ASSESSING THE CHRONOSTRATIGRAPHY OF LATE PLEISTOCENE AND HOLOCENE COASTAL LITHOSOMES USING OPTICALLY STIMULATED LUMINESCENCE TECHNIQUES: INTRIGUING RESULTS FROM NC AND FL

Investigators are actively researching the development of the late Pleistocene coastal section in North Carolina and Florida using cutting-edge optically stimulated luminescence (OSL) techniques, ground penetrating radar, and sedimentological methods. Ages are being determined on sediments from a variety of siliciclastic, and mixed carbonate-siliciclastic coastal environments, and include nearshore, overwash, tidal flat, inlet-fill, and eolian facies. The geophysical, lithostratigraphic and chronostratigraphic data are being combined to understand the detailed paleoenvironmental evolution of these coastal systems, and to place constraints on late Pleistocene and Holocene relative sea level. Samples from the Suffolk Scarp in North Carolina, and correlative shelf deposits yield dates corresponding to Marine Isotope Stage (MIS) 5A. Paleoshoreline ridges east of the Suffolk Scarp, and beach ridges on Merritt Island, Florida, yield ages corresponding to MIS 3. The Kitty Hawk beach ridges, on the modern Outer Banks, yield ages of ca. 3 to 2 ka. OSL ages are consistent within and between sites, and are also consistent with previously reported U-series and amino acid racemization ages. The SPECMAP oxygen-isotope curve and GISP2 ice core data are being used to place these deposits in the context of global climate and sea-level change. The occurrence of the MIS 5A and MIS 3 shorelines suggests that glacio-isostatic uplift of the study area may be ca. 22 to 27 m, as suggested by other workers, and/or MIS 3 sea level was briefly higher than suggested by some coral reef studies. The age of the Kitty Hawk beach ridges places the Holocene (MIS 1) shoreline well west of its present location at ca. 3 to 2 ka. The age of shoreline progradation is consistent with the ages of other similar beach ridge complexes in the southeast USA, suggesting some regionally contemporaneous forcing agent.