PP43C-2301
New chronology for Pleistocene shoreline deposits on the central US Atlantic Coast: implication for relative sea level during MIS 5 and 7
Thursday, 17 December 2015
Poster Hall (Moscone South)
Zhixiong Shen1, Eric Eaton Wright1 and Barbara Mauz2, (1)Coastal Carolina University, Department of Marine Science, Conway, SC, United States, (2)University of Liverpool, School of Environmental Sciences, Liverpool, United Kingdom
Abstract:
Emerged shoreline deposits are the most important records for studying relative sea level (RSL) of previous interglacial and understanding glacial/hydro isostasy. The Lower Atlantic Coastal Plain in the U.S. is characterized by coast-parallel barrier beaches and back-barrier deposits formed during maximum Pleistocene marine transgressions. Thus, they offer an opportunity to investigate RSL changes of multiple Pleistocene interglacials. However, the chronology of these deposits has been controversial due to the lack of reliable numerical ages, especially in South Carolina. Here we present stratigraphy and OSL dating results for both the late Pleistocene barrier and the back-barrier deposits between Georgetown and Myrtle Beach, South Carolina and discuss their sea-level implications. The barrier ridge near Georgetown is covered by about 1 m aeolian deposits dated to ~20 ka. The aeolian deposits overlie humic sand and laminated beach sand that is dated to ~80 ka, corresponding to Marine Isotope Stage (MIS) 5a. Stratigraphy of back-barrier deposits exposed along the Intracoastal Waterway near Myrtle Beach reveals a unit of back-barrier deposits separated from underlying shallow marine deposits by a paleosol. The back-barrier deposits are dated to MIS 5a while the lower shallow marine deposits yielded OSL ages corresponding to MIS 7 (~200 ka).
The beach sand near Georgetown and the back-barrier deposits near Myrtle Beach together suggest that MIS 5a RSL was up to about 5 m above present sea level while the shallow marine deposits near Myrtle Beach indicate a MIS 7 RSL at or above present sea level along the northeastern South Carolina coast. The MIS 5a and MIS 7 RSL are in agreement with previous studies along other U.S. Atlantic coast. However, the missing of MIS 5e deposits between MIS 5a and MIS 7 deposits at the exposure near Myrtle Beach needs be confirmed with additional work.
