The cause of the extinction event is still unclear, but on the basis of the rough coincidence of the eruption of the Siberian Trap flood basalts and the extinction event a link has been suggested . The flood basalt volcanism released CO2. In addition, related thermal metamorphism of Siberian coal measures and organic-rich shales led to the emission of methane, which would have affected global climate and carbon cycling, according to model simulations. This scenario is supported by evidence for volcanic eruptions and gas release in the Siberian Tunguska Basin, but direct indicators of coal combustion have not been detected until now. This article presents analyses of terrestrial carbon in marine sediments that suggest a substantial amount of char was deposited in Permian aged rocks from the Canadian High Arctic immediately before the mass extinction. Based on the geochemistry and petrology of the char, the authors propose that the char was derived from the combustion of Siberian coal and organic-rich sediments by flood basalts, which was then dispersed globally. The char is remarkably similar to modern coal fly ash, which can create toxic aquatic conditions when released as slurries. It is speculated that the global distribution of ash could have created toxic marine conditions.
Nature Geoscience 4, 104–107(2011)