Processes & Events in the Terrane Assembly of Trinidad … · 1 Pindell et al, GCSSEPM 2001 Processes & Events in the Terrane Assembly of Trinidad and E. Venezuela James Pindell*

1 Pindell et al, GCSSEPM 2001

Processes & Events in the Terrane Assembly of Trinidad and E. Venezuela

James Pindell* and Lorcan Kennan

Tectonic Analysis, Ltd., Chestnut House, Burton Park, Duncton, West Sussex, GU28 0LH, England *Also: Dept. Earth Science, Rice University, Houston, Texas, USA Email: [email protected] or [email protected] Web: http://www.tectonicanalysis.com Originally published in: GCSSEPM Foundation 21st Annual Research Conference Transactions, Petroleum Systems of Deep-Water Basins, December 2-5, 2001, pages 159-192.

Abstract

Neogene-Recent arrival of the Caribbean Plate and subsequent development of the Southern Caribbean plate boundary zone as well as coeval deposition of Orinoco deltaic sediments in Eastern Venezuela-Trinidad have profoundly changed the region’s earlier basin setting, including some very large vertical and horizontal displacements of original tectonic elements and depositional systems. Plate kinematic analysis provides the geometric and temporal framework in which to see past these late developments and to deduce the region’s earlier paleogeographic evolution, and constrains the primary setting, style and timing of basement structure in the region’s shallow-water and deep-water continental margins through time. Palinspastic restoration of deformations, terrane accretions, and sedimentary additions to the region’s continental areas back through time to the breakup of Pangea allows fine-tuning of the kinematics, and prediction of parameters such as paleo-heatflow, paleo-sedimentary provenance, and aspects of source and reservoir potential. In Eastern Venezuela-Trinidad, Jurassic rifting produced a serrated crustal margin, with rift segments oriented ~070° separated by sinistral transfer zones at ~140°. A Late Jurassic-Cretaceous “passive” margin along the Proto-Caribbean Seaway developed above this basement, but sinistral shear between South American and Bahamian crusts along the Guyana Escarpment may have caused continued tectonism into Early Cretaceous, prior to truly passive margin Late Cretaceous source rock deposition. Paleogene convergence between North and South America caused uplift and erosion in Venezuela’s northern Serranía del Interior, the flyschoid depositional results of which are found in northern Trinidad. This is because the northern Trinidad depocenter, here called the Northern superterrane, was situated much closer to the Serranía at that time, as opposed to southern Trinidad. During Oligocene-middle Miocene arrival from the west and dextral-oblique arc-continent collision of Caribbean Plate with the margin, Northern superterrane strata have been translated ESE and imbricated with strata of the Southern superterrane, producing strong foredeep subsidence in the Maturín-early Southern Basin. Coeval strike slip faults such as Coche-North Coast may have taken up some of the strike-slip component of the oblique relative motion. Since the end of middle Miocene, the southeast Caribbean plate boundary zone has been dominated by E-W simple shear, with relatively minor N-S shortening and extension adjacent to faults. A 3-stage model involving variable strain partitioning describes the tectonic and basin history of Eastern Venezuela and Trinidad for the last 12Ma. The various stages of development have produced exploration settings of different aspect across the greater Trinidad region.

mailto:[email protected]

mailto:[email protected]

http://www.tectonicanalysis.com/default.htm


Introduction

The Trinidad region (Figure 1, 2): (1) straddles the present Caribbean-South America plate boundary (Molnar and Sykes, 1969); (2) was involved in Paleogene convergence between North and South America (Pindell et al., 1991; Pindell et al., 1998) as well as Oligocene-middle Miocene oblique collision between the Caribbean and South American crusts (Dewey and Pindell, 1985; 1986; Speed, 1985); (3) formed part of the northern South American Cretaceous (Proto-Caribbean) passive margin (Pindell and Drake and papers therein, 1998); and (4) served as the juncture of the northern South American rift zone and the Guyana Escarpment transform margin in the Jurassic-Early Cretaceous. Therefore, understanding the tectonics and the associated depositional history of the Trinidad region involves the integration of plate kinematics, crustal and structural modeling, palinspastic reconstruction, detailed paleogeographic analysis through time, and analysis of neotectonics. In addition, comparison and integration with the geology of Eastern Venezuela is vital to forming a complete picture of the region’s geology and evolution. Here we address several of these issues to build an overview of Trinidad’s tectonic and exploration framework, with implications for the eastern deep water offshore.

Onshore Trinidad comprises two very different rock suites, here called the “Northern” and “Southern”

superterranes to allow further subdivision in future, defined generally by the absence (north) and presence (south) of the Gautier and Naparima Hill formations, and the presence (north) and absence (south) of a Paleocene-middle Eocene clastic section (Chaudière/Pointe-a-Pierre Fms. (north) vs. Lizard Springs/Navet Fms. (south) (Figure 3). Onshore, the Northern superterrane is represented in the northern flank of Central Range and Caroni Basin, was involved in or located adjacent to an early Paleogene tectonic event in northeastern Venezuela, and was carried ESE as it was accreted into the Caribbean accretionary prism in the Oligocene-middle Miocene. The Southern superterrane comprises a parautochthonous/autochthonous zone ahead of the migrating Northern superterrane, and is represented in the Brighton-San Fernando Hill [middle Miocene] “subthrust” belt, the Southern Basin, and the Plata-Campana Highs. These two superterranes are now separated onshore Trinidad by a high-angle, anastomosing and often en-echelon fault system along the Central Range (loosely termed “Central Range Fault Zone” pending further study; Kugler, 1959; Figures 1, 2), which nearly coincides with the active (since Pliocene) trace of dextral fault motion (Figures 2, 4). In the Gulf of Paria, the superterrane boundary appears to roughly follow the active zone of displacement, but borehole density is insufficient to map it in detail, and it may stray south of the active strike-slip zone where it could be imbricated in thrusts comprising the northern flank of the Plata and Campana Highs. If it does follow the trace of active displacement, it likely continued in middle Miocene time into the trace of the Pirital and/or San Francisco Faults of the Serranía del Interior, with a possible genetic relationship. Some distance out in the eastern offshore, the superterrane boundary deviates from the surface trace of active displacement; the trace of active displacement steps southward across the Pleistocene Southeastern Extensional Province (upper level pull-apart system) and ties into the toe of the Barbados prism (Figures 2, 4). Eastward gravitational collapse here feeds down-slope imbrication in the southernmost Barbados prism. Also at some poorly known distance offshore to the east, we would expect the boundary to curve north and become more transitional across its original middle Miocene imbricated fold-thrust belt.

Although the aforementioned stratigraphic differences in southern vs. northern Trinidad have long been

noted (e.g., Carr-Brown and Frampton, 1979), this paper will show that the boundary between them is abrupt for structural rather than stratigraphic reasons. The structural arguments employed may help to guide exploration, essentially delimiting the occurrence of good Upper Cretaceous source rocks to the south side, and prospective early Paleogene reservoir rocks to the north side. There is potential, along the superterrane structural interface, to reap the benefits of both, especially if rocks of the Southern superterrane can be shown locally to be overthrust by rocks of the Northern superterrane. Also, strike-slip displacement of reservoir packages from above early source kitchens, as well as emplacement of reservoirs upon existing kitchens, is possible. In this paper, we trace the origin and history of these “terrane” assemblages by integrating the region’s plate kinematics, seismic tomography, stratigraphy, and palinspastic paleogeography. Our main objective is to integrate and tie the various geological parameters into an internally consistent and viable working model that can serve to guide continued

Pindell et al., 2001, Trinidad Terranes, Figures

Gulf of PariaSerraniaInterior

Caroni Basin

Manzanilla Pt.

Pt-a-Pierre

Columbus Channel

Plata

Galeota Pt.

Maturín Basin

Delta Amacuro

North Range

Southern Range

Carupano Bsn

Galera Pt.

North Coast Ft.

10

Central Range

Nariva Belt

62

Darien Ridge

Guyana Escarpment

K Shelf Edge?

63

11

61

Coche Fault

Projection of continent-ocean basement boundarybeneath Trinidad

Tobago

El Pilar Ft.

Warm Springs Ft.

Arima Ft.

Campana

Pirital Ft.

El Furrial

San JuanGraben

Pedernales

12 3

45

8

1, San Fernando Hill. 2, Brighton3, Dunmore Hill, Debe-Wellington Faults.4, Penal-Barrackpore anticlinal thrust stack.5, Southern Basin. 6, Rock Dome7, Mary Assy Thrusts. 8, Guayaguayare High

6

7

Figure 1. Locality map of the Trinidad region for features referred to in text.

GUYANA TRANSFORM - earthquakesindicate possible tearing under weightof advancing Barbados Prism

Guayaguayare Terrane (absent mid. Mioc.)Southern Basin BlockNariva Fold Thrust BeltDeepest Paria depocentresNorthern Range, Caroni BlockSerrania del Interior OrientalCarupano Platform, N.most SOAM deep crust

NTFPBF

ARIMA F.

Pull-apart? DARIEN RIDGE

S. COASTFAULT

EL FURRIAL -PEDERNALES TREND

S. FRANCISCO F.

URICA F.

CARIBBEAN PLATE

EL PILAR F.

COCHE F.

PIRITAL THR.

PLATA-CAMPANAHIGH

Evaps. onGulf High

C.Coro, Soldadobackthrusts

WARM SPRINGS F.

?No evaps. onDomoil High

GALEOTAFAULT

Dunmore Hill and otherout-of-sequence thrusts

Rock Dome, LizardSprings thrusts

Pliocene growth fault province shown in red.Pleist. growth fault province shown in black

San Juan Graben

“MANZANILLAPT.” FAULT

CRF

CRF - Central Range Fault, southern boundary of Cuche outcropNTF - Nariva Thrust Front, leading edge of accretionary prism and assoc. thrustingPBF - Penal Barrackpore Fault, anti-formal stack of late middle Miocene age

TOBAGO

LEADING EDGEOF CARIB. CRUST Structure from

Boettcher et al., 2000

Position of ocean crustedge relative to SOAM

Trench where Proto-Caribbeanunderthrusts SOAM.

Carupano Platform occurs where Carib. Plateoverthrusts edge of SOAM - note this drives the sub-sidence of Maturin Basin and ?Columbus Channel

64 63 62 61 60 59 58

64 63 62 61 60 59 58

9

10

11

12

9

10

11

12

Figure 2. Map of major fault traces and tectonic elements in the Trinidad region.


research and exploration in the region. The exercise also serves to define problems that need further work, the results of which can eventually be re-integrated to further refine the model.

Regional geology: crustal boundaries, faults, basins, and terranes

Geological sub-regions and their boundaries are shown in Figures 1, 2 & 4. Although the North Coast Fault Zone and Coche Fault Zone form the primary petrologic plate boundary between Caribbean/South America, almost all of the fault displacement between the Caribbean Plate and South America since at least the Pliocene has been taken up farther to the south.

The El Pilar Fault system and the Gulf of Paria pull-apart basin lie to the south of the Araya-Paria

Peninsula and Northern Range and allow strike-slip displacement to step southward into the Central Range of Trinidad and offshore into the Darien Ridge. Many earlier papers (e.g. Robertson and Burke, 1989) explicitly assume that the major interplate displacement lies either off the north coast of Trinidad or on the Arima Fault (eastward projection of a strand of El Pilar). As a result, the idea has become rooted that there is a sharp E-W boundary between the Caribbean Plate driving the Barbados Accretionary Prism to the north, and deformed passive margin to the south (latter is likely to be more prospective for exploration). We suggest that this is fundamentally in error and that the boundary between allochthonous and parautochthonous terranes lies farther south than previously supposed and is broader and more complex than early models suggest. Below we outline some of the evidence for our terrane interpretation.

Northern Range

The Northern Range (Algar, 1993a,b; Algar and Pindell, 1993; Weber et al., 2001) comprises Jurassic-Lower Cretaceous, and Maastrichtian continental slope to basin floor strata, now metamorphosed with most of Upper Cretaceous missing or extremely condensed. No Tertiary is known and metamorphic grade generally increases to the west either progressively or across unclear faults. The first significant tectonic deformation is characterised by a low angle foliation with a strong E-W trending stretching lineation. This fabric was later modified by more open folding and, in late Miocene, gentle southward tilting as a rigid body which has produced or increased the first foliation’s southward dip. Peak metamorphism is dated by 23-26 Ma Ar-Ar mica growth ages within the first foliation (Foland et al., 1992), while zircon fission track ages indicate cooling below ~250°C in the late middle Miocene in western and central areas. Apatite fission track ages from the lower grade rocks in the east indicate cooling below ~110°C in early Miocene (Algar et al., 1998; Weber et al., 2001).

The strong E-W stretching lineation in the first foliation strongly suggests that interaction with the Caribbean crust (leading edge of basement now SE of Tobago) or its accretionary wedge drove the ~25Ma deformation and metamorphism. Approximate positions of the leading of edge of the Caribbean are well-constrained (Pindell, 1993; Pindell et al., 1998; Pindell et al., in press) and indicate that the Northern Range was originally situated up to 500 km west of its current position (25 m.y. of ~20 mm/yr inter-plate displacement). Disregarding the complicating effects of internal E-W stretching in these terranes, this puts the Northern Range depocenter to the north of the western part of the Serranía del Interior, and the Paria Peninsula and lower (passive margin) nappes of the Araya Peninsula north of Caracas. In support of this, we note that the shallow water deposits of the Caracas Group along central Venezuela show no “slope facies” belt between them and the Caribbean Plate, while Eastern Venezuela and especially Trinidad have two parallel belts of “slope” facies. The geochronology and structural and stratigraphic relations suggest that the Lower Araya-Paria-Northern Range terrane was obliquely picked up by the Caribbean prism by 25Ma (start of first deformation) and obliquely thrust across slope/outer shelf strata to the south. Uplift and cooling began during early to middle Miocene, and by 10-12 Ma, most zircons ages were locked in. Seismic lines through the Dragon’s Mouth (gap between Norhtern Range and paria) suggests that the northern flank of the Range is defined by a N-dipping detachment where the Carupano Platform of the Caribbean Plate (top nappe in oblique collision) has subsequently detached transtensionally from the overthrust Northern Range, probably at 10-12 Ma when zircons underwent final cooling.


