T179 Advances and New Voices in Marine and Coastal Geoscience (Posters)

Tuesday, 17 October 2023
8:00 AM - 5:30 PM
Hall B

LATE PLEISTOCENE-HOLOCENE CLIMATE CHANGE IN THE LOWER CHESAPEAKE BAY RECORDED IN VIBRACORES FROM CUSTIS POND, SAVAGE NECK DUNES NATURAL AREA PRESERVE (SNDP), EASTERN SHORE, VIRGINIA

Paper number: T179-10
Program: Technical Sessions
Time: 8:00 AM – 5:30 PM

Authors

Abstract

Recent studies put local SLR along the coasts of the Delmarva Peninsula at 3-4 times the global average, making this region highly vulnerable. At SNDP, located on the Chesapeake Bay, the rapidly eroding shoreline exposes layers of the late Pleistocene Tilghman paleosol which is overlain by large, Holocene sand dunes and threatens a diverse maritime forest and freshwater bogs and ponds. Custis Pond, located just east of the shoreline, contains a sedimentary record of environmental change likely resulting from sea level changes since the last glacial maximum, ~20K years ago. This study aims to determine the depositional environments represented by sediments obtained from 5, 1-3 m-long vibracores extracted from the pond in 2021-2022, tie the sediment cores to historical records and aerial photography, determine how core sediments correlate with the paleosol at the shoreline, and add to the broader understanding of climate change and SLR in this region.

Core analyses include loss on ignition for organics taken at 5 cm intervals, grain size, micro and macro-fossil ID, and detailed descriptions of sediments. We use these analyses to divide the core into units representing different depositional conditions. Unit I represents sedimentation in the modern fresh water pool characterized by eutrophied stagnant waters. Unit II is dune sand washed/blown into the pool from storms, wind, and other disturbances which appears in the core as thin layers of well-sorted, fine-grained sand. Unit III contains silt-sized sediment with high (20-50%) organic matter, possibly indicating compacted pond sediments or the uppermost paleosol horizon. Organic matter decreases sharply with a transition to Unit IV, which is characterized by the finest grained sediments (silty-clay) characteristic of a lower energy environment. Unit V is composed of organic-rich, medium-grained sands possibly deposited as part of a fluvial system during a time of lower sea level. Organic matter increases in Unit VI and grain size decreases. Overall grain size decreases upcore, indicating a shift towards a less energetic depositional environment over time and pollen analysis of the palesol suggests the region experienced a change from cool to warm temperate conditions. Radiocarbon dating will be completed to provide age control for the cores.

Geological Society of America Abstracts with Programs. Vol. 55, No. 6

doi: 10.1130/abs/2023AM-395497

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