SREL Reprint #2276

New constraints on the evolution of Carolina bays from ground-penetrating radar

John A. Grant1, Mark J. Brooks2, and Barbara E. Taylor3

1Earth Sciences, SUNY College at Buffalo, 1300 Elmwood Ave., Buffalo, NY 14222, USA
2Savannah River Archaeological Research Program, South Carolina Institute of Archaeology and Anthropology, University of South Carolina, P.O. Drawer 600, New Ellenton, SC 29809, USA
3Savannah River Ecology Laboratory, University of Georgia, Drawer E, Aiken, SC 29802, USA

Abstract: Ground-penetrating radar (GPR) data for the Savannah River Site (SRS) in the Upper Coastal Plain of South Carolina, combined with geological, archaeological, and ecological data place new constraints on the evolution of Carolina Bays.  Extant SRS bay morphology formed mainly during the Holocene and did not involve migration of bays across the landscape. Multiple periods of bay-rim accretion with intervening intervals of erosion may characterize the longer-term evolution of the bays. Bay evolution, however, did not involve significant modification of the Upland Unit underlying the region. During fluctuating, but generally open water conditions, breaking waves along bay shorelines eroded and transported sediment which was subsequently exposed for deflation during periods of low water. Deflation and transport of sand into standing vegetation along the margin of the bay depression created a rim in the form of a parabolic dune lacking obvious internal stratification. Simultaneously, infilling occurred by shoreline erosion and transport from adjacent elevated suifaces. This, coupled with growth of emergent vegetation, resulted in decreased hydroperiod, wave energy, shoreline modification, and rim accretion. Transport of some rim sediments back into the bays via alluvial and colluvial activity created wedges of infilling sediment during waning stages of evolution. The apparent contradiction of bay orientation with respect to prevailing winds might reflect seasonal changes in water level and wind direction: southwesterly winds during spring high water causes NW-SE elongation of the bays, whereas northwesterly winds during lower water in the fall and winter account for nearshore deflation and rim accretion along the east-southeastern bay margins.

Keywords: Carolina Bays; ground-penetrating radar; eolian/lacustrine; Holocene

SREL Reprint #2276

Grant, J.A., M.J. Brooks, and B.E. Taylor. 1998. New constraints on the evolution of Carolina bays from ground-penetrating radar. Geomorphology 22:325-345.

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).