ENVIRONMENTAL RECONSTRUCTION DURING THE LATE HOLOCENE FROM CAVE SEDIMENTS IN JENNING'S CAVE, MARION COUNTY, FLORIDA

Cave sediments collected from Jennings Cave in Marion County, Florida show variations in the δ¹³C values of their fulvic acids (FAs), which indicate periods of vegetation change influenced by climatic changes during the Late Holocene. The carbon isotope record ranges from -35‰ to -21‰, exhibiting variability of ~14‰, which is within the range of C₃ vegetation. This is to be expected in a humid, subtropical forested environment and likely indicates changes in C₃ plants from canopy- to understory-dominated conditions. The most negative δ¹³C value of ~ -35‰ occurred around 1,870 cal yr BP, abruptly becoming less negative to – 21‰ around 1,800 cal yr BP. A general trend toward more negative values continues until approximately 700 cal yr BP (-34‰). These changes in plant assemblages were in response to changes in available water resources, with increased temperatures and evapotranspiration leading to arid conditions and a shift toward understory-dominated C₃ vegetation during the MWP and then canopy dominated vegetation during the cooler LIA. Prolonged migration of the ITCZ and NAH affects