BRADSHAW, BARRY E., AHMAD B.IBRAHIM, and JOEL S. WATKINS, Texas A & M University, College Station, TX

ABSTRACT: Structural and Stratigraphic Evolution of the Corsair-Wanda Fault System: Brazos OCS Area, Gulf of Mexico

The structure and stratigraphy of the Corsair-Wanda fault system in the Brazos OCS area and vicinity, northwestern Gulf of Mexico, have been studied in detail using over 1500 km of multichannel seismic data integrated with 30 paleontologic reports.

The structural style of the Corsair-Wanda fault system varies along strike with distinctly different characteristics in the northeast, middle, and southwest sectors. The three sectors are characterized respectively by a concave-up Corsair fault plane in the southwest system; a pronounced flattening and landward deviation of the Corsair fault plane in the middle system; and bifurcation of the Corsair fault trend in the northeast system.

Structural and stratigraphic development of the Corsair-Wanda fault system were controlled by rapid deltaic sedimentation during the Middle Miocene, over a deep, mobile salt substrate. The Corsair Fault trend formed downdip of the Brazos Ridge during the Middle Miocene, and probably soles out into a Jurassic salt basin. Evacuation of salt beneath an extensive supralobal basin provided the subsequent sediment-accommodation space for the large expansion of Middle Miocene sediments downdip of the Corsair fault. During the later stages of the Amphistegina B-Textularia W regression, sediment loading had squeezed mobile salt out of the basin. This caused depocenters to shift basinwards, thus initiating growth fault development within the Wanda fault trend. As sediment influx into the study rea began to diminish and shift northwards in the Late Miocene, depocenters decreased in size and formed interdomal basins between salt domes near the present-day shelf edge.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.