ABSTRACT

Three regional arbitrary lines were extracted from the 3-D seismic data volume in Ship Shoal, South Marsh Island, and High Island South additions. These lines were integrated with biostratigraphic studies to reveal stratigraphic ages and structural styles along the transects. Twelve to fifteen sequence boundaries associated with nannofossil extinction were recognized and mapped in the Miocene - Pleistocene rocks.

The 64 km (40 mi) long Ship Shoal line shows that the Mahogany salt moved to the south into the younger section and left salt welds and a counter-regional fault system to the north and created the "Ewing Bank Thrust System" to the south. A basin inversion process associated with deflation and evacuation of salt from the Green Canyon 18 Field ("Boxer") is exhibited at the southern end of the line.

The 96 km (60 mi) long South Marsh Island line shows a major decollement surface indicating gliding of salt during lower Pliocene time. Significant basin rotation above this surface also occurred. A 48 km (30 mi) long, and 16 km (10 mi) wide "Miocenica Fan" (upper Pliocene), known to be productive across the Gulf of Mexico, occupies the central part of this line. Palyobathymetric data along the line indicate that the majority of the sediments in the South Marsh Island area were deposited in the slope fan environment.

The (64 km) (40 mi) long High Island line shows "Texas Style" listric fault systems which are not interrupted by numerous salt basins that are prevalent in offshore Louisiana. Sequence boundaries associated with channel-levee complexes and slumps are well resolved in the High Island Area.