Abstract: Sequence Stratigraphy of Pleistocene Sediments, Northwestern Green Canyon, Gulf of Mexico

Alonso F. Navarro, Paul Weimer

A sequence stratigraphic study of Pleistocene sediments in northwestern portion of the Green Canyon Area has identified five depositional sequences: 1.1-0.8, 0.8-0.7, 0.7-0.5, 0.5-0.4, and 0.4-0.3 Ma. Detailed seismic and geologic facies maps were constructed for each of these sequences. The data base for this study comprises 882 miles (1419 km) of multifold seismic, petrophysical information from 20 wells and 23 biostratigraphic reports. The area is characterized by several large mini-basins, separated by complex salt bodies and minor faults. The depositional settings are structurally controlled by these salt bodies and normal faults.

Paleoecology indicates that the sequences were deposited in water depths ranging from lower slope to middle shelf. Bathyal turbidite systems represent most of sediments in the study area. Prominent basin-floor fan deposits are interpreted to be present only in sequences 1.1-0.8 Ma and 0.8-0.7 Ma in the southeastern portion of the study area. All of the sequences consist primarily of channel-levee systems and overbank deposits (slope fan facies). Abrupt facies changes within these deposits are common. Well logs indicate that most of the area is mud-dominated, with sands primarily occurring in channel-fill facies. Extensive slides are also present in these slope fan facies, and are the product of rapid rates of sedimentation and possibly high gradient of inclination of the slope. In the northern part of the study area, the younger sequences (0.7 Ma and younger) also contain sediments deposited in prodelta/delta environments (prograding complex/HST). Upward-coarsening log trends are present in well logs. Relatively thick TST are also present and stacked along the downthrown sides of faults.

Fields/discoveries in the study area are in Green Canyon 18, and in the Mahogany sub-salt discovery (SS 349). The petroleum potential for additional prospects the area is good for both supra-salt and sub-salt targets.

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