SEDIMENTARY ANALYSIS OF THE BARRIER ISLAND SYSTEMS AT WATIES AND DEBORDIEU ISLAND, SOUTH CAROLINA

This study focuses on Waites and Debordieu barrier islands located at the central and southern sections respectively of Long Bay, which extends from Cape Fear, North Carolina to Cape Romain, South Carolina. Building on previous ground penetrating radar and shallow vibracores studies, the purpose of this study is to better understand the islands' underlying deeper (5-15 m depth) stratigraphy through sedimentary analysis of narrowly-spaced cores collected along shore-normal transects across these two barrier islands. Cores were described visually and subsamples were analyzed for grain size using standard sieve and pipette methods and for organic content by the loss-on-ignition method. The stratigraphy for central Waties Island is composed of: semi-lithified fine sandy mud with few bivalve shell fragments below 13 m; landward medium fine sand to sandy mud with Donax spp. shell fragments overlain by cleaner sand with thin soil horizons, and seaward basal coarse shelly sand grading upward to cleaner sand below 4.4 m; and laminated fine sand at the top. The stratigraphy from the southern portion of DeBordieu Island however is composed of: semi-lithified sandy mud with flaser bedding and shell fragments below 8 m; muddy sand with large shell fragments fining upward to a dense mud below 4.5 m; a thin landward wetland peat overlain by sandy mud with shell fragments below 3 m; and coarse sand with shell fragments fining upwards to the top. Observations and analyses from this study help to better understand the deeper stratigraphy of barrier island systems within the Long Bay compartment.