Figure 3. Summary of stratigraphy and distinctions between “Northern” and “Southern”superterranes in Trinidad, separated generally by the Central Range Fault Zone. The Northern Rangecan be considered as a terrane within the Northern superterrane, and the boundary with the Northernsuperterrane may be a gradual transition, achieved by thrust imbrication with a strong component ofdextral shear. The Chaudière and Pointe-a-Pierre Fms. of the Northern superterrane may interdigi-tate as shown in the column. These units rest unconformably on Cuche Fm. in the Northernsuperterane, which is a trademark feature of the northern half of Trinidad’s Central Range as well asof the NE corner of the Venezuelan Serranía del Interior Oriental.

Cuche (thermally altered) Cuche (not altered)

Gautier/Naparima Formations,conformable

Largely missing, but noteoccurrences near Chert Hill

Chaudiere/Pt-a-Pierre clastics

San Fernando North

Nariva in wedge top basin

Cunapo 1/Brasso in wedge top basinUpper Cipero unfilled foredeepNariva in imbricated prism,Lower/middle Cipero foredeepSan Fernando SouthNavetLizard Springs

Southern Basin, andS-flank Central Range

Jurassic

EarlyCretaceous

LateCretaceous

Paleocene

Eocene

Oligocene

Early-Mid.Miocene

L. Miocene

Plio-Pleist

Maraval/Maracas

Chancellor/GrandeRiviere/ Rio Seco

Toco-Laventille

Galera, Lopinot Guayaguayare

Lengua/KaramatManzanilla

Not known ormissing

NorthernRange

Caroni Basin, andN-flank Central Range

Couva marine evaporites

UnknownUnknown

Eroded off ornot deposited

C

Springvale

Nariva accre-tionary prism

Northern Range

Caroni Basin

Southern Basin

A

?

?

Paleocene Chaudiere Shale withOlistoliths (olistostrome),middle? to outer? bathyal

Eocene Pointe-a-Pierre Grits,quartz sand and shale,turbiditic deposition

Early Oligocene San FernandoFormation, carbonate debristransported into deep-water

Cuche Formation:1, shallow marine shale in NW2, deeper marine shale in Central Rng3, metamorphic in Caroni Basin

Central Range, Trinidad, Paleogene"flysch" units derived from a shallow source

B


Jurassic

Espino Graben

Gulf of PariaCariaco Basin

Jurassic trans-form edge ofOceanic Crust

PalinspasticallyreconstructedCretaceousshelf edge

Edge ofCaribbeanCrust

Limit ofBarbadosPrism

SE Extensionalprovince "basin"

Trace of Paleogenesubduction zone

TrinidadReentrant,ß=3-4

12

10

8

12

10

864 6062 5866

64 6062 5866

Serrania, ß<2

Limit of "normal"continental Crust

Figure 4. Simplified map of tectonic elements showing the locus of Caribbean-SouthAmerica strike-slip motion, stepping south across the Cariaco Basin, Gulf of Paria Basin,and Southeastern Extensional Province towards the toe of the Barbados AccretionaryPrism.


Basement of the Caroni Basin

The Caroni Basin between the Central and Northern Ranges deepens into the Gulf of Paria Basin to the west, and may in general be considered as part of the Gulf of Paria pull-apart basin (Algar and Pindell, 1993). A strong seismic reflector beneath the northward-onlapping late Miocene to Pliocene sedimentary fill dips south, wedging into and beneath N-vergent backthrusts of the Central Range. The surface can be traced northward up to surface exposures of the Northern Range. Wells onshore and offshore indicate that the surface is an unconformity or pediment upon overmature Barremian-Aptian “Cuche Fm.”. The commonly overlying Cunapo Fm. contains metamorphic clasts derived from the Northern Range, generally fining to the south into age equivalent Manzanilla Fm. The “Cuche Fm.” is lithologically similar to age equivalent strata in the eastern part of the Northern Range (e.g. Rio Seco Fm.). The northern margin of the basin is defined by the Arima Fault, which clearly shows several km of down to the south motion, decreasing eastward to nil at the eastern coast. There is little definitive evidence of strike-slip motion along the south side of the Northern Range (but see Robertson and Burke, 1989), and neither the Arima nor El Pilar faults can be confidently traced into the eastern offshore on seismic data. Thus, we infer that the Caroni Basin basement of onshore Trinidad is continuous with that of Northern Range but distinct from that of the Southern Basin (see below).

There is strong E-W extension within the late Miocene-Pliocene section of the Caroni Basin. Overall, the

area serves as the NE null quadrant of the greater Gulf of Paria-Caroni pull-apart, while faults along the crest of Central Range serve as the active quadrant of the pull-apart, transferring motion from El Pilar fault and Gulf of Paria eastward across Trinidad. The south flank of the Caroni Basin was inverted in the late Pliocene, with considerable erosion of the southern Caroni section.

Central Range

The Central Range is a prominent ridge of imbricated middle Cretaceous to Pleistocene strata cut by range-parallel dextral strike-slip faults. Current structural expression is Plio-Pleistocene. In addition, the middle Miocene Brasso Fm. records the middle Miocene uplift of the Central Range (and probably Caroni Basin as well), as a piggy back basin or overlap assemblage upon the underlying submarine Nariva fold-thrust belt/accretionary prism (Erlich et al., 1993). In cross section, today’s Central Range looks like a doubly vergent set of high-angle thrusts overthrusting both to the north and the south, with a central strike-slip fault system (Central Range Fault Zone) down the middle. To the south, thrusting has an “accretionary” character with large folds thrust over piggy back basins. Recent inversion of the northern flank of Central Range has caused northward thrusting of strata over the southern Caroni Basin. This late phase is clearly of a dextral strike-slip (transpressive) nature. GPS motion studies (Weber et al., in press) show about 14-16 mm/yr of strike-slip motion along the strand of the Central Range Fault that passes through Pointe-a-Pierre, such that dextral offset since the ~2?Ma onset of transpressive inversion could reach about 30km, and longer term magnitudes could be more. The strike-slip component makes balancing cross sections very misleading.

The Central Range Fault Zone appears to define two paleogeographic zones in the Central Range. To the

north of the fault: 1) the lowest known unit is thermally altered Cuche Formation;

2) the Gautier and Naparima Hill Fms. are generally missing (except at Chert Hill exposure in the eastern Central Range; Kugler, 1959);

3) the Paleocene Chaudière Fm. is unconformable on Cuche/Chert Hill Upper Cretaceous, bears mica and floating sand and quartz-sandstone grains, and has a flyschoid appearance, and is strictly a Northern superterrane unit: the “Chaudière Member” of Lizard Springs Fm. at San Fernando Hill in the Southern-superterrane apparently was mapped as Chaudière by Kugler (1959) due to the occurrence of the St. Joseph's Conglomerate there, but this conglomerate is distinctive from the sandy micaceous flysch of the Northern superterrane, and can be interpreted as passive margin submarine channel fill, to be expected in the Southern Terrane;


4) Pointe-a-Pierre Fm. is usually associated with Chaudière Fm., and is the sandy correlative to Navet marls in the Southern superterrane. In the eastern Central Range, beds mapped as Chaudière shales and Pointe-a-Pierre sands (Kugler, 1959) are interbedded (Figure 3), suggesting to us a basin floor model of Chaudière overbank shales and debris flows, and Pointe-a-Pierre sandy turbidite channels and fans across the basin plain. However, the section does appear to become much sandier upward, such that a distinction between the two formations can usually be made: by Pointe-a-Pierre time, sand dominated shale in the system.

5) the Vistabella and Plaisance members of the latest Eocene-earliest Oligocene San Fernando Formation represent a coarsening and increase carbonate content in this re-sedimented Paleogene clastic section of the Northern superterrane (Tectonic Analysis, Inc., 1997), although sandy conglomeratic beds of similar age also occur in the south (e.g., Oligocene section of the Rocky Palace borehole), requiring further analysis of this possible distinction between the two terranes.

The reason for the widespread absence of Upper Cretaceous in the Northern superterrane (and Northern

Range) remains unclear, but non-deposition, Late Cretaceous (pre-Galera Fm.) erosion, and severe depositional condensation have all been considered.

The Nariva Thrustbelt

The Nariva Fold Thrust Belt is a poorly exposed area of highly deformed late Oligocene-middle Miocene muds and sandstones, imbricated during the early and middle Miocene, that separates the Central Range to the north from the Southern Basin. Depth to main detachment appears to drop to the north on seismic, where early Paleogene (Chaudière and Point-a-Pierre Fms.) and Lower Cretaceous (Cuche Fm.) strata become involved in out of sequence faulting. (Plio-Pleistocene transpression). The Southern Basin stratigraphy (except Chert Hill) forms the footwall to this fold-thrust belt (but was also imbricated in sequence at, at least, Brighton and San Fernando Hill during middle Miocene). Restoration of estimated younger shortening in southern Trinidad combined with our integrated plate kinematic modeling indicates that, during the early to middle Miocene, the Nariva fold-thrust belt was located where the leading edge of the Caribbean Accretionary Prism should have been during oblique collision with the South American margin. We summarize similarities between the Nariva belt and recognized accretionary prism phenomena below:

Table 1. Four characteristics of accretionary prisms and of the Nariva fold-thrust belt, Trinidad

1. Accretionary prisms comprise imbricates of sediment deposited ahead of an advancing thrust front. The trace of the prism

(trench) is usually a bathymetric low, in which gravity flows preferentially accumulate. Sedimentation commonly enters the trench along its axis, ie laterally, but sediment can also spill into the trench from either side of the trench.

2. Sediments get accreted as packages (slices) into prisms by episodic propagation of the leading thrust into the sedimentary section at the toe of the trench, resulting in downward younging in the sediments contained in the package. Already-accreted packages of sediment become progressively uplifted and rotated away from the trench as new packages are accreted at the prism base. Each package boundary can continue to act as, usually, a thrust fault during rotational uplift, and piggyback basins may develop between major thrusts.

3. Newly accreted packages are water rich and de-water after accretion, leading to mud diapirism up through the hanging walls of already-accreted sediment. Mud volcanoes commonly serve as conduits for fluids and blocks stoped from the strata they have migrated through. Thus, blocks may be older or younger than the matrix. Erosion of sub-marine mud volcanoes by bottom currents can create lag deposits of blocks across and within the surface of the prism that can look like sedimentary olistostromes.

4. Matrices of mud diapirs show signs of ubiquitous shear, often as slickensides of all orientations. Blocks may show shear textures along their margins as well, depending on the relative shear strength of the block and the matrix, or whether multiple blocks have come into contact during uplift.

We interpret the Nariva Belt as part of the early to middle Miocene Caribbean Prism for the the following

reasons. The Nariva Formation (Belt) comprises latest Oligocene to early middle Miocene muds, sands, and sandy muds, and is thought to be a source of many mud diapirs. It overlies the Lower Cipero Fm. and is laterally continuous into middle Cipero Fm. southwards, hence there is southward stratigraphic diachroneity, consistent


with advance of a foredeep basin ahead of a thrust front. The Lower Cipero Fm. is shown on maps as stringers within the Nariva Fm.: this may be structural or stratigraphic, or both, but the style is reminiscent of accretionary prisms. Outcrops of Nariva Fm. often show “scaly” phacoidal fabrics (with concoidal fracture) on which slickensides occur on all surfaces and in all directions, indicative of shale diapirism. Overlying the Nariva Fm. are the Retrench and Herrera Fm. sandy “fairway” units, which we consider to be at least partly controlled by syn-sedimentary folding in the accretionary prism, ie “piggy-back” basins. Development of the Nariva thrustbelt caused progressive shallowing of the Central Range into the middle Miocene, but thrusting failed to cause emergence to the south (foredeep depocenter). The Brasso Fm. depocenter farther north was a piggy back basin of sorts, marking the shoaling of the Nariva foldbelt. During middle Miocene time, the Nariva thrustbelt would have continued northeastward into the Barbados accretionary prism.

SouthernBasin and Maturin Basin south of Serranía del Interior

To the south, the Southern superterrane stratigraphy (Figure 3) prevails across fold-thrust domain that is ultimately detached on or below Lower Cretaceous strata, but with major detachments also present beneath the Miocene section. Typically, top Cretaceous is found at ca. 3.5sec depth, dropping to 6-8sec in the Columbus Basin offshore. In the Guayaguayare area in the southeast, the middle Miocene succession is restricted to a thin Herrera section and this contrasts with areas currently only a few kms to the north. Prior to Plio-Pleistocene thrusting, there may have been dextral transtensional shear through the region now occupied by the Rock Dome and Mary Assy structures. The two sub-domains were juxtaposed by latest Miocene time, as shown by the Springvale-Forest “overlap” assemblage (Kugler, 1959).

