MAPPING SURFICIAL SAND SHOALS ON SOUTH CAROLINA’S OUTER CONTINENTAL SHELF: RELATIONSHIPS BETWEEN STRATIGRAPHY, BATHYMETRY, AND SAND DEPOSITION

Understanding the distribution and composition of sand shoals in the offshore marine environment can provide information relating to benthic habitats, paleoenvironmental features, and economically significant beach-compatible renourishment sands. Marine seismic data, vibracores, and grab samples collected for the BOEM-funded Atlantic Sand Assessment Project (ASAP) offshore of South Carolina (SC) in 2015 were used to delineate shoal areas and calculate associated sand volumes in the 3-8 nautical mile outer continental shelf (OCS). Data were collected in targeted locations where historical data were lacking or where potential need for beach-compatible renourishment sand is high: offshore of Hilton Head Island, Folly and Kiawah Islands, Cape Romain, and North Myrtle Beach.

Shoals with a 5 foot or greater sand thickness were identified in data collected offshore of Hilton Head Island, Cape Romain, Folly Beach, and Kiawah Island, SC. In total, kriging analyses accomplished using Surfer data modeling software show the volume of sand within these shoals to be upwards of an estimated 348 million cubic meters. Mapping efforts are currently underway to consider the role that bathymetry plays in the occurrence and distribution of sand shoals on the seafloor, and comparing those results with analyses of trends in textural data, specifically grain size, of samples collected from vibracores. The spatial distribution and average relief of the sand-shoal data are presented with consideration given to other features identified in the seismic data, such as paleochannels, and placed in the context of the overall paleolandscape of the near OCS offshore of South Carolina.