Maps Showing the Stratigraphic Framework of South Carolina's Long Bay from Little River to Winyah Bay

Specific goals of the Phase II study include: 1) quantifying historic shoreline change and identifying erosional hotspots; 2) mapping geologic framework and determining its role in the area's coastal evolution; and 3) calculating a sediment budget and identifying transport mechanisms within the study area. In November 1999, to address the second goal of Phase II of the SC/GCES, the USGS, Coastal Carolina University (CCU) and Scripps Institution of Oceanography (SIO) began a program to systematically map the geologic framework within the South Carolina segment of Long Bay.

Data sources used to produce these maps include high-resolution sidescan-sonar, interferometric sonar swath bathymetry and sub-bottom profiling. Surface sediment samples, vibracores and video data provide groundtruth for the geophysical data. The goals of the program include determining regional-scale sand-resource availability (needed for ongoing beach nourishment projects) and investigating the role that inner-shelf morphology and geologic framework play in the evolution of this portion of coastal South Carolina.

This report presents preliminary maps generated through integrated interpretation of geophysical data, which detail the geometries of Cretaceous and Tertiary continental shelf deposits, show the location and extent of paleochannel incisions, and define a regional transgressive unconformity and overlying bodies of reworked sediment. Defining the shallow sub-surface geologic framework will provide a base for future process-oriented studies and provide insight into coastal evolution.

[Summary provided by the USGS.]