LATE PLEISTOCENE STRATIGRAPHY AND RELATIVE SEA-LEVEL CHANGE IN NORTHEASTERN NORTH CAROLINA, USA WITH IMPLICATIONS FOR GLACIO-ISOSTASY AND GLOBAL SEA LEVELS

Multiple depositional sequences corresponding to late Pleistocene Marine Isotope Stages (MIS) occur in the shallow geologic section of eastern North Carolina and southeastern Virginia. These depositional sequences have been defined and correlated based on lithostratigraphy, micropaleontology, palynology, geophysics, optically stimulated luminescence (OSL), amino acid racemization (AAR), and U-series dating. Late Pleistocene depositional sequences consist of shelf, estuarine, fluvial and aeolian deposits. The basal depositional surface is marked by the MIS 6 subaerial unconformity and the Termination II transgressive ravinement surface. These deposits contain a record of past sea level, morphodynamic and environmental conditions that provide an analog for future conditions. The MIS 5e depositional sequence (DS-5e) consists of a basal estuarine to inner shelf section (based on a low diversity foraminiferal assemblage) grading upward to an open shelf section (higher diversity foraminiferal assemblage). Pollen data indicate conditions cooler than present grading upward to warmer than present. The MIS 5c unit (DS-5c) is patchy throughout the region, but generally exhibits estuarine facies. The MIS 5a unit (DS-5a) is widespread and exhibits tidal bedding and estuarine sand shoals. Pollen data indicate temperatures ranging from cooler than modern to modern conditions. MIS 4 deposits consist of source-bordering dune deposits with interdune swale interbeds, and possible braided stream deposits. The MIS 3 unit (DS-3) is only found in the northern study area and consists of tidal flat and barrier island deposits. Pollen data indicate conditions cooler than present. Relative sea-level (RSL) data include vertical errors derived from hydrodynamic modeling of tides (models indicate enhanced tidal range) and uncertainty in elevation based on inferred paleoenvironment. The derived RSL curve indicates marine inundation during MIS 5e, 5c, 5a, and 3. Data may be explained by glacio-isostatic subsidence of the region, higher global sea level and reduced ice sheet volume during MIS 3 and MIS 5 than predicted using stacked δ¹⁸O data from deep sea cores. This corroborates other recent investigations and models of late Pleistocene ice sheet volume based upon empirical data from the northern hemisphere.