mesozoic carbonate Pre-drift restoration of Middle America (Fig. 3a) cover recording subsidence surrounds the Gulf requires removal of sinistral offset and extension of Mexico and Yucata´n basins and underpins the between North and South America and removal of Florida–Bahamas platform and the submerged volcanic-arc crust and serpentinized mantle (Fig. 1). extension, as far as Jamaica, of continental Chortı´s The Gulf of Mexico (NAm) is closed up around the along the Rise. The internal Gulf of Maya Block. Maya and Chortı´s are united (removal Mexico, Yucata´n, Colombian, Venezuelan and of c. 900 km of Jurassic–Cretaceous, early Cayman basins carry extended continental blocks offset and 300 km of Oligocene–Recent Cayman flanked by half- with wedge-shape fill, offset) by aligning their faulted eastern margins bounded by areas of thin (c. 3 km) pseudo oceanic and Jurassic rifts associated with the Rı´o Hondo crust of serpentinized mantle. and Guayape´ faults (Fig. 2). This also restores north of and , them- Tectonic fabric selves closed up by removal of Cenozoic pull-apart. Thick crust of the Caribbean ‘Plateau’, western Middle America manifests a regional tectonic Basin, lies close to South America. fabric (Fig. 2) that demonstrates regional geological Similar crust seems to be present in the Yucata´n coherence and shows that no major block rotations and Colombian basins. Cenozoic oroclinal or plate migration occurred. The –strain bending of the Motagua and Agalta areas and ellipse (inset) for sinistral movement of North western Cuba (James 2007) is removed. The Hess America away from South America along N608W Escarpment/southern limit of the Nicaragua Rise fractures (a) reactivated N358E Palaeozoic sutures restores against the Me´rida trend of NW Venezuela.

From:JAMES, K. H., LORENTE,M.A.&PINDELL, J. L. (eds) The Origin and Evolution of the Caribbean Plate. Geological Society, London, Special Publications, 328, 127–138. DOI: 10.1144/SP328.4 0305-8719/09/$15.00 # The Geological Society of London 2009. 128 K. H. JAMES

Fig. 1. Middle America crustal types/distribution. Continental blocks, indicated by crustal thickness (gravity, seismic), high silica rocks and dredge samples, beneath southern Central America (SCA) and the Greater –northern (NLA) are hidden beneath obducted /oceanic crust. Thick crustal areas on the Lower Nicaragua Rise (LNR), eastern Yucata´n Basin (EYB), Caribbean ‘Plateau’ (CP) and west Basin (WCB) are underpinned by extended continent and locally overlain by Upper Cretaceous basalts. Serpentinized mantle possibly includes extremely attenuated continental crust. The Oligocene–Recent area in the Cayman Trough (red) is the only area with spreading magnetic anomalies.

Northwestern South America – the ‘Bolivar Block’ continental margin. Here, asymmetric basins is restored several hundred kilometres to the SW accommodated red beds, carbonates and evaporites along the Me´rida – Eastern Cordillera of as seaward-dipping wedges along the eastern sea- Venezuela–Colombia. The Aruba–Blanquilla island board of North America to Caribbean latitudes. chain does not exist at this time. Southern Central Major N608E trending features such as the Hess America (Chorotega–Choco´) restores to the SW and NW Campeche escarpments and the La of Chortı´s (present day Gulf of Tehuantepec, Trocha F. formed as the extensional strain within James 2007). the regional N608W sinistral system of offset This schematic reconstruction suggests continu- between North and South America (Fig. 2). The ity of major faults crossing Maya and Chortı´s with resultant new basins accommodated salt deposition. southern Florida and the eastern seaboard of North Since salt diapirs and ultramafic rocks are seen America and its continuation into NW South along northern (Pinet 1971, 1972) and America, possibly through the Sierra Nevada de since serpentinites occur in the Motagua zone Santa Marta in Colombia. in the Cretaceous (Harlow et al. 2004), this paper suggests that the early Cayman Trough extended Geological evolution between Maya and Chortı´s as a salt basin at this time (Figs 4 & 