The Environmental Context of Gastropods on Western Laurentia (Basin and Range Province) During the Great Ordovician Biodiversification Event.

摘要

Gastropods are a major component of modern marine ecosystems and can be found in nearly every type of marine ecosystem. They experienced their first notable radiation during the Great Ordovician Biodiversification Event (~470 Ma), during which their diversity tripled. This study examines the gastropod assemblage preserved in the Basin and Range Province of the Western United States to establish the environmental context for the Ordovician gastropod radiation. Gastropods are present within every facies examined, but their relative abundance and distribution varies. Gastropods are rare in normal marine settings and abundant in harsh (i.e., dysoxic, hypersaline) environments. Their environmental context is shown to impact survivorship through the end-Ordovician extinction event and throughout the Paleozoic and Mesozoic.;Collecting accurate density data for fossil deposits can prove challenging, especially when beds are not exposed in plane view. In these cases, paleontologists are tasked with reconstructing shellbed density from cross section exposure. This study presents a mathematical model to calculate the density of fossil material within a bed from bedding cross section counts. The model is calibrated against an Ordovician biofacies comprised of oncoids, macluritid gastropods and receptaculitids exposed in the Arrow Canyon Range of Southern Nevada, where unique preservation provides both cross section exposures and plan view of fossil concentrations.;University Earth Science Departments seeking to establish impactful geoscience outreach programs often pursue large-scale, grant funded programs. While this type of outreach is highly successful, it is also extremely costly, and grant funding can be difficult to secure. Here, we present the Geoscience Education Outreach Program (GEOP), a small-scale, very affordable model tested over five years in the Department of Earth Sciences at UCR. GEOP provides a variety of outreach events and allows UCR Earth Sciences to participate in a wide range of community events. The GEOP model prioritizes simplicity, flexibility and affordability in order to best meet the educational needs of Riverside County, CA.