[Keith_McClary]

Biggest extinction in history caused by climate-changing meteor
(Phys.org) —It's well known that the dinosaurs were wiped out 66 million years ago when a meteor hit what is now southern Mexico but evidence is accumulating that the biggest extinction of all, 252.3m years ago, at the end of the Permian period, was also triggered by an impact that changed the climate.
...
Last year Dr Tohver redated an impact structure that straddles the border of the states of Mato Grosso and Goiás in Brazil, called the Araguainha crater, to 254.7m years, with a margin of error of plus or minus 2.5m years. Previous estimates had suggested Araguainha was 10m years younger, but Dr Tohver has put it within geological distance of the extinction date.
The Chicxulub crater in Mexico, is 180km in diameter while the Araguainha is 40 kilometres across and was thought to be too small to have caused the chain reaction which brought about such mass extinction.
...
The results of an extensive geological survey of the Araguainha crater funded by UWA and the Australian Research Council and published in Palaeogeography, Palaeoclimatology, Palaeoecology, revealed that a sizeable amount of the rock is oil shale. The researchers calculated that the impact would have generated thousands of earthquakes of up to magnitude 9.9, significantly more powerful than the largest recorded by modern seismologists for hundreds of kilometres around, releasing huge amounts of oil and gas from the shattered rock.
Dr Tohver believes the explosion of methane released into the atmosphere would have resulted in instant global warming, making things too hot for much of the planet's animal life.
"Martin Schmieder and I are currently working on documenting some of the more extreme environmental effects of the impact, including giant tsunamis. In addition, ongoing work with Kliti Grice at Curtin University and her Ph.D. student Ines Melendez will be fundamental to documenting changes in the organic geochemistry of the target rocks," Dr Tohver said.
It's estimated more than 90 per cent of all marine species and about 70 per cent of land-based species disappeared in the Permian extinction.

[dorlomin]

Colour me sceptical. The 'kill' mechanisms for that event took place of 10 000s of years.

[dissident]

There are no estimates for the amount of CH4 involved. Following the links at the bottom do not yield any numbers. It is not obvious at all that even 9.9 magnitude earthquakes are equivalent to fracking. You can have massive seismic energy release without breaking up huge volumes of surrounding rock. There was a huge earth quake in Alaska in 1964 which occurred near Anchorage. Anchorage happens to lie on a rather large coal basin. There is no indication of massive CH4 outgassing during this 9.2 quake.

Appealing to earthquakes indicates that the authors believe that the direct "fracking" in the crater was not enough to release much CH4 (in fact most of it would have been turned into CO2 anyway).