SURFICIAL AND SHALLOW STRATIGRAPHY OF THE CAPERS INLET 7.5-MINUTE QUADRANGLE, SOUTH CAROLINA

The surficial geology of the USGS Capers Inlet (1:24,000) Quadrangle (South Carolina, USA) is presented. High-resolution sidescan sonar, subbottom profiler, and GPR surveys, supplemented by ground-truthed bottom grabs and vibracores, were used to collect data in both terrestrial (20%) and marine (80%) environments. The resulting geologic maps display a combination of surficial sediment distribution data gathered offshore alongside Holocene barrier island and Pleistocene upland sediment deposits. The boundary between Quaternary and Tertiary-aged sediments was identifiable throughout marine areas of the quadrangle using an acoustic subbottom profiler. Additionally, OSL (Optically Stimulated Luminescence) dating was used to optically date a set of 6 sediment samples on the Holocene barriers and Pleistocene upland areas. The area encompassed by the quadrangle is highly variable in terms of surficial sediment distribution, containing sections dominated by sand, mud, and shell hash. Features described as ‘sorted bedforms’ or ‘ripple scour depressions’ in other coastal areas were identified in sidescan sonar imagery in the nearshore, oriented shore-perpendicular to the barrier islands. Surficial seafloor features are larger and less defined farther offshore. Maps produced through this study provide a detailed view of the distributions of surficial sediments as well as sediment thickness patterns, allowing for a better understanding of the relationship between stratigraphy, geomorphology, sediment distributions, and modern coastal processes.