24-9 A Sediment Record of Environmental Change from the Pleistocene to Present from The Great Marsh in Exton PA

Session: Lake Sedimentary Records of Past Climate and Environment (Posters)

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Marsh ecosystems play an important role in carbon storage and sediment accumulation. Organic matter preserved in marsh sediments originates from many sources including local vegetation, transported matter, and mineral sediments. Stable carbon isotope ratios (δ¹³C) in marsh plant and sedimentary organic matter reflect differences in vegetation type and carbon sources, offering a tool for interpreting past environmental conditions. The Great Marsh in Exton, Pennsylvania is a preserved wetland system where organic matter accumulation reflects environmental interactions and therefore environmental history. This study aims to examine the sources and delivery of organic matter to Great Marsh by comparing modern marsh vegetation δ¹³C signatures with down core δ¹³C values. Furthermore, we will use organic carbon concentrations (%OC) to determine the onset of the modern marsh system. A 162 cm sediment core was extracted from a portion of the marsh with high sedimentation rates and subsampled at 3 cm intervals. In addition, organic matter from dominant modern marsh plants was collected and their δ¹³C signatures were measured to establish local isotopic end members. Analysis of δ¹³C and %OC reveal evidence for a transition to marsh sedimentation at the termination of the Pleistocene and relatively stable sources of organic matter delivery throughout the Holocene. This study supports the use of marsh δ¹³C records as archives of local environmental change, shaped by regional climate variability and site specific history.

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