Timing, kinematics and style of deformation are complex. Middle Miocene thrusting advanced south from

the Nariva Thrust Belt to the southern edge of the Penal-Barrackpore Anticline, where frontal bathymetry was onlapped by Lengua-Karamat strata. Brighton and San Fernando Hill include the southern stratigraphy that was involved in the middle Miocene thrusting. We expect this stratigraphy to have originally continued to the north by an amount equal to the shortening in the Nariva Foldbelt.

Starting at ~10-12Ma, the middle Miocene Serranía-Central Range thrust wedge began to collapse,

detaching upon overthrust Carapita-Cipero foredeep shales and extending internally at NW-SE trending faults that cut older thrusts. The Lizard-Mary Assy trend appears to have been the limit of this collapse, and depending on the azimuth of collapse, it may have been either a low-angle detachment (northward collapse) or a transfer zone that relayed dextral shear (ENE trantension) toward the toe of the migrating accretionary prism. Late Miocene strata appear to thicken south towards the Rock Dome and Lizard-Mary Assy suggesting that these structures were not yet in compression. To the west, the transtensional detachment at this time (late Miocene) surfaced in the Maturín Basin (Figures 1, 2), where up to 30 km of extension has been mapped south of El Furrial (di Croce et al., 1999).

Compression in this region started at about 4-6 Ma, with growth apparent on out-of-sequence thrusts south

of Brighton in late Lower Cruse Fm. time. Out-of-sequence thrusting (Debe-Wellington, Dunmore Hill thrusts) continued into the middle Pliocene, and thrusting may have started in the Rock Dome area by no earlier than 3-4 Ma, folding previously active extensional (E-directed extension - see below) faults onshore. Detachment level for Rock Dome, Lizard Springs and Dunmore Hill Thrusts is beneath Naparima Hill Fm. while the Debe-Wellington thrusts reactivate a base Nariva Fm. detachment. Cretaceous lies ca. 2.5s higher in the Southern Basin than in Columbus Channel indicating that deeper levels of stratigraphy must also be involved in thrusting. Shortening and excess area calculations indicate a thickness below known Cretaceous of ca. 3 km, possibly suggesting involvement of older (Jurassic-Neocomian) sediments. Pleistocene shortening direction may have been close to parallel with the 110° Los Bajos Fault (a tear, or shallow-rooted strike-slip fault linking with intra-Cretaceous detachment), along which minor bends in the fault’s trace produce transpressive pop-ups. The Los Bajos Fault separates an area of greater thrust shortening to the east (Rock Dome, etc.) from a zone of lesser shortening to the west. Linkage geometry through the Plata-Campana area is not clear.


Muertos Trough

ColombiaBasin

Pindell etal. data

Muelleret al. data

-80 -75 -70 -65 -60

10

15

20

25

10

15

20

25-80 -75 -70 -65 -60

300 km

Venezuela

Cuba

05

613

21 25 3234

56

13 21

25 32

34

0

5

6

13

21 25 3234

0

5

6

1321

25 32

34

0

A

17

10

33

46

56

Present

1710

334656

TobagoFlowline

BlanquilaFlowline

B

Figure 5. (A) Points labeled with magnetic anomaly numbers representing the former relative positions (since Campanian) ofNorth America with respect to a fixed South America; after Müller et al. (1999) and Pindell et al. (1988). Anomalies 34=~84Ma;32=~72Ma; 25=~56Ma; 21=~46Ma; 13=~33Ma; 6=~19Ma; 5=~10Ma. (B) Points labeled in time (Ma) showing Tertiary motionhistories of Tobago (representing Tobago Terrane) and Blanquilla (representing Caribbean Plate) relative to South America,based on modelled plate reconstructions of Pindell and Kennan (this volume). Although the average path is shown between 10Ma and 0 Ma as a solid line, Trinidad’s structural history suggests that motion for this period may have been that of transtensionfor ca. 10-4 Ma and transpression for ca. 4-0Ma (dashed lines). However, this is not the only mechanism that could have pro-duced these structural styles (see text).


The south coast of Trinidad is characterized by N-vergent backthrusts growing during the Pleistocene. These must link to S-vergent deeper detachments imaged on some deep seismic lines in the eastern offshore. The youngest compressive structures (as young as or younger than South Coast, Galeota structures) are gentle SE-directed folds. The Maturín-Pedernales Fault system (middle Miocene thrustfront that was later reactivated as a normal (late Miocene-early Pliocene) and then compressive (Plio-Pleistocene) fault is quasi-continuous with the Trinidadian Southern Range fault zone, the backthrusts of which appear to root at 4.5s to 6s depth into detachments below the Southern Basin.

Columbus Basin and Southeastern Extensional Province

The offshore Southeastern Extensional Province lies within the Columbus Channel and to the east, comprising areas of both Pliocene (including onshore extent) and Pleistocene extension (Figures 1, 2, 4). The province lies to the south of the Darien Ridge and has a diffuse southern margin close to the maritime border between Trinidad and Venezuela. The Barbados Prism accretionary front is well-defined in the east and can clearly be traced southwest towards the Columbus Channel. This strongly suggests that some of the accretion at least is driven by large magnitude eastward movement of Trinidad and that the extensional province marks a third southward step in the locus of strike-slip (the others being the Cariaco Basin and the Gulf of Paria Basin). Almost all extensional faults trend N-S or NW-SE including Pliocene faults onshore in the Southern Basin. The extensional province south of Maturín may be a late Miocene geometric analogue whose motion was transferred east through the Lizard-Mary Assy trend (see above).

There is not much extension, onshore or offshore, west of the projection of Los Bajos Fault. Onset of

extension was probably triggered by the incorporation of the Southern Basin strata into the allochthon as deformation migrated to the southeast. During the Pleistocene, extension migrated eastwards (Wood et al., 2000) as compression started to dominate onshore southern Trinidad and total extension in the east may be up to 40-50km. Some of the massive accommodation space (6-8 km since 4 Ma) may reflect shale bulge migration (Wood et al., 2000) but the majority appears be tectonic. Rapid subsidence reflects not only the magnitude of extension, but the likely thickness of the sediments underlying the Province which have been extended. Note that we have crossed a major crustal boundary, from continental to oceanic crust east of the Guyana Transform (Figures 1, 2; Pindell and Kennan, 2001, companion paper in this volume), where accommodation space, and presumably sediment thickness, has been greater since at least Late Jurassic time.

Plate Kinematics and Tomography: Support for Five Phases of Evolution

A simple five phase history adequately describes the geological history of Eastern Venezuela and Trinidad. The five phases are: 1) rifting and separation of Yucatan from the Americas; 2) Paleogene subduction of Proto-Caribbean oceanic crust beneath northern South America; 3) early Neogene oblique transpression with the Caribbean Plate overriding the older passive margin; 4) late Neogene oblique transtension and collapse of the orogen; 5) localized Pliocene-Pleistocene inversion of previously extensional structures while, overall, transtension continues to dominate. Evidence in support of this history is outlined below.

North America-South America Relative Motions

Figure 5a summarizes the motion of North America relative to South America since Campanian time (Müller et al., 1999; Pindell et al.; 1988). Separation of North and South America (by seafloor spreading in the Proto-Caribbean Seaway) came to an end sometime between the ages of anomalies 32 and 25 (ca. late Maastrichtian) and since then slow, generally north-south, convergence has occurred. Total convergence is greater in the west (350km in Colombia dropping to 200 km in Eastern Venezuela) due to clockwise rotation of South America. Significantly, ~42km of the total 200km in Eastern Venezuela had occurred by the middle Eocene and ~56km by end of the Eocene, an amount which must be explained by plate boundary processes which had nothing to do with the Caribbean Plate, which then lay far to the west, and which we will argue affected the northern South American margin in Paleogene time.


Figure 6. Interpreted positions of top of Proto-Caribbean slab, location of tears in that slab, andposition of subduction zone between South America and North America now buried by over-riding Caribbean lithosphere, based on seismic tomography data from van der Hilst (1990). Fig-ure 6a) E-W cross-section showing thick (1) and thin (2) Caribbean lithosphere, presumablyreflecting differing degrees of magmatic underplating of Late Cretaceous age. The Proto-Caribbean lithosphere (3) is clear as a cold region, subducted by at least 1,200 km beneath theCaribbean lithosphere. Note that seismicity (dots) is limited to the upper 200 km of the slab,close to the trench. In all profiles deep cold pre-existing “shadows” (4) are seen at ca. 550-650km which appear to merge with the cold cores of subducting slab, indicating that care must betaken when interpreting the data. b) N-S line through the Gulf of Barcelona clearly shows theProto-Caribbean slab subducting beneath northern South America, with warmer ?asthenospherebetween the two lithospheres (5). The asthenospheric wedge is clearer to the north (6), where itspresence allows melting at depths of ca. 100 km beneath the overriding Caribbean Plate. Againnote seismicity clustered only close to the trench (7). c) N-S line through the Gulf of Paria, far-ther east. Note that on first examination this line appears to show a deep slab attached to SoAmdipping to the north. However, when interpreted in the light of line b, and others, the true inter-pretation, as a south-dipping slab subducted below the northern edge of SoAm, becomes clear(8). Again, we note the presence of deep cold shadows (9) at ca. 600 km which can confuse theinterpretation. Note in both b and c that the magnitude of overlap between NoAm and SoAmindicates that this subduction must predate the arrival of the Caribbean off of eastern Venezuelaand Trinidad by at least 20-30 Ma. d) Hypothetical lithospheric geometries in Eastern Venezuelabefore (Paleogene) and after (Neogene) arrival of Caribbean Plate from the west. Only conver-gence occurs between SoAm and Proto-Caribbean slabs, while dominantly transcurrent motionoccurs between those slabs and the allochthonous Caribbean Plate. Arc magmatism in LesserAntilles indicates that a mantle wedge occurs between the Caribbean and Proto-Caribbean crusts:this wedge thickens southwestward. Proto-Caribbean subduction beneath SoAm is too slow tocreate an arc there. e) Map showing: location of cross-sections through seismic tomographicmodel for Caribbean region (modified from van der Hilst, 1990); paleopositions of South Ameri-can (relative to NoAm) coastline and interpreted continent-ocean crust transition at 72 Ma(coastlines in Maracaibo/Colombia area adjusted to remove Cenozoic displacement on MéridaAndes, Oca and Santa Marta faults); and interpreted contours on top of Proto-Caribbean slab.Stippled area shows how much of the Proto-Caribbean has been subducted beneath South Ameri-ca (has moved north since 72 Ma). Also note that in the west, a tear formed in the Proto-Caribbean slab as its leading edge sank to the ca. 650 km discontinuity in the mantle. Proto-Caribbean slab is only completely imaged on sections in the east. There, the imaged overlapmatches extremely well with the calculated northward motion of SoAm since the early Cenozoic.


E

?

?

B C

AProto-Caribbean istearing and sinkingto the south

Proto-Carib.-SOAMtrench now buried byadvancing Carib. Plate

SOAM coastat 72 Ma

Westwardextension ofTiburon Rise

CaribbeanTrench

Proto-Caribbean isoverthrust byCaribbean Plate inthis region

Edge ofcont. crustat 72 Ma

Depth contours of proto-Caribbean slab (km)

500

Edge of cont.crust at 72 Ma

Diffuse deformationcloser to SOAM-Proto Carib pole ofrotation

60 556570

5

10

15

20

Proto-Caribbean isoverthrust by SOAMin this region

Proto-Caribbean slab known to exist at least tohere, but if trench had nucleated within cont.-ocean transition, then slab would continue to here

300

400

400

300

200

100

200

SoAm Lithosphere Proto-Caribbean Lithosphere

S N

PALEOGENE TIME, PRIOR TO ARRIVAL OFCARIBBEAN PLATE FROM THE WEST

South Proto-Caribbean trench

SoAm Lithosphere Caribbean Lithosphere

Proto-Caribbean Lithosphere

PuertoRico

Trench

NEOGENE TIME, AFTER ARRIVALOF CARIBBEAN PLATE IN NORTH-SOUTH CROSS-SECTION

Serrania/Trinidad foldbelt,and East Ven foredeep

SoAmadvancingnorth overtrench, causingsubduction by rollback only

S N

D

Carib.

Proto-Carib.

SoAm 5 6 7

250 500 750 1000 1250 1250S N

0

200

400

600

800

B

0

200

400

600

800

250 500 750 1000 1250W E

Carib.

Proto-Carib.

1 2

4

3

A

Carib.

Proto-Carib.

SoAm8

9

250 500 750 1000 1250 1250S N

0

200

400

600

800

C


Caribbean-South America Motions

Using detailed Caribbean plate reconstructions through time, Pindell and Kennan (2001, this volume) deduced the Caribbean-South America relative motion history shown in Figure 5b. On Figure 5b, only the actual points shown define former relative positions of the two plates. The tie lines connecting the points serve only as guidelines to define an approximate flow path between the two plates from one point to the next. Structural style may be sufficient to indicate that motions from one point to the next were somewhat different to these longer-term flow lines. We raise this point because we have not yet been able to define any convergent tectonism in the Trinidad region for the period ~9Ma to ~6Ma (the interval was dominated by transtension), whereas there is ample evidence for convergent deformation since 6Ma. This could indicate that between anomaly 5 (9.5Ma) and the Present, which is shown in Figure 5b as an ~085°-trending line, the true motion history might have started out with a sub-interval of more northeasterly relative motion, only to finish up with a more southeasterly sub-interval of relative motion (dashed alternative of Figure 5b).

