The end-Permian mass extinction : a rapid volcanic CO2 and CH4 – climatic catastrophe

The end of the Permian was a time of crisis that culminated in the Earth’s greatest mass extinction. There is much speculation as to the cause for this catastrophe. We provide a full suite of high-resolution and coeval chemical results (trace and rare earth elements, carbon, oxygen, strontium and clumped isotopes) reflecting ambient seawater chemistry and water quality parameters leading up to the end – Permian crisis. Preserved brachiopod low-Mg calcite-based seawater chemistry, supplemented by data from various localities, documents a sequence of interrelated primary events such as coeval flows of Siberian Trap continental flood basalts and emission of carbon dioxide leading to warm and extreme Greenhouse conditions with sea surface temperatures (SST) of ~ 36°C for the Late Permian, and followed by increased continental weathering. Although anoxia has been touted as a cause for the mass extinction, most biotic and geochemical evidence suggests that it was briefly relevant during the early phase of the event and in areas of upwelling, but not a cause of it. Instead, renewed and increased end of the Permian Siberian Trap volcanic activity, about 2,000 years prior to the event, released massive amounts of carbon dioxide and aided by methane emissions triggered extreme global warming and continental acid precipitation. Eventually, these rapidly discharged greenhouse gas emissions, less than 1,000 years before the event, ushered in a global Hothouse period leading to extreme tropical SSTs of ~ 39°C and higher. Based on actual sea surface temperatures, atmospheric CO2 concentrations were about 1400 ppmv and 3000 ppmv for the Late and end – Permian, respectively. The most elevated atmospheric CO2 level, about 1,500 years before the end – Permian event, lead to increased acid precipitation and triggered massive continental weathering and soil erosion. Leading up to the mass extinction, there was a brief interruption of the global warming trend when SST dropped by about 5°C concurrent with a slight but significant recovery in biodiversity in the western Tethys. It is postulated that emission of volcanic sulphate aerosols brought about the brief cooling just after the onset of intensified warming during the end of the Permian. With aerosol deposition, global warming resumed and the biotic decline proceeded, and was accompanied by collapse of the thermohaline circulation and suboxia, in places, of the surface ocean, destabilization of marine and terrestrial foodchains, in part through enhanced acid precipitation and continental weathering-erosion, and eventual ecosystem collapse accelerated by hypercapnia during the end of the Permian, culminating in the greatest mass extinction in Earth history.