Investigation of sedimentary records of Hurricane Irma in sinkholes, Big Pine Key, Florida

Abstract

Few paleotempestological studies have focused on coastal sinkholes, a common feature in Florida, which can receive and preserve storm overwash sediments. The major goal of this research is to improve our understanding of the characteristic signatures of storm sediments in sinkholes thereby determining reliability of these environments as proxies for hurricanes. Hurricane Irma as a category 5 storm provides an excellent case study for characterizing storm deposits in sinkholes on Big Pine Key. We cored at four sinkholes along a 350 m transect normal to the shoreline. Core sediments were characterized using physical description, short-lived radioisotope dating, sediment grain size analysis, loss-on-ignition, microfossil analysis, and x-ray fluorescence elemental analysis. We found that Irma deposits had higher abundances of marine foraminifera, less total organic matter and elevated Si/Al and Ca/Ti ratios, compared to pre- or post-Irma sediments. In addition, there was a thinning of the storm sediments along the inland transect. Consequently, we propose that sinkholes, particularly those that are closer to the shoreline, can provide reliable sites for paleotempestology studies.