HOLOCENE SHORELINE DEPOSITS OF FOLLY BEACH, SC: GEOMORPHOLOGY, STRATIGRAPHY, AND OSL DATING

The central South Carolina coastal zone comprises a series of classic mixed-energy barrier islands separated from the Pleistocene uplands by wide marsh systems and scattered hammock, or marsh islands. This dynamic coastal system rests south of the modern Charleston Harbor entrance and Morris Island, north of the much larger Kiawah Island (classic drumstick barrier of M.O. Hayes), and is constrained by the very large Stono Inlet (>15m depth by 600m width) to the south and the smaller Morris Island Inlet (>8m depth by 100m width). Shore parallel tidal rivers, large tidal flats, oyster reefs, and shore-parallel marsh islands cover the roughly three kilometers from the shoreline to the mainland. The stratigraphy builds off Harris (2000) and is supplemented with new vibracores, new OSL age estimates, recent LiDAR topography, modern aerial photographs, historical shorelines, and some ground-penetrating radar data. Overall, the oldest Holocene shoreline in the system eroded into the inland margin MIS-5a (80kya) barrier and has an age of approximately 4-6 kya. Approximately half-way across the lagoon between the modern shoreline and the Pleistocene highland, Long Island is approximately 2-3 kya, and the ‘modern’ barrier system is less than a thousand years old. The results of this research indicate a systematically prograding barrier coastline that has stepped seaward over the last >4ka, similar to other regions in South Carolina.