Document Type

Thesis

Abstract

Understanding faunal response to past climate change can help us to predict the impacts of current anthropogenically-driven warming. The fossil record provides an ideal opportunity to explore the effects of climate change on ecological communities. The goal of this research is to quantify changes in diversity and community structure, recorded in the molluscan assemblages of southeastern Virginia, that coincide with an interval of cooling across the Miocene-Pliocene boundary (approximately 5.3Ma). To explore the effects of this cooling, we compared community characteristics before and after the climate change, including species composition, richness and abundance. The Cobham Bay Member of the Eastover Formation, a silty sand, was deposited during the late Miocene warmer interval and records an abundant and diverse assemblage of subtropical mollusks. This contrasts with the more depauperate warm temperate fauna of the Sunken Meadow Member of the Yorktown Formation, which is early Pliocene in age. The two stratigraphic units are similar sedimentologically and paleoenvironmentally, allowing us to compare diversity while controlling for substrate. Climate influences taxon distribution because of species-specific temperature tolerances (Walther et al. 2002). As the temperature decreases from the Miocene (Cobham Bay Member) to the Pliocene (Sunken Meadow Member), molluscan assemblages should change drastically. Specifically, we would expect an overall decrease in species richness, a decrease in the abundance of subtropical species, an increase in the abundance of temperate taxa, and an extinction of subtropical species.

Date Awarded

2007

Department

Geology

Advisor 1

Rowan Lockwood

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