HOLOCENE GEOLOGIC DEVELOPMENT OF THE CAPE HATTERAS REGION, OUTER BANKS, NORTH CAROLINA

The late Holocene evolution of the Hatteras Flats and Buxton beach ridges was reconstructed using sedimentological, micropaleontological, geophysical and chronostratigraphic data. Sixteen vibracores were collected from the Hatteras Flats and seven geoprobe cores were collected from the Buxton beach ridges. Geophysical data (ground penetrating radar and seismic surveys) were obtained throughout the study area to aid in paleoenvironmental reconstructions. Using ten lithofacies, five foraminiferal biofacies and geophysical data, five environmental facies were distinguished: low salinity estuary, high salinity estuary, normal marine salinity/flood tidal delta/submarine shoal, normal marine salinity/flood tidal delta/beachface and barrier island sand.

Thick sequences of normal marine salinity deposits comprised of foraminiferal species such as Hanzawaia strattoni, Quinqueloculina seminula and Eponides repandus were present in all sixteen vibracores between 1.5 and 8.5 m below MSL. These data indicate that normal marine salinity conditions occurred over the Hatteras Flats in the study area approximately 1,100 yrs BP. Five optically stimulated luminescence (OSL) dates within normal marine salinity units gave age estimates ranging from 1,420 to 1,060 yrs BP, corresponding with a previously documented barrier island collapse in the southern Outer Banks. Hatteras Island was likely reduced in size by erosion of the beach ridges and the creation of large gaps in the barrier islands between Buxton and Hatteras Village and between Buxton and Avon. These conditions resulted in open bay environments on the Hatteras Flats. An OSL age estimate of 675 ± 180 yrs BP within this normal marine salinity unit indicates that marine water influenced the central Hatteras Flats for several hundred years. By 500 yrs BP, it is likely that the simple barrier islands near Cape Hatteras had reformed, returning estuarine conditions to the Hatteras Flats. An OSL age estimate indicates that an inlet was present between Cape Hatteras and Avon 375 ± 60 yrs BP.