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Abstract: Biostratigraphic Sequence Analysis of Oligocene-Lower Miocene Sections in the Orocual Field, Eastern Venezuela Basin

Genaro Giffuni, Marianto Castro-Mora

A detailed biostratigraphic study of the Oligocene-Miocene boundary was carried out in sections 1000 ft thick of ten wells of the Orocual Field, Eastern Venezuela. The sequences under investigation carry a rich microfauna of benthic and planktonic foraminifera and calcareous nannoplankton. About 500 samples were analyzed and nearly 150 species of foraminifera and 60 of nannoplankton calcareous were identified. The planktonic assemblages allow the identification of zones N3 and N4 of Blow, 1969; zones NP23, NP24, NP25 and NN1 of Martini, 1971; and zones F and E of Stainforth et al., 1959 of the Carapita Formation.

The paleoenvironments of these sediments were determined rather precisely and vary from inner shelf to middle slope. Paleobathymetric curves of several wells are included.

High and low fossil abundance and diversity peaks were used to recognize two sequences of the third order and five of the fourth order between 24.8 Ma and 26.5 Ma.

A generalized transgressive trend is evident from the Late Oligocene to the Early Miocene.

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