Continental shelf landscapes of the southeastern United States since the last interglacial

Abstract

The wide, sediment-starved continental shelf and modern coastal areas of the southeastern United States retain well-preserved but scattered remnants of a submerged paleolandscape. This paper presents a conceptual model of stratigraphic deposition and landscape formation since the last interglacial on the continental shelf of South Carolina, with portions of North Carolina, Georgia, and Florida (USA). Data for this study include multibeam bathymetry surveys, sidescan sonar mosaics, high-resolution subbottom profiles, and ground-truth surveys from −250m to the modern tidewater region.Four bathymetric zones are recognized with eleven landforms and landform indicators. The described zones range in depths from the modern shoreline, across the shelf, and over the shelf edge to −250m MSL. Relative sea level curves are presented for the area and discussed in conjunction with cultural and climatic events.The potential for preservation of Paleoamerican sites is high at the shelf edge between −130m and −45m, with Archaic and later occupations likely in depths of less than −25m. Prominent vantage points for Paleoamericans (>11kya) would have existed at the shelf edge, and tidewater resources would have been available nearby for a period of almost 6ka. Rapid transgression rates (>60km/ka) after the sea level rose over the shelf edge make preservation of tidewater sites less likely on the outer and middle shelf. Searches for the earliest Paleoamericans should focus on promontories at the edge of the shelf and along future discoveries of paleoincisions on the shelf. Mapping and delineating this paleolandscape and associated unconsolidated sedimentary deposits interspersed with rocky plains and ledges will continue to be a priority to marine archeologists, coastal managers, fishery scientists, and marine spatial planners over the next several decades.