The end-Permian mass extinction event as the most se-vere biotic crises in Earth history is still a matter of de-bate regarding the responsibility of several environmen-tal factors, such as ocean acidification, widespread ma-rine anoxia and global temperature rise. In our study, we focus on the detailed reconstruction of a possibly global climate changes and its biological responses. For this purpose we analyse the ostracod diversity of the north-western Iranian Aras Valley section as well as oxygen isotope values (δ18O) of ostracod shell calcite, which give a hint on the ancient ambient sea water tempera-ture. This combination of geochemical and the palaeo-ecological approaches allows us to evaluate the role of temperature during the end-Permian mass extinction event. With the application of a new method – measur-ing the oxygen isotope proportion of 18O and 16O of os-tracod shell calcite by application of SIMS technology – we are able to propose a detailed oxygen isotope curve. The data indicate a drastic temperature rise of nearly 10°C during the extinction interval. The comparison with other temperature reconstructions, which for example used conodont apatite, shows that ostracod shell calcite yields reliable results with similar trends. Ostracod di-versity patterns show a restructuration of the community from low diverse assemblages in the pre-extinction phase to assemblages with higher diversity in the direct post-extinction phase. The extinction horizon itself is marked by a monospecific assemblage and a subse-quent complete faunal turnover. The combination of these palaeontological results to the reconstructed tem-perature curve indicates a diversity drop, taking place during the initial phase of the temperature rise.

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