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Abstract: Paleogeography of the Late Cretaceous of Western Venezuela

R. N. Erlich, O. Macsotay, S. Hall, C. Yeidling, A. J. Nederbragt, D. T. Pocknall, M. T. Steinbis

Depositional environments of Late Cretaceous rocks of Western Venezuela were studied using published and proprietary seismic, biostratigraphic, and geochemical data from 155 subsurface and outcrop locations. Six paleogeographic maps (Cenomanian, Turonian, Coniacian/Santonian, early Campanian, late Campanian, Maastrichtian) show the influence of tectonic activity, climate, and oceanographic changes on the deposition of hydrocarbon reservoirs and source rocks. Cenomanian deposition was controlled by a regional transgression that began in the late Albian. La Luna and Capacho formation limestones and shales were deposited in the Maracaibo Basin, while Escandalosa Formation reservoir sandstones were deposited in the Barinas Basin. The La Luna was deposited in an anoxic environ ent, and is the most important source rock for Maracaibo. Deposition of organic-rich Navay Formation (Turonian) shales in Barinas marked the first maximum flooding event of the Late Cretaceous. Uplift in the southwestern ancestral Merida Andes caused deposition of condensed siliceous and phosphatic units, and reflects the influence of tectonic activity in Colombia. Paleobathymetric shallowing of this area continued through the Coniacian/Santonian and early Campanian with the Tachira Chert in the south, and Tres Esquinas Member phosphatic gravels in the north. Early Campanian deposition of Socuy Member limestones in Maracaibo was accompanied by Navay shales in Barinas. A second flooding event in the late Campanian produced the organic-lean Colon Formation shales. Deposition of the Tres Es uinas continued into the early Maastrichtian in the southwestern Andes, while uplift in Colombia caused shallowing and infilling of Maracaibo and Barinas by the Mito Juan and Burgunita formations, respectively.

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