SHALLOW MARINE MARGIN SEDIMENTS, MODERN MARINE EROSION AND THE FATE OF SEQUENCE BOUNDARIES - GEORGIA BIGHT (USA)

Shallow shelf lithofacies of Late Pleistocene age have yielded a new understanding of the relationship of sediment lithification, sequence and relative sea level (RSL) just prior - and post - Last Glacial Maximum (LGM) for the Georgia Bight. Vibracores, hand samples and cores, have been taken from two offshore sites - Gray's Reef National Marine Sanctuary and J-Reef. Both sites are shallow (-20 mbsl) rock outcrops dated to the Pliocene - Pleistocene. Macro and micropaleontological, vertebrate and invertebrate, confirm this dating along with direct age determination using AMS-radiocarbon; Uranium Series and Optical Stimulated Luminescence (OSL) methods. Using analyses of sediments, inclusions together with the geological mapping of outcrops/exposures, we have identified provisional elements of the late Pleistocene marine sequence for this portion of the Georgia Bight. Direct dating of the unconsolidated sediment prism and lithified exposures indicate a subaerial exposure from MIS 3 through late MIS 2 with the subsequent, post –LGM transgression. The survival of these, and other sedimentologically observed markers for relative sea level and sequence stratigraphic architecture, are tenuous in shallow marine margins like the Georgia Bight.