5). Triassic–Early Jurassic rifting (Fig. 3b) reactivated Late Jurassic–Early Cretaceous spreading in Palaeozoic continental sutures as rifts, accommo- the Central Atlantic resulted in WNW drift of North dating red beds and basalts (Manspeizer 1988; for America from Gondwana (South America–) a more regional vision of the Central Atlantic Mag- and great extension in Middle America (Fig. 4a, matic Province and continental margin wedges James 2009, fig. 4). Slip along major NW transfer see McHone et al. 2005, Fig. 1). Inboard basins faults within southern North America continued, off- were then abandoned as extension moved to the setting the formerly linear Appalachian–Ouachita IN SITU CARIBBEAN PLATE MODEL 129

Fig. 2. Interpretation of Middle America tectonic fabric as the result of (1) reactivation of ancient lineaments (N358E), (2) extension (N608E) and strike–slip (east–west) strain within the sinistral offset (N608W) of North from South America. AI, Aklins–Inagua–Caicos; BF, Beata F; BR, Beata Ridge; BRR, Blue Ridge ; CE, Campeche Escarpment; CT, Catoche Tongue; EG, Espino ; GF, Guayape FM; HE, Hess Escarpment; LT, La Trocha FM; MG, Me´rida Graben; MiG, Mississippi Graben; M-SF, Motagua–Swan FM; OR, Oachita Rift; PF, Patuca FM; PG, Perija´ Graben – Urdaneta; RBFZ, Rı´o Bravo fault zone; RGR, Rı´o Grande Rift; RHF, Rı´o Hondo FM; SAL, San Andre´s Lineament; TF, Ticul FM; TG, Takutu Graben; TT, Texas Transform; TSZ, Tenochtitlan Zone; TZR, Tepic– Zacoalco Rift; VF, Veracruz FM; YC, Yucata´n Channel. Red line, SE limit of Caribbean Plateau, the Central Venezuela FZ. Green lines, magnetic anomalies. Compiled from many sources. trend and opening the Gulf of Mexico as the conti- introduced strike–slip along the nent interior pulled away from the Maya Block Plate boundary, possibly provoking HP/LT and the NW Campeche Escarpment. metamorphism in rapidly subsiding/filling deeps, Maya moved west relative to Chortı´s by some enhanced Caribbean extension and resulted in a 900 km (early Cayman displacement). Chortı´s first phase of basalt extrusion (120 Ma). Atlantic– moved around 900 km NW relative to South Caribbean convergence resulted in subduction America and 400 km NW relative to Chorotega/ below dispersed continental fragments along the Choco´. Marginal areas subsided to accommodate Lesser Antilles with resultant volcanism. Uplift to platform carbonates several kilometres thick wave base, formation of an unconformity capped (Florida–Bahamas platform–, by shallow marine limestones and change of Limestone Caribbees, Campeche–Yucata´n– arc chemistry from primitive to calc-alkaline Nicaragua Rise). Further outboard, NE-trending (continental input) occurred plate-wide, possibly normal faults (Triassic–Jurassic rifts) became reflecting intra-plate expansion due to decompres- listric as continental crust thinned into horsts sion melting. A further plate-wide unconformity flanked by wedges of sediments. formed in the Cenomanian. Extrusion occurred Albian commencement of westward drift of again in the Turonian (90–88 Ma), forming the South America from Africa at Caribbean latitudes probably subaerial smooth seismic Horizon B00, 130 K. H. JAMES

Fig. 3. (a) Schematic Pangaean restoration of middle America, modern coastlines shown for reference. Cayman offset between Maya and Chortı´s removed. Chorotega/Choco´ restored to SW Chortı´s. NW South America (Bolivar Block, B) restored S608W along Me´rida Andes–Eastern Cordillera. Lesser Antilles basement represented by a single block, later dispersed by radial spreading. Extension of Bahamas Plateau, Nicaragua Rise and oroclinal bending of western Cuba removed. B, Bolivar Block; BP, Bahamas Platform; C, Chortı´s; Ch, Chorotega/Choco´; Cu, Cuba; Hi, Hispaniola; J, Jamaica; LA, Lesser Antilles; M, Maya; NAm, North America; NR, Nicaragua Rise; SAm, South America; YB, Yucata´n Basin. (b) Triassic–Early Jurassic rifting accommodated intracontinental Triassic red beds (Jurassic in South America) and continent margin red beds and salt (Callovian? in Gulf of Mexico). Rifts reactivated N358E Palaeozoic sutures. Offset along major transforms in southern North America pulled the Maya Block from the Gulf of Mexico and the Nicaragua Rise away from NW South America – the parallel Campeche and Hess Escarpments are the extensional strain of N608E sinistral movement of North relative to South America (inset Fig. 2). Early Cayman offset (east–west sinistral synthetic to N608W movement) began to separate Maya from Chortı´s along the northern Caribbean. C, Chortı´s Block; CB, Colombia Basin; CE, Campeche Escarpment; HE, Hess Escarpment; LT, La Trocha F; M, Maya Block; VB, Venezuela Basin; YB, Yucata´n Basin. IN SITU CARIBBEAN PLATE MODEL 131

