FLOOD TIDE DELTA FORAMINIFERA, OCRACOKE INLET, NORTH CAROLINA, USA

The Outer Banks barrier islands of northeastern North Carolina extend for ca. 270 km along the seaward edge of a vast, shallow, sand platform (Hatteras Flats) in eastern Pamlico Sound. Previous work has suggested this platform was formed by coalesced flood-tide deltas. Detailed knowledge of the anatomy of a modern, active flood-tide delta is necessary to further elucidate the origin and evolution of Hatteras Flats. Currently, seventeen surface samples have been collected from an active Inlet flood-tide delta (OFTD) and analyzed to provide the basis for paleoenvironmental interpretations of foraminiferal assemblages encountered in cores through the OFTD sedimentary section. Surficial sediments are predominantly very fine-grained quartz sand, and contain foraminiferal assemblages composed of 35 taxa but strongly dominated by Elphidium excavatum (average 66%), accompanied by Ammonia parkinsoniana (average 13%) and Elphidium mexicanum (average 6%). The geographical distribution of foraminiferal assemblages can be related to distance from the inlet. The abundance of Elphidium excavatum and, with a more irregular pattern, of Ammonia parkinsoniana increases with distance from the inlet. These taxa are partially replaced by secondary (<5%) and rare (<1%) species, comprising up to 20% of assemblages, in the proximity of the inlet. These data provide the base line to interpret downcore data to reconstruct the Holocene evolution of the OFTD. In addition, seismic data (boomer and chirp), AMS radiocarbon age estimates, OSL age estimates and sedimentologic/micropaleontological data from vibracores are being analyzed to provide enhanced understanding of the OFTD evolution.