Type of Document	Dissertation
Author	Forrest, Beth Margaret
Author's Email Address	forrest@quartz.gly.fsu.edu
URN	etd-04062007-174654
Title	Evolution of the Beach Ridge Strandplain on St. Vincent Island, Florida
Degree	Doctor of Philosophy
Department	Geological Sciences, Department
Advisory Committee	Advisor Name Title Joseph Donoghue Committee Chair Alan Niedoroda Committee Member Philip Froelich Committee Member Sergio Fagherazzi Committee Member Sherwood W. Wise Committee Member Stephen Kish Committee Member
Keywords	Sea Level St. Vincent Island Barrier Island Evolution Beach Ridges Gulf of Mexico Sea Level Holocene
Date of Defense	2007-04-02
Availability	unrestricted
Abstract The goal of this investigation was to determine whether highly accurate sampling and dating methods could be employed to develop a high-resolution history of barrier evolution and sea-level change. The focus of the study was St. Vincent Island, an undeveloped barrier island beach ridge plain in the northeastern Gulf of Mexico. The island consists of more than 100 beach ridges organized into a dozen groups or sets based on their topographic expression and geographic pattern. These ridges represent sequential paleo-shoreline positions over the 4000+ year history of the island. Given the long-term tectonic stability of the northern Gulf of Mexico throughout the Quaternary, the island holds the potential for a unique high-resolution chronology of mid- to late-Holocene sea-level change. The sampling of the beach ridges by means of trenches, rather than just cores, allowed for the collection of basal deposits as well as visual confirmation of the origin and structure of the ridges. Ground penetrating radar (GPR) profiles confirmed the origin and structure of the ridges. Based on these techniques it is evident that the beach ridges on the island were built by swash processes rather than by storms. The direct dating of quartz grains collected from the base of several of the islands beach ridges via optically stimulated luminescence dating (OSL) provided an accurate measure of the depositional ages of the ridges. The ridges on St. Vincent Island have ages ranging from zero to 4,100 years, with the oldest ridges on the north side of the island and the youngest ridges on the southeast side of the island. These ages can be correlated with the most recent sea level curve produced for the northern Gulf of Mexico. These ages have also been used in conjunction with topographic maps, leveling or topographic profile surveys and LIDAR data, to calculate the rates of beach ridge plain progradation and beach ridge formation over time. Results show that during times of sea level fall, the progradation rates on St. Vincent Island were relatively fast while during times of sea level rise, rates were considerably slower. The result of this project is a better and more detailed understanding of the influence of sea-level change on barrier island development.
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