HOLOCENE PALEOENVIRONMENTAL CHANGE IN SOUTHERN PAMLICO SOUND, NORTH CAROLINA

Response of barrier islands to the current regime of global warming and sea-level rise is of great interest given the economic importance of these coastal features. To understand the range of probable responses, it is necessary to investigate the Holocene record of barrier island history. Seventeen vibracores were collected from southern Pamlico Sound (PS) to investigate the distribution of lithofacies and biofacies through foraminiferal and sedimentological analysis in order to define the Holocene evolution of this coastal system. Four biofaces were recognized: (1) Normal Marine Salinity (inlet): dominated by Elphidium spp. with Quinculoculina spp., Ammonia parkinsoniana, Nonionella atlantica, Hanzawaia concentrica, and rare planktonics; (2) Normal Marine Salinity (shelf): dominated by Elphidium spp. with Ammonia parkinsoniana, Nonionella atlantica, Hanzawaia concentrica, and planktonics (Globorotalia menardii and Globigerinoides ruber); (3) High Brackish Estuary: dominated by Ammonia tepida, A. parkinsoniana, and Elphidium excavatum; and (4) Undifferentiated Estuary: dominated by Elphidium excavatum.

The occurrence of Biofacies 2, with its tropical to subtropical planktonic foraminifera and in situ inner shelf benthic foraminiferal assemblages, indicates that open shelf, normal marine salinity waters penetrated into the otherwise estuarine southern PS during two intervals in the mid to late Holocene. The first, short interval (ca. 4,000 cal. yr B.P.) resulted from sea-level rise overtopping an interstream divide. The abundance of shelf species (juveniles to adults) and their good preservation, suggests that their presence in southern PS during the second, longer interval (ca. 1,100 to 500 cal. yr. BP) is due to a large-scale collapse of the barrier islands south of Cape Hatteras rather than through inlet processes. It is proposed that a storm-driven collapse of the barrier islands south of Cape Hatteras allowed offshore waters into the estuarine PS during this time. The cause of barrier island collapse was most likely a major hurricane or a series of hurricanes and/or nor'easters.