Alexandra Curley
Pronouns: She/her/hers
Research Mentor(s): Sierra Petersen
Research Mentor School/College/Department: Earth and Environmental Sciences / LSA
Program:
Authors: Alexandra Curley, Yunhan Fang, Lucas Gomes, Sierra Petersen
Session: Session 4: 1:40 pm – 2:30 pm
Poster: 98
Abstract
Understanding how past climates and environments have changed can provide information about how the planet may evolve in the future, which is important given the rate of present-day global environmental changes. According to prior research, a local extinction event particularly affected marine Florida species at the end of the Pliocene Epoch (~3 million years ago). The goal of this research is to learn about the potential causes of this regional extinction event by examining how local environments shifted near this time period. Buck Hammock Quarry near Orlando, FL contains shelly sediment deposits from the Nashua Formation (~2 million years old) and the Anastasia Formation (~120,000 years old). Here, we analyzed grain size distributions and molluscan fossil assemblages contained within bulk sediment samples collected from exposures of each formation. These samples were sieved into 5 size fractions for grain size analysis, and the 3 largest size fractions were further studied to examine the most prevalent molluscan taxa throughout the units and across formations. The most common sediment size through both formations was sand (63µm – 2mm), suggesting a primarily sandy environment throughout both time periods, although the Nashua Fm. had a higher proportion of mud-sized sediments (<63µm). The Anastasia Fm. also contained more intact shells, meaning it was likely a lower-energy environment. The two genera found in the Nashua Fm. samples were the bivalve Mulinia sp. and Pectinidae, while for the Anastasia Fm., the most abundant genera were Mulinia sp., followed by specimens of Donax sp., Arcidae, and Crepidula sp. These organisms prefer shallow, sandy environments, in agreement with findings from our sediment size analysis. However, the change in relative abundance of each genus through time can indicate how the local environment shifted, such as by becoming less marine and consequently less habitable to Pectinidae and more favorable to Donax sp. and Arcidae. Sediment sizes and molluscan taxa in the samples suggest that during the early–mid Pleistocene, Florida’s coasts were shallow, sandy marine environments that were in the process of changing. These changes may help explain the local extinction event that occurred in Florida at this time, information which may begin to clarify how changes in climate correspond with changes in ecosystems.
