2008 Joint Annual Meeting (5-9 Oct. 2008): A Permo-Triassic Meteorite Impact and Its Effects on the Carbon Isotope Record

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.