SEDIMENTOLOGICAL ANALYSIS OF THE CONTINENTAL SHELF OFF CHARLESTON, SC

Research conducted on the continental shelf off Charleston, SC was designed to examine sediment grain size and composition.  Eleven stations across the inner-, mid-, and outer-shelf regions as well as along the shelf edge were sampled at least three times during four College of Charleston Transect Program cruises. Generally, sediments in the study region are a thin veneer of modern and relict sands, underlain by limestone hardground.  Grain size variations deviated from the classic fining-outward shelf model in that mean grain sizes irregularly progressed from fine sand (2.5-3.0 Phi) on the inner-shelf to medium sand (1.5-2.0 Phi) on the middle and outer shelf regions.  Sediments were composed predominantly of lithogenic sands, with a higher concentration of relict lithogenics on the outer shelf, most likely remnant from shoreline migrations since the Pleistocene.  Conversely, shelf-edge sediments were fine biogenic sands deposited in association with the Gulf Stream.  Transitional sea level phases have sculpted the continental shelf across this area of South Atlantic Bight, leaving morphologies that skew sediment distribution across the shelf.  In addition to spatial variability, temporal variations in sedimentology were observed in this study.  Several samples collected on different cruises at the same location varied significantly in both grain size and composition.  Videos collected of the seafloor collected by a diver and with a remotely operated vehicle show evidence of migrating sand megaripples, which may be responsible for the seasonal reworking and redistribution of sediments.