The operation of the sulfur cycle is intimately linked to several key processes proposed as drivers of mass extinction events in the Phanerozoic. Both anoxia and productivity have the potential to impact pyrite burial, whilst the release of volcanic sulfur dioxide is suggested as a one of a suite of drivers for the acidification of terrestrial environments.
Studies of carbonate associated sulfate (CAS), an isotopic proxy for marine sulfate, for multiple volcanically driven extinction events are revealing evidence of an empirical association of low ocean sulfate and mass extinction. I will outline a mechanism to connect these observations, linking evaporite drawdown of sulfate to enhanced bottom water oxygen demand during warming, favouring the rapid spread of anoxic conditions. More recent work on the early Toarcian extinction explores combined CAS and pyrite sulfur isotope records as a way of understanding the sulfur cycle response by constraining the isotopic offset between reduced and oxidised sulfur through the event.
Lastly, I will present a case study exploring the role of volcanic sulfur emissions in the terrestrial Permo-Triassic extinction. Here we use some novel approaches to generate records of terrestrial sulfur cycle operation which, in conjunction with mercury concentration and multiple sulfur isotope data, suggest that the terrestrial extinction mechanism was related to multiple pulses of volcanically driven acidification and poisoning, but not complete ozone layer collapse.