Resumen

LOPEZ C., Myriam C.; MORENO-SANCHEZ, Mario  y  AUDEMARD M., Franck A.. RECENT TECTONIC DEFORMATION AT THE FOOTHILLS OF THE CENTRAL AND WESTERN CORDILLERAS, CAUCA VALLEY, COLOMBIA. bol.geol. [online]. 2009, vol.31, n.1, pp.11-29. ISSN 0120-0283.

The intermountain basin of the Cauca River, located close to the active margin in western Colombia, is one of the keys to understand the evolution and recent seismic activity in the westernmost Andes in Colombia. The discovery of evidences of neotectonic activity in this basin, between Cali and Cartago, and the application of tectonic and radiometric analysis led to the characterization of three zones with distinctive morpho-structural expressions: 1) Foothills of the Cordillera Central. It shows contemporary normal faulting with Miocene deposits that were reactivated as reverse faults during Quaternary, and backthrusts indicating the existence of a subcritical wedge. Radiometric analysis indicate the episodic nature of the neotectonic activity. 2) Foothills of the Cordillera Occidental. The horizontal component of faulting is predominant over the dip-slip one. 3) Floodplain of the Cauca river. Extensional faulting is common on recent fuvial and lacustrine deposits. Sedimentary structures related to faulting suggest that most of them were produced by liquefaction of the substrate during seismic shaking. The topographic gradient, along the Cauca River is not uniform, it shows a higher slope and greater sinuosity in front of the thrust sheets of the Buga Salient. The results of this work are discussed and compared with existing information and a structural model is provided for this area of western Colombia.

Palabras clave : Active anticline; fold and thrust belt; active blind faulting; liquefaction; Cauca river gradient and sinuosity.

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