Masters Thesis

Documenting Fossil Abundance from Middle Triassic Outer Ramp Environments, West-central Nevada

Paleozoic shallow marine communities differ considerably from Modern shallow marine communities. for example, Modern animals such as gastropods and bivalves occupy niches once occupied by Paleozoic brachiopods and echinoderms. Researchers suggest the end-Permian mass extinction reset the stage by reorganizing past marine communities, thus allowing new communities to take over. Once ocean chemistry conditions returned to normal in the Middle Triassic, modern communities stabilized and took on their modern ecological state. Bivalves and gastropods increased in diversity and abundance, grew thicker shells, and some began burrowing deeper into sediment. Scientists describe these changes in life habit as the Mesozoic Marine Revolution (MMR), a transition initiating in the Middle and Late Triassic. Previous research focused on European sites, however, data are lacking from western Panthalassa. Here, we present new taxonomic and environmental data from Favret and American Canyons, Nevada, which help piece together the story of how shallow marine communities modernized in the eastern Panthalassic Ocean. Results suggest low fossil abundance in outer ramp systems consistent with other Middle Triassic marine environments. Taxonomic data reveal a combination of Paleozoic and Modern Fauna, which suggests that the Marine Mesozoic Revolution (MMR) has begun but had not fully developed. This study is important because can be used as an analogue to understand how modern ecologies are and will be affected by climate change.

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