Published 1995 as part of Memoir 62
Copyright © 1995 The American Association of Petroleum Geologists.  All Rights Reserved.

The Eastern Cordillera of Colombia is an east-vergent Dahlstromian fold and thrust belt of Neogene age involving 5-10 km of upper crust, 3 km of synrift fill of an early Atlantic embayment, and 11 km of Cretaceous thermal sag basin fill. The Mesozoic rift event created an estimated 67-100 km of extension in a 200-km-wide field with an average extensional strain (b) of 2. The fold and thrust belt contains 170 km of imbricate thrust overlap at its front and at higher thrusts and 60 km of west-vergent back-thrusting at its west slope and at its crest affected by incipient plateau collapse tectonics. The Oriente foreland load flexure suggests a rigid lithosphere and more than 100 km of intracontinental subduction.

We have assembled and numerically processed public domain data about the surface geology, Mesozoic basin history, and subsurface structure in the Oriente foothills. Andean crustal data and northeastern Pacific plate tectonic data suggest a Miocene age change from low-dip subduction to Recent steep-dip subduction. Therefore, a polyphase history of foreland upthrusts redeforming the fold and thrust belt is unlikely. However, upper crustal detachment and foreland upthrusting prior to Cordilleran thrusting is possible.