Assessing the role of anoxia as a potential extinction driver in the shallow marine Neotethys during the Permian-Triassic mass extinction

Anoxia has been hypothesised as a major kill mechanism for marine ecosystems during the Permian-Triassic mass extinction, but its importance is increasingly debated for shallow marine settings. For the Neotethys Ocean, in particular, geochemical data that is suitable to verify a local anoxic signal is lacking. Here, we investigated two shallow marine successions from the Antalya Nappes, Türkiye, for their redox sensitive metal and rare earth element and Yttrium (REY) composition to reconstruct local redox changes before, during and after the Permian-Triassic mass extinction. The investigated sections recorded reoccurring enrichments in the redox sensitive trace metals Re, U and Mo, supporting dynamic local redox conditions cycling between oxic and anoxic throughout the investigated Permian interval. No clear changes in redox conditions compared to the pre-extinction interval nor evidence of anoxic upwelling coinciding with the extinction event could be identified, questioning the role of anoxia as a local extinction driver. Above the extinction horizon, the sections were generally characterised by low redox sensitive metal enrichments and negative Ce anomalies revealing that post-extinction sediments were deposited in a consistently oxic environment. Hence, local anoxia within the shallow marine ecosystem of the Antalya Nappes appears not persistent enough around the extinction, and did not occur during the recovery, rendering it unlikely to explain biodiversity changes. Therefore, alternative environmental factor(s) should be considered as potential drivers of biodiversity changes for shallow marine ecosystems of the western Neotethys during the Permian-Triassic mass extinction and its recovery. • Redox conditions were constrained for two Permian-Triassic sections from Türkiye. • The Permian strata recorded dynamic redox conditions cycling between oxia and anoxia. • No worsening or abrupt changes in oxygenation coincided with the mass extinction. • The earliest Triassic was marked by oxia providing oxygen for a potential recovery. • Anoxia does not appear to drive biodiversity changes in the western Neotethys.