AUDEMARD, FELIPE, Intevep, S.A., Caracas, Venezuela
ABSTRACT: Triangle Zones of the Maracaibo Basin
The seismic reflection profiles perpendicular to the eastern front of the Sierra de Perija and the northern front of the Venezuelan Andes enable the interpretation of triangle zones. These structures resulted from the stacking of basement involved imbricates which include the entire Cretaceous platform section and the 650m thick shaly interval of the late Cretaceous Colon Formation. This later interval is commonly overpressured and acts as a passive roof decollement (backthrust) of the triangle zones.
This type of structure defines the present slope break of the mountain ranges and is responsible for the abrupt verticalism of the sedimentary section deposited on top of the Colon shales. The seismic profiles along the Andean front show the wedge of sediments associated with the growth of the structures. This feature dates these triangle zones as Upper Miocene in age, post-deposition of the Lagunillas Formation.
The triangle zone northeast of El VigIa has been disrupted during the Pliocene-Pleistocene by two major thrusts. The well exposed Las Virtudes Thrust to the south and a younger, deeper thrust which clearly deforms the wedge of sediments associated with the generation of the triangle zone.
AAPG Search and Discovery Article #90988©1993 AAPG/SVG International Congress and Exhibition, Caracas, Venezuela, March 14-17, 1993.