FORAMINIFERAL EVIDENCE FOR RECENT PALEOENVIRONMENTAL CHANGE IN CORE SOUND, NORTH CAROLINA

Albemarle-Pamlico Sound, the second largest estuarine system along the Atlantic seaboard, lies between the Outer Banks and the mainland of North Carolina. Core Sound is a shallow estuary located in the southern Outer Banks, between the mainland of Carteret County and Core Banks, a series of barrier islands characterized by the irregular opening and closing of a series of small inlets. Grossman and Benson (1967) mapped the distribution of foraminifera in surficial deposits of Core Sound and the southern part of Pamlico Sound. They recognized five biofacies including, estuarine, open-sound, salt-water-lagoon, tidal-delta, and marsh. To investigate whether foraminiferal biofacies have changed in Core Sound over the past half-century, recent foraminifera were collected in 2004 using a Ponar grab sampler along nine transects throughout Core Sound. Modern foraminiferal biofacies were determined via Q-mode cluster analysis on the 76 surface samples. Four biofacies were identified. Biofacies 1 contains calcareous and agglutinated species and is dominated by Ammotium salsum and Ammonia parkinsoniana. The assemblage of biofacies 2 is characterized by the calcareous foraminifera Ammonia parkinsoniana and Elphidium excavatum as well as additional Elphidium species. Biofacies 3 also contains Ammonia parkinsoniana and various Elphidium species, but is distinguished from biofacies 2 by an increase in abundance of Quinqueloculina impressa and Quinqueloculina tenagos. Marsh foraminifera are dominant in biofacies 4 which is characterized by Trochammina inflata and Haplophragmoides wilberti. Five cores in mainland low salinity bays were also collected to evaluate, via foraminiferal analysis, changes occurring in these restricted environments during the last century. Radionuclides (Pb-210 and Cs-137) were used to determine sediment accumulation rates and to establish a chronostratigraphic framework for the cores.