A NEW INDICATOR OF MARINE ISOTOPE STAGE 3 SEA LEVEL NEAR PRESENT-DAY HEIGHT FROM THE US SOUTHERN ATLANTIC COAST

Terrestrial records of Quaternary sea level in the peripheral region of former ice sheets are important to understand glacial ice distribution and interglacial isostatic adjustment. Marine Isotope Stage (MIS) 3 sea-level indicators situated today close to present-day sea level have so far been reported only on the US mid-Atlantic coast, which requires significant revision of MIS 3 ice sheet distribution and global mean sea level according to a recent sea-level modeling study (Pico et al., 2017). Here we report on a MIS 3 beach deposit at about present-day sea level in Murrells Inlet, South Carolina, the first of such records outside the US mid-Atlantic region. Murrells Inlet has a Holocene salt marsh onlaps Pleistocene beach and shallow marine deposits which in turn overlies Paleocene calcareous deposit. The beach deposit found from -2 to 3 m is progradational as revealed by ground-penetration radar and dated by optically stimulated luminescence (OSL) to MIS 3 (55±2 ka). Our result supports previous findings about the exceptionally high MIS 3 relative sea level on the US Atlantic coast. It indicates that terrestrial MIS 3 sea-level indicators are more widespread than previous thought, concordant with the latest sea-level modeling study.

Pico, T., Creveling, J. R. & Mitrovica, J. X. Sea-level records from the U.S. mid-Atlantic constrain Laurentide Ice Sheet extent during Marine Isotope Stage 3. Nature Communications 8, 15612.