Yunhan Fang
Pronouns: He/him
Research Mentor(s): Sierra Petersen
Research Mentor School/College/Department: Earth and Environmental Sciences / LSA
Program:
Authors: Yunhan Fang, Alexandra Curley, Eric Waters, Lucas Gomes, Sierra Petersen
Session: Session 4: 1:40 pm – 2:30 pm
Poster: 99
Abstract
The Florida Platform was periodically submerged multiple times under higher global sea levels over the past ~3 million years, during a period of profound changes in global climate. Fossil shell communities preserved in marine sedimentary deposits from Florida record how thriving marine ecosystems in this region responded to shifting environmental conditions. Beeline Mine (near Orlando, FL) contains two fossil-rich geologic formations from this period: the Nashua Fm. (~2 million years old) and the Anastasia Fm. (~120,000 years old). Here, we analyzed grain size distributions and fossil mollusk assemblages within bulk sediment samples collected from both formations to determine how local environments and ecological communities changed over the past several million years. The older Nashua Fm. contains a wide diversity of mollusks, with major abundances of Mulinia sp. and Anadara sp. along with minor populations of oysters and Chione sp. Collectively, these indicate normal marine salinity conditions. Grain size analyses suggest that these fossils were likely deposited in a sandy, shallow marine environment. However, the top of the Nashua Fm. is characterized by a freshwater river deposit which contains an extreme abundance of Planorbella sp., a type of freshwater snail. The younger Anastasia Fm. is dominated almost entirely by specimens of Mulinia sp., except for an emergent population of Mercenaria sp. observed near the top of the deposit. This faunal shift may represent a sudden change in the local environment, perhaps due to declining sea level. Grain size analyses indicate deposition within a muddy sand environment. These paleontological and sedimentological results reveal ecological shifts on both short- and long-term timescales, highlighting the environmental dynamism of the ancient Florida Platform.
