Insights into thermal stress during the Permian-Triassic mass extinction using ostracods from the Southern Alps (Italy)

Ostracods are among the most abundant microfossils recorded across the Permian/Triassic boundary (252 million years ago). Their fossil record provides an opportunity to assess the impact of environmental changes on the ecosystem and to understand the main drivers behind the biggest mass extinction event in Earth's history. Previous studies have suggested that rapid temperature increase, widespread anoxia, and ocean acidification were the environmental changes driving the extinction. This study uses secondary ion mass spectrometry (SIMS) to measure the geochemical signal of Changhsingian (late Permian) ostracods from the Southern Alps in Italy. We measured the oxygen isotope ratio (δ¹⁸O_ostracod) as a proxy for temperature and the carbon isotope ratio (δ¹³C_ostracod) to assess carbon cycle perturbations. We compared isotopic signals from ostracods found in two shallow-water sections with corresponding sediment data (δ¹³C_carb). Our results show that the δ¹⁸O_ostracod and δ¹³C_ostracod values are similar in the two examined species, and these values parallel the δ¹³C_carb recorded in the host sediments. Our findings highlight the value of ostracods as indicators of temperature change, providing insights into the environmental changes preceding the extinction event and its potential drivers. Further analyses of these microfossils will enhance our understanding of the marine ecosystems' response to dramatic climate warming during the Permian-Triassic mass extinction.