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Abstract: Sequence Stratigraphy of the Plio-Pleistocene Sediments, Northeastern Green Canyon and Eastern Ewing Bank Areas, Northern Gulf of Mexico

Fadjar M. Budhijanto, Paul Weimer

A sequence stratigraphic study of the Plio-Pleistocene sediments in the northeastern Green Canyon and Ewing Bank areas has defined seven depositional sequences (5.5, 4.2, 3.8, 3.0, 1.4, 1.1, 0.8, 0.7, and 0.5 Ma). These sequences were correlated, and detailed seismic and geologic facies were constructed for each sequence. Data base for the study comprises 1,436 line miles of forty-fold, migrated, 2-D seismic data, as well as logs from 25 wells, and biostratigraphic data from 17 wells.

The area consists of seven mini-basins separated by salt features with differing geometries, and faults. Paleoecology indicates that the area rested primarily in bathyal settings. The early Pliocene sequences (5.5 to 3.0 Ma) consist of sand-rich, areally widespread turbidite systems comprising basin-floor fans (amalgamated sheet sands), surrounded and over lain by overbank shales. Petroleum discoveries in the area occur primarily in reservoirs in this interval. Structural restorations indicate that most of the mini-basins in the study area began to develop during this period of time associated with loading of shallow salt sheets.

The interval between 3.0 - 1.4 Ma represents a major condensed zone, including three stacked condensed sections. Lithologies are dominantly shales with some thin sands. This interval varies from 50 to 200 feet in thickness. During the Pleistocene (1.4 Ma to present), mud-rich turbidite systems were deposited extensively in the area, including channel-levee systems and related settings. Sands tend to he concentrated near sequence boundaries and primarily in channel-fill facies. Extensive overbank settings are interpreted for the mud-rich portion of these sequences, based on both seismic facies and regional distribution. Extensive slides are present also in this interval. By 0.5 Ma, submarine canyons also began to develop in this area; these canyons are interpreted to have fed sediments in the Mississippi Fan in the deep Gulf of Mexico.

AAPG Search and Discovery Article #90955©1995 GCAGS 45th Annual Meeting and Gulf Section SEPM, Baton Rouge, Louisiana