STRATIGRAPHIC ARCHITECTURE AND GEOMORPHIC EXPRESSION OF HARDGROUNDS ON THE CONTINENTAL SHELF IN THE SOUTH ATLANTIC BIGHT

This paper provides details on the association between subsurface geological elements and their surficial hardground expression on the seafloor in the South Atlantic Bight (SAB) off the coast of Charleston, South Carolina. Three primary areas of differing water depth across the Continental Shelf are being studied to document the position and character and expression of the geologic framework and the resultant critical hardground habitats in this biologically sensitive and important region of the Western North Atlantic. Four research cruises into the SAB over the last three years have focused on training a segment of the next generation of ocean scientists while conducting research critical to understanding the overall nature and distribution of rocky outcrops on the seafloor. As part of a larger seafloor mapping program highlighted in this session, the primary focus areas along the Charleston Transect at 15-m to 200-m water depth are analyzed through various geophysical and sea-truth tools. Multibeam bathymetry, acoustical backscatter, and subbottom profiling techniques provide detailed information on the geometry and arrangement of the position of geological materials in the near surface and surface deposits. Sea truthing has been conducted with bottom grabs, shallow push cores, biological bottom trawls, remotely operated vehicle video tows, and diver observations. Hardground exposures and subsurface geometries may be classified based on surficial exposure, bedding inclination, bedding thickness, and bathymetric position. Using this multi-tiered approach allows for a clearer understanding to the architecture and structure of hardground habitats and provides a baseline for future studies into the details of these biologically diverse and important economic resources.