Eastward Extent Of The Late Eocene-Early Oligocene Onset Of Deformation Across The Northern Andes: Constraints From The Northern Portion Of The Eastern Cordillera Fold Belt, Colombia, And Implications For Regional Oil Exploration

New geologic information supports the interpretation for the initiation of tectonic uplift in the eastern margin of the Eastern Cordillera of Colombia and the onset of deformation across the northern Andes during the Late Eocene-Early Oligocene. The eastern edge of Late Eocene-Early Oligocene deformation was located at the present location of the eastern margin of the Eastern Cordillera. This uplift can be linked to the tectonic events already described in the literature for the western margin of the Eastern Cordillera. Based on the interpretation of geologic maps, a new regional balanced cross-section across the region, seismic reflection profiles, remote sensing images, and biostratigraphic data, three major deformation events are invoked to describe the evolution of this fold belt. A first event is interpreted to have occurred early during the Late Eocene-Early Oligocene, forming a northeast-vergent imbricate system. This imbricate system was eroded and covered by Upper Oligocene deposits, forming a major angular unconformity. A subsequent compressional event in Miocene-Pliocene times (Andean Orogeny) reactivated pre-existing thrust faults and created new ones that re-folded those formed during the earlier event. These younger thrust faults also offset and folded the angular unconformity. Finally, a more recent tectonic event has re-folded all the structures from the previous events. The complex imbricate system of the northeastern margin of the Eastern Cordillera of Colombia can be linked to a foot-wall shortcut of the inverted Servita Fault that was formed during the Late Eocene-Recent inversion of a Jurassic-Cretaceous extensional basin. A better understanding of the complex structural history of the eastern margin of the Eastern Cordillera of Colombia is critical when evaluating the real potential for oil exploration in this region.