Radiocarbon dating of Loess-Palaeosol-Sequences from Remagen-Schwalbenberg using Earthworm Calcite Granules
Final Report Abstract
Loess-Palaeosol-Sequences (LPS) are valuable terrestrial archives to investigate palaeoclimatic and palaeoenvironmental changes associated to abrupt variations that effected the climate of the Northern Hemisphere on millennial to centennial timescales during the Upper Pleistocene. Such climate fluctuations, known as Dansgaard-Oeschger events, are characterised by rapid warming at the beginning of interstadials and gradual cooling back to stadial conditions and are well recognised in Greenland ice cores and North Atlantic marine records. Still, their propagation onto the continents and potential force-feedback mechanisms are less well documented and understood. LPS often record these climatic changes in the form of brown soils and tundra gley horizons - indicating milder interstadial conditions - intercalated with primary loess deposits reflecting cold stadial conditions. LPS are more widely distributed than other comparable archives, but dating of such sequences remained difficult and inaccurate, hampering the correlation with other high-resolution archives of climate change. In addition, the possibilities to reconstruct and quantify climate variables such as temperature and precipitation were limited so far. To overcome these problems, we used a newly developed approach. Earthworm Calcite Granules (ECG) secreted daily by the species Lumbricus terrestris, allow for precise radiocarbon dating. In addition, land-surface temperatures of the warmest month (LSTws) and mean annual precipitation (MAP) can be quantified by analysing the composition of oxygen and carbon isotopes of ECGs. Thus, they provide unique archives for palaeoclimate reconstruction allowing measuring different proxies on one and the same sample. We tested this approach for the Schwalbenberg LPS in the Middle Rhine Valley (Germany) and compare our results with the Nussloch LPS in the Upper Rhine area (Germany). In addition, we applied radiocarbon dating on ECGs for the Schwalbenberg key LPS of sediment core REM3. Our results covering the period from ~45,000 to 22,000 years before present for the two overlapping LPS from Schwalbenberg and Nussloch show that the Rhine valley was characterized by annual precipitation values reduced by up to 70% compared to the present day. Reconstructed mean summer temperatures were also significantly lower than today (-3.8 up to -10.6°C) but show that cold stadial phases were only 1-4°C colder than interstadial phases indicating strong attenuation of climate signals compared to Greenland or North Atlantic marine records. Overall, the approach combining high-resolution age-depth modelling and geochemical proxy-based climate reconstruction can be readily adopted to other LPS. We envisage a widespread application of this approach that would improve our understanding of regional variability over the European continent in response to North Atlantic climate changes over millennial to centennial timescales. The application of ECG dating on samples from the Schwalbenberg key LPS REM 3 yielded consistent ages covering the period from ~51 to 22 ka. The new age model will allow for investigating significant changes in the Schwalbenberg LPS associated with northern hemispheric climate oscillations in more detail than reported from any other site until