MESOZOIC-CENOZOIC TECTONIC EVOLUTION OF NORTHWESTERN SOUTHAMERICA, CONSTRAINTS FROM THE NORTHERN CULMINATION OF THE EASTERN CORDILLERA FOLD BELT, COLOMBIA

A tectonic model of evolution of Northwestern South America, during the Mesozoic-Cenozoic, is presented here based on the interpretation of the structural styles present at the northern culmination of the Eastern Cordillera of Colombia.

During the Mesozoic the northwestern corner of South America was formed by a complex system of highly fractured half grabens bounded by major normal faults as a result of the back-arc basin formed during the subduction of the pacific plate around the Gondwana supercontinent. This system of half grabens was inverted in three phases of contraction during the Cenozoic. A first phase of deformation began during the late Eocene-early Oligocene time that gave place to a northeast vergent imbricate fan as a result of the oblique convergence of the proto-Caribbean plate and northern South America. This Oligocene fold belt was eroded and covered by late Oligocene continental deposits, thus forming an angular unconformity. Later, during the Miocene a new event of contraction reactivated pre-existing thrust faults and created new ones that folded those formed during the earlier event and offset the late Oligocene angular unconformity forming an east vergent passive-roof thrust triangle zone. A more recent event of tectonism has folded all the structures from the previous events and has a vergence towards the southeast.

The clockwise rotation in the direction of tectonic transport for the different events here described are the result of the clockwise rotation and translation of the Caribbean plate against northern South America during the Cenozoic. The thrust belt systems of the eastern margin of the northern culmination of the Eastern Cordillera of Colombia can be linked to the inversion of Jurassic-early Cretaceous age extensional faults since the Oligocene, which are still active.