However, this two-phase relative motion history for the 9.5 Ma to Present interval is only one mechanism

that might explain the two intevals of contrasting structural styles. A second is that, during continuous relative motion at 085°, net strain toward 085° may have been well partitioned for the late Miocene interval, such that E-W transcurrent offset occurred on the Coche-North Coast Fault Zone, and N-S extension occurred within the former Serranía-Trinidad thrust belt: by Pliocene time, partitioning may have failed, such that shear stepped south and the components of the thrust belt began to move toward 085° with the Caribbean Plate, leading to transpression at all faults with orientations less than 085° (e.g., Central Range). A third possible mechanism is that southward rollback of South American lithosphere beneath the Maturín-Columbus foredeep may have continued into late Miocene time, after the change in relative motion, but ceased in Pliocene time thereby providing a fixed buttress against which motion toward 085° may have been able to drive transpression. Finally, a fourth mechanism is that the 070° trend of the original basement rift geometry beneath Trinidad may have produced a situation in which oblique plate motion above it toward 085° led to progressively greater amounts of continental choking at the plate interface. All four possibilities must be considered for their potential contribution to the overall history; at present, we favor the idea of variable strain partitioning as a primary cause for the Pliocene change in structural style.

Implications of Seismic Tomography Data in the Caribbean Region

Van der Hilst’s (1990) seismic tomographic data (Figure 6) showed the existence and geometry of mappable oceanic slabs beneath the Caribbean and adjacent plates. The Pindell et al. (1991) model called for southward dipping subduction of Proto-Caribbean lithosphere beneath northern South America since the Maastrichtian, prior to the arrival of Caribbean crust from the west, such that the Caribbean Plate has obliquely overthrust, toward the southeast, the trace of a pre-existing, southward-dipping, Proto-Caribbean trench at the foot of the South American margin (see Figure 6d). In contrast, Russo and Speed (1992) proposed northward dipping subduction of South America’s Proto-Caribbean slab as the source of the subducted material and northward tectonic wedging by South America, coincident with the arrival of the Caribbean Plate, as a means of dislocating South American continental crust from its former oceanic root. A critical reappraisal of the seismic tomographic data, integrated with the plate motions, and forward modeling of the implications of the two types of models (north vs south dipping subduction) indicates to us that southward-dipping subduction of Proto-Caribbean crust prior to the arrival of Caribbean Plate is the more likely interpretation (Pindell et al., 1991). Figures 6 a-c present our interpretations of the position of the top of the subducted Proto-Caribbean slab on seismic tomographic cross-sections along the eastern and southern margins of the Caribbean Plate (after van der Hilst, 1990). Critical to all interpretations are the deep, cold shadows at 400-500km depth beneath South America at latitude 6°-12°N which represent true oceanic crust that is eastwardly continuous with the Atlantic slab presently being subducted beneath Barbados and Tobago. Several key implications are immediately clear from a contour map of the Proto-Caribbean slab (Figure 6e).

First, a large tear exists within the western portion of the subducted Proto-Caribbean slab which tapers out

eastwards at approximately 12°N and 65°W. The tear may be due simply to gravitationally-driven extension


within the southward-dipping slab as it was subducted beneath northern South America. We do not know when such tearing might have occurred. A significant amount of internal deformation within the slab is likely. Second, the trace of the trench at which Proto-Caribbean lithosphere was subducted beneath South America can be seen as an ENE-trending break in the images beneath Tortuga, Margarita, and north of Tobago. This trend roughly coincides with the bathymetric definition of the Carupano Platform suggesting that this is caused by the Caribbean ramping up onto the northward limit of South American continental crust. Third, Proto-Caribbean lithosphere can be traced beneath the northern fringe of continental South America by some 200 to 300 km in the east, increasing considerably westwards. In the mantle reference frame, it is actually the northward migration of South America since Maastrichtian which has dominated this apparent subduction. The total amount of subduction, beneath Eastern Venezuela, roughly matches the total amount of Maastrichtian to Recent convergence between North and South America (200-300km, Figure 5a). This indicates that subduction must have started in the Maastrichtian, at the onset of the plate convergence, and that effectively all of the convergence has been achieved in this way. Therefore, in Eastern Venezuela at least, this convergence was underway long before the late Oligocene arrival of the Caribbean Plate from the west. We conclude that models which relate the arrival of the Caribbean Plate to the dislocation of Proto-Caribbean lithosphere from the South American continental crust are incorrect. If they were correct, the amount of overthrusting of Proto-Caribbean crust by South American crust would be far less than that seen in the tomography. Finally, the tear and possible southward gravitational sinking of the Proto-Caribbean slab hinders our ability to define the southerly limit of subducted Proto-Caribbean crust, and therefore our ability to predict the former position of the trench when it nucleated. The tear has to be closed in order to learn the approximate shape and size of the subducted slab. Existing tomographic images can trace it at least to the position shown, but if the trench nucleated within the continent-ocean transition zone, as we believe, then the slab may actually continue farther south than the tomography has imaged.

Assuming this southward dipping subduction zone existed from Maastrichtian time on, there are no

definitive structures in the Atlantic crust east of Barbados which necessarily are related to the pre-Caribbean trench, and thus it is not clear how the Cenozoic convergence was taken up in that area. However, the pole of rotation for North-South America convergence was situated very close to or within this area throughout the Cenozoic (Müller et al., 1999), and several fracture zones are clearly disturbed from their presumed original oceanic fabric (e.g., Doldrums, Tiburon and Barracuda fracture zones). It may be that the convergent strain in this area was sufficiently small and distributed over a wide enough area that a distinct convergent structure did not form. If so, we consider that the trench tapers eastward into a zone of diffuse convergent strain somewhere beneath the present Barbados prism. In Figure 7, we present a preliminary gravity model along a N-S section through the Gulf of Paria which demonstrates that the gravity anomaly is consistent with the concept of southward dipping subduction of Proto-Caribbean lithosphere.

The concept of Proto-Caribbean crust underthrusting northern South America in the Paleocene-Eocene,

and possible associated deformation, before the arrival of the Caribbean Plate has some first-order stratigraphic implications and predictions for the late Cretaceous and Paleogene of Eastern Venezuela and Trinidad which are discussed below.

Implications of Jurassic Breakup History and Basement Configuration

Much may be learned about Trinidad’s tectonic setting and basement geometry by addressing the region’s plate kinematics during Mesozoic rifting and the subsequent dispersal of the western Pangean continents and continental blocks. The Mesozoic plate kinematic history has recently been outlined by Pindell et al. (2000a,b). The methodology and implications are discussed further in Pindell and Kennan (2001, this volume), from which we summarize that:

1. Rifting did not begin in the Equatorial Atlantic (between Niger Delta and reconstructed Demerara-

Guinea Plateau) until the Aptian (Pindell, 1985). Thus Africa and South America can be treated as a single plate until then as the Central Atlantic and Proto-Caribbean opened, and Central Atlantic magnetic anomalies can be used to deduce the growth of the Proto-Caribbean from the time of rifting to

Pin

dell et al., 20

01, T

rinid

ad T

erranes, F

igures

Figure 7. Gravity model which crosses obliquely into the inferred “Trinidad Embayment” (crossing both the Bohordal Fault and the Columbus Basin shelf edge.Key features: 1) crustal thickness in Guyana Shield inferred to be ca. 35 km or more; 2) gravity bulge may be flexural bulge south of Maturín Basin; 3) gravitylow in Maturín is composite of downwarping and filling of Neogene sediments and pre-existing Jurassic depocenter at NE end of Espino Rift, and to the north,gravity gradient and height requires substantial crustal thinning; 4) overthrusting Northern Range and Tobago Terranes drive flexure of thinned crust; 5) totalcrustal thickness in north is only ca. 27 km; 6) sharp downturn in leading edge of SoAm is imaged in seismicity and tomography data (van der Hilst, 1990; Russoand Speed, 1992); 7) arc has been thinned (due to axis parallel extension in oblique collision (Avé-Lallemant, 1997) and sutured to edge of SoAm; 8) sharpboundary (slighty backthrust recently) with Grenada Basin (Eocene oceanic crust formed in intra-arc basin); 9) inferred deep asthenospheric wedge, required byactive volcanism in southern Lesser Antilles (reflects aqueous melting at ca. 100 km depth).

50 100 150 200 250 300 350 400 450 500 550 600 650 700 750

SSE

0

-20

-40

-60

-80

-100

-160

-200

-140

-120

-180

6°/298.5° 13°/297°

-200

-100

0

100

-5000

-2500

0

250050 100 150 200 250 300 350 400 450 500 550 600 650 700 750

GRAVITY(dashed is modelled)

BATHYMETRY

2 3 5 6

4 7 8

9

Maturin Basin Gulf of Paria Carupano Basin Grenada Basin

1

NNW

Darien Ridgeetc thrustbelt

N. Range, Paria Tobago Terrane

Asthenospheric wedge

Proto-Caribbean Slab

mG

alm

etre

sK

ilom

etre

s

50 100 150 200 250 300 350 400 450 500 550 600 650 700 750

Kilometres

2.75

2.9

2.5

3.23

2.7 2.752.9

2.1 2.1 2.12.1

2.95

2.95

3.3

1.03

Intense seismicity in deforming olivine richlayer of South American lithospheric mantle


anomaly M0 (119Ma; early Aptian). From 119Ma to Present, both Central Atlantic and South Atlantic magnetic anomalies must be used.

2. Reconstruction of western Pangea prior to Jurassic rifting shows that the straight Guyana margin lay adjacent to the SW flank of the Bahamas now buried beneath the Cuban forearc allochthons. From Middle Jurassic (175Ma) through Valanginian (130Ma) sinistral shear occurred along the long transform at the base of the Guyana Escarpment, separating the growing Central Atlantic from the Proto-Caribbean Seaway (Figure 8). NW-SE transfer faults along the early Proto-Caribbean margin (including the Urica Fault and a proposed “Bohordal Fault” beneath the western Gulf of Paria) would have separated crustal segments with varying amounts of crustal stretching. Aptian-Albian reefal deposits occur in Venezuela’s Serranía del Interior Oriental as far north as Cumaná but are unknown in the generally deeper-water deposits of Trinidad, suggesting that crustal stretching was higher in the Trinidad crustal segment. The Southern Trinidadian depocenter thus may have formed in a NW-SE sinistral pull-apart setting (Figure 9) with “slope”, as opposed to shelf, depositional environments for the Cretaceous Cuche, Gautier, and Naparima Hill Formations.

3. Initially, the Central Atlantic spreading ridge lay adjacent to the Demerara Rise, migrating northwestward along the Guyana Escarpment and passing Trinidad by the Barremian-Aptian. This may have enhanced or rejuvenated heat flow and caused uplift and complex block faulting. During the Aptian, the Equatorial Atlantic South America-Africa plate boundary was initiated, with a transform entering the Central Atlantic from north of the Demerara Plateau (Pindell and Dewey, 1982). This dextral transform lay relatively far to the north and thus probably had little effect on Trinidad. Simple passive margin thermal subsidence is expected for late Aptian through Maastrichtian time (~110Ma to ~65Ma).

4. A kink in South America-North America flow lines predicts transpression for the Trinidad-Guyana portion of the long transform between 150 Ma and 130 Ma, possibly causing regional uplift in the Trinidad and Eastern Venezuela area (Pindell and Erikson, 1994). This may explain the absence of known Neocomian strata in Trinidad (eroded?). The kink had ended by Hauterivian to Barremian (130-120 Ma), predicting renewed subsidence with possible fault control; the Barremian Cuche Formation with its local exotic blocks of older and ?coeval shallow-water limestones may record such syn-depositional tectonism.

5. Finally, by the Albian (~100Ma) and into the Upper Cretaceous, the plate motions and the stratigraphy suggest the establishment of a north-facing passive margin whose strata were strongly source-prone (Gautier and Naparima Hill formations). The depositional configuration by this time was one of shelf sedimentation to the west and south of Trinidad, with “slope” conditions dominating the known sections of Trinidad itself, forming a deeper water re-entrant above thinned continental crust. The shelf-slope boundaries defining this re-entrant, after crude palinspastic reconstruction, were situated approximately along the present western margin of the Gulf of Paria (NW trend) and the northern margin of Delta Amacuro (ENE trend; Figure 9). This setting lasted until the Maastrichtian or early Paleocene, when convergent conditions were established across the Proto-Caribbean Seaway (see below).

Model for Early Paleogene Orogenesis

The late Maastrichtian to Eocene stratigraphies of Eastern Venezuela and Trinidad suggest that an early Tertiary orogenic event took place. Most geologists consider the timing of thrusting to be late Oligocene to middle Miocene, based on stratal involvement in the Serranía’s southern fringe. However, we note that the level of erosion becomes significantly deeper towards the north and east, and Upper Cretaceous strata are entirely absent even in syncline cores and thrust footwalls, in contrast to the south and west. Thus, there are actually no stratigraphic constraints on the timing of thrusting in the northern Serranía other than its being post-middle Guayuta Group (~Campanian). In fact, several lines of evidence suggest that tectonism could have begun in the Maastrichtian-Paleogene, including: (1) the probable erosional truncation of San Juan Formation in the northern Serranía; (2) the occurrence of a latest Paleocene-Eocene conglomerate in depositional contact on eroded Barranquín Formation in the north-central Serranía (Vierbuchen, 1984); (3) evidence for subaerial erosion and


105 707580859095100

105 70758085909510010

15

20

30

35

40

10

15

20

30

40

Yucatán

North America(present daycoordinates)

Chiapas

MagneticAnomaly M10

Chiapas Massifin final position

Chortis

Jamaica, Cuba

New ridge is cutonce rotation stops

Proto-CaribbeanSeaway

Mexicanback-arc

Chihuahua,Sabinas Basins

Reefedge

Early Cretaceous 130 Ma

Transitional?

