DEVELOPING LATE HOLOCENE HIGH-RESOLUTION RELATIVE SEA-LEVEL RECORDS IN SOUTHERN NORTH CAROLINA

Millennial-scale relative-sea level records are a necessary benchmark to assess present rates of accelerated sea-level rise, future sea-level predictions and their implications to coastal zones. The Atlantic coast of the United States serves as a significant area of latitudinal RSL variability because of the gradient of isostatic adjustment with distance from the center of the Laurentide Ice Sheet. Since the Last Glacial Maximum (since ~26ka) deglaciation has caused areas along the U.S. Atlantic coats that were formerly under the ice sheet to uplift and those on the margins and beyond to subside as the peripheral forebulge collapsed.

Near the North and South Carolina border the coastal zone is experiencing lower than expected rates of RSL rise in the late Holocene (last 4,000 years). This divergence from the anticipated GIA trend is thought to be attributed to non-isostatic, long-term tectonic processes resulting from uplift of the underlying crystalline basement, the Cape Fear Arch (CFA).

This project will develop a new high-resolution RSL record to help resolve the structural spatial footprint of the CFA and fill a 125 km gap in RSL data between Southport, NC and the Croatian National Forest. We will use foraminifera preserved within salt marsh sediment as sea-level indicators. Six modern marshes were sampled to define the relationship between foraminifera and sea level. This relationship was then applied to fossil foraminiferal assemblages within sediment cores and combined with AMS radiocarbon dated plant macrofossils to produce a history of sea-level during the late Holocene.