INVESTIGATING THE UTILITY OF CAVE SEDIMENTS FOR LATE HOLOCENE PALEOENVIRONMENTAL RECONSTRUCTION IN FLORIDA

Cave sediments collected from Jennings Cave in Marion County, Florida were analyzed using a multi-proxy approach. Fulvic acids (FAs), humic acids (HAs), bulk organic matter, and phytoliths were extracted from the sediments for carbon isotope analysis to determine periods of vegetation change caused by climatic influences during the Late Holocene (~ 3,000 years BP). Magnetic susceptibility and density analyses were also performed to compare physical sedimentary characteristics related to precipitation to the carbon isotopes. The carbon isotope record ranges from -35‰ to -14‰, exhibiting variability of ~21‰, within the different proxies, which indicates changes between C3 and C4 vegetation. Density analysis closes matches the FAs, indicating changes in the sediments during shifts in the vegetation regime. This likely indicates changes between a sub-tropical forested environment and more arid, grassy plains conditions.

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 less C3 vegetation (increased C4 vegetation) during the MWP. The cave sediment fulvic acid carbon isotope record agrees well with ä13C values from a speleothem collected nearby that covers the same time period. Prolonged migration of the NAO and ITCZ affects precipitation in Florida and likely caused vegetation changes during these climatic shifts.