Temperate rainforests near the South Pole during peak Cretaceous warmth

Klages, J.P. and Salzmann, U. and Bickert, T. and Hillenbrand, C.-D. and Gohl, K. and Kuhn, G. and Bohaty, S.M. and Titschack, J. and Müller, J. and Frederichs, T. and Bauersachs, T. and Ehrmann, W. and van de Flierdt, T. and Pereira, P.S. and Larter, R.D. and Lohmann, G. and Niezgodzki, I. and Uenzelmann-Neben, G. and Zundel, M. and Spiegel, C. and Mark, C. and Chew, D. and Francis, J.E. and Nehrke, G. and Schwarz, F. and Smith, J.A. and Freudenthal, T. and Esper, O. and Pälike, H. and Ronge, T.A. and Dziadek, R. and Afanasyeva, V. and Arndt, J.E. and Ebermann, B. and Gebhardt, C. and Hochmuth, K. and Küssner, K. and Najman, Y. and Riefstahl, F. and Scheinert, M. and PS104, the Science Team of Expedition (2020) Temperate rainforests near the South Pole during peak Cretaceous warmth. Nature, 580 (7801). pp. 81-86. ISSN 0028-0836

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Abstract

The mid-Cretaceous period was one of the warmest intervals of the past 140 million years 1–5, driven by atmospheric carbon dioxide levels of around 1,000 parts per million by volume 6. In the near absence of proximal geological records from south of the Antarctic Circle, it is disputed whether polar ice could exist under such environmental conditions. Here we use a sedimentary sequence recovered from the West Antarctic shelf—the southernmost Cretaceous record reported so far—and show that a temperate lowland rainforest environment existed at a palaeolatitude of about 82° S during the Turonian–Santonian age (92 to 83 million years ago). This record contains an intact 3-metre-long network of in situ fossil roots embedded in a mudstone matrix containing diverse pollen and spores. A climate model simulation shows that the reconstructed temperate climate at this high latitude requires a combination of both atmospheric carbon dioxide concentrations of 1,120–1,680 parts per million by volume and a vegetated land surface without major Antarctic glaciation, highlighting the important cooling effect exerted by ice albedo under high levels of atmospheric carbon dioxide.