UNDERSTANDING THE COASTAL RESPONSE TO LATE PLEISTOCENE RELATIVE SEA-LEVEL CHANGES IN NORTH CAROLINA, USA: AN ANALOG FOR FUTURE COASTAL EVOLUTION (Invited Presentation)

A record of late Pleistocene rapid relative sea-level (RSL) changes exists in the shallow geologic section of eastern North Carolina and southeastern VA. The westward extent of the late Pleistocene shoreline is marked by the Suffolk Shoreline (a.k.a., the Suffolk Scarp), a highstand prism located up to 120 km inland from the modern ocean shoreline. Multiple late Pleistocene transgressive to highstand deposits occur seaward of the paleoshoreline, on the coastal plain and beneath the modern estuaries, and occur above the MIS 6 subaerial unconformity. These deposits contain a record of paleoenvironmental and morphodynamic conditions occurring during rapid rise and highstand that provide an analog for future conditions. Stratigraphic sequences and facies are being mapped using CHIRP seismic data, ground penetrating radar data, and core data (sedimentology and microfossil analyses). The chronostratigraphic framework is provided by optically stimulated luminescence and radiocarbon ages (for Holocene samples). Lithofacies corresponding to a variety of coastal depositional environments are being mapped regionally, within the context of the sequence stratigraphic framework, to understand how the system evolved during late Pleistocene episodes of relative sea-level rise. Hydrodynamic models are being developed and calibrated using the geological data to understand the changes to currents and wave energy that occurred as the system was inundated. Notably, MIS 6 incised fluvial valleys are filled with tidalite facies (wavy, lenticular and flaser beds, inclined heterolithic strata, etc.) associated with the transgressive systems tract (TST) of Termination 2 (MIS 6/5 transition). These beds indicate a significantly greater tidal regime than that which exists today. The valley-fill is cut by a transgressive ravinement surface and overlain by other facies indicating shallow shelf, barrier island and tidal shoal deposition within this system. OSL and radiocarbon ages suggest deposition occurred during MIS5 and MIS3 (a result of glacio-isostatic adjustment). Facies are being correlated and mapped to understand the spatial and temporal changes that occurred to depositional environments during sea-level rise. Characteristics of the deposits, and associated hydrodynamics, can inform on what can be anticipated during the next several centuries.