Yucatán-NOAM pole(Mid. Jur. - E. Cret.)

35

Unstretched

Ocean crust

Thin SaltNeogenehalokinesis (Sigsbee)

Stretched continent

Basalt Plateau

Thick Salt

South America

Figure 8. Early Cretaceous (Valanginian) reconstruction of the Gulf of Mexico and Proto-Caribbean region, post-Gulf formation stage, when seafloor spreading in the Gulf had ceasedbut was continuing in the Proto-Caribbean seaway (after Pindell et al., 2000b).


DCRidge

Sea-levelR ? R ? R ?

Slope environment

ColumbusChannel

Continent- Ocean

Boundary

Yucatán

Bahamas

Serrania delInteriorOriental

RR R

RR

RR R

RR

RR R

RR

R?? ?

SE. Gulf of MexicoSpreading Center

DemeraraRise

GuineaPlateau(Africa)

GuyanaFracture

Zone

Continent- Ocean

Boundary

A

B

D

C

ColumbusChannel

BohordalTransfer

Zone

BARidge

Sea-levelR R

Serraniadel Interior

Oriental

Aptian-AlbianReef Trend

Projectionof EspinoGraben

Restored shape ofSouthern Trinidad

for reference

CentralAtlantic

SpreadingCenter

A

B

Figure 9. Model illustrating possibility of wide zone of crustal attentuation in the Trinidad rift segment accommodat-ed by transform motion on both the Guyana and Bohordal transfer zones, contrasting with a narrower rift zone with-in the present day Serranía del Interior Oriental of Venezuela. “R” marks the possible Aptian-Albian reef trend con-tinuing eastward from known El Cantil Fm. The very broad zone of attenuation allows for slope depositionalenvironments across all of Trinidad (Blake Plateau analogue).


incision at the top of the early to middle Eocene Caratas Formation near Barcelona (Pindell and Erikson, 2001); (4) zircon fission track ages from Barranquín Formation in the northern and eastern Serranía which give depositional rather than syn-thrusting reset ages (Locke, in press), suggesting a lesser degree of structural burial (thinner thrusts) there than to the west and south where the Cenozoic is preserved today.

The existence of the ?Eocene subaerial unconformity in the northern Serranía del Interior suggests that

significant volumes of clastic material may have been shed into adjacent marine areas at that time. Further, the observation that this unconformity cut down at least locally to Barranquín Formation levels (Vierbuchen, 1984) suggests that the unconformity was produced by a fairly strong tectonic event (~2km missing).

The relationship of Paleogene sitting unconformably on Lower Cretaceous, as seen by Vierbuchen (1984)

but not yet revisited by us, is also a trademark feature of the northern half of Trinidad’s Central Range (Northern superterrane), although in much deeper marine water (Chaudière, Pointe-a-Pierre and San Fernando Fms. on Cuche Formation; Figure 3). The Chaudière and San Fernando are well known for their olistoliths of shallow-water material resting in deeper water deposits, and the Pointe-a-Pierre is a turbiditic and locally very coarse sandstone. Further, the Chaudière and Pointe-a-Pierre can be seen in the eastern Central Range to be interbedded, suggesting a transitional contact (Figure ). All of these can be interpreted as erosional products of a developing unconformity in the Serranía, if it can be shown that Neogene-Quaternary tectonic motions were sufficient to carry these formations from near the Serranía to their present positions along the Central Range (see below). The same argument may apply to the Northern Range as well: if the Maastrichtian age reported for Galera Formation (highly olistostromal) is actually Maastrichtian-Paleocene, then it too could record erosion from the Serranía del Interior (Galera resting on a variety of Jurassic-Lower Cretaceous formations). These relationships hint that the Northern Range and the northern flank of the Central Range might be related, and that they and the Serranía del Interior were involved in a common tectonic event of Paleogene age.

The plate kinematic history of the region calls for about 200km of north-south convergence between North

and South America since the Maastrichtian (Figure 5a), all of which is accounted for (see seismic tomography, Figure 6) by observed overthrusting of the Proto-Caribbean by South America. About 70km of this convergence had occurred by the late Eocene, prior to the Oligocene arrival from the west of the Caribbean Plate. An event such as the onset of subduction is sure to cause orogenic effects which should be recorded by structures, facies relationships, and steps in thermal histories. Given the inferred greater crustal thickness in Venezuela (Figure 9), we would expect the chances for subaerial exposure due to such convergence to be far greater in the Serranía del Interior Oriental of Venezuela than in Trinidad.

Figure 10 shows the Maastrichtian Cretaceous passive margin being terminated in the Early Paleocene by

the onset of Proto-Caribbean underthrusting. We do not know precisely how far out the margin the break in the crust occurred, but speculate, on the basis of our interpretation of the tomography, that it occurred where stretching (ß) of the lithopshere was about 2. By the Late Paleocene, uplift of the northern Serrania had begun as a result of flexural support of South American crust by the underthrusting Proto-Caribbean crust. To the north, underthrusting would have produced a wide deformed, mainly north-vergent prism of shaly slope and rise sediments above the trench, possibly represented today by the material of the Paria Peninsula and Northern Range. Northward gravity sliding of slope strata may have occurred as well. To the south of this flexural uplift, a “negative flexural” trough was created, we suggest, in which the Vidoño Fm. was deposited. We further suggest that material shed off of the outer high was funneled eastward across the trough and into the deep-water depocenter of the Northern superterrane, thereby giving rise to the Chaudière and, eventually, the Pointe-a-Pierre Fms. Maastrichtian-Paleocene olistostromal deposits shed directly northward (into the Northern Range depocenter) may be seen today as the Maastrichtian? Galera Fm. The thermal effect of this uplift on the outer Serrania would have been to cool the uplifted rocks as they approached the erosional surface. Such Paleogene uplift and cooling in the north may explain why some zircon fission track ages retain detrital ages today in the northern Serrania (Locke, in press); perhaps the absence of Upper Cretaceous section during Neogene thrusting prevented them from sufficient burial for Neogene thermal resetting.


Begin Proto-Caribbean underthrusting

Paleocene onset ofNoAm-SoAm convergence

B: LATE MAASTRICHTIAN - EARLY PALEOCENE

N S

MOHO

Proto-CaribbeanOceanic Crust

South AmericanContinental Crust

Rifted Margin

basementrift blocks

Passive marginprism

water column

A: MID-MAASTRICHTIAN

N S

~40km of accumulatedshortening by Mid-EoceneD: MIDDLE EOCENE

Erosion to Barranquín level in outer Serranía,leaving lags w/ Late Paleocene/Eocene matrix

Broad, upwardly-shallowingtrough, Caratas Formation.Tinajitas Limestone on outerflank?, isolated from clasticinput from Shield to south

N S

Pointe-a-Pierre Fmto east?

?S-ward (Lower Vidoño)transgression, "starved"basal limes/glauconite,sandier facies to north

Uplift of outer high causes negativeflexural bending of interior trough

Vidoño trough

Oversteepened slope? slumping?at mid-K detachment, creation ofParia-Northern Range belt?

C: LATE PALEOCENE

N S

Figure 10. Hypothetical cross sections of the onset and progression of Proto-Caribbean subduc-tion beneath northern South America from Maastrichtian to Eocene time.


The negative flexural basin was characterized by southward onlap of the condensed, southern lower Vidoño Fm. (i.e., glauconitic greensands, basal limestones; Erikson and Pindell, 1998). Erosional detritus (lithics, quartz grains, turbid water giving rise to a muddy matrix) from the rising orogen (mainly San Juan Formation and the Guayuta Group, but locally down to the mica-bearing Barranquín Fm.) would show up in: the northern Vidoño in the outer portion of the trough (quartz granules floating in shale); the Chaudière Fm. in the slope setting east of the orogen (quartz grains and some mica, various upper Cretaceous blocks, floating in shale; deep marine debris flows); and, by the Eocene, the Pointe-a-Pierre Fm. (quartz sand turbidites, possibly as submarine channel fill within the greater Chaudière/Pointe-a-Pierre depocenter). By middle Eocene, the erosional surface was probably heavily peneplained, and the trough to the south had been essentially filled by the upward shallowing (and shoaling) Caratas Formation (shelf sands and shales). By early late Eocene, the Tinajitas (rhodolith-bearing) Limestone was deposited in an area that roughly matches much of the outer high palinspastically, and we speculate that the carbonate was able to accumulate due to isolation from clastic influence from the south (Figure 10). In the latest Eocene-earliest Oligocene, as the Caribbean Plate approached Eastern Venezuela-Trinidad, the topography of the Serrania salient may have been exacerbated by flexure and active normal faulting associated with the arrival and passage of the Caribbean peripheral forebulge, thereby providing a tectonic driver for erosion, transport and deposition of the Northern superterrane’s Plaisance conglomerate and Vistabella [redeposited] limestones of the San Fernando Formation. Finally, in middle to late Oligocene time, the Serranía del Interior was characterized by southward-onlapping Caribbean foredeep deposition (Los Jabillos/Merecure and Areo/Naricual Formations). In Trinidad, conditions were always deeper water (no in situ shallow maerial known to us), and the encroachment of the Caribbean foredeep is marked by the Lower and Middle Cipero Fms.

Paleogeographic Snapshots for Paleocene-Middle Miocene Oblique Caribbean Collision

Here we outline simple paleogeographies for the pre-middle Miocene Tertiary units showing the evolution of stratigraphic units prior to the structural imbrication associated with the Trinidad fold-thrust belt (Figures 11-13). The maps are portrayed on a generalized palinspastic base (Pindell et al., 1998), showing two rhomboidal areas of continental crust (Serranía and the Trinidad “segments”) of the original Cretaceous passive margin which have been stretched to differing degrees. The Serranía segment maintained carbonate reefal water depths through the middle Albian, and crustal thinning was probably modest (crust ~20km? thick). Between 70 and 110km of late Tertiary shortening has occurred in the Serranía, and Albian reefs occur in the far northwest. Thus, the folds and thrusts of the Serranía need to be restored to the NW and the original Serranía rhomboid must have extended at least to this restored position. In the Trinidad segment, water depths were always relatively deeper than in the Serranía, and there is no proof of Lower Cretaceous in situ reef development. Basement was probably more stretched and probably subsided fast and early enough that Lower Cretaceous reefs were never able to develop. Figures 11-13 show the restored segment shapes, with Proto-Caribbean (Atlantic) oceanic crust beyond the rhomboids. A line south of which rifting was presumably minor can be drawn, coinciding roughly with the hinge zone of the margin. In Trinidad, this might have served as the Cretaceous-Paleogene depositional shelf edge, with perhaps a broad and stepped slope to the north. In Venezuela, the Early Cretaceous shelf edge rimmed the Serranía rhomboid, but in the Late Cretaceous it retreated southwards toward the southern fringe of the Serranía Range itself, allowing shallow slope conditions across most of the Serranía. Southeast of Trinidad, the margin is defined by the Guayana Transform Margin beyond which lies Jurassic and Early Cretaceous Atlantic oceanic crust.

Paleocene Map

Before the arrival from the west of the Caribbean Plate, Figure 11 (Paleocene paleogeography) shows a south-dipping Benioff Zone to the north of the margin (Proto-Caribbean beneath South America), such that the trench occurs in the attenuated portion of the rifted continental margin. An outer high developed during the Paleocene-early Oligocene which fed clastic material to the Northern superterrane’s Paleocene-early Eocene olistostromes and sandy shales (Chaudière Fm.) and early to middle Eocene quartz sand (submarine channel) turbidites (Pointe-a-Pierre Fm.). The Paleocene Lizard Springs and Eocene Navet Fms. of the Southern


12

10

8

12

10

864 6062 5866

64 6062 5866

Trinidad continentalre-entrant, ß=3-4,deep water

~Edge Oceanic Crust

Proto-Caribbean floor

Paleocene-Eocene trench, at which some ofJurassic SoAm rifted margin was subducted

~Cretaceousshelf edge

Vidoño (condensed)

??

Deforming belt (N-vergent?) of slope-risesediments in Araya-Paria-Northern Range?

Eastward trace of trench unknown,probably diffuse, near pole of rotation

Chaudière

Galera?

Serrania continentalre-entrant, ß<2

~Paleogene shoreline

Axis of "negative flexural trough"

Vidoño (sandy)

SpringsLizard

PALEOCENE, 60Ma

Exposed outer high

12

10

8

12

10

864 6062 5866

64 6062 5866

??

?

CaribbeanForebulge

~Edge Oceanic Crust


Caribbeanplate edge

Areo Trinidad continentalre-entrant, ß=3-4,

deep water

EARLY OLIGOCENE, 33Ma

E. Oligoceneshoreline

Proto-Caribbeantrench axis

Tobago

San Fernando

As bulge moves south, LowerCipero will replace San

Fernando in Southern Basin

San Fernando Fm is deep waterdeposit of shallow-water (shelf)derived, transported material

Caribbeantrench axis

Lecherias

San FernandoLos Jabillos

Los Jabillos

exposed

slopeshelf

Figure 11. Paleocene paleogeography, showing a south-dipping Benioff Zone to the north of the Venezuela-Trinidad margin(Proto-Caribbean beneath South America). The trench and the subducting Proto-Caribbean plate are imaged through seismictomography. Reconstruction of the margin suggests that the trench formed at the toe of the north-facing passive margin slope, inthe transition to very thin continental crust. Uplift of the outer edge of the South American margin due to underthrusting pro-duced an outer, erosional high and a “negative flexural” trough to the south. Clastic detritus derived from this high is seen in thePaleogene units of northern Trinidad (Chaudière, Pointe-a-Pierre, ?San Fernando Fms.).

