Sea-Floor Features on Mississippi and Alabama Outer Continental Shelf

Richard Rezak, William W. Sager, J. Scott Laswell, Stephen R. Gittings

Approximately 400 mi² were surveyed on the Alabama outer continental shelf during October 1987 and March 1988 using an Edo-Western 4 kHz High Resolution Subbottom Profiler, an EG&G Model 260 Seafloor Mapping System and Starfix Navigation. The mapping is part of a larger project, "The Mississippi-Alabama Marine Ecosystems Study," funded by the U.S. Department of the Interior, Minerals Management Service, Gulf of Mexico Regional Office. Bathymetric maps and side-scan mosaics are being prepared from the raw data. Sea-floor features recognized on the side-scan and subbottom records include: (1) low topographic features--possibly bed-rock outcrops, and an enigmatic feature we are calling "footprints," (2) moderate topographic features--low reefs or bed-rock outc ops, (3) major topographic features--pinnacles and large reefal masses, (4) pox--patches of closely spaced strong reflections with no relief, (5) ridges--closely spaced outcrops along clearly defined features such as shorelines and scarps (possibly truncated dunes or beach ridges), (6) patch reefs, closely spaced, which look like pox but have relief, (7) wave fields--closely spaced sand or gravel waves, and (8) wrecks--sunken rigs or platforms. Except for the wave fields, we believe that the remaining sea-floor features are relict and related to the post-Pleistocene rise of sea level.

AAPG Search and Discovery Article #91029©1989 AAPG GCAGS and GC Section of SEPM Meeting, October 25-27, 1989, Corpus Christi, Texas.