Anoxia – Driver of the Late Permian Mass Extinction in shallow marine basins?

The Late Permian mass extinction (LPME) was the most catastrophic extinction of marine life during the Phanerozoic. Widespread marine deoxygenation associated with the eruption of the Siberian Traps is considered one of the main drivers of the drastic diversity decline seen in the fossil record. However, while evidence of photic zone euxinia has been reported for some regions, others appear to have, at least locally, oxic conditions during the LPME. Here we present redox sensitive metal concentrations (e.g. Mo & V) combined with other redox proxies (e.g. V/Cr) from shallow marine carbonate sections from the southern Alps to assess local marine redox during the LPME. Our results show an increase in Mo, V and U in the sediment just prior to the LPME, suggesting the development of local anoxia. However, the sedimentary V/Cr and Ni/Co ratios support consistently (dys-)oxic conditions before and throughout the LPME, with values generally <2 and <4.5, respectively. These seemingly contradictory observations are likely due to increased weathering following the eruption of the Siberian Traps, which could explain the increased concentrations in redox sensitive metals even under oxidizing conditions. This suggest that the LPME within the shallow marine sediment of the southern alps might not have been triggered by deoxygenation, but by other environmental changes, such as temperature rise or increased metal toxicity.