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. Here we provide a full suite of high-resolution and coeval geochemical 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. Although anoxia has been touted as a cause for the mass extinction, most biotic and geochemical evidence suggest that it was briefly relevant during the early phase of the event and only in areas of upwelling, but not a general cause. Instead, we suggest that renewed and increased end-Permian Siberian Trap volcanic activity, about 2,000 years prior to the extinction event, released massive amounts of carbon dioxide and coupled with thermogenic methane emissions triggered extreme global warming and increased continental weathering. 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° and higher. Based on these sea surface temperatures, atmospheric CO2 concentrations were about 1400 ppmv and 3000 ppmv for the Late and end-Permian, respectively. Leading up to the mass extinction, there was a brief interruption of the global warming trend when SST dropped, concurrent with a slight, but significant recovery in biodiversity in the western Tethys. It is possible that emission of volcanic sulphate aerosols resulted in brief cooling, just after onset of intensified warming during the end of the Permian. After aerosol deposition, global warming resumed and the biotic decline proceeded, and accompanied by suboxia, in places, of the surface ocean culminated in the greatest mass extinction in Earth histor