A precisely dated speleothem isotope record from the Sieben Hengste cave system, Switzerland, reveals a Last Interglacial (LIG) climate optimum centred at 128.1 ± 1.2 ka. The oxygen isotope signal is consistent with a temperature-dominated record and shows a strong correlation with the modelled Greenland δ18O signal. The comparison with speleothems formed during the Last Glacial Maximum (LGM) in the same cave indicates a 4–5‰ difference in δ18O between peak LIG and peak LGM conditions, suggesting peak LIG temperatures being up to 3 °C higher than the Holocene average. Pollen extracted from the stalagmite indicates a vegetation response delayed by up to 3 ka with maximum pollen concentrations recorded at 125 ± 2.2 ka. Our results support a regional vegetation dominated by thermophile tree species including Corylus (hazel), Quercus robur-type (oak), Ulmus (elm), Tilia (lime tree) and Hedera (ivy), consistent with slightly warmer conditions than today. Despite the relatively low pollen concentration, the speleothem-based pollen spectra are consistent with regional pollen assemblage zones from paleolake sediments and provide the first direct paleovegetation evidence of thermophilization during the LIG at high altitudes in the Alps.
Bibliographical noteFunding Information:
We would like to thank Manuela Wimmer for support in the stable isotope laboratory, Werner Kofler for the preparation of pollen samples and Arguitxu De la Riva-Cavallero for the identification of the mite. Two anonymous reviewers are also warmly thanked for their constructive and helpful comments improving an earlier version of this manuscript. ML acknowledges partial funding from the Swiss National Science Foundation (grant number CRSK-2_195321 ) and the Austrian Academy of Sciences (grant number ESS-0001 ).
© 2021 The Author(s)
- Last interglacial