Permian ice volume and palaeoclimate history: Oxygen isotope proxies revisited

A high-resolution oxygen isotope record based on 356 measurements of conodont apatite from several low latitudinal sections in South China, USA and Iran was composed in order to unravel Permian palaeotemperature and ice volume history. The conodont apatite δ18O record is compared to published brachiopod calcite δ18O records. Brachiopods and conodonts from different palaeocontinents show significantly different δ18O values, suggesting differences in local climatic conditions (e.g., evaporation/precipitation ratio). As a consequence, secular changes in palaeotemperature and oxygen isotope composition of Permian sea water cannot be reconstructed from records combined from different areas, but have to be based on records from a specific area.Oxygen isotope analyses of different conodont taxa suggest that Streptognathodus and Hindeodus lived in near-surface seawater and recorded surface water temperature, whereas the habitat of gondolellid genera was variable depending on sea level, with both near-surface and deeper waters as potential life habitat. The oxygen isotope record measured on conodonts from South China exhibits relative high values between 22 and 23‰ VSMOW during the glaciated Early Permian, translating into warm seawater temperature between 26 and 30 °C, assuming that the Late Palaeozoic ice volumes were comparable to the Pleistocene glacial maxima. In contrast to the earlier view that the Late Palaeozoic Ice Age (LPIA) terminated in the late Sakmarian, the South China conodont apatite oxygen isotope record suggests waning of the ice sheets in the Kungurian. Ice melting is indicated by a pronounced decrease in δ18O of 2‰ VSMOW, which is interpreted as reflecting the combined effect of climatic warming and glacial ice melting. Significant temperature fluctuations (4 °C warming succeeded by 6 to 8 °C cooling) are observed during the Guadalupian–Lopingian transition, interpreted as combined climate changes induced by Emeishan volcanism and changes in habitat depth of gondolellid conodonts. Oxygen isotope values increase to 22‰ VSMOW in the Changhsingian, which suggests climate cooling and Clarkina moving to deeper waters because of the Changhsingian sea level rise. Across the Permian–Triassic boundary, δ18O values decrease from 22 to 19‰ VSMOW, parallel to the significant negative carbon isotope excursion and the eruption of the Siberian Traps. The latter is pointing to a cause–effect relationship as a consequence of the massive release of volcanic greenhouse gases derived from the Siberian volcanism and related processes.

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► This manuscript presents a high resolution Permian oxygen isotope record based on conodont apatite.
► The conodont apatite oxygen isotope record suggests termination of LPIA in the Kungurian.
► Seawater temperatures fluctuated significantly during the Guadalupian–Lopingian transition.
► Dramatic global warming occurred in the latest Permian and earliest Triassic.