38 Past and Future Coastal Evolution in Response to Sea-Level Changes and Storm Impacts (Posters)

Friday, 29 March 2019
1:00 PM - 5:00 PM
Carolina Ballroom

SEA-LEVEL CHANGES OVER HISTORIC AND GEOLOGIC TIMESCALES IN WINYAH BAY, SC

Paper number: 38-5
Program: Theme Sessions
Time: 1:00 PM – 5:00 PM

Authors

Abstract

The study of past relative sea-level variability has important implications for understanding future changes in sea level, especially for potential impacts on coastal areas that rely heavily on waterfront activities, both economically and culturally, like Georgetown, South Carolina. This project combines water level logging, historic tide gauges, and sediment cores in order to reconstruct past sea level.

Hand-written tide gauge records from the Georgetown Lighthouse were documented hourly for the years 1899 and 1900 and two high and low water levels daily for 1901-1904. We recovered these documents from the US National Archives, digitized these records and located the old 1899 benchmark used as a vertical reference (originally related to the 1819 MHW datum). A HOBO water-level logger was installed at the original lighthouse dock in Oct 2018 to measure current sea level. An RTK-GPS survey was conducted to determine the elevation of the historic benchmark and of the water level logger. The two records will be related to each other in order to calculate a rate of change for sea level from 1899 to today.

Sea level will also be reconstructed over the past 2,000 years using intertidal foraminifer assemblages from a sediment core transect across a North Inlet marsh. These foraminifera live in a narrow tidal range making them a good indicator of past sea level. The modern vertical faunal zonation along with the exact elevation will be used to calibrate the fossil assemblages to their respective paleo-elevation. The cores will be dated using 210Pb/137Cs and 14C to obtain robust age models.

These two independent records of regional sea level history will produce a better understanding of variability over various timescales in order to quantity how sea level has changed in the past and is fundamental to sustainable management decisions in Georgetown into the future. The data will also close an existing spatial gap in the regional vertical behavior of the US Atlantic coast.

Geological Society of America Abstracts with Programs. Vol. 51, No. 3

doi: 10.1130/abs/2019SE-327591

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