A Preliminary Drought History From 4000 Years Ago To Present As Indicated By Lake Lowstands in Lake Jackson, Florida/Alabama

Instrumental and observational data recorded in the southeastern United States indicates that the region has undergone extreme drought conditions as recently as 2006-2008, and an estimated $1.3 billion was lost in the southeastern U.S. in 2007 alone due to destruction of major field crops such as wheat and corn. In addition, paleo-hydrologic reconstructions indicate that the southeastern U.S. has experienced extreme droughts throughout the Holocene. Paleo-hydrologic reconstructions completed in central and southern Florida indicate that climatically induced hydrologic conditions have affected long-term changes in vegetation during the late Holocene; however, there is a lack of continuous hydrologic records from northern Florida and Alabama. Extreme droughts have a profound impact on lake water levels; this sensitivity makes lake sediment cores ideal for investigating drought history. Here, we present a continuous, high-resolution record of climate and environmental change for the past 4000 years from Lake Jackson, a sinkhole lake located on the Florida-Alabama border. ²¹⁰Pb and ¹⁴C dating, X-ray fluorescence (XRF), x-radiography, loss on ignition, smear slide, and grain size analyses were completed on a 6.7 meter core. We compare these data to previously collected CHIRP seismic data. The lithology of the core is dominated by very thick to medium-bedded very fine clayey silt. Fluctuations in geochemical and geophysical data document changes in organic matter preservation, mineral composition, and grain size in Lake Jackson sediments, which highlight centennial-scale variability in the depositional environment. This record from Lake Jackson deepens our understanding of the hydrologic variability in the SEUS over the late Holocene, advancing towards a clearer explanation of the mechanics behind drought events and the impact they may have on the region in the coming decades.