The cause(s) of the event are incompletely understood, but the stratigraphic distributions of fossil species and associated radiometric age constraints indicate that extinction was geologically rapid, occurring in less than 500 ky. On many carbonate platforms, fossiliferous uppermost Permian beds are abruptly overlain by microbial buildups. Shallow-marine carbonate strata exposed in South China, Japan, and Turkey are each characterized by abrupt transitions from fossiliferous uppermost Permian beds to microbial buildups. In each case, uppermost Permian strata are erosionally truncated. However, biostratigraphy and carbon isotope stratigraphy indicate that little time is missing at the boundary. Moreover, petrographic observations and isotope data reveal no positive evidence for subaerial exposure associated with the episode of erosional truncation. Hence, it appears that erosion occurred in a submarine environment. An episode of submarine carbonate dissolution induced by rapid, massive CO2 release from a sedimentary carbon reservoir could explain the coincidence of erosion with the selective extinction of heavily calcified marine invertebrate genera and the onset of a large negative carbon isotope excursion. Thermal metamorphism and decarbonation of coal and carbonate rocks on the Siberian Craton during intrusion of Siberian Trap magma may account for massive carbon release at this time.-Geological Society of America
