BACK-BARRIER/ESTUARINE STRATIGRAPHY AND RECENT MORPHOLOGICAL EVOLUTION OF HATTERAS FLATS, GULL ISLAND VICINITY, OUTER BANKS, NORTH CAROLINA

Lithologic, geophysical (high resolution single-channel seismic and ground penetrating radar), and foraminiferal data are being used to define the stratigraphy and to reconstruct the geologic history of the back-barrier and estuarine environments of the Gull Island area of Hatteras Flats, Outer Banks, North Carolina. Gull Island is a 35 acre estuarine island in eastern Pamlico Sound, on the western edge of Hatteras Flats, a bathymetric high that extends between 4 and 6 kilometers off the back-barrier portion of Hatteras Island. Lithologic data from 19 vibracores reveal that the surficial 4 m of Holocene sedimentation has been dominated by fine-grained estuarine sands, and to a lesser degree, muddy sands, and interbedded muds. Three high-amplitude reflectors have been identified in the seismic data (0.015, 0.04, 0.055 sec) around Gull Island, which represent 3 sequence boundaries of Quaternary sedimentation. Time-slice aerial photography is being used to show the recent morphological evolution of the back-barrier portion of Hatteras Island in the Gull Island vicinity. Previous, less detailed studies have calculated back-barrier erosion rates between 0.2 and 2.4 feet per year. This investigation is part of a USGS-ECU-NCGS cooperative research program aimed at interpreting the Quaternary evolution of the northeastern North Carolina coastal system.