ABSTRACT

Approximately 1036 square kilometers (400 square miles) 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. Seafloor features recognized on the side-scan and subbottom records include: 1) low topographic features; possibly bedrock outcrops and an enigmatic feature we are calling "footprints," 2) moderate topographic features; low reefs or bedrock outcrops, 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; look like pox but have relief, 7) wave fields; closely spaced sand or gravel waves, 8) wrecks; sunken rigs or platforms. Except for feature numbers 7 and 8, above, we believe that the remaining seafloor features are relict and related to the post-Pleistocene rise of sea level.