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ABSTRACT: Sequence Stratigraphy in Neogene Expanded Sections, Gulf of Mexico

Robert M. Mitchum, John B. Sangree, Peter R. Vail

Recent developments in sequence stratigraphy offer an approach to the stratigraphic interpretation of the thick, highly structured Neogene sediments of the Gulf of Mexico Basin. The general sequence-stratigraphic model consists of a depositional sequence with lowstand basin floor fan, slope fan, and prograding wedge, transgressive systems tract, and highstand systems tract. Each systems tract is deposited at a predictable position in an interpreted eustatic cycle and has recognizable signatures in well logs and seismic data. The high-frequency eustatic cyclicity is superimposed on the equally important tectonic and sediment-supply controls of a given basin.

The depositional model for the Gulf of Mexico is in a typical diapir-controlled subbasin with a large contemporaneous expansion fault. A high depositional rate controlled by high-frequency glacio-eustatic oscillations coupled with rapid subsidence produces a very thick, complex sediment column whose environment of deposition is closely related to the history of fault development. The approach is based upon the integration of four basic data sets, each of which is independently reached but incomplete within itself. These include (1) core-calibrated well-log responses of deposits in each system tract, (2) seismic facies of each systems tract (reflection termination and configuration patterns), (3) biostratigraphic and paleoecologic zonation of wells penetrating the section, and (4) eust tic cycle charts with correlation of local biostratigraphy for dating physically recognized sequence boundaries.

Reservoir sand distribution is characteristic and predictable for each systems tract. Carefully planned evaluation and completion techniques are based on these characteristics.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990