NEW BIOSTRATIGRAPHIC DATA BASED ON EXAMINATION OF FORAMINIFERA IN THE TACATA AREA OF THE EASTERN VENEZUELAN BASIN

The Tacata Area comprises 600 km2 and is located in the Eastern Venezuela Region. The foraminifera studies include chronostratigraphy and paleoenvironmental definitions to understand the realtionship between age, lithostratigraphy and the tectonic setting. Structurally the area is complex with the presence of reactivated normal faults, reverse faults and transverse faults of low angle with associated folding. An allochthonous unit of Cretaceous age, corresponding to the Tala Thrust, overlaps the para-autochthonous section of Lower Miocene to Pliocene age in part of the area. The para-autochthonous section comprises sediments from the Lower Miocene to the Pleistocene. The section of exploratory interest is confined to the Lower Miocene deposits of the Capaya Fm. In this work, a generalized stratigraphic column was defined for the Tertiary para-autochthonous section with the aid of biostratigraphy, sedimentology, and seismic stratigraphic calibrations. It contains Early Miocene (N8 to lower part of N9 Zone; Globigerinatella insueta Zone to Praeorbulina glomerosa Zone) deposits of the Capaya Fm. (Inner nerithic to littoral), deeper marine (outer nerithic to bathyal) fossiliferous deposits of the Carapita Fm. and nerithic facies of the Uchirito Fm., both deposited between Early to Middle Miocene (N8 to N10 zones; Globigerinatella insueta Zone to Globorotalia fohsi fohsi Zone). The overlapping upper section comprises the unconformably littoral to continental deposits of Pliocene/Pleistocene age of the Mesa/Las Piedras Fms. The three key wells were chosen for high resolution biostratigraphy studies, where the foraminifera and nannoplankton calcareous analysis were fundamental. Foraminiferal biostratigraphic studies were important to locate repeated sections and to define the presence of biostratigraphic reversal faults. A paleobathymetric curve was defined and faunal charts and histograms of abundance and diversity were useful to suggest maximum flooding surface (MFS) candidates for each well. To define ages, Planktonic Zonal Schemes of Blow, 1969 and Bolli,H.M. & Saunders,J.B.,1985 for Foraminifera proved to be useful for this circum-Caribbean area. This work is basic to establish a chronostratigraphic framework for the area of Tacata in order to locate reservoirs, seals and stratigraphic traps.