Abstract: Tectonic Evolution of the Cordillera Oriental of Colombia

Peter Brown, Humberto Caceres, Emmanuel Malterre, Cristina Lopez

The construction of a regional 250-km cross-section of the Cordillera Oriental of Colombia provides insights into the structural relationships between the basins of the Middle Magdalena, Western Margin, Sabana fold belt, Eastern Foothills and the Llanos. A model of the tectonic evolution can thus be derived for some of these new exploration provinces.

Starting during the Eocene, compressional pulses created episodes of increased subsidence due to lithospheric flexure within the pre-existing Triassic to Neocomian rift basins, with resultant preservation of the Sabana basin, and the onset of deformation in the Magdalena Valley.

More severe compressional movements during the Neogene created the Guaicaramo overthrust system, verging to the southeast and the related La Salina backthrust system to the northwest. Large-scale upward displacement along reactivated extensional faults and inversion of up to 8,000 m of sediments can be observed on both sides of the cordillera, simultaneously creating both inversion and thin-skinned thrust structures, with dextral strike-slip accommodation.

It is believed that the Guaicaramo thrust soles out into a major decollement surface, which rises to the southeast up stratigraphic ramps and along ancestral basin bounding faults, and which originates below the Cordillera Central and Magdalena Valley. The overall shortening of the Andean foreland basin is estimated at over 100 km.

The structural asymmetry of the inverted cordillera can be restored to a rift system following the Wernicke model with crustally involved low-angle normal faults, initiated during continental break-up.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994