EXAMINING LATE PLEISTOCENE TO HOLOCENE ECOSYSTEMS IN NORTHEASTERN PENNSYLVANIA THROUGH LAKE SEDIMENT ORGANIC MATTER CARBON AND NITROGEN STABLE ISOTOPE ANALYSIS

Paleoclimate records developed from lake sediments in Northeast Pennsylvania have provided insights into late Pleistocene to Holocene shifts in climate and environmental conditions. Previous studies have documented the timing of ice-sheet retreat across the landscape through radiocarbon dating of postglacial sediments, millennial-scale shifts in vegetation through pollen analysis, and lake-levels through grain size analysis of core transects. Collectively, these studies demonstrate dramatic changes in temperature and precipitation amounts on century to millennial timescales across the last ~15,000 years. However, no studies to date have focused on reconstructing terrestrial and aquatic ecosystem productivity through multi-proxy analysis of sediment organic matter. Here we present a ~19,200-year record of paleoenvironmental change from Nuangola Lake, located in Luzerne County, Pennsylvania. The 11.7-meter length composite core consists of basal minerogenic, glaciolacustrine sediments overlain by more organic rich lake and peaty sediments. Age control of the sediment sequence is constrained by 7 radiocarbon dates and 6 known age cryptotephra deposits. We analyzed sediment organic matter Carbon and Nitrogen amounts, C/N ratios, and stable Carbon (δ¹³C) and Nitrogen (δ¹⁵N) isotope values at 5-10 cm spacing across the composite core sequence (n = 145) that corresponds to an average temporal resolution of 140 years/sample. Results indicate large changes in organic carbon concentrations on century to millennial timescales and a primarily mixed algal-terrestrial source of organic matter. We compare these data against other physical, biological, and geochemical proxy data from Nuangola Lake, along with other regional paleoclimate records and records of external forcing, to better understand the controls on variations in climate and environmental conditions.