Fig. 4. (a) Late Jurassic–Early Cretaceous. Severe extension and subsidence of continental margin crust accommodated kilometres-thick carbonate platforms (Florida–Bahamas–Greater Antilles–Limestone Caribees, Yucata´n–Campeche, Nicaragua Rise). Early ‘Cayman’ offset of Maya and Chortı´s continued. Chortı´s was offset NW from Chorotega/Choco´. NW trending grabens formed in SW Mexico–West Central America. Subduction volcanism began in Central America and the Lesser Antilles. C, Chortı´s; Ch, Chorotega/Choco´; F-B, Florida–Bahamas Platform; GA, Greater Antilles; LC, Limestone Caribbees; NR, Nicaragua Rise; Y-C, Yucata´n Campeche Platform. (b) Middle– Late Cretaceous. Basaltic intrusion/extrusion occurred over highly extended continental crust, forming the ‘Caribbean Plateau’ in the Venezuela Basin. Similar seismic signature is seen in Colombia, north Grenada and Yucata´n basins. Severe extension resulted in serpentinization of upper mantle (pink areas). Back-arc spreading at the Aves Ridge (AR) drove the Lesser Antilles eastwards over Atlantic crust. Peripheral volcanic arc rock chemistry shows continental input since the Albian and rocks contain ancient zircons. 132 K. H. JAMES

Fig. 5. (a) Middle Eocene. of ‘oceanic’, volcanic arc and continental margin rocks emplaced around the Caribbean, covered by erosional unconformity and shallow marine limestones (uplift to wave base). Volcanism ceased along northern and southern Caribbean Plate boundaries. Beginning NE movement of NW South America along the Me´rida Andes/Eastern Cordillera. (b) Oligocene–Recent. East Pacific Rise spreading drives the orthogonally against Central America, reactivating Jurassic rifts as sinistral faults, resulting in oroclinal bending of Motagua (Mo), Agalta (Ag) and western Cuba (James 2007, figs 11 & 12). It also drives the Caribbean Plate eastwards, triggering central Cayman Trough spreading and strike–slip (300 km) along the northern and southern boundaries. Transtensional extension disperses the Greater (GA) and Leeward (LA) Antilles. Southern Choco´ sutures to NW South America (SB, Serranı´a de Baudo); northward extrusion of the Panama´ arc (PA) and the Bolivar Block (BB) drives the Panama´ (PDF) and South Caribbean (SCDB) Deformed Belts. capping the horsts and half grabens of extended con- sections sandwiched between the 120 and tinental crust in the Caribbean Plate interior. The 90 Ma basalts. presence of basalt flows dated 120 and 90 Ma in areas such as Ontong Java suggests episodes of Middle Eocene global activity. This paper suggests that the thick areas of crust in the Venezuelan, Yucata´n Flysch deposition became common in the Late and Colombian basins include thick carbonate Cretaceous. It culminated violently with Middle IN SITU CARIBBEAN PLATE MODEL 133

Eocene emplacement of extremely large olistoliths Basin and great thickness of young Cenozoic sedi- of ‘oceanic’, volcanic arc and continental margin ments in the Columbus Basin testify to the highly rocks in the Greater Antilles and along northern dynamic nature of the strike–slip system, capable South America, where arc volcanism ceased (Fig. 5a, of driving rocks quickly to depths where HP meta- James 2005a). Uplift raised allochthons through morphism can occur at low temperatures. wave base where a regional Middle Eocene uncon- Along the northern plate boundary a second formity developed, overlain by regional Middle phase of Cayman offset was accompanied by spread- Eocene shallow-water carbonates (James 