Figure 12. Early Oligocene paleogeography showing the leading edge of the Caribbean Plate over-riding the pre-existing Proto-Caribbean trench in the northwest. The rocks of the future Northern Range are being buried, deformed and metamorphosed sever-al hundred kilometres west of their present position, consistent with strain assessments and peak metamorphic ages (see text).Note the inferred separation between “Northern” (offshore Serranía and in NW corner of Trinidad Embayment) and “Southern”(near in-situ south-central Trinidad) stratigraphies. Passage of the Caribbean forebulge across the Serranía platform may havecaused the coarsening of detritus being transported and redeposited in Trinidad (San Fernando Fm.). Middle Ciero Fm. to southrecords progressive and diachronous onlap of the, foredeep section, downflexed by the arriving Caribbean load.


superterrane remained far removed from the orogenic effects and related sedimentation of the uplifted northern Serranía.

We will argue later that the clastic material spilled into the deep marine setting adjacent to the northern

Serranía was later tectonically carried ESE-wards to a middle Miocene “end collision” position, and then translated east to its present position along the northern flank of the Central Range by strike-slip faulting. Given (1) the relative greater (extremely so?) depths of deposition in Trinidad than Venezuela; (2) the apparent absence of uplifted continental crust or blocks in northern Trinidad; (3) the 25Ma peak metamorphic age with E-W stretching lineations in Northern Range, implying 500km displacement; and (4) the fact that this Paleogene event may only be inferred from subtle evidence in Venezuela where we know continental crust was more likely to be located (e.g., Dragon Gneiss in Paria Peninsula), we see no reason to believe that northern Trinidad (e.g., Northern Range) was the source of Paleogene clastic material in the Caroni Basin and northern Central Range.

We do not show an Eocene map because plate boundary configurations had not changed for that time - the

only significant change would be to replace Chaudière with Pointe-a-Pierre, Lizard Springs with Navet and Vidoño with Caratas Formations.

Early Oligocene Map

The approach of the Caribbean Plate from the west began to affect the stratigraphic development of the Trinidadian depocenters by late Eocene to early Oligocene time (Figure 12). For example, the Caribbean peripheral bulge had migrated into the region (at the time of Figure 12 it had reached the southwest corner of the Trinidad rhomboid). The bulge flexed and elevated any exposed or shelf areas of the Serranía and Columbus Channel by about 200 meters, thereby creating a significant erosional source area (SE-wardly diachronous?) to the west and south of the Trinidad rhomboid. Both the Northern and the Southern superterrane’s deep water “San Fernando Formation” conglomerates and redeposited shallow-water material, as recognized for example at the Rocky Palace borehole (Southern) and near Pointe-a-Pierre (Northern), are likely derived from the shallower areas to the west and/or south but deposited in the deeper water of the rhomboid. In the Serranía, the region in the wake of the migrating bulge progressively deepened, marked by the onlapping Los Jabillos sands and upward deepening Areo shales of the foredeep basin. For this interval, the northern Serranía was no longer an erosional source area.

Secondly, the Caribbean trench and accretionary prism had started to encroach upon the outer face of the

Serranía rhomboid, accreting the Paria-Northern Range strata into the prism and possibly constricting it along the shelf margin: peak metamoprhism was reached by 25Ma, and strains would be highly transpressional with E-W stretching lineations in Northern Range strata at this setting. Along the trench axis, the “Lecherias” outcrops near Barcelona (dated for us as Oligocene by T. King, pers comm., 2001) are interpreted here as trench fill (innermost foredeep, with large-scale olistostromes and strong syn-sedimentary tectonism, slumping) as the accretionary prism migrated up the face of the margin. The northeasterly continuation of this depositional setting would predictably comprise turbidites of orogenic character, i.e., dirty, poorly sorted, coarse to fine, mica bearing, and of dual sedimentary provenance (Serranía and Caribbean prism). We suggest that this depositional setting, by late Oligocene time, would be that of the Nariva Fm. in Trinidad. In southern Trinidad, the Lower Cipero would replace the “San Fernando” unit as the Caribbean forebulge migrated farther southeastwards.

Early Middle Miocene (18Ma) Map

By the early middle Miocene (Figure 13), the Caribbean forebulge had migrated sufficiently far south that all of the area now comprising Trinidad was situated in the flexural foredeep basin. However, the absence of Oligocene to early middle Miocene in the Guayaguayare area may indicate that this area remained positive (horst on flexural bulge?) or non-depositional, perhaps due to currents along the Guyana Escarpment. To the northwest, a portion of the Caribbean prism had been thrust onto the northern Serranía del Interior, driving the folding and thrusting to the south, and, in turn, loading the Maturín foredeep basin (Carapita Fm.). Much of the Serranía orogen was subaerial by this time, as probably was the Northern Range (peak metamorphism had been reached


12

10

8

12

10

864 6062 5866

64 6062 5866

EARLY MIOCENE, 18Ma

Carapita

Fluvialtrunk

system

Carupano Shelf erodingto Cretaceous

~Edge Oceanic Crust


Tobago

Merecure

Middle Cipero

Nariva/Retrench

E. Mioceneshoreline

Caribbeanprism edge

Naricual

NorthernRange

Caribbeanplate edge

E. Mioceneshoreline

CaribbeanForebulge

Figure 13. Early middle Miocene paleogeography showing the leading edge of theCaribbean prism (Nariva thrustbelt) advancing towards the Southern superterrane.Northern superterrane strata had been incorporated into the allochthonous belt and werebeing carried at this time to the east-southeast. Subsequent strike-slip motions will trans-port these strata further east into their present positions.


and cooling was underway there), but most of the deforming Trinidad depocenter to the SE was still deep marine. Clastics of dual provenance derived from the rising Serranía/Caribbean prism (Nariva Fm.) were shed out onto, and in front of, the imbricating folds and thrusts of central Trinidad. The Brasso Fm. of the Caroni Basin and northern flank of the Central Range (Northern superterrane) represents the shallower and more proximal (relative to erosional source areas) deposits of the hanging wall of the orogen.

At the Trinidadian thrustfront, the Northern and Southern superterranes were coming together by dextral

transpressive thrusting, but the “boundary” was likely transitional at this stage. Nariva Fm. sands and shales were being fed longitudinally along the trench axis and accreted to the toe of the deformation front. Structural control on Nariva deposition here was strong, such that sands were “fairwayed” along the trench and synclinal fold axes of the prism. This aspect of the tectonostratigraphy also applies to the Herrera and Retrench sands at their respective times of deposition. We infer potentially large amounts of telescoping of the Northern across the Southern superterrane strata during juxtaposition, with possibly some interleaving of respective strata; the total shortening seen within the Nariva Belt (30-40km) is just a minimum estimate for this telescoping.

At this point, it is essential to clarify that the structures of today’s onshore boundary between the Northern

and Southern superterranes have very little to do with the structures of the original, middle Miocene, imbricated juxtaposition of the Northern and Southern superterranes. This is because significant E-W dextral strike-slip offset has cut obliquely across the original ENE thrust front since the end of middle Miocene, thereby carrying Northern superterrane rocks eastward and emplacing them in high-angle fault contact with Southern superterrane rocks (next section).

Caribbean-South America Transcurrent Motion Since 12Ma

About 240km of Caribbean-South America displacement has occurred at an azimuth of 085° in the Trinidad region since 12Ma (@20mm/yr), and this value of offset must be accounted for in the collective structures of the Trinidad region. A detailed analysis of this period is underway by the authors, and is well beyond the scope of this paper; however, some of the principles for this period are outlined below.

Pindell (1993), Algar and Pindell (1993), and Pindell et al. (1998) developed the concept that a change in

the azimuth of Caribbean motion, relative to the Americas, occurred at 12Ma which produced a major change in the tectonic style of development in the southeastern (and northeastern) Caribbean region at that time; in short, dextral oblique collision as described above gave way to east-west dextral strike slip tectonics (see change of Caribbean-SoAm azimuth in Figure 5b). During this latter phase, the hanging wall of the middle Miocene fold-thrust belt essentially has failed and collapsed eastwards, probably largely under the influence of gravity toward the Atlantic Ocean, but certainly prodded by Caribbean relative plate motion. Despite the fact that a strain ellipse for E-W dextral simple shear suggests that SW-NE extension and NW-SE shortening should occur concurrently, our analysis of the trend along the fold-thrust wedge in Trinidad and eastern Venezuela shows that ENE-directed transtension and associated sedimentation (late Miocene-early Pliocene) clearly preceded SE-directed transpression and inversion of older faults (Plio-Pleistocene). However, to the north of Trinidad and east of Tobago in the Caribbean accretionary prism (Figure 14), the strain ellipse (prior to Plio-Pleistocene? time when the prism has been little deformed there) appears to describe strain history quite satisfactorily.

At the end of the middle Miocene, profound changes in subsidence, uplift and erosion patterns, structural

styles, and basin development took place, including: (1) rapid collapse and renewed (Late Miocene) sedimentation on Carupano Platform (highest nappe in middle Miocene collision); (2) renewal of deposition (late Miocene) in a half-graben geometry above the Serranía-Plata-Campana thrust wedge in the Maturín Basin; (3) late Miocene growth of the Gulf of Paria and Cariaco pull-apart basins (Erlich and Barrett, 1990); and (4) 12Ma setting of fission track ages on zircons from Northern Range metasediments, interpreted as cooling due to the normal detachment of the Tobago Terrane from the Northern Range (Algar and Pindell, 1993). New GPS solutions (Weber et al., in press), interpretation of slip vectors from earthquake focal mechanisms (Deng and Sykes, 1995), and seismic mapping (Robertson and Burke, 1989) all suggest that active relative motion has an azimuth of 085°, but it is critical to recognize that this azimuth of motion began at 12Ma. This position conflicts


20mm/yr

s1 s3

SoAm

Carib

Incremental (5 steps shown) strain history of folds: • 50km accumulated dextral shear (in this example); • 60% axis-parallel extension (in this example); • clockwise rotation and tightening of fold axes.

50km

1 2 3 4 5

Dextral-oblique sub-duction along thesoutheastern Caribbe-an Plate Boundary.Strike-slip componentincreasing southwards,expressed as arc-parallel extension

Strain ellipse:

C. Clockwise rotation and fold axis-parallel extension in accretionary prism.

CaribbeanPlate

AccretionaryPrism

Carib

SoAm

A. Transcurrent motion along discreet E-W strike-slip fault(s);

Carib

SoAm

B. Horsetailing of motion into tightening folds of accretionary prism;

Figure 14. Processes allowing progressive Caribbean-South American dextral displacement since about 12Ma. A)Simple transform motion (dip of fault not important), curving around into Caribbean Trench. B) Transform processaccompanied by addition of shortening at a number of horsetails in the accretionary prism which take up portions ofthe total displacement, such that strain is distributed over a large area. C) Transform and horsetail processes accom-panied by addition of fold axis rotation and fold axis-parallel extension in a broad simple shear zone. Note break-down of compressive and strike-slip components of subduction along strike of trench; southward increase in strike-slip component is expressed as axis-parallel extension in the hanging wall prism (Avé Lallemant and Sissons, 1993).A combination of all processes (i.e., “C”) is closest to actual development of southeast Caribbean plate boundaryzone in the offshore prism, and can be applied generally to the Central Range and Southern Basin, as well.


with the belief of others (e.g., Speed, 1985; Russo and Speed, 1992) that NW-SE relative motion continues to the present.

With regard to our Northern and Southern superterranes, a first-order result of the post-12Ma

transcurrent phase is shown in Figure 15, which demonstrates the effect of crossing the original imbricated thrust front with a high-angle transcurrent fault zone (A). Ignoring details in fault style and placement, dextral shear along the Central Range fault zone has juxtaposed internal (north) and external (south) portions of the original fold-thrust belt, thereby causing the appearance of a very sharp Northern and Southern terrane boundary along the Central Range in the Trinidadian onshore. Plio-Pleisocene transpression has been strong along the Central Range, hence the subaerial exposure. In contrast, we would expect a more gradual, imbricated transition between the two terranes in the offshore to the west and east.

A second primary aspect of the post-12Ma phase was the nearly regional occurrence of late Miocene-

early Pliocene dextral transtensional structures, subsidence and renewed sedimentation above previously eroded orogenic areas. Although in transpression since the Pliocene, late Miocene transtension was surely the case along the entire toe of the Serrania-Naparima thrustfront, and it appears to have occurred within the Caroni Basin as well (Figure 16). In these areas, probable ENE-directed collapse has occurred on low angle detachments extending below and within the fold-thrust belt, producing half-graben geometries of renewed basin fill (growth and rotational fanning of strata up to 8°, listric rollovers, sedimentary onlap toward the keels of hanging walls, etc.).

