Terminal Pleistocene braided to meandering transition in rivers of the Southeastern USA

Abstract

Thirteen paleomeanders on the oldest parts of meander belts on floodplains in the Coastal Plain of Georgia and the Carolinas (southeastern USA) were selected for radiocarbon dating to determine the onset of meandering following braiding during the Late Pleistocene during Oxygen Isotope Stage 2. The radiocarbon ages were compared to previously reported Late Pleistocene ages for braid bars and eolian dunes. Results indicate that meandering commenced at circa 15,000 to 16,000 cal years BP and continued throughout the terminal Pleistocene and Holocene. Correlation with other paleoenvironmental records indicates that this shift to meandering was associated with global warming and moister conditions in the southeastern United States that led to a denser vegetation cover and a reduction in sediment yield. The shift to meandering was also associated with some incision and terracing of the Late Pleistocene braided fluvial surfaces. Paleodischarge of the bankfull condition of early Holocene meandering channels was apparently greater than under modern conditions, suggesting wetter conditions at that time than at present. This braided to meandering transition in the southeastern United States provides an example of river response to global climate change in a relatively low latitude region of the world that was not influenced by glacial or periglacial landscape conditions. © 2005 Elsevier B.V. All rights reserved.