RADIOCARBON DATES AND THE GENESIS OF PHYTOGENIC NEAR-SHORE SEDIMENTS ON ST. CATHERINES ISLAND, GEORGIA

St. Catherines Island consists of Pleistocene and Holocene sediments that accumulated at the center of the Georgia Bight of the southeastern United States. For over 40,000 years the island has experienced physical, biological, and anthropological changes brought about by climatic, biotic, depositional, and human-induced events. Sediments have been studied from diverse perspectives, with researchers employing palynology, dendrology, sedimentology, and radiocarbon chronology. Our current focus is on interpretation of environments of deposition of strata found within the surf zone, yet that bear the signatures of inland/back-barrier environments. Late Pleistocene and Holocene accumulations of peat and mollusk- and wood-bearing strata of on-shore and near-shore origins reveal diverse events relating to shoreline dynamics, plant community changes and net shoreward migration of this island. Analyses of peat from a Late Pleistocene fern marshland, now buried far below Mean Sea Level close to the island’s interior, indicate the presence of a Woodwardia-dominated wetland where Woodwardia could not possibly now exist. There are also peats bearing remains of live oak (Quercus virginiana) dating from just prior to the Spanish occupation of the island (620 +/-30 BP), and peach wood (Prunus persica) of more modern origin. The latter deposits were exposed by waves on the seaward side of the island; peats lying within the breakers demonstrate a significant level of shoreline regression over a relatively short period of time.