PALEOECOLOGY OF THE MIDDLE TRIASSIC STAR PEAK GROUP OF SOUTH CANYON, CENTRAL NEVADA

The end-Permian mass extinction was the biggest faunal crisis in the history of Phanerozoic life. Following this mass extinction, marine benthic ecosystems underwent complete reorganization. Prior to the extinction, Paleozoic faunas dominated benthic communities. Suspension-feeding epifauna, especially rhynchonellid brachiopods, crinoids, and bryozoans covered the sea floor. The Modern fauna dominant by infaunal burrowing organisms, particularly bivalves, crustaceans, and echinoids, diversified after the end-Permian mass extinction. Referred to as the Mesozoic Marine Revolution (MMR)(Vermeij, 1977), this reorganization of ecosystems is characterized by an increase of infaunalization that takes place during the Triassic (McRoberts, 2001). Workers suggest that this increase of infaunalization results from an increase of predators and/or environmental stresses (e.g., McRoberts 2001, Stanley, 1968, Vermeij, 1977). Understanding the timing and cause of this transition is the main goal of this project. Though much work has been conducted from the Middle Triassic Tethyan realm of Europe, little abundance data from the eastern Panthalassic realm exists. Middle Triassic sections from the eastern Panthalassic realm can be found in British Columbia, Canada, northwestern Nevada, U.S.A. and in northern Mexico. This project focuses on the Middle Triassic section in South Canyon within the New Pass Range of central Nevada. The Favret and Augusta Mountain Formations comprise the fossiliferous Middle Triassic section at South Canyon. This study uses petrographic and relative abundance analyses to preliminarily document living strategies within an environmental context. Results from 13 bulk samples reveal that suspension-feeding epifauna dominate the Middle Triassic section at South Canyon. Thus far, no evidence of drilling predators exists within the data and a complete analysis of environmental conditions is pending. These results suggest that this regional community resembles a Paleozoic faunal structure rather than a Modern faunal structure.