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By Alejandro Escalona.

Abstract:
The Geosat free air gravity image of the northern margin of South America indicates the presence of five, continuous tectonic terranes involved in the oblique collision between the Caribbean arc system and the passive margin of northern South America in northern Colombia, Venezuela, and Trinidad and Tobago. These terranes can be traced for up to 1000 km in length and extend from obliquely collided areas of northern South America to uncollided areas of the Lesser Antilles subduction zone. Along-strike correlations between the collided and uncollided areas include the following:

In order to document along-strike continuity of terranes and their associated basins, I have used GIS to compile seismic lines and wells in the region. Sources include published and unpublished thesis studies, journal articles, and previously unpublished Gulfrex lines collected by Gulf Corporation in the early 1970s and donated to UTIG in 1984. Using these data I show a depth to basement map that documents the variation in sedimentary thickness along the strike of the major basins. I also use well data to provide control on the age of deformation in the basins. Main results of this study include:

1. Deformation of western basins is characterized by inversion of preexisting, basin parallel, normal faults probably created in the extensional Caribbean arc system, similar to the Lesser Antilles today.

2. Collapse and reorientation of the Caribbean arc terranes against the northern margin of South America has produced strike-slip faulting and strike-slip related basin formation along the EW-oriented terrane boundaries.

3. Oblique collision has produced lateral ramp faults oriented in a NW-SE direction. These faults disrupt the lateral continuity of basins and terranes, subdivide deep and shallow water areas, and act as pathways for sediments to pass across-strike from shallow to deep water areas.