Abstract: The Inverted Lamar Sub-basin, Lake Maracaibo, Venezuela: Tectonic Evolution and Hydrocarbon Habitat

J. F Arminio, A. M. Growcott

In the central part of the Maracaibo basin, integration of recently acquired 3-D seismic and existing geological data has led to the definition of the Lamar sub-basin as an array of partially inverted half grabens which formed during Late Cretaceous and Early to Middle Eocene times as a result of transtensional episodes along older rift structures. This integration exercise has also led to the addition of new reserves in a mature oil province.

Six major tectonic phases can be distinguished: (a.) Extension of the existing Paleozoic substrate during Jurassic rifting; (b.) Passive margin tectonic quiescence from Middle to Late Cretaceous; (c.) Paleocene uplift and erosion; (d.) Eocene transtension along reactivated Jurassic lineaments; (e.) Late Eocene to Mid Miocene inversion; (f.) Late Miocene to Recent post inversion and regional tilt.

Distinctive tectonically induced unconformities within the Eocene sedimentary fill imply tectonic overprint rather than eustatic controls. The Eocene extensional structures were inverted in a selective manner depending upon their orientation relative to the dominant compressional vector. This in turn resulted in significant hydrocarbon re-migration and a rather complex fluid distribution throughout the area.

AAPG Search and Discovery Article #90951©1996 AAPG International Conference and Exhibition, Caracas, Venezuela