f Effects of Paleogene Subduction on Basin Segmentation and Oil Migration in NW South America

In the Northern Andes, inversion of Mesozoic extensional structures controlled location of synorogenic successions, dispersal of detritus and migration pathways since Paleocene time. Detailed tectonostratigraphic analysis conducted in several basins of NW South America indicate that reactivation of former normal faults broke the single Late Cretaceous basin into different depocenters. In the Paleocene to early Eocene, reverse reactivation broke the syn-orogenic basin into two depocenters. The western depocenter (Magdalena and Rancheria basins) was bounded to the west by eastward-tilted crustal blocks and to the east by reactivated structures; crustal tilting and Paleocene marginal and intraplate magmatism were associated to subduction of the buoyant Caribbean plate. Reactivation of older structures migrated eastward and disrupted the eastern depocenter (presently along the axial zone of the Eastern Cordillera, Llanos foothills, Llanos, Catatumbo and western Maracaibo basin). Basin configuration and patterns of deformation changed drastically in middle Eocene time, as subduction of the buoyant Caribbean plate stopped. Strike-slip deformation and localized burial process that favored for oil maduration along western depocenters (southern and middle Magdalena Valley) depict marginal deformation associated to northward migration of the Caribbean plate,. In contrast, quiescence in eastern depocenters favored deposition of reservoir units. As subduction process renewed in Oligocene time, deformation spreadout. The uplift of the bivergent Eastern Cordillera broke definitively the connection of eastern and western depocenters, and began the segmentation of the Llanos basin from the axial zone of the Eastern Cordillera.