Abstract

Coastal barrier features in northeastern North Carolina and southeastern Virginia host a number of eolian back-barrier dunes, both active and stable. Effective management of active dunes and preservation of the unique ecosystems of stabilized dune fields in the face of rapid economic development along this coastline requires knowledge of geomorphic systems. A first step towards understanding these dunes is to determine their history and to identify whether local or regional factors have influenced dune formation, migration and stabilization. In four representative active crescentic dunes distributed over 100 km of the coast, ground penetrating radar (GPR) permitted delineation of subsurface sedimentary structures and paleosols. These interpretations were confirmed with trenches and auger-holes. Packages of foreset beds 10-15 m thick dominate the interior of all dunes studied and indicate an overall southerly migration direction. The two smaller (10-15 m high) northern dunes, Penny/Luark Hill and Snow Hill, have no buried paleosols; paleosols are preserved within the larger (20-25 m high) dunes to the south (Jockeys Ridge and Run Hill), indicating more than one phase of dune activity. Rooted stumps and wood fragments from these soil horizons give two radiometric ages; the younger date for soils on both Jockeys Ridge and Run Hill is 1650 cal AD or later, indicating that the most recent phases of dune activity occurred since European settlement. Jockeys Ridge also has a second, older soil that was dated at 1260-1410 cal AD, indicating that at least two phases of dune activity occurred prior to the current phase. Complete description of the depositional history of these dunes awaits the results of optically stimulated luminescence dates from each dune sediment package (currently being processed). Because sand is rapidly stabilized by vegetation above the high-tide line in this humid environment, a large source of sediment is needed to generate an active back-barrier dune. Each dune studied lies south of a closed tidal inlet; the larger, more complex southern dunes are also adjacent to the Albemarle River paleochannel.