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Abstract: Stratigraphic and Tectonic Definition of the Northeastern Margin of the Maracaibo Basin

Andres Pilloud, Felipe Audemard, Maritza Canache, Jason Crux, Bruno De Toni

The Maracaibo Basin is surrounded by areas of active plate reorganization between the South American craton and the Caribbean oceanic crust. The western and southern margins of the basin coincide with the Sierra de Perija and the Merida Andes basement uplift. The northern and northeastern margins are less clearly defined by the emplacement of the Caribbean allochthon.

In Paleogene times the Caribbean foreland basin had its depocenter in the northeastern Maracaibo Basin. The southern and western limits of the Lara nappes that were emplaced during this time are today eroded and disappear progressively northwards beneath the overlying Oligocene and Neogene sequences of the Falcon foldbelt. The nappes were originally more extensive, with a deformation front in the para-autochthonous Paleogene units. An abundant lithostratigraphic nomenclature inhibits our ability to recognize the different tectonosequences.

We have made an integrated study with geological field work, biostratigraphy, sedimentology and seismic interpretation, between the Valera fault and the eastern shore of lake Maracaibo. The biostratigraphic studies have defined the age and environments of deposition of the lithostratigraphic units. Correlation of these and a simplification of the terminology is proposed. The Trujillo Formation (Paleocene?-middle Eocene) and the Mene Grande Formation (middle Eocene) both contain transported blocks and conglomerates of basement, Cretaceous and Paleogene formations. Comparisons of the lithologies and fossils of these blocks with potential source areas suggest a northerly source from the advancing Lara nappes.

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