Paper No. 63-6
Presentation Time: 2:55 PM
CATASTROPHIC MIDDLE PERMIAN EXTINCTION AND AN EXTRAORDINARY RECOVERY IN HIGH LATITUDES
The controversial Capitanian (Middle Permian, 262 Ma) extinction event is only known from equatorial latitudes and consequently its global, mass extinction status is unresolved. The results of three seasons' fieldwork in Spitsbergen has revealed that there was a severe extinction amongst brachiopods in northern Boreal latitudes prior to the well-known latest Permian mass extinction. This event seems to be pan-Arctic because abundant brachiopods also disappear in contemporaneous strata in Greenland (and summer 2014 fieldwork is intended to reveal a similar crisis in Siberia). There were thus two Permian mass extinctions in higher latitudes. New age dating of the Kapp Starostin Formation of Spitsbergen, using strontium isotopes and carbon isotope chemostratigraphy reveals the earlier extinction to be contemporaneous with the low latitude Capitanian extinction and to coincide with a negative carbon isotope perturbation. The Capitanian crisis is thus established as a true, global mass extinction. Redox proxies show that the crisis coincided with an intensification of oxygen depletion in offshore settings although euxinia was not developed. The Capitanian extinction in South China coincides with the onset of Emeishan flood basalt volcanism, and our findings suggest the effects of these eruptions were global. The subsequent Late Permian recovery was spectacularly rapid in Spitsbergen and saw the appearance of several new bivalve groups (inoceramids and buchiids) and the increased dominance of these mollusks relative to brachiopods is reminiscent of younger Mesozoic assemblages. However, the end-Permian mass extinction ensured that this brief phase of evolutionary innovation and radiation was a “false dawn”.