2005a). ing in the Trough and separation of the eastern Allochthons included the 250 km long Villa de Greater Antilles along the Mona, Windward and Cura (Venezuela), with its former western Anegada Passages (Fig. 5b). North–south faults extension, the Aruba–Blanquilla island chain, the divided the Hess Escarpment into three c. 200 km 1000 km long ophiolite belt of Cuba and the long elements and the Nicaragua Rise became Duarte and Bermeja complexes of Hispaniola and segmented (Muttia et al. 2005). Puerto Rico. Horizontal movement was as much Convergence of the Farallon/ with as 140 km in Cuba (Cobiella-Reguera 2009). At NW South America, low (44 + 26 mm/annum) the same time thrust slices in Mexico’s Veracruz during the Oligocene–Early Miocene and high Basin stacked 6 km high and moved eastward at (125 + 33 mm/annum) from Middle Miocene– least 30 km (Mossman & Viniegra-O 1976, fig. 2). Recent (Daly 1989), continued to drive the Bonaire Rapid (204 + 80 mm/annum, Daly 1989) Late Block NE. The northern part of the block trans- Eocene convergence between the Nazca Plate and gressed the South America–Caribbean dextral northwestern South America began to drive the boundary, driving the South Caribbean Deformed Bolivar Block (Fig. 5a) of northwestern South Belt ahead of it. Extrusion occurred along the America (James 2000) NE. NNW Santa Marta–Bucarramanga Fault and NE Sometime in the Late Cretaceous, possibly Early faults in the Colombian Eastern Cordillera– Cenozoic, back arc spreading in the eastern Carib- Venezuelan Me´rida Andes. A large positive bean extended the plate eastwards over Atlantic gravity anomaly associated with the 5800 m high crust and dispersed continental blocks below the Sierra Nevada de Santa Marta, Colombia, indicates Lesser Antilles. the absence of isostatic equilibrium and witnesses The most recent phase of Caribbean history the dynamism of this system. (Fig. 5b) involved some 300 km of Oligocene– Pull-apart extended the northern Bonaire Block, Recent strike–slip, sinistral and dextral respect- formerly the western continuation of the Villa de ively, along the northern and southern plate Cura nappe, as it crossed the plate boundary. The boundaries, driven by convergence of the Cocos Aruba–Blanquilla islands, highs of 5.4 km s21 Plate with the western Caribbean. Along both material separated by basins with thick Oligo- margins uplift occurred earlier and is greater in the cene–Recent sediments, exhibit the same structural west. The size of Greater Antillean islands and the periodicity as the nappe (Edgar et al. 1971; Curet height and depth of erosion in the Coastal Range– 1992; James 2005b, c, fig. 14). Northern Range of Venezuela and dimin- Northern Choco´ separated from Chorotega along ish eastwards. Erosion has exposed the strata lying the Panama´ F., moving northwards to form the below allochthons in the west (continental basement Panama´ arc and driving the Panama Deformed Belt. in Cuba and the Venezuelan Coastal Range as far as NE convergence of the Cocos Plate along the Gulf of Paria). In the east these rocks remain Central America drives a regional system of NE occulted. From Hispaniola to the trending sinistral faults in the western Caribbean only uplifted oceanic and volcanic arc rocks crop (James 2007). They transform in the north and out; however, gravity and chemical data indicate south into oroclines and and thrust-belts and thick and siliceous basement. accommodate shortening between the bounding The episode began with a pulse of block faulting zones of North Cuba and Central and pull-apart extension, possibly triggered by the America. The most impressive system runs along Middle Eocene event. Once again, highly extended eastern Maya, linking the Motagua ‘orocline’ with areas subsided. Middle Eocene, shallow marine western Cuba. An estimated 350 km of shortening carbonates on the Beata and Aves Ridges now lie (Rosencrantz 1990; James 2007) here closed the in thousands of metres water depths. It was followed western extension of the Cayman Trough by by eastward-migrating thrusting over complemen- NE-moving Chortı´s. tary