Processes and Events in the Terrane Assembly of Trinidad and Eastern Venezuela

Pindell, James, Tectonic Analysis, Ltd., West Sussex England, Also at: Dept. Geology and Geophysics, Rice University, Houston, TX; and Lorcan Kennan

Abstract

The Neogene-Recent arrival of the Caribbean plate and coeval deposition of many kilometers of Orinoco deltaic sediments in the Eastern Venezuela-Trinidad region has produced profound changes in the region’s basin setting, including some very large vertical and horizontal changes in original tectonic elements and depositional settings. Plate kinematic analysis of the southeastern Caribbean region, and palinspastic restoration of the region’s continental margins and terranes, are fundamental to understanding the region’s full exploration framework. Plate kinematic analysis provides the geometric framework in which to develop paleogeographic evolution, as well as 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 and magmatic additions to the region’s continental areas back through time to the breakup of Pangea allows fine-tuning of the kinematics, as well as prediction of parameters such as paleoheatflow, paleo-sedimentary provenance, and aspects of source and reservoir potential.

In the eastern Venezuela-Trinidad region, Jurassic rifting produced a serrated shelf edge; rift segments were oriented at ~070° and sinistral transfer zones between rift segments at ~140°. The Guyana escarpment formed as a sinistral transform between South America and the Bahamas block(s). A Late Jurassic-Cretaceous passive margin along the proto-Caribbean seaway developed above this basement setting, and a blanket of mid-Cretaceous and likely other source rocks were deposited across the shelf and well down the slope onto the continental rise/abyssal plain. Clastic reservoir material began to be shed northward in late Maastrichtian/Paleogene times, partly due to global sea level fall, but also partly due to still poorly understood tectonic causes, prior to the arrival from the west of today’s Caribbean plate.

The early and middle Miocene arrival of the Caribbean plate in the region was manifested as a dextral oblique arc-continent collision and produced an extensive fold-thrust belt (Serrania del Interior-Northern Range) and an enormous foredeep basin (Maturín-early Southern basin). Coeval strike slip faults such as Coche-North Coast may have taken up the strike-slip component of the oblique relative motion.

Since the end of this middle Miocene orogeny, the southeast Caribbean PBZ has been dominated by east-west simple shear and only minor amounts of north-south shortening and extension adjacent to faults. A new 3-stage model describes the tectonic and basin history of eastern Venezuela and Trinidad for the last 12Ma. Transtension dominated from ~12Ma to Pliocene time, allowing renewed regional subsidence and creating a new set of basins above the previously-eroded, Serranía del Interior-Northern/Central Range thrust belt, as well as in the offshore Carúpano section. Since Pliocene, transpression has dominated and the transtensional basins have become inverted to varying degrees depending on location, thereby producing many late exploration targets. The Central Range fault zone and the "Pedernales Lineament", which may extend into the Southern Range, are examples of inverted, previously transtensional faults. It is speculated that the southern flank of El Furrial structure in the Maturín basin is also an inverted transtensional fault, and that all these faults are systematically interconnected and genetically related. The model is presented in map view and cross sections to demonstrate paleogeographic implications during this time of peak hydrocarbon generation. Further, the strains associated with the PBZ deformations are extended and examined eastward from Trinidad in order to elucidate the structural history of this potential future deep-water exploration setting.