This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). This project involves a collaboration between scientists at the Berkeley Geochronology Center, University of California, University of New Mexico, New Mexico State University, and Southern Methodist University. The project?s overarching goal is to determine environmental conditions in terrestrial environments preserved in sedimentary strata of northwestern Texas and southeastern New Mexico, over a brief time interval including the transition between the Paleozoic and Mesozoic Eras, when the greatest mass extinctions known in Earth?s history occurred. A detailed program of paleomagnetism integrated with geochronology (using the 40Ar/39Ar and U/Pb methods) are used to provide a high resolution, regional chronostratigraphic framework. Supported by the chronostratigraphy, a regional model of depositional conditions and environments for the Quartermaster Formation will be developed. Analysis of fossil pollen, where present, will elucidate ecological conditions (and changes) across the time interval spanning the extinction horizon. Isotopes of oxygen and carbon are used to quantify atmospheric carbon dioxide concentrations and surface air temperatures. The results will help clarify the environmental tolerances of the Earth system, and aid understanding of the causes of the most profound biotic catastrophe known in our planet?s history. As participants in field and laboratory components of the research, undergraduate and graduate students at the participating institutions will receive hands-on training in the diverse scientific disciplines employed in the project.