Abstract Numerous structural, tectonic, and geometric aspects of the eastern South Caribbean plate boundary zone are assessed or reassessed in the light of seismic reflection data, field studies from 2000-2007, heavy mineral analysis, updated interpretation of seismic tomography, seismicity, GPS data, and refined plate kinematic constraints for the Cenozoic. We show that the Cretaceous passive margin of northern South America was transformed to a north-facing, slowly convergent margin in the late Maastrichtian, and that the collision between the Caribbean and South America was a collision of two convergent margins above an intervening, “doubly subducting” proto-Caribbean oceanic lithosphere. The new assessments are iteratively integrated to create semi-quantitative palinspastic reconstructions for 5, 10, 25, 31, and 42 Ma, on which paleogeographies are developed. The origin of key sandstone units are considered, due to their importance as major reservoirs, as well as the implications of the kinematic and dynamic modeling for structural timing. The primary collision between the two plates was completed by 10 Ma; subsequent motion was essentially east-west strike slip; and the deformations were driven mainly in a bow-wave model of transcurrent simple shear.

Abstract The peripheral bulge of the Eastern Venezuela Basin is located along the Orinoco Heavy Oil Belt. The forebulge developed as a direct result of flexure of the continental lithosphere in Eastern Venezuela that resulted from the load of the overriding plate, the Interior Range. The Eastern Venezuela foreland basin lies mostly over crystalline basement that has been affected by three distinct phases of crustal evolution. The southernmost region, south of the Merey Fault, is Archean crystalline basement covered by thin late Paleogene to Neogene sediments. Archean crystalline basement and late Precambrian allochthonous terrains dominate the region between the Merey Fault and the Pirital Fault. This region underwent crustal attenuation during late Precambrian rifting. Jurassic rifting associated with the area north of the Pirital fault trend further attenuated the crust. Variations in thickness of lithosphere subjected to elastic deformation control the amount of flexure in the basin and the position of the peripheral bulge. The Pirital trend acted as a buttress to the southern migration of the principal thrusts. As a result, the peripheral bulge did not migrate significantly. Uplift on the bulge was episodic and slow. Fluvial systems from the shield had sufficient time to maintain their course and, as a result, continued to flow north across the slowly rising peripheral bulge but were focused in specific north-south-trending depressions. By latest Miocene/Pliocene an east-west-trending back-bulge depozone formed south of the Heavy Oil Belt and presently forms the Orinoco River valley. During most of the Miocene, the peripheral bulge acted as a major trap for the hydrocarbons generated along the northern portions of the Eastern Venezuela Basin.

Abstract Current models for the tectonic evolution of northeastern South America invoke a Palaeogene phase of inter-American convergence, followed by diachronous dextral oblique collision with the Caribbean Plate, becoming strongly transcurrent in the Late Miocene. Heavy mineral analysis of Cretaceous to Pleistocene rocks from eastern Venezuela, Barbados and Trinidad allow us to define six primary clastic domains, refine our palaeogeographic maps, and relate them to distinct stages of tectonic development: (1) Cretaceous passive margin of northern South America; (2) Palaeogene clastics related to the dynamics of the Proto-Caribbean Inversion Zone before collision with the Caribbean Plate; (3) Late Eocene–Oligocene southward-transgressive clastic sediments fringing the Caribbean foredeep during initial collision; (4) Oligocene–Middle Miocene axial fill of the Caribbean foredeep; (5) Late Eocene–Middle Miocene northern proximal sedimentary fringe of the Caribbean thrustfront; and (6) Late Miocene–Recent deltaic sediments flowing parallel to the orogen during its post-collisional, mainly transcurrent stage. Domain 1–3 sediments are highly mature, comprising primary Guayana Shield-derived sediment or recycled sediment of shield origin eroded from regional Palaeogene unconformities. In Trinidad, palinspastic restoration of Neogene deformation indicates that facies changes once interpreted as north to south are in fact west to east, reflecting progradation from the Maturín Basin into central Trinidad across the NW–SE trending Bohordal marginal offset, distorted by about 70 km of dextral shear through Trinidad. There is no mineralogical indication of a northern or northwestern erosional sediment source until Oligocene onset of Domain 4 sedimentation. Paleocene–Middle Eocene rocks of the Scotland Formation sandstones in Barbados do show an immature orogenic signature, in contrast to Venezuela–Trinidad Domain 2 sediments, this requires: (1) at least a bathymetric difference, if not a tectonic barrier, between them; and (2) that the Barbados deep-water depocentre was within turbidite transport distance of the Early Palaeogene orogenic source areas of western Venezuela and/or Colombia. Domains 4–6 (from Late Oligocene) show a strong direct or recycled influence of Caribbean Orogen igneous and metamorphic terranes in addition to substantial input from the shield areas to the south. The delay in the appearance of common Caribbean detritus in the east, relative to the Paleocene and Eocene appearance of Caribbean-influenced sands in the west, reflects the diachronous, eastward migration of Caribbean foredeep subsidence and sedimentation as a response to eastward-younging collision of the Caribbean Plate and the South American margin. Supplementary material: Location maps and detailed heavy mineral data tables are available at http://www.geolsoc.org.uk/SUP18365.