High Resolution Seismic/Sequence Stratigraphic Framework for the Evolution of Pleistocene Intra Slope Basins, Western Gulf of Mexico: Depositional Models and Reservoir Analogs

Beaubouef, R.T. and S.J. Friedmann, ExxonMobil Production Research Company, P.O. Box 2189, Houston, TX 77252-2189

Abstract

High resolution 2D seismic, sidescan sonar images, and shallow penetration cores have been used to study a portion of the upper to middle Texas continental slope. Within the study area are four intra-slope basins presently connected to one another via submarine channels. The Pleistocene, sedimentary fill of these basins, exhibits vertical cyclicity reflecting alternating deposition of mass transport complexes, distributary channel-lobe complexes, leveed channel complexes, and hemipelagic drape. A multi-stage depositional model is presented to explain

1. the vertical and lateral arrangement of these units within sequences,
2. the vertical and lateral arrangement of sequences within each basin,
3. changes in depositional style during basin filling, and
4. the progressive downslope filling of basins.

Within this framework, deposition of mass transport and distributary channel-lobe complexes dominate the early stages of basin filling while leveed channels are depositional elements formed during the latter stages of basin filling and represent an integral part of the sediment transport system linking the basins. However, post-depositional processes have significantly modified these channels and the fill of the basins. Most notable among these processes are headward erosion and m ass wasting due to upslope migration of knickpoints in response to local gradient changes along the system, as individual basins were filled and subsequently bypassed by sediment gravity flows. In particular, active structures within the slope play a key role in changing the organization and fill history of the linked basin-channel network system.