2008 Joint Meeting of The Geological Society of America, Soil Science Society of America, American Society of Agronomy, Crop Science Society of America, Gulf Coast Association of Geological Societies with the Gulf Coast Section of SEPM

Paper No. 11
Presentation Time: 11:00 AM

A Permo-Triassic Meteorite Impact and Its Effects on the Carbon Isotope Record

TOHVER, Eric1, CAWOOD, Peter2, ESTRADA, Beatriz1, SHERLOCK, Sarah3, LANA, Cristiano4, TRINDADE, Ricardo5, MARANGONI, Yara5 and SOUZA, Carlos Roberto6, (1)School of Earth and Geographical Sciences, University of Western Australia, 35 Stirling Hwy, Crawley, 6009, Australia, (2)School of Earth and Geographical Sciences, University of Western Australia, 35 Stirling Hwy, Crawley, 6009, (3)Department of Earth and Environmental Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA, United Kingdom, (4)Department of Geology, Stellenbosch Universiteit, Private Bag X1, Matieland, 7602, South Africa, (5)Departamento de Geofisica, Instituto de Astronomia e Geofisica, Rua do Matão, 1226, Universidade de Sao Paulo, Cidade Universitária, São Paulo, 05508-090, (6)Instituto de Geociencias, UNICAMP, Rua Pandiá Calógeras, No. 51, Campinas, 13983-970, etohver@cyllene.uwa.edu.au

The events at the Permo-Triassic boundary mark the largest mass extinction in Earth history, an event accompanied by strong fluctuations in the carbon isotope record. Herein, we report U-Pb age data from SHRIMP analysis of shocked zircons of the Araguainha impact crater of central Brazil and 40Ar/39Ar age data from pseudotachylite veins and neoformed biotite grains from impact-generated melts. These data indicate an age for the 40 km diameter crater that is essentially synchronous with the end-Permian mass extinction. Calculated amounts of carbon released by the impact and its seismic reverberations include carbon from the vaporized bolide (100-101 Gigatons), vaporized target rock (101 Gigatons), and methane release (102-103 Gigatons) from seismically-destabilized sediments of the deglaciated Paraná-Karoo-Kalahari seaway. The potential for massive release of isotopically light C (δ12Cin the form of highly volatile methane is significant in terms of the global carbon budget. Thus, the small size of the Araguainha crater belies the importance of the impact location and its potential for unleashing geochemical havoc on Paleozoic biota.