Isotope excursions and palaeotemperature estimates from the Permian/Triassic boundary in the Southern Alps (Italy)

The end-Permian mass extinction event coincides with a dramatic negative shift in both the δ13C and the δ18O isotope record, at or near the extinction horizon, from multiple marine and terrestrial sections round the globe. This study has identified the isotope excursions in a shallow water, carbonate-dominated, section at Val Brutta in the Southern Alps. High resolution bulk rock sampling revealed that there is an average δ13Ccarb negative shift of − 4‰ and a δ18Ocarb shift of − 6‰. This is similar to the isotope record at other nearby localities. This section, like many others, shows a degree of recrystallisation which hampers absolute palaeotemperature calculations. However, some brachiopod fossils, including specimens of Comelicania and Janiceps, found within the beds that contain the bulk rock anomaly, appear to be remarkably well preserved and still retain their internal structure and the primary isotopic variation across the shell. As such, they have been successfully analysed and the data used to produce a palaeotemperature estimate, at the time of the isotope anomaly, of between 26 and 29 °C for latest Permian.