A Paleoecological Study Of The Middle And Late Triassic Within Favret And American Canyon, West-Central Nevada

Abstract

Paleozoic shallow marine communities differ considerably from modern shallow marine communities. Modern animals such as gastropods and bivalves occupy niches once occupied by Paleozoic organisms such as brachiopods and crinoids. Researchers suggest the End-Permian mass extinction reset the stage by removing past communities, thus allowing new communities to take over. However, this transition did not occur immediately after the mass extinction. Once ocean conditions returned to normal in the Middle Triassic, modern communities stabilized and took on their modern ecological shape. Bivalves increased in diversity and abundance, grew thicker shells and some began burrowing deep into sediment. Gastropods also increased in diversity and abundance and grew thicker shells, while some developed new drilling adaptations and became carnivorous. Researchers suggest that changes in shell thickness and deeper burrowing occurred as competition increased among newly evolved predators (e.g.: marine reptiles and crabs). Scientists describe these changes in life habit as the Mesozoic Marine Revolution, a transition initiating in the Middle and Late Triassic. Previous research focused on European fossil sites, however, we lack data from the western Panthalassa region (i.e.: present day western North America). Our research will provide new paleoecological data to help piece together the story of how shallow marine communities modernized. Favret and American Canyon's host shallow to deep marine carbonate rock formed off the coast of modern Nevada. These study sites provide data that help better understand western Panthalassan paleoenvironment and paleoecology conditions of the Middle and Late Triassic. Such paleoenvironment and paleoecological conditions can then be used as modern environment analogues. The main goal of this project is to track and document taxonomic and ecologic patterns within an environmental context through time. We plan on comparing fauna and environmental context to determine causal mechanisms for observed patterns.

AAPG Datapages/Search and Discovery Article #90215 © 2015 Pacific Section AAPG Convention, Oxnard, California, May 3-6, 2015