Tectonics of western Venezuela

[摘要] The Mesozoic-Cenozoic tectonic evolution of western Venezuela occurred in five major stages; (1) Jurassic extension was superposed on peneplaned Late Paleozoic folded-belts. NNE-trending half-grabens developed in a back-arc setting and were filled with continental red-beds and volcanics. (2) A thin, southwardly onlapping, Cretaceous passive margin sequence was related to the opening of the Atlantic. Carbonates dominate the lower portion of the section but the upper Cretaceous is mainly clastic. (3) A Late Cretaceous ? - Tertiary foredeep evolved from an A-Type subduction which advanced from the west and from the north across northern Venezuela, and was the result of interactions between the subducted Pacific-Caribbean Plates and the overriding South American Plate. The peak of deformation occurred at the end of the Middle Eocene, at which time the Sierra de Perija, its southwestern extension and the Internal Caribbean folded-belts, emerged as positive structures. During this compressional event, the Jurassic half-grabens were partially inverted and doubly-vergent basement-involved thrusts branched from a major decollement underlying the Andean active margin (Santa Marta block). (4) Eastward progression of the Sierra de Perija persisted during the Oligocene - Middle Miocene, at which time the Santander Massif was uplifted. North of the Oca Fault and farther east, a series of half-grabens were formed from a right-stepping relay system of right-lateral strike-slip faults superimposed on the Internal Caribbean Folded-belt (Falcon area). (5) The NW-vergent Venezuelan Andes emerged as the main structure during the Late Miocene - Pliocene and were probably associated with a deeper decollement than the one related to the Perijas. The Andes succeeded the Perijas as the main sediment source and separated the foredeep into distinct sub-basins; The Maracaibo Basin to the north and the Barinas-Apure Basin to the south. Coeval with the Andean deformation are two inversion phases affecting the transtensional Falcon structures that are responsible for the present configuration of the Falcon Anticlinorium.

[发布机构] Rice University

[效力级别] Geophysics