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JORGE, M., and D. LOUREIRO, Universidad Central de Venezuela, Caracas, Venezuela, and M. OSTOS, Universidad Central de Venezuela, Caracas, Venezuela, and Fairfield Industries of Venezuela, Caracas, Venezuela

ABSTRACT: Pre-Mesozoic Rectangular Network of Crustal Discontinuities: One of the Main Controlling Factors of the Tectonic Evolution of Northern South America

Two sets of major pre-Mesozoic crustal discontinuities are recognized in the cratonic areas of northern South America. A N 50 E trend is parallel to the Guri fault and the Espino and Apure grabens. The other is oriented N 40 W, parallel to the northeastern continental margin of South America, the paleo-Urica fault, the El Baul and Merida arches, the southeastern projection of the Santa Marta fault and the Sierra La Macarena.

Tectonic reconstructions suggest that, depending on the angular relation between the displacement field of the surrounding plates and the orientation of the discontinuities, some of them were activated as extensional systems while others were the sites of transpressive deformation. Due to changes of the relative displacement fields through time, a given discontinuity may show inversion with respect to its previous behavior. The network of discontinuities bounds blocks which suffered translation and rotation with respect to their neighbors and, in some cases, minor internal deformation.

It is suggested that these discontinuities controlled the location of the following Mesozoic tectonic features: (a) Jurassic grabens (Espino II, Uribante, Barquisimeto and Machiques); (b) mobile belts surrounding the Maracaibo block (Santander massif, Venezuelan Andes and the Perija range): (c) major offsets of the Caribbean-related frontal deformation (Goajira-Lara and Unare-Monagas); and (d) pull-apart basin development (Falcon, Cariaco and Carupano).

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