MID-HOLOCENE DROUGHTS IN THE SOUTHEASTERN U.S RECORDED IN LACUSTRINE SEDIMENT LITHOLOGY AND SUB-BOTTOM STRATIGRAPHY

Paleoclimate data is important for understanding past climate change and its environmental impacts. While paleo-hydrologic reconstructions have shown that large portions of the North American continent experienced a dry period in the mid-Holocene, few high-resolution paleoclimate records exist from the southeastern U.S. Lake sediments can record detailed histories of extreme hydrologic events, as changing water levels are reflected by changes in sub-bottom stratigraphy and sediment lithology. To provide a more detailed timeline for Holocene droughts in the southeastern U.S., we reconstructed Holocene paleo-hydroclimate using ground penetrating radar (GPR) and CHIRP seismic reflection data along with proxy data from two sediment cores from Little Rattlesnake Lake, a 5.5m-deep sinkhole lake in northern Florida. We reconstructed sub-bottom stratigraphy to outline the 3-dimensional sediment structure of the lake. Erosional truncation and onlap features were used to identify lake regressions and transgressions, respectively. X-ray fluorescence (XRF), ¹⁴C dating, loss on ignition, grain size, and smear slide analyses were performed on both cores to provide additional evidence of lake level rise and fall and give timing to the lake level fluctuations. Erosional truncation in the sub-bottom stratigraphy and abrupt increases in grain-size indicate dry conditions in the mid-Holocene, and onlap features, decreased grain-size, and increased primary productivity indicate wet conditions in the early and late Holocene. Our data suggest that the southeastern U.S. was dry during the mid-Holocene, which supports previous research indicating mid-Holocene moisture reduction across the mid-latitudes. These findings strengthen our understanding of Holocene paleo-hydroclimate and contribute to a growing dataset that can bolster our paleoclimate models on a regional scale.