HOLOCENE GEOLOGIC DEVELOPMENT OF THE CENTRAL HATTERAS FLATS AND BUXTON BEACH RIDGES, OUTER BANKS, NORTH CAROLINA

Numerous inlets have opened and closed since the mid-Holocene formation of the Outer Banks barrier islands of North Carolina. The dynamic nature of these islands has led to the preservation of a complex geologic framework. The purpose of this study is to define the geologic framework, chronostratigraphy and origin of the central Hatteras Flats and Buxton beach ridges near Cape Hatteras, from Avon to Hatteras Village. The Hatteras Flats are a broad, shallow, bathymetric high located on the estuarine side of the barrier island from Oregon Inlet to Hatteras Inlet and are hypothesized to be coalesced relict flood-tide deltas. The Hatteras Flats and adjacent Buxton beach ridges have not been adequately characterized geologically or dated.

The paleoenvironments of the Hatteras Flats and Buxton beach ridges are being defined to understand the origin and evolution of this coastal area. Specific objectives for this study include determining the lithofacies, biofacies and geochronology of the region. This project will aid in the understanding of barrier island sediment budgets and evolution in response to Holocene sea-level change, which is critical for forecasting how this system may respond to future sea-level rise and climate change.

Ground penetrating radar data from the Buxton region reveal numerous sets of southward-dipping radar reflections that represent shoreface progradation associated with beach ridges. Cores from this region contain primarily shell- and heavy-mineral-rich quartz sands. Grain-size statistics are being correlated to GPR data to yield information on sea-level position at the time of deposition. Seismic surveys from the Hatteras Flats reveal large-scale (>100-m width) channel cut-and-fill features in the subsurface that are abandoned tidal channels. Channel-fill and adjacent sediments have been cored and are being dated using optically stimulated luminescence techniques, to determine age of activity.