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Abstract: High Resolution Biostratigraphy of the Trujillo Formation, and Its Implications on Exploration in the Maracaibo Basin, Venezuela

Maibi C. Ruiz, Santosh K. Ghosh

The Eocene Trujillo Formation, so far known only from the "Serrania de Trujillo", is extensively present in the subsurface of the northeastern part of the Maracaibo Basin.

High resolution biostratigraphic analysis, combined with sedimentologic data, reveals that the Trujillo turbidites occur in a belt trending northwest-southeast along the western-eastern shore of the present day Lake Maracaibo.

Data of six wells on the northwest area of Mara-Maracaibo, and from outcrops and two wells from the eastern Zulia area, show that the Trujillo Formation was deposited in a uniformly outer neritic-bathyal setting in the area between the Maracaibo platform and the Lara Nappes.

Two principal sequence boundaries were determined by a shift in biofacies assemblages. A shallow to deep water transition from the infrajacent Marcelina Formation (on the northwest) and Rancherma and Valle Hondo formations (on the southeast) to the Trujillo Formation was observed. Similarly a deep to shallow water facies change was observed in the transition from the Trujillo to Misoa formations.

This study is significant in that it points to the presence of lowstand turbidite deposits at the onset of foredeep sedimentation across the basin. The wider paleogeographic distribution of the Trujillo turbidites is meaningful as it might indicate the northwestward extension of the potentially important reservoirs associated with submarine fan lobe deposits, earlier interpreted on the southeast in eastern Zulia.

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