Sauerstoffisotopie von Conodontenapatit zur Rekonstruktion des Klimas im Perm
Zusammenfassung der Projektergebnisse
The research project “Sauerstoffisotopie von Conodontenapatit zur Rekonstruktion des Klimas im Perm“ focused on composing an oxygen isotope record for the entire Permian based on the analysis of conodont apatite from various sections in China, Iran and the USA in order to test the following hypotheses: • Did the main deglaciation of the Late Palezoic Ice Age occur in the Sakmarian? • Was climate changing as consequence of Emeishan LIP volcanism at the transition Guadalupian-Lopingian? • Did Sibirian trap volcanism result in climate warming at the end of the Permian and, if so, did climate warming contribute to the Late Permian mass extinction? The oxygen isotope ratios of conodont apatite are generally around 22‰ in most part of the Early Permian and only started to decrease in the early to middle Kungurian. Minimum oxygen isotope values are measured in the Capitanian. The 2‰ decrease is best explained by the combined effect of melting of high latitude ice masses and global warming suggesting that the main deglaciation of the LPIA took place in the Kungurian to Middle Permian. This is in contrast to the widely accepted interpretation that the large ice caps in Gondwana melted in the Late Sakmarian. Across the Guadalupian-Lopingian transition, oxygen isotope ratios indicate warming of water temperatures up to 8° C in the late Guadalupian (Capitanian) and major cooling in the latest Guadalupian to early Lopingian. The decrease in δ18O and thus warming in the late Guadalupian coincides with the onset of Emeishan trap volcanism, maximum temperatures are recorded during the latest volcanic phase. Weathering of freshly deposited basalts may have acted as an efficient sink of CO2 after the cessation of Emeishan volcanism and may thus be responsible for the observed cooling that starts in the latest Guadalupian. Across the Permian-Triassic boundary, oxygen isotopes of conodont taxa Clarkina and Hindeodus decrease by 1.5 and 2‰, respectively, translating into significant warming of low latitudinal surface waters of 6 and 8° C. This significant temperature increase is confirmed by oxygen isotope analyses on conodonts from the Shangsi section (Sichuan Province/South China). The minor temperature increase recorded by Clarkina suggests that Clarkina may have migrated to slightly deeper and thus colder waters in conjunction with the sea level rise in the latest Changhsingian. The negative shifts in the oxygen isotope ratios coincide with globally well-documented negative shifts in δ13C of inorganic and organic carbon carbon isotopes suggesting that Siberian trap volcanism and related thermal metamorphism of organic carbon rich sediments resulted in higher atmospheric greenhouse gas levels and may thus have initiated global climatic warming. However, reconstructed temperatures start to increase at the latest Permian extinction horizon with more or less normal water temperatures observed at the event horizon. Consequently, climatic warming was probably not the main cause of the extinction pulse in the latest Permian. However, climatic warming and very warm temperatures in the Early Triassic are suggested to have played an important role for the pattern of the slow recovery of marine and terrestrial ecosystems in the aftermath of the Permian-Triassic crisis.
Projektbezogene Publikationen (Auswahl)
- (2011): Carbon and conodont apatite oxygen isotope records of Guadalupian–Lopingian boundary sections: Climatic or sea-level signal?- Palaeogeography, Palaeoclimatology, Palaeoecology, 311, 145-153
Chen, B., Joachimski, M.M., Sun. Y., Shen, S. & Lai, X.
- (2012): Climatic warming in the latest Permian and the Permian-Triassic mass extinction.- Geology, 40, 195-198
Joachimski, M.M., Lai, X., Shen, S., Jiang, H., Luo, G., Chen, B., Sun, Y.
(Siehe online unter https://doi.org/10.1130/G32707.1) - (2012): Lethally hot temperatures during the Early Triassic.- Science, 338, 366-370
Sun, Y., Joachimski, M.M., Wignall, P.B., Yan. C., Jiang, H., Wang, L. & Lai, X.
- (2013): Conodont apatite oxygen isotope record of the Permian: ice volume and palaeotemperature evolution.- Gondwana Research 24, 77-89
Chen, B., Joachimski, M.M., Shen,S.-Z., Lambert, L., Lai X.L., Wang, X.D., Yuan D.X.
