--> Abstract: Seismic Evidence for Blind Thrusting of the Northwestern Flank of the Venezuelan Andes, by B. De Toni and J. Kellogg; #91012 (1992).

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ABSTRACT: Seismic Evidence for Blind Thrusting of the Northwestern Flank of the Venezuelan Andes

DE TONI, BRUNO, INTEVEP S. A., Caracas, Venezuela, and JAMES KELLOGG, University of South Carolina, Columbia, SC

Surface geology, seismic, gravity, and well data from the northwestern flank of the Venezuelan Andes indicate overthrusting of Andean Basement rocks toward the adjacent Maracaibo basin along a major blind thrust fault. The frontal monocline is interpreted as the forelimb of a northwestward-verging fault-bend fold deformed over a crustal-scale ramp. The Andean block has been thrust 20 km to the northwest and uplifted 10 km on a ramp that dips about 20 degrees southeastward. The thrust fault ramps up through crystalline basement rocks to a decollement horizon within the shaly units of the Cretaceous Colon-Mito Juan formations. The rigid Andean uplift was caused by northwest-southeast compressive tectonic forces that could have begun as early as Lower Miocene. This crustal shortening was related to the convergence of the Caribbean plate and the North Andean microplate of the collision of the Panama volcanic arc with northwestern South America. Since Upper Miocene times, the Venezuelan Andes have been under oblique compression.

 

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)