A RECONSTRUCTION OF LATE PLEISTOCENE AND HOLOCENE PALEOCLIMATE RECORD USING RADIOCARBON DATING AND NOBLE GAS THERMOMETRY OF GROUNDWATER IN SHELBY COUNTY, TENNESSEE

Paleoclimate proxies, including groundwater, tree rings, ice, deep-sea sediments, and speleothems, have identified climate changes of various magnitudes throughout Earth’s history. Previous research has utilized noble gas temperatures and radiocarbon (¹⁴C) dating of groundwater to understand prehistoric climate, and the groundwater under Shelby County, Tennessee, is ideal for obtaining high-precision paleoclimate data for the south-central region of North America. This research will derive groundwater recharge temperatures ranging from Pleistocene and Holocene ages utilizing available noble gas data modeled with the program PANGA. The program estimates paleotemperatures using inverse modeling with models relevant to the study site's gas partitioning environment. Samples collected from production wells in three different wellfields have ¹⁴C ages ranging from 13,650 to 1,330 years before present. The wells are screened in the Memphis and Fort Pillow aquifer at varying depths, with the top of the screens ranging from 49.8 to 225.8 meters below mean sea level. The results are hypothesized to refine regional paleotemperatures through the Holocene Climatic Optimum and constrain late Pleistocene paleotemperatures. The south-central region of North America currently lacks proxy data that can provide Pleistocene to Holocene paleotemperature estimates. Ample paleoclimate data are essential to modeling future climate and helps to gain insight into forcing mechanisms that impacted our climate before anthropogenic alteration of the global climate system. Therefore, this study has the potential to provide numerically based data, which can aid in future climatic projections for the region.