USING SEDIMENT ORGANIC GEOCHEMISTRY TO INTERPRET BARRIER ISLAND INTEGRITY IN THE LATE HOLOCENE

In previous research from a sediment core (PS-03) collected in southern Pamlico Sound, North Carolina, researchers interpreted a dramatic downcore shift in foraminiferal assemblages at ca. 4000 and 1100 yrs. BP as the result of wide-spread segmentation of the southern Outer Banks barrier island system. It was hypothesized that these large-scale erosional events was the result of severe mid-Atlantic storms. Deconvoluting the historical relationship between climate change and its potential impacts, such as segmentation of the Outer Banks, is critical to an understanding of the likely future of coastal systems worldwide. In this research we apply a multiproxy approach combining organic geochemistry, foraminiferal distributions, grain size analysis, and heavy metal analysis to the late Holocene stratigraphic record of coastal NC. In this study, we specifically analyze downcore trends in total organic carbon (TOC), black carbon (BC) abundance, and their isotopic signatures (δ¹³C_TOC and δ¹³C_BC) in order to assess the varying inputs of marine and terrestrial organics into Pamlico Sound. For example, because BC is ubiquitous and results from the combustion of terrestrial material, its downcore abundance and isotopic signature can offer useful information about sediment provenance. Preliminary data from a Roanoke Island salt-marsh shows a δ¹³C_TOC shift from -26‰ to -22‰ at ca. 700 yrs. BP possibly representative of increased marine influence, similar to the findings on core PS-03. Similarly, preliminary data from a recently-collected Pamlico Sound core shows two intervals where δ¹³C_TOC abruptly shifts from a value of ~-24‰ to -22‰ at both intervals. These are also interpreted as two marine excursions as they are concomitant with PS-03 shifts. These data, as well as downcore trends in BC abundance, will be compared to existing paleoclimate proxies of the Atlantic Ocean (e.g. North Atlantic Oscillation and Atlantic Multidecadal Oscillation Indices), to gain a better understanding of the relationship between Atlantic climate change and its potential impacts on coastal ecosystems.