foredeep basins in Venezuela–Trinidad (Gua´rico Basin–Oligocene; Maturı´n Basin– Implications Miocene; Gulf of Paria–Pliocene; Columbus Basin–Pleistocene–Recent). Earth’s largest nega- Data (James 2005c, 2006, 2009) and the interpret- tive gravity anomaly at sea level over the Maturı´n ation of this paper suggest learnings for aspects 134 K. H. JAMES of global geology. Indications of continental 5 km, common around the Caribbean, testify to sig- fragments below the Caribbean ‘Plateau’ and the nificant extension, presumably close to thinned con- Greater and Lesser Antillean and Central American tinental crust. volcanic arcs imply that it is perilous to assume What caused repeated episodes of convergence, purely intra-oceanic origins for oceanic plateaus metamorphism, uplift, erosion and unconformities and volcanic arcs (Leat & Larter 2003; Kerr et al. covered by shallow marine limestones? Trans- 2009). Accepted discriminatory chemical/isotope pression? Vigorous plate expansion, driven by data for such areas need to be statistically qualified decompression melting? Pulses of Pacific Plate and examined independently of presumed origins to convergence? see what messages they carry. Geology of the Carib- The Middle Eocene event was remarkable for bean volcanic arcs suggests answers to the ‘andesite its suddenness and violence (Stainforth 1969). It problem’ – it is not a case of understanding how abruptly emplaced sections of serpentinite up to subducting basalt gives rise to such silica-rich 5 km thick and up to 1000 km long by as much as rocks (Takahashi et al. 2007) but rather of recogniz- 140 km onto continental margins in Cuba and ing that arc roots, related by seismic velocities to Venezuela – outward moving in response to a continental rocks (Tatsumi & Kosigo 2003), plate interior compressional stress or sudden conver- involve original continental fragments. gence of North and South America. Coeval deposits HP/LT metamorphic rocks are not necessarily in Peru and Ecuador and an eastward verging stack signals of subduction. Transcurrent faulting is of thrusts 6 km high in the Veracruz Basin of capable of generating rapid, deep burial and exhu- Mexico rule out the latter. Conventional wisdom mation of such rocks. suggests convergence of such material should lead The Caribbean Plate lies between the giant oil to subduction, not . Did salt and/or ser- provinces of the Gulf of Mexico and northern pentinite assist de´collement? Did hydro-pressure South America. Oil is seen on Puerto Rico, Hispa- due to hydrocarbon generation play a role? What- niola, Jamaica, , , Honduras, ever the cause, the regional and coeval occurrence Nicaragua, , Panama´, Colombia, Vene- of these deposits correlates continental margin zuela, Trinidad and , circumscribing with Caribbean Plate boundary and internal geology. practically the whole of the plate. This signals over- What is the age and nature of thin crust in the looked potential on the Caribbean Plate. Some oil is Haiti Basin, the SW Colombian and Venezuelan thought to come from Cenozoic sources but oils of basins? Jurassic, Cretaceous, Cenozoic? Guatemala, Belize, Jamaica, Costa Rica and Barba- Did high standing blocks in the Caribbean and/ dos have Jurassic or Cretaceous chemical signatures or shallow/subaerial basalt outpouring cause (Larue & Warner 1991; Babaie et al. 1992; Burggraf restriction and supply nutrients for Albian and et al. 2002; Cameron 2004; Emmet 2002; Lawrence Turonian organic rocks? et al. 2002). Why are there no return path metamorphic rocks Source rocks are likely in Jurassic and Creta- associated with the Lesser Antilles or Central ceous sections on the Caribbean Plate interior. The American subduction arcs? former developed in narrow marine basins; the Why is there no major difference in chemistry latter in seas restricted by subaerial basalt extrusion between the northern (descent of oceanic crust over extended continental crust, since subsided close to the arc) and southern (descent of ocean below thousands of metres of water. A risk is that crust east of the Barbados Accretionary Prism and they were