GPR AND VIBRACORE ANALYSES FROM CUSTIS POND, SAVAGE NECK DUNES NATURAL AREA PRESERVE (SNDP), EASTERN SHORE, VIRGINIA REVEAL LATE PLEISTOCENE-HOLOCENE ENVIRONMENTAL CHANGE IN THE LOWER CHESAPEAKE BAY

Recent studies put local SLR along the Delmarva Peninsula at 3-4 times the global average. Coupled with other metrics, this region is highly vulnerable to SLR. At SNDP, located in the lower Chesapeake Bay, erosion has exposed layers of the late Pleistocene Tilghman paleosol and overlying Holocene sand dunes and threatens a diverse maritime forest and inland freshwater bogs and ponds. Custis Pond, located 300m east of the shoreline, contains a sedimentary record resulting from environmental change since the last glacial maximum, ~20K years ago. This study aims to determine the depositional environments represented by sediments obtained from 5, 1-4 m-long vibracores extracted from the pond in 2021-2022. We completed loss on ignition (at 5 cm intervals), grain size analyses, micro/macro fossil ID, and detailed core descriptions. These data were used to inform facies interpretations representing paleosol, paleodune, paleovalley, and pond environments. VC5, taken 465m west of the eroding shoreline, contains all four facies, including the Tilghman paleosol (2.23-2.78 m depth). Basal dune sediments are characterized by medium-grained quartz sand with subrounded pebbles. These are overlain by sandy silts interpreted to be loess and local sediments reworked by a paleodrainage channel. The topmost section of each core is characterized by very fine-grained, organic-rich pond sediments with thin beds of well-sorted, fine dune sands that washed or were blown into the pool during storms. The modern freshwater pond is surrounded by maritime forest and is currently stagnant and populated by duckweed. The two western-most cores contain sediments that represent pond sedimentation down to 3.25 meters. GPR radargrams, collected in 2021, show multiple reflectors and sediment packages that coincide with stacked sand dune complexes and an underlying anomaly we tentatively interpret to be a couplet representing the Tighlman Paleosol and the overlying loess. Here we correlate the GPR anomalies to the sediment cores to refine the stratigraphic record of Custis Pond in order to determine environmental changes that occurred in SNDP since LGM. Radiocarbon dating will be completed to provide age control.