DEVELOPMENT OF HOLOCENE EOLIAN BACK-BARRIER DUNE FIELDS AND BEACH/DUNE-RIDGE SYSTEMS ON COMPLEX BARRIER ISLANDS, NORTH CAROLINA OUTER BANKS

The evolutionary model for the Outer Banks, northeastern NC, defines two basic types of barrier islands. Simple barrier islands are low, narrow, and sediment-poor, dominated by inlet and overwash dynamics with geomorphic surfaces that are generally < 500 years old. Complex barrier islands are high, wide, sediment-rich islands that represent multiple stages of formation over the last three millennia. Complex islands contain various combinations of extensive back-barrier dune fields and shore-parallel beach/dune ridge and swale features. Beach/dune ridge and swale features dominate the Kitty Hawk Woods and Buxton Woods areas. Back-barrier dune fields dominate the Kill Devil Hills, Nags Head Woods, and Seven Sisters Dune Field areas, which are now mostly urbanized or heavily vegetated with maritime forests. Run Hill and Jockey’s Ridge are active dune fields today. Study of the evolution of these geomorphic features utilized ground-penetrating radar (GPR) surveys in conjunction with vibracores and several age-dating techniques that include ¹⁴C and OSL (Optically Stimulated Luminescence). Within back-barrier dune fields (e.g., Jockey’s Ridge) a series of paleosols were mapped below the dune surface. Paleosol age-data indicate that several periods of active dune development were separated by periods of dune-stability during the past1000 yrs. In comparison, beach/dune- ridge features (e.g., Kitty Hawk Woods) represent a sequence of seaward-building accretionary ridges, that formed over the past 3000 years. Back-barrier dune fields and beach/dune-ridge features on complex barrier islands are the interactive products of variable sediment input during periods of climate change, sea-level fluctuation, and storm dynamics. The sediment source feeding the Kitty Hawk to Nags Head complex island segment are interpreted to be the near-shore paleo-Roanoke River delta deposits and erosion of the associated Albemarle interstream divide, whereas the sediment source for Buxton Woods is interpreted to be Diamond Shoals, a shore-perpendicular, cross-shelf sand deposit.