In all cases where we have been able to verify it, Upper Miocene sections are thicker on the north sides

(grabens) of faults than south sides (footwalls). Also, in most cases late Pliocene-Pleistocene transpressive inversion was not strong enough to destroy seismic evidence for the late Miocene half graben stage. However, along the Southern Range of Trinidad, transpression either has destroyed the original half-graben geometry, or transtension did not occur here. We suggest, given a similar structural style of the transpression stage to that seen in other areas where the half-grabens are recorded, that late Miocene-early Pliocene transtension was responsible for nucleating the Southern Range where it is; further, late Miocene extension may have been nucleated there because it lay near the shelf-slope break beneath the Columbus Channel.

Figures 17 & 18 summarize our proposed sequence of events (transtension and transpression) in cross

section and map view. Further, we suggest that the change from transtension to transpression along the Furrial, Pedernales, Central Range and Southern Range trends was caused by the breakdown of strain partitioning of motions between the Caribbean and South American plates. In the late Miocene, effective partitioning allowed ENE collapse of the thrust toe, accompanied by shear in the northern offshore, but by Pliocene the thrust toe began to move with the Caribbean Plate. This is corroborated by a significant reduction in plate boundary deformation in the northern offshore at about Pliocene time. In fact, at present, it is difficult to define a plate boundary in the northern offshore, and we believe that most plate boundary displacement has occurred south of the Northern Range for the last few million years. Recent GPS studies (Weber et al., in press) agree with this view.

The Pliocene onset of transpression produced a fairly widespread unconformity initially, occurring in Maturín Basin (above La Pica Fm.), Central Trinidad (above Manzanilla Fm.), and over much of the Gulf of Paria (boundary between extensional half-graben and syn-inversion portions of basin fill; Figures 16-18). This regional event seems to relate to a reduction (near termination?) of transcurrent motion along the Coche-North Coast Fault, such that all displacement occurred in the south, in Trinidad. The oblique (085°) advance of the Caribbean crust toward the 070°-trending segments of the continental basement of the rifted margin may have led to a progressive increase in interplate coupling, which may have led in turn to a southward shift in the locus of transcurrent faulting.

In Figure 4, we summarized the configuration of the present surface trace of relative plate displacement.

Most late Pliocene to Recent transcurrent displacements along the Central and Southern Range faults have been transferred southward again (as with Gulf of Paria Basin) across the zone of gravitational collapse along the


Figure 15. Schematic fault/terrane maps for late Neogene time, showingstrike-slip juxtaposition of Northern (internal zone) and Southern(extenal zone) super-terrane stratigraphies. A) Concept map showingstrike-slip fault (with pull-apart basin) cutting across grain of orogenicfront; points 1 and 2 can be juxtaposed by fault movement. B) Conceptapplied to Trinidad for 12Ma, where the El Pilar-Gulf of Paria-CentralRange fault system cuts across the middle Miocene orogenic front.Paria and Northern Range displaced 100km to west; Tobago displaced240km to west. Horsetails and fold axis rotation and stretching (Fig. 14)operate in the Caribbean prism to the north (we do not know of a dis-creet fault zone that cuts through to toe of prism; hence, query mark).Note representative points 1 and 2, not yet juxtaposed along CentralRange fault zone. C) Late structures shown on Present day map. Gulfof Paria has opened, Northern and Southern superterrane stratigraphies(points 1 and 2) are abruptly juxtaposed, and the strike-slip offset alongthe Central Range has been (since Pliocene) transferred to the southerntip of Barbados prism across the Southeastern Extensional Province(fault pattern after Wood, 2000). Note that the Central Range (and north)has been translated to the east of the Jurassic oceanic-thinned continentcrustal boundary. Question mark and dashed line in eastern offshorerefers to the uncertain break up and eastward displacement of blockscomprising the middle Miocene subthrust belt.

Figure 16. (a), Locality map of four interpreted line drawings of seismiclines (b-e). Note in all cases the two-fold evolution since 12Ma: (1) lateMiocene-earliest Pliocene northeast-directed listric half-graben rotationand infilling, followed by (2) southeast-directed Plio-Pleistocene inver-sion of certain faults. The similarity of these structural developmentsover this large of an area demonstrates that the processes are controlledregionally.

1•

100 km

Serraníathrustbelt

?

subthrust belt

"accretionary" belt

future Gulf of Paria Central Range shear zone

horsetails, fold rotation,fold axis stretching

K shelf edge

oceaniccrust

Tobago

B. 12 Ma

PariaN. Rng

El Pilar•2

Southern Range

C. Plio-Pleistocene

Gulf of Paria

Caribbean crust

InternalCaribbean

Prism

here,prism fedby gravity

sliding

?1•

•2

•2 Points 1 (internal zone)and 2 (more external zone)

can be juxtaposed by strike-slipto cause the appearance of two distinct

tectonostratigraphic terranes of different origins

South AmericanAutochthon

CaribbeanPlate

1•

A. Concept

1

2

3

4 5 km

A=half graben stageB=Inversion stage

Peneplaned top ofMid-Miocene orogen

NS Caroni Basin, Trinidad

WarmSpringsFault

Central Range

GuaicoFault?

reversefaults

after Payne, 1991TW

T (

sec)

E

AB

S NParia West Block

1

2

3

4


A

B

A=half graben stageB=Inversionstage

Courtesy PDVSA5 km

Warm Springs Ft

TW

T (

sec)

D

S NGuarapiche Block

1

2

3

4


A

B

A=half graben stageB=Inversion stage

5 km

TW

T (

sec)

5Courtesy PDVSA

C

B S NEl Furrial area

1

2

3

4


A=half graben stage

B=Inversion stage

5 km

A

B

modified after Aymard et al, 1990TW

T (

sec)

A

10

606264

6264

BC

D

E?10

60


6 km

B Late Miocene relaxation of thrust front)

Allochthon

Rotatedunconformity

Late Miocene-Early Pliocenehalf-graben depocentre

Trace of detachment is unknown,but was probably within Carapitasection, and may have anastomosedPre-Miocene Section

A Mid-Miocene: emplacement of thrust front

6 km

erosional unconformity,sub-marine in places

Allochthon

Early Oligocene foredeep unconformity(extensional structures due to flexure)

Carapita/Lr Ciperoforedeep basin

wedgetop basin?

C Plio-Pleist. dextral compressive inversion

6 kmAllochthon

Rotatedunconformity

Pre-Miocene Section

Seismicallytransparentzone, mud diapirsrise along dextralcompressivetransfer zone,inverting flanks

post-Early Pliocene depocentre,showing growth on master fault

S N

0 km ~20 km ~40 km

Figure 17. Three-stage cross-sectional idealization ofthe line drawings of Figure 16, showing the three pri-mary stages of structural development since 13Ma:(1) end of oblique collision between Caribbean Plateand South American autochthon; (2) northward exten-sional collapse of the former thrust front; and (3) dex-tral compressive inversion of the bounding normalfaults. With this model in mind, note probable differ-ences in up-dip migration direction within the half-graben strata before and after inversion. Several largetar lakes occur at the up-dip keels of the half grabens.

Arrows show azimuth, not rate,of terrane motion rel to stable SOAM

Former positions of blocks

?

10

Tobago

Margarita


Trench

Carapita-Ciperoforedeep basinsouth of thrusts

Present-day base

End of dextral oblique collision

Stage 1: 13 Ma Edge of NarivaPrism

Guarico thrustbelt

Area of half-grabensedimentation G. Paria Basin

10

11

10

11

6466

Tobago

Margarita

Sthn. sourceof clastics

BarbadosPrism

Well partitioned trantension(wrenches and half-grabens)

Stage 2: 10 Ma

Stage 3: 4 Ma

Poorly partitioned transtension(transpressional inversion alongfaults trending less than 085°)

??

?

?

Cariaco Bsn


Cariaco Bsn

Margarita

Tobago BarbadosPrism

?

Figure 18. Map view evolution of the same three stages asin Figure 17. In the center map, transtensional movementsbetween the Caribbean and South American plates werewell partitioned into strike-slip at the Coche-North CoastFault and Gulf of Paria pull-apart, and northward listricextension along the half-graben faults in Maturín andSouthern Basins. (Note: A half-graben bounding faultalong Trinidad’s South Coast is partly conjectural at thispoint. In the last map, the half-grabens move toward 085°with the Caribbean plate and throw the pre-existing 070°-trending structures into strong dextral transpression.


Southeastern Extensional Province. This motion is then relayed to the toe of the Barbados Prism along an E-W transcurrent zone (lateral ramp) located roughly at the international border with Venezuela. Thus, the current locus (at the surface) of Caribbean-South American shear lies in Central and Southern Trinidad, achieved by low-angle detachments along which stratal packages are allowed to slump gravitationally from the Serranía del Interior (much higher previously) toward the Atlantic oceanic basin across the Guyana transform margin, and transferred out to the Barbados prism along the southern limit of the extensional collapse zone. Ultimately, this shear most likely roots northwards into the Caribbean-South American crustal boundary along the Coche-North Coast Fault, as we see no evidence for basement involvement in the Trinidadian fold-thrust belt. It will be important to decipher the level(s) of detachment beneath Trinidad, and how the detachment levels of the thrust belts onshore merge into the extensional detachments offshore. Finally, we suggest that the early Pliocene regional unconformity may pertain to the development of compressional stress that were relieved by the development of the Central Range-Southeastern Extensional Province releasing bend.

Conclusions and Final Thoughts

The big picture: exploration provinces of the Trinidad region

In Figure 19, we divide the Trinidad region into 5 crustal provinces (CP), some of which have sub-provinces. Province 1 comprises continental crust, and is subdivided into “normal thickness” (1a) and “thinned” crust with initially high heat flow (1b): CP1b has deformed parautochthonous strata over it, and likely possesses a Middle Jurassic rift section, locally with basalts and/or evaporites, and a Late Jurassic marine shelf to slope section toward the north. Province 2 is oceanic, although the inner edge of this province may comprise highly sheared, thinned, and heavily intruded continental crust which has behaved since rifting like oceanic crust, with initially high heat flow but now cool. Province 3 is the far-travelled allochthonous Caribbean accretionary prism which had formed prior to the 12 Ma change from oblique collision to transcurrent relative motion; CP3a rests above thinned continental crust, and CP3b overlies oceanic crust. Province 4 is the parautochthonous accretionary prism which has formed since 12 Ma, and which comprises sedimentary section that was deposited within the Trinidad region. Province 4 can probably be subdivided into two parts based on structural style, the northern part being essentially the younger portion of the Barbados accretionary prism (CP4a), and the southern part forming the compressional toe of the eastwardly-collapsing shelf section along southeastern Trinidad (CP4b). However, we see only a semantic difference here, although Griboulard et al. (1991) interpreted a shear zone along the line indicated which may indicate a minor displacement but certainly not a major fault zone. Depositionally, the main difference between sub-parts 4a and 4b will be a gradual, not an abrupt, change from more continental to more oceanic influences. Finally, Province 5 is underlain by Caribbean Plate crust whose cooling history (e.g., Tobago) suggests heat flow today; CP5a is overriding Proto-Caribbean lithosphere, and CP5b overrides thinned South American continental basement.

Relationship between the Trinidad “Prism” and typical Accretionary Prisms

Accretionary prisms can accrete material from a variety of environments. Typically, deep sea prisms form ahead of an intra-oceanic arc, consisting of pelagic materials, some volcanic detritus from the arc, and distal turbidites from nearby land areas. However, when an arc begins to override a continental margin, such as happened in Eastern Venezuela-Trinidad, elements of the margin become accreted and form important parts of the prism, prior to final emplacement onto the margin. With continued convergence, elements of the shelf can also become incorporated (e.g., Serranía del Interior, Venezuela). In most cases, the material near the toe of the prism, regardless of age, will have been the latest material to have been accreted. The boundary between the farther-traveled Caribbean prism and the imbricated margin strata may not be simple. If allochthonous prism strata override the marginal strata before the marginal strata become detached themselves, then the marginal material may underlie the distal prism, and the boundary will be a thrust. Further, each newly incorporated thrust slice will have progressively more “marginal characteristics”, such that the prism itself will become transitional from more distal to more marginal (e.g., abyssal to rise to slope to shelf to foredeep). Alternatively, the distal prism may indent the marginal strata, underriding those strata by backthrusting, thereby creating a range of structural complexities and intermixing of former depositional settings.


Possible shearboundaryof Griboulardet al., 1991

CP 1a

CP 2

CP 4a

CP 4b

12

10

8

12

10

864 6062 5866

64 6062 5866

CP 1bCP 1b

CP 5b

CP 3a

CP 3b

CP 5a

Figure 19. Summary map showing Crustal Provinces (CP) in Trinidad as discussed in text.Crustal Province 1 comprises “normal” (CP1a) and “thinned” (CP1b) continental crust.CP1b has deformed parautochthonous strata over it, and may have a Middle Jurassic riftsection and a Late Jurassic marine shelf to slope section. Crustal Province 2 is oceanic.CP3 is the far-travelled allochthonous Caribbean accretionary prism: CP3a rests abovethinned continental crust, and CP3b overlies oceanic crust. CP4 is parautochthonousaccretionary prism and comprises sedimentary section that was deposited within theTrinidad region. The northern part is the younger portion of the Barbados accretionaryprism (CP4a), and the southern part is the compressional toe of the eastwardly-collapsingshelf section along SE Trinidad (CP4b). The boundary between sub-parts 4a and 4b is agradual, not an abrupt, change from continental to oceanic influence. The basement ofCP5 is Caribbean Plate crust; CP5a basement has overthrust Proto-Caribbean lithosphere,and CP5b is that portion of the Caribbean Plate overriding thinned South American conti-nental basement.


