THE CAPITANIAN (MIDDLE PERMIAN) MASS EXTINCTION: DEATH BY VIOLENT VOLCANISM

We have studied Middle-Upper Permian boundary sections in China, Japan, Hungary and Greece with a view to investigating the cause of the Capitanian mass extinction. This has revealed that, contrary to previous reports, the extinction event, seen in the foram, brachiopod and calcareous algae record, does not occur at the end of the Capitanian Stage (the Guadalupian-Lopingian series boundary) but significantly earlier, in the middle of the Capitanian. This has significant implications for extinction mechanisms. Thus, a major eustatic regression in the latest Capitanian is now seen to post-date the mass extinction making it unlikely this event was directly related to eustatic changes. Similarly, a decline of seafloor oxygenation in the Panthalassa Ocean is a Late Permian phenomenon and so unrelated to this Mid Permian crisis. In contrast, the extinction in South China is seen to precisely coincide with the onset of eruptions of the Emeishan large igneous province (LIP). Despite its epithet this province is relatively small by the standards of LIPs probably not greatly exceeding half a million cubic kilometers of extrusives, but in its initial stages it saw a series of spectacularly violent, giant phreatomagmatic-style eruptions producing beds in excess of 100 m thick. The temporal link between these eruptions and extinctions suggests a mechanism involving volcanic aerosols. Such aerosols are only resident in the atmosphere for a few years implying the extinction losses either occurred geologically instantaneously or in a series of closely spaced crises coinciding with the initial phase of LIP formation.