Sequence Stratigraphy of Neogene Turbidite Systems, Northern Green Canyon and Ewing Bank, Northern Gulf of Mexico

Paul Weimer, Peter Varnai, Zurilma M. Acosta, Fadjar M. Budhijanto, Rafael E. Martinez, Alonso F. Navarro, Mark G. Rowan, Barry C. Mcbride, Tomas Villamil

The Neogene turbidite systems of northern Green Canyon and Ewing Bank lease areas in the northern Gulf of Mexico are a major exploration play. The regional sequence stratigraphy for this area has been interpreted to help define the potential areas for future exploration. Data base consists of 6300 miles of 2-D multifold seismic data, well log data for 175, wells, and biostratigraphy from 180 wells. The study area includes 14 fields/discoveries primarily in turbidite-related reservoirs. Good potential for future exploration exists both in sub-salt opportunities and in the deeper water portions of the area.

Four main intervals have been identified, which reflect different kinds of turbidite systems based upon lithologies and seismic facies. Exploration and development concepts must be different in each of the four intervals. Paleoecology data indicate that deposition of these turbidite systems occurred in bathyal water depths. Lower Pliocene sediments (5.5 to 3.0 Ma) include the 5.5, 4.2 and 3.8 sequence boundaries. The interval consists of sand-rich turbidite systems (up to 50 % sand in some sequences). Sand bodies are interpreted to be widespread sheet and amalgmated sheet sands. The upper Pliocene interval (3.0 to 1.4 Ma) comprises the 3.0, 2.6, 2.4, 1.9 sequence boundaries. The interval is thin in the eastern portion of the area, and becomes thicker to the west. Significant sands dev lop in the western portion of the area. The interval corresponds to when the Mississippi River avulsed to farther in the western Gulf of Mexico and sediment supply decreased significantly.

The lower Pleistocene interval (1.4 to 0.7 Ma) includes the 1.4, 1.1 and 0.8 Ma sequence boundaries. The interval is predominantly shale-rich with localized thick sands developing in channel-levee systems and unchannelized sands (basin-floor fans). The upper Pleistocene interval (0.7 Ma to Present) consists of shale-dominated turbidite systems. Notable submarine canyons develop in this interval to the east, which fed the Mississippi Fan. Localized turbidite systems within these sequences have been mapped and serve as analogs for some of the older, intraslope turbidite systems.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995