In Trinidad, the arc-continent collision was underway in the middle Miocene and then two things happened: (1) the Caribbean Plate changed its relative direction of movement from ESE to 085°, and (2) the continental crust has “run out”, i.e., the margin changes trend to the SE along the Guyana Escarpment, such that no new continental crust has entered the collision zone for several million years. Hence the Barbados prism has migrated past the continental crust beneath Trinidad by about 200-300 km and is once again entirely in the oceanic environment. Because of the known strike-slip history of the South Caribbean plate boundary, it is often assumed that there must be a discreet boundary between the migrating, far traveled prism and the Trinidadian marginal strata. But the considerations outlined here would argue against this. Until about 10 Ma, the Trinidad marginal strata were very much a part of the growing prism, and the “boundary” between distal prism and marginal strata material was a thrust complex, possibly with some lateral ramps where higher-angle juxtapositions of differing material may occur. Further, the youngest material added to the prism is not far traveled, and is essentially of the Trinidad margin. This is certainly true of the upper level strata, but it would also be true of strata as old as Jurassic, if it could be shown that the time of accretion was young. Thus, we need to think carefully about the nature of the “boundary” of the distal prism and marginal strata. It is not a simple fault where the prism has come in along the margin. For the early and middle Miocene, most of Trinidad was very much a part of the prism, and its entire thrust geometry needs to be restored in order to understand the boundary between the distal prism and the marginal strata. Since the end of middle Miocene, the plate boundary zone has been more transcurrent, but our studies thusfar show that the E-W shear is distributed all the way to the Orinoco Delta, with most of it coming to the surface between the Delta and the Caroni Basin (i.e., Central and Southern Ranges). Thus, even the late transcurrent phase is not producing a discreet boundary between the distal prism and the Trinidad marginal strata.

The Columbus Basin eastward gravitational slump zone is the site of toe thrusts and folds in the very

deep-water to the east in addition to the extensional half-grabens along the shelf. These toe structures are certainly “accretionary” with respect to the hanging wall of the zone undergoing slumping into the deep offshore. In the absence of a discreet prism/margin boundary to the north of this area, the toe thrusts of the Columbus Basin system must be considered part of the Barbados accretionary prism. The only difference is that there is progressively more extension within the hanging wall as one comes south. This extension appears to be approximately matched by the strike-slip displacement amount and rate along the Central and Southern Range; hence, it appears as a shallow-level pull-apart. An important question, however, is the respective levels of detachment between the Columbus extensional and toe structures, the rest of the Barbados prism to the north, and the depth to which the strike-slip faulting occurs in the Central and Southern Ranges. We currently believe that they must become one and the same at depth beneath Trinidad, merging into a common, north-dipping, oblique transcurrent zone between the South American crust and the base of the Caribbean Plate beneath the North Coast Fault.

Acknowledgements

This work has evolved over many years of ongoing research with a number of colleagues. In particular, we are grateful to Sam Algar, Hans Avé Lallemant, Kevin Burke, Barry Carr-Brown, Johan Erikson, John Frampton, Roger Higgs, Anthony Ramlackhansingh of PetroTrin, and John Weber for ongoing collaboration and input. Mr. Guy Flanagan of Phillips Petroleum provided initial gravity modeling on the crustal profile of Figure 7. We thank the sponsors of the Tectonic Analysis Ltd Trinidad Tectonics Study Program (2001) for continued support: BP, BHP, Talisman, Repsol-YPF, TotalFinaElf, Chevron, Venture, Phillips, EOG, Petrotrin and Shell.

References Cited Algar, S.T., 1993a, Structural, stratigraphic and thermo-chronological

evolution of Trinidad: Ph.D. thesis, Dartmouth College, USA, 433 p.

Algar, S.T., 1993b, Controls on Jurassic through Early Tertiary sedimentation in Trinidad, in J.L. Pindell and R.F. Perkins, eds., Mesozoic and Early Cenozoic Development of the Gulf of Mexico and Caribbean Region: A Context for Hydrocarbon

Exploration: Gulf Coast Section, SEPM Foundation, 13th Annual Research Conference, p. 221-235.

Algar, S.T., and J.L. Pindell, 1993, Structure and deformation history of the Northern Range of Trinidad and adjacent areas: Tectonics, v. 12, p. 814-829.

Algar, S.T., Heady, E.C., and J.L. Pindell, 1998, Fission track dating in Trinidad: Implications for provenance, depositional timing, and tectonic uplift, in Pindell, J.L., and C.L. Drake, eds., Paleogeographic Evolution and Non-glacial Eustasy, northern South America: SEPM Special Publication 58, p. 111-128.


Ave Lallemant, H.G., and V.B. Sisson, 1993, Caribbean-South American plate interactions: Constraints from the Cordillera de La Costa Belt, Venezuela, in J.L. Pindell and R.F. Perkins, eds., Mesozoic and Early Cenozoic Development of the Gulf of Mexico and Caribbean Region: A Context for Hydrocarbon Exploration: Gulf Coast Section, SEPM Foundation, 13th Annual Research Conference, p. 211-219.

Carr-Brown, B., and J. Frampton, 1979, An outline of the stratigraphy of Trinidad, in Field Guide, Trinidad, Tobago, Barbados: Fourth Latinamerican Geological Congress, Port of Spain, Trinidad, p. 7-19.

Deng, J., and L. Sykes, 1995, Determination of an Euler pole for contemporary relative motion of Caribbean and North American plates using slip vectors of interplate earthquakes: Tectonics, v. 14, p. 39-53.

Dewey, J.F., and J.L. Pindell, 1985, Neogene block tectonics of eastern Turkey and northern South America: Continental applications of the finite difference method, Tectonics, v. 4, p. 71-83.

Dewey, J.F., and J.L. Pindell, 1986, Neogene block tectonics of eastern Turkey and northern South America: Continental applications of the finite difference method: Reply, Tectonics, v. 5, p. 703-705.

Di Croce, J., Bally, A.B., and P.R. Vail, 1999, Sequence stratigraphy of the Eastern Venezuela Basin, in Mann, P., ed., Caribbean Basins: Sedimentary basins of the world, v. 4, p. 419-476.

Erikson, J.P., and J.L. Pindell, 1998, Cretaceous through Eocene sedimentation and paleogeography of a passive margin in northeastern Venezuela, in Pindell, J.L., and C.L. Drake, eds., Paleogeographic Evolution and Non-glacial Eustasy, northern South America: SEPM Special Publication 58, p. 217-259.

Erlich, R., and S.F. Barrett, 1990, Cenozoic plate tectonic history of the northern Venezuela-Trinidad area: Tectonics, v. 9. p. 161-184.

Erlich, R.N., Farfan, P.F. and P. Hallock, 1993, Biostratigraphy, depositional environments, and diagenesis of the Tamana Formation, Trinidad: a tectonic marker horizon: Sedimentology, v. 40, p. 743-768.

Foland, K.A., Speed, R. and J. Weber, 1992, Geochronologic studies of the Caribbean mountains orogen of Venezuela and Trinidad: GSA Abstracts with Programs, v. 24, p. A148.

Griboulard, R., Bobier, C., Faugères, J.C., and G. Vernette, 1991, Clay diapiric structures within the strike-slip margin of the southern leg of the Barbados Prism: Tectonophysics, v. 192, p. 383-400.

Kugler, H.G. 1959, Geological maps of Trinidad - 1:50,000 and spot maps at various scales: Treatise on the Geology of Trinidad, Natural History Museum, Basel.

Locke, B.D., in press. Thermal evolution of the eastern Serranía del Interior foreland fold and thrust belt, northeastern Venezuela, based on apatite fission-track analyses, in Ave-Lallemant, H., ed., Caribbean/South American plate interactions, Venezuela: GSA Special Paper.

Molnar, P., and L.R. Sykes, 1969, Tectonics of the Caribbean and middle America regions from focal mechanisms and seismicity: GSA Bull., v. 80, p. 1639-1684.

Müller, P., Royer, J.-Y., Cande, S.C., Roest, W.R., and S. Maschenkov, 1999, in Mann, P., ed., Caribbean Basins: Sedimentary basins of the world, v. 4, p. 33-62.

Pindell, J.L. and J.P, Erikson, 1994, The Mesozoic passive margin of northern South America, in J.A. Salfity, ed., Cretaceous Tectonics in the Andes: International Monograph Series, Earth Evolution Sciences, Vieweg Publishing, Weisbaden, p. 1-60.

Pindell, J.L. and J.P. Erikson, 2001, Stratigraphy and structure of the northwestern Serranía del Interior Oriental, Venezuela: Constraints on dynamic evolution, Eastern Venezuela/Trinidad: 2001 International Field Trip of the Geological Society of Trinidad and Tobago, May 2-5, 2001.

Pindell, J.L., 1985, Alleghanian reconstruction and subsequent evolution of the Gulf of Mexico, Bahamas, and Proto-Caribbean: Tectonics , v. 4, p. 1-39.

Pindell, J.L., 1993, Regional synopsis of Gulf of Mexico and Caribbean evolution, in J.L. Pindell and R.F. Perkins, eds., Mesozoic and Early Cenozoic Development of the Gulf of Mexico and Caribbean Region: A Context for Hydrocarbon Exploration: Gulf Coast Section, SEPM Foundation, 13th Annual Research

Conference, p. 251-274. Pindell, J.L., and C.L. Drake, eds., Paleogeographic Evolution and

Non-glacial Eustasy, northern South America: SEPM Special Publication 58, 324 p.

Pindell, J.L., and J.F. Dewey, J.F., 1982, Permo-Triassic reconstruction of western Pangea and the evolution of the Gulf of Mexico/Caribbean Region: Tectonics, v. 1, p. 179-211.

Pindell, J.L., and L. Kennan, this volume, Kinematic evolution of the Gulf of Mexico and Caribbean.

Pindell, J.L., Cande, S.C., Pitman III, W.C., Rowley, D.B., Dewey, J.F., LaBrecque, J., and W. Haxby, 1988, A plate-kinematic framework for models of Caribbean evolution: Tectonophysics, v. 155, p. 121-138.

Pindell, J.L., Erikson, J.P. and S.T. Algar, 1991, The relationship between plate motions and sedimentary basin development in northern South America: from a Mesozoic passive margin to a Cenozoic eastwardly progressive transpressional orogen, in, K.A. Gillezeau, ed.: Transactions of the Second Geological Conference of the Geological Society of Trinidad and Tobago, Port-of-Spain, 1990, p. 191-202.

Pindell, J.L., Higgs, R., and J.F. Dewey, 1998, Cenozoic palinspastic reconstruction, paleogeographic evolution, and hydrocarbon setting of the northern margin of South America, in Pindell, J.L., and C.L. Drake, eds., Paleogeographic Evolution and Non-glacial Eustasy, northern South America: SEPM Special Publication 58, p. 45-86.

Pindell, J.L., Kennan, L. and S.F. Barrett, S., 2000a. A Removal-Restoration Project. Part 3 of a series: “Regional Plate Kinematics: Arm Waving, or Underutilized Exploration Tool”: AAPG Explorer, August 2000.

Pindell, J.L., Kennan, L., and S.F. Barrett, 2000b. Putting It All Together Again. Part 4 of a series: “Regional Plate Kinematics: Arm Waving, or Underutilized Exploration Tool”: AAPG Explorer, October 2000.

Robertson, P. and K. Burke, 1989, Evolution of southern Caribbean plate boundary, vicinity of Trinidad and Tobago, AAPG Bulletin, v. 73, p. 490-509.

Russo, R.M., and R. Speed, 1992, Oblique collision and tectonic wedging of the South American continent and Caribbean tarranes: Geology, v. 20, p. 447-450.

Speed, R.C. 1985. Cenozoic collision of the Lesser Antilles arc and continental South America and the origin of the El Pilar fault: Tectonics, v. 4, p. 41-69.

Tectonic Analysis Ltd., 1999, Exploration Framework Atlas Series, Volume 4: Venezuela-Trinidad. Unpublished commercial report.

Tectonic Analysis, Ltd., 1997, Tectono-sedimentary Evolution of Trinidad, Unpublished commercial report.

van der Hilst, R., 1990, Tomography with P, PP, and pP delay-time data and the three-dimensional mantle structure below the Caribbean region: Ph.D. thesis, Univ. of Utrecht, Holland, 250 p.

Vierbuchen, R., 1984, The geology of the El Pilar Fault Zone and adjacent areas in northeastern Venezuela, in Bonini, W.E., Hargraves, R.B., and R. Shagam, eds., The Caribbean-South American Plate Boundary and Regional Tectonics: GSA Memoir, 162, p.189-252.

Weber, J., Dixon, T., Demets, C., Ambeth, W., Jansma, P., Matioli, G., Bilham, R., Saleh, J., O. Perez, O., in press, a GPS estimate of the relative motion of the Caribbean and South American plates, and geological implications: Geology.

Weber, J., Ferrill, D. A., and M.K. Roden-Tice, 2001, Calcite and quartz microstructural geothermometry of low-grade metasedimentary rocks, Northern Range, Trinidad: Jour. Structural Geology. v.32, p. 93-112.

Wood, L. J., 2000, Chronostratigraphy and tectonostratigraphy of the Columbus Basin, eastern offshore Trinidad: AAPG Bull., v.84, p.1905–1928.

Documents

Processes & Events in the Terrane Assembly of Trinidad … · 1 Pindell et al, GCSSEPM 2001 Processes & Events in the Terrane Assembly of Trinidad and E. Venezuela James Pindell*