Date of Award

Spring 5-12-2022

Degree Type

Masters Thesis

Degree Name

Master of Science (MS)

School

Biological, Environmental, and Earth Sciences

Committee Chair

Dr. Carl Andy Reese

Committee Chair School

Biological, Environmental, and Earth Sciences

Committee Member 2

Dr. David Cochran

Committee Member 2 School

Biological, Environmental, and Earth Sciences

Committee Member 3

Dr. Thomas Patterson

Committee Member 3 School

Biological, Environmental, and Earth Sciences

Abstract

This study presents the findings of fossil pollen analysis performed on terrestrial sediments preserved on the northern Gulf of Mexico continental shelf (site hereafter known as the Underwater Forest or DF). This research aims to establish vegetation composition on a continental shelf glacial refuge and provide a better understanding of vegetation response to sea-level rise. Two cores (15DF1 and 15DF3B) located at different locations within the forest were recovered and analyzed. Pollen results from both cores were similar, with high percentages of Taxodium and Nyssa pollen in the lowermost sections reflecting an assemblage typical of contemporary baldcypress swamps. Pollen assemblages then shift in both cores, as Poaeceae becomes dominant in the upper sections. I interpret this as a transition from a baldcypress swamp to more open coastal marsh as marine transgression occurs. During the marsh period in both cores, Alnus becomes a major taxon. This rise in Alnus occurs with high percentages of Taxodium in Core 15DF1, but occurs with high percentages of Poaceae in Core 15DF3B, possibly indicating localized differences. Radiocarbon dates of 15DF1 revealed an age of 45,210 cal a BP placing the core in Marine Isotopic Stage (MIS) 3. An extrapolated optically-stimulated luminescence (OSL) date from a sister core to 15DF3B, revealed an age of 72,000 years (early MIS 4 or 5). However, the pollen results from both cores indicate that the peat sections have recorded the same event in the paleoenvironment, making additional dates necessary to establish more reliable time control.

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