TESTAMARCK, J. S., Maraven, S.A., Caracas, Venezuela

ABSTRACT: A Structural Interpretation of the Southwestern Venezuelan Andes

An interpretation of the structural evolution of the southwestern Venezuelan Andes is presented, based primarily on analysis of radar and Landsat images, and supported by field mapping and seismic profiles acquired in 1987 to 1991 over the northwestern flank of the Andes.

The Andean core is interpreted as a collage of basement tectonic blocks which behaved independently during a Jurassic block-faulting event, upon which was superimposed northwest-vergent overthrusting in Miocene-Pliocene times. The resulting structural style is an imbricate series of thrust slices, each comprising pre-Cretaceous basement and its sedimentary cover, and displaced tens of kilometers from their original position.

The northwestern Andean flank between Rio Chama and La Fria is interpreted as a complex block bounded in the southeast by the Rio Mocoties Fault, which is probably very similar to the frontal thrusts of the Andes but deeper and with a stronger surface expression. The dominant structural style of the Andean flank in this sector is a monocline dipping northwest towards the foreland, with shortening increasing to the northeast, towards the Rio Chama-Rio Nucujepe region, where overthrusts are more prominent.

Farther southwest along the Andean front, between Rio La Grita and Santo Domingo, at the southwestern extreme of the Venezuelan Andes, the structural style is dominated by a system of northwest-southeast left-lateral faults, such as the fault complexes of Bramon, Rio Uribante and La Grita, forming a series of parallel structural blocks which are subdivided into smaller blocks by minor northeast-southwest faults.

AAPG Search and Discovery Article #90988©1993 AAPG/SVG International Congress and Exhibition, Caracas, Venezuela, March 14-17, 1993.