Three-Dimensional Geometry and Kinematics of the Western Thrust Front of the Eastern Cordillera, Colombia

Freddy O. Corredor

The Western Thrust Front of The Eastern Cordillera of Colombia consists of a series of west verging thrusts, reverse faults and associated folds and faults. This faulted and folded belt is limiting the East flank of the Middle Magdalena Basin and the western flank of the Eastern Cordillera fold belt of Colombia.

The interpretation of digital Landsat-TM data using the ERDAS/Imagine software package and the use of the axial surface mapping technique (Shaw et al, 1994) on seismic reflection data has allowed to stablish the three-dimensional geometry and kinematics of a small portion of this belt in detail. Satellite data interpretation has provided a new view of the geological

features outcopping in the area. The thrust front geometries are illustrated by several parallel balanced cross sections linked with the satellite images that have been constructed using geometric relations (Suppe, 1983 and Jones, 1987) and the techniques of the modern structural geology.

The fold belt geometry is being controlled by both, NE-SW and a NW-SE strike slip components and a compressional stress field in direction NW-SE. Four major deformational events have been interpreted in the geological time: Paleocene, Middle Eocene, Miocene and Pleistocene time events.

The geometry and kinematics of the structures related to the western thrust front of the Eastern Cordillera can be explained by fault slip changes along the strike over a detachment level (Thin Skin Tectonic). The lower Cretaceous shales of the villeta Formation are proposed as the main detachment level for this fold belt. The geometry of this thrust front might be explained by changes in the thrust angles and depths along the dip and strike too (Thick Skin Tectonic). The deformation of this portion of the Eastern Cordillera fold belt has resulted in a minimum of 15 km of horizontal shortening.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California