THE BRAZOS/TRINITY INTRA-SLOPE BASIN COMPLEX, TEXAS CONTINENTAL SLOPE, GULF

Located within the upper to middle Texas continental slope is a late Pleistocene, depositional system known informally as the Brazos/Trinity Intra-Slope Basin Complex. High resolution 2D seismic, conventional 3D seismic, Seamarc sidescan sonar images, shallow piston cores, and research boreholes were used to study this portion of the western Gulf of Mexico. Within the study area are four intra-slope basins presently connected to one another via a network of submarine channels. The depositional setting occurs in water depths of 400 to 1500 m and is located down-dip of the ancestral Brazos and Trinity rivers and their associated late Pleistocene deltas. These shelf systems represent the source of sediment delivered to the intra-slope basins. Three of these basins are filled, while the fourth, most southerly basin is presently underfilled. A remarkable aspect of the stratigraphy and depositional history of these basins is their filling occurred very rapidly and with pronounced cyclicity, in perhaps less than 100 Ky during the late Pleistocene. The fill of these basins contains regular alternations of mass transport complexes, distributary channel - lobe complexes, leveed - channel complexes, and hemipelagic drape. In this presentation we will focus on the stratigraphy, geometry and depositional facies of these basin-filling units within the context of an integrated sequence stratigraphic framework.