Graduation Year

2021

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Geology

Major Professor

Philip E. Van Beynen, Ph.D.

Co-Major Professor

Ping Wang, Ph.D.

Committee Member

Gregory S. Herbert, Ph.D.

Committee Member

Gregg R. Brooks, Ph.D.

Keywords

storm overwash, paleotempestology, carbonate reef environment, Florida Keys

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. I 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. I 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. Another major goal of this study is to investigate the sedimentary characteristics of hurricane Irma for three neighboring environments, lagoonal, mangrove, and sinkholes. This event and location are significant because it allowed for the comparison of all three environments for a single storm. I cored at coastal sinkholes, a backshore lagoon, and a small mangrove island. These cores were compared for their stratigraphy, short-lived radioisotope dating, total organic matter, grain size, and trace elements. We found clear evidence of Irma’s overwash deposited in the sinkholes 1-3 and for the lagoon and mangrove island but not as distinctly. We suggest this difference arises from the lagoon and mangrove environments being impacted by bioturbation, constant tidal influences, and less protection from the storm surge. Therefore, we propose that, for BPK, sinkholes are the most reliable sites for providing excellent proxies to reconstruct past major hurricanes.

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