GEOARCHAEOLGY AND GEOCHRONOLOGY OF RELICT DUNES AND ALLUVIAL TERRACES IN THE NORTH CAROLINA COASTAL PLAIN

Geoarchaeological work on relict dunes in North Carolina has shown the potential for these sites to provide high resolution chronological and paleo-environmental data concerning the nature and timing of climate fluctuations and fluvial change along coastal plain rivers. Relict sand dunes were identified through the use of high resolution LiDAR (Light Detection and Ranging) elevation data produced by the NCDOT Floodplain Mapping Program. LiDAR data provide extremely high resolution (+/- 25 cm) digital elevation models for the North Carolina Coastal Plain and have allowed the recognition of complex fluvial deposits including a stacked sequence of paleo-braid terraces, meander deposits, and numerous source-bordering dunes. The asymmetry of the Tar River valley indicates that the river has been migrating to the south/southwest, preserving Pleistocene and Holocene sediments north of the river.

Preliminary geophysical, stratigraphic and grain size analysis of dune sediments along with OSL dating indicate dunes and dune drapes accreted episodically throughout the Holocene. Stratified deposits recovered from the Squires Ridge site show more than a meter of aeolian sand drape overlying lower braidplain scarps and braid bars adjacent to the incised modern river channel. Artifacts were recovered at Squires Ridge diagnostic of the Early Holocene near the base of dune deposits and above the alluvial braidplain sediment. This indicates that fluvial incision of the modern river channel into the lower paleo-braidplain occurred sometime before ca.10,000 BP. Optically Stimulated Luminescence (OSL) dating of the upper paleo-braidplain at the Owens Ridge site indicates a Late Pleistocene age for buried aeolian deposits with artifacts underlying an Early Holocene occupation. The presence of buried Late Pleistocene-age sites on the upper paleo-braidplain and the apparent absence of these sites on the lower paleo-braidplain suggest braided river conditions may have continued later than ca.12,000 BP. Alternatively, Pleistocene-age archaeological sites may have been scoured from the lower paleo-braidplain during high magnitude floods. These data demonstrate the potential for using stratified archaeological materials and OSL dating to constrain the ages of source-bordering dunes and terraces in the coastal plain.