RECONSTRUCTION OF PALEOSTORM HISTORY USING GEOCHEMICAL PROXIES ARCHIVED IN THE SEDIMENTS OF A COASTAL LAKE IN NORTH FLORIDA

Hurricanes are the costliest natural catastrophes in the U.S. Gulf Coast. High resolution geologic records of major storm impacts and environmental changes during the late Quaternary is essential to better understand the long-term pattern in hurricane activity and its relation to climate change. Here, we present a nearly 2000-year long record of severe storm landfalls and environmental changes based on initial results of radiocarbon dating of plant fragments and analyses of organic geochemical proxies preserved in sediment cores from a coastal lake (Mullet Pond) in north Florida. Our data show that the lake area is dominated by C₃ plants with an insignificant amount of C₄ vegetation. The primary sources of organic matter in the lake are aquatic and terrestrial C₃ plants. The initial data from one sediment core show significant temporal variations in organic geochemical proxies including δ¹³C, δ¹⁵N, C%, N% and C/N, reflecting changes in lake environment. Positive shifts in both δ ¹³C and δ ¹⁵N values of sedimentary organic matter (OM) in the lake suggests an influx of marine OM and nutrients due to seawater flooding which leads to a high lake productivity. Radiocarbon dating of plant fragments indicates that the sediment in this core was deposited over the last ~ 2000 years. These initial data from the sediment core suggest a higher storm frequency in the recent past than the long-term average frequency derived from grain size analysis. Analyses of additional sediment cores from this lake with improved chronology will help us to develop a better understanding of storm history and environmental change in the area.