overmatured by igneous activity. Gas Trough) parts of this arc? might be expected. Are there hydrocarbons on the Caribbean Plate interior? Questions Predictions Juxtaposition of continental, volcanic arc and ophio- litic rocks in locations such as the supposed The model described by this paper suggests the between Maya and Chortı´s and along northern following. Venezuela is problematic (Giunta & Oliveri 2009). El Tambor rocks of the Motagua ‘suture’ are the Ophiolites, once attributed to mid-ocean spreading, exhumed western continuation of the Cayman today are seen to form in several different environ- Trough. ments, including pull-apart intra-arc basins, Thin, ‘oceanic’ crust in the southeastern Colom- back-arc basins and extensional zones in forearcs bian and Venezuela Basins and in the Grenada Basin during development of island arcs (Moores 2003). is serpentinized mantle, Cretaceous or Cenozoic All these settings can be envisaged in Middle in age. America as extension occurred during the Dispersed continental blocks underpin the Jurassic–Cenozoic. Ophiolite thicknesses up to Cayman Ridge, the Upper Nicaragua Rise, Costa IN SITU CARIBBEAN PLATE MODEL 135

Rica, Hispaniola, Puerto Rico, the Virgin Islands, Tests the northern Lesser Antilles, Chorotega/Choco´. Thick crust of the Venezuela, Colombia, The understanding of this paper suggests the Yucata´n and Grenada basins is underlain by blocks following tests. of continental rocks flanked by wedges of Triassic– Many data are easily obtainable. Dredge samples Jurassic–Cretaceous rift sediments, evaporites and of the Cayman Trough walls, walls of the Puerto carbonates, overlain by subaerial basalt flows. Rico Trough and the Aves Ridge and core samples The Lower Nicaragua Rise is underpinned by of the deeper Venezuelan and Colombian basins highly extended/transitional crust – there are could be re-investigated for lithology, age and local continental blocks. zircon content. Existing seismic data could be The N608E Hess Escarpment is the outer marginal revisited and new data gathered that would dis- limit of the Nicaragua Rise/Chortı´s continental block. tinguish between in situ and allochthonous It formed as a major extension in the Jurassic– models. It should be possible to distinguish defini- Cretaceous sinistral N608W offset of North from tively between seamounts and salt diapirs, to see if South America. It became segmented by north– thickened parts of the Colombian, Grenada and south trending faults during Cenozoic extension. Yucata´n basins have the same architecture as the Pull-apart extension along the Nicaragua Rise/ western Venezuelan Basin and to see if combined Hess Escarpment, the Greater Antilles and Aruba– velocity/magnetic/gravity data can distinguish Blanquilla sums to around 300 km, equal to between igneous/volcanic and extended continental Central Cayman spreading in the north and exten- origins. Much could be learned by systematic repro- sion of the Falco´n Basin and separation of the cessing/reinterpretation of existing seismic data. in the south. † Age date zircon in volcanic/oceanic rocks in The Greater Antilles mirror-image northern South Central America, Hispaniola, Puerto Rico, America. They are built of north verging thrust sheets, Lesser Antilles and Aves Ridge. some inverting stratigraphy, and mixed blocks of † Age date zircon in volcanic rocks from DSDP allocthonous, mainly Jurassic–Cretaceous, oceanic samples of the Caribbean Plateau. and volcanic arc rocks deposited as Middle Eocene † Age date zircon in dredge samples from the wildflysch above continental blocks. Caribbean. The Beata and Aves Ridges were the focus of † Age date clasts in rocks dredged from the back-arc spreading in the Mid–Late Cretaceous Cayman Trough. and Late Cretaceous–Early Cenozoic, respectively. † Palynological study of salt/cap rock at Salinas, There are salt diapirs in the Caribbean, predicted Puerto Rico, Cerro Sal, Dominican Republic salt age Jurassic. and Salt Pond Pen, Jamaica. Hydrocarbons are present on the Caribbean † Gravity and heat flow investigation of seamounts interior. v. diapirs.

Fig. 6. Suggested drill sites to test ideas of this paper. 136 K. H. JAMES

† Examination of Middle Eocene sections for suffered serpentinization of upper mantle, forming evidence of impact (tektites, iridium). rough Horizon B00. † IODP drilling of Cayman Trough basement, The Middle Eocene regional, convergent event predicted to be Early Cretaceous serpentinite terminated most volcanic activity along the northern (Site 1, Fig. 6). and southern Caribbean Plate boundaries, where † IODP drilling of ‘seamounts’ – predicted to be Oligocene–Recent strike–slip followed. The only salt diapirs, north of Honduras, Yucata´n Basin, spreading crust in Middle America, with recogniz- Beata Ridge, seismic line 1293 (Sites 2–5). able spreading ridges and magnetic anomalies, † IODP drilling with greater penetration of the formed in the central 300 km of the Cayman Caribbean Plateau (Sites 5 and 8). Trough during this latest . † IODP drilling to ‘oceanic crust’ Haiti and Vene- Continued divergence of North and South zuela basins (Sites 5 and 10). America, shown by diverging fractures in the † IODP drilling to test a circular bathymetric low east of North and South America in the Venezuela Basin (Site 8), a possible and by a wedge of fractures east of Caribbean impact crater (James 1997). latitudes recording 650 km of north–south growth † IODP drilling to date early sediments exposed in of the Mid-Atlantic Ridge, created space for the Guajira Canyon (Site 9). back-arc growth of the Caribbean Plate. Analogy † IODP drilling to test deep section on the southern with the , which occupies as similar wall of the Puerto Rico Trough, predicted conti- tectonic setting, suggests that this occurred firstly nental crust (Site 11). along the Beata Ridge and later along the Aves Ridge. Many unrecognized fragments of continental Conclusions crust are dispersed around and on the Caribbean Plate. They underlie the whole of Central America The geology of the area between North and South and the Greater and Lesser Antilles and at least America shows regional harmony and a shared the northern and southern Lesser Antilles. history among the various geographic components, The strength of the in situ model is that it incor- all of which are autochthonous. Following porates data in a regionally coherent, simple evol- Triassic/Jurassic extrusion of the Central Atlantic ution that conforms to the wider geology of Magmatic Province North America separated from eastern North America and the Gulf of Mexico. It South America/Africa. Triassic–Jurassic rifting compares with the well-calibrated geology of the reactivated ancient NE-trending basement linea- analogous Scotia Plate. It is a model that can be ments. This structural grain is regionally preserved tested. In contrast, models deriving the Caribbean today in Middle America, including the Caribbean Plate from the Pacific models are complicated. Plate interior. No major block rotations have Required processes such as slab-rollback beneath occurred. an overriding plate and below the Yucata´n Basin Volcanism accompanied extension but com- are not recorded by data and are not testable. pressional events in the Middle and Late Creta- ceous and Middle Eocene led to pause or cessation I pay tribute to those geologists of the past who, with far of activity, uplift to wavebase and subaerial less data than I have, also saw Caribbean geology in erosion, development of unconformities and simple terms. shallow marine carbonates, karstification. Abundant extrusion accompanied the Middle and Late Cretaceous events in the Colombia and Vene- zuela basins. Coeval high organic productivity References resulted from restriction and formed hydrocarbon BABAIE, H. A., SPEED, R. C., LARUE,D.K.& source rocks. CLAYPOOL, G. E. 1992. Source rock and maturation Subsidence of proximal areas (Bahamas and evaluation of the Barbados accretionary prism. Yucata´n–Campeche platforms, Nicaragua Rise) Marine and Geology, 9, 623–632. accommodated kilometres-thick carbonate sections. BURGGRAF, D., LUNG-CHUAN, K., WEINZAPFEL,A.& Horsts of continental crust flanked by wedges of SENNESETH, O. 2002. A new assessment of Barbados Jurassic–Cretaceous sediments, flows and salt onshore oil characteristics and implications for formed in more distal areas along the eastern regional petroleum exploration. 16th Caribbean Geo- logical Conference, Barbados, Abstracts, 3. margin of North America and within Middle CAMERON, N. 2004. Jamaican oil biomarkers require a America (Yucata´n, Colombian and Venezuelan re-examination of the petroleum geology of the Basins). Shallow/subaerial flows of smooth northern Caribbean. American Association of Pet- seismic Horizon B00 capped the Caribbean areas in roleum Geologists International Conference, Cancu´n, the Late Cretaceous. Areas of extreme extension Mexico, Abstracts, A11. IN SITU CARIBBEAN PLATE MODEL 137

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