REGIONAL QUATERNARY LANDSCAPE EVOLUTION OF THE SOUTHEASTERN U.S. CONTINENTAL SHELF AND ADJACENT COASTAL PLAIN

The Coastal Plain (CP) and Continental Shelf (CS) of the Southeastern United States (SEUS) represent a continuum of environments and highly-varied processes and habitats extending from the Fall Zone to the CS edge and beyond. This presentation focuses on the evolution of this region throughout the last several sea level cycles, with particular focus since the last glacial maximum (LGM) approximately 23ka.

Using multibeam surveys, sidescan sonar mosaics, chirp subbottom profiles, cores, bottom grabs, and previously collected data from the region, the CS is subdivided into four major regions undergoing varied processes and containing widely varying marine habitats: shelf edge, middle and outer shelf, inner shelf, and the modern coastal zone. Adding GPR and LiDAR to the data, the CP is subdivided into at least ten marine surfaces (constructional phase) with superposed fluvial, aeolian, and dissolution features (destructional phase). These constructional and destructional phases of CP evolution likely had significant influence on the shelf that was exposed during sea level lowstands under highly varied climatic conditions throughout its history.

Scattered landscape indicators and preserved stratigraphic records across the shelf include swamp deposits, fluvial incisions, and shelf-edge deltas, with scatttered rocky outcrop across the shelf. Poorly dated shelf-edge features are tuned with glacial cycles and existing sea level and isostatic models for the region to develop a general model of sea level rise and shoreline migration rates. The modern shelf above -40m was dry land for the last 50ka, while shorelines migrated inland at rates of up to 60-km per thousand years after breaching the shelf edge approximately 11ka.

Using this model of coastline advance over the last 20,000 years, a model of potential human occupation has been created. Current research is focused on high-resolution, detailed surveys in areas of high-probability occupation both for post- and pre-Clovis time.