Paleogene to Recent tectonic and paleogeographic evolution of the Cariaco Basin, Venezuela

The Cariaco basin region, located offshore of north-central Venezuela, includes the Ensenada de Barcelona shelf, the Tortuga-Margarita platform and the Cariaco basin, the largest and deepest fault-bounded late Neogene basin within the South American-Caribbean right-lateral strike-slip plate boundary. Four active fault systems are recognized in the Cariaco basin region: 1) east-west striking San Sebastian-el Pilar right-lateral strike-slip fault system, expressed as a narrow sea floor valley overlying a negative flower structure that diagonally crosses the Cariaco basin; 2) east-west striking Tortuga-Margarita fault system that exhibits mainly down-to-basin, oblique-slip throw; 3) east-west striking Ensenada de Barcelona normal-fault system,, which displays a preferential downthrown to the south; and 4) northwest-striking, right-lateral Urica fault zone, located on the Ensenada de Barcelona shelf. The Urica fault is a lateral ramp fault that forms the western edge of thrusts and folds of the Serrania del Interior fold-thrust belt. Cenozoic convergence between the Caribbean arc and the South American passive margin was highly oblique, and diachronous with migration from west to east during Eocene to Recent time. Oblique convergence in the Cariaco basin began in the Early Miocene and continued migrating eastward along major right-lateral, strike-slip fault systems. Five tectonosequences record the interplay of tectonic and sedimentation in the Cariaco basin: 1) a ~ 0.6 km-thick Paleogene tectonosequence formed when a Cretaceous-Caribbean volcanic arc rifted to form the Tortuga and Margarita basins; 2) a ~1.65 km-thick Lower Miocene tectonosequence was controlled by a fold-thrust belt developed in the Ensenada de Barcelona shelf; 3) a 1.2 km-thick Middle-Upper Miocene tectonosequence formed by a period of extension associated with tectonic loading and thrusting in the south; and a major basin, the Cariaco pull-apart basin initiated because of misalignment between the east-west striking, right-lateral San Sebastian and El Pilai strike-slip faults; 4) a ~0.6 km-thick Pliocene tectonosequence was controlled by a period of transtension, along the San Sebastian-El Pilar right-lateral fault system; the Ensenada de Barcelona shelf subsided to form a deep basin bounded by a horst structure in the north and was filled by northward-progradational delta complexes; 5) a 1.8 km-thick Pleistocene to Recent tectonosequence formed during growth and expansion of the rhomboidally-shaped Cariaco pull-apart basin; the large expansion of the basin is attributed to mass wasting and continued filling by south-sourced progradational delta complexes