At www.livescience.com/52017-catastrophic-volcanoes-caused-biggest-extincti… … geologists working in Siberia (Russian and American) are blaming volcanics for the extinction event at the Permian boundary, a somewhat obvious discovery as they were looking at the Siberian Traps (a huge outpouring of basalt lava). What caused the volcanics is another matter.
The Siberian Traps coincide with end of Permian therefore volcanism caused the extinction – simples. No need to look at anything else. However, the research is itself plagued by geological dating strictures – or the effects of Gradualism. The Traps are thought to have endured with their outpourings over a period of tens of thousands of years – its the thickness of the deposit. It may of course have been much worse, rather than a leak of lava it might have been rapid and immediate.