ALEZONES, R., Escuela de Geologia, Minas y Geofisica, Universidad Central de Venezuela, Caracas, Venezuela, T. BOESI, Maraven S.A., D. LOUREIRO and F. MENENDEZ, Escuela de Geologia, Minas y Geofisica, Universidad Central de Venezuela, Caracas, Venezuela, M. OSTOS, Escuela de Geologia, Minas y Geofisica, Universidad Central de Venezuela, Caracas, Venezuela and Fairfield Industries of Venezuela, S. PADRON J. PEREZ, Escuela de Geologia, Minas y Geofisica, Universidad Central de Venezuela, Caracas, Venezuela and Maraven S.A.
ABSTRACT: Models for the Structure of the Northwestern Mountain Front of the Venezuelan Andes: Neogene Inversion of Jurassic Grabens
The present Venezuelan Andes match the location of a system of grabens active from Jurassic to Neocomian. Neogene oblique convergence between the Maracaibo block and South America, turned the old extensional system into a southeasterly dipping A-type subduction. Right-lateral slip along the Bocono fault zone assimilated the tangential component of the displacement. The perpendicular component inverted the buried normal-faults as reverse high angle structures, developing a mountain front syncline in the overlaying sedimentary sequences.
The steep southeastern limb of the syncline, is truncated by northwesterly vergent high angle reverse faults involving basement. In some sections a triangle zone is recognized below the syncline. The zone is bounded by thrusts, detached within the Capacho-Colon package, southeasterly vergent backthrusts and high angle reverse faults that cut through the syncline. In some other sections however, the space below the syncline is filled by a wedge of basement rocks dissected by a fan of blind or buried reverse faults. It is suggested that the structure evolved from early fault-bend folding, with relatively little shortening, to fault-propagation folding. The transition was probably associated with the development and propagation of an imbricated fan of faults in the hanging wall of a sout easterly dipping basement ramp.
AAPG Search and Discovery Article #90988©1993 AAPG/SVG International Congress and Exhibition, Caracas, Venezuela, March 14-17, 1993.