A Geochemical Record of Late-Holocene Hurricane Events From the Florida Everglades

A 5.25-m sediment core SRM-1 and 45 surface samples from mangrove forests at the Shark River Estuary in the Everglades National Park, Florida, were examined by using X-ray fluorescence and carbon isotopic analyses to study the history of intense hurricane landfall during the Late-Holocene. Significance testing of the surface samples in relation to storm deposits from Hurricane Wilma suggests that elemental concentration of Sr and Cl and the ratio of Cl/Br are the most sensitive indicators for major hurricane events in our study area. The geochemical data sets of core SRM-1 identified five active periods of intense hurricane activities during the last 3,500 years at ~3,400-3,000, ~2,200-1,500, ~1,000-800, ~600-300, and ~150 calibrated years before present to present. This is the longest paleohurricane record to date from South Florida. Our results are consistent with the view that intense hurricane activities in South Florida were modulated by Intertropical Convergence Zone (ITCZ) movements, El Niño/Southern Oscillation (ENSO) activities, and North Atlantic Oscillation (NAO) strength. This study contributes to the methodological advancement in paleotempestological studies by demonstrating that geochemical signals, particularly signals of saltwater intrusions, can be preserved in the sediment profiles on millennial time-scale and measured by X-ray fluorescence techniques, thereby enabling more storm records to be produced from otherwise suboptimal sand-limited coastal systems such as the Florida Everglades. More work needs to be done to explore the use of geochemical and stable isotopic analyses in detecting storm signals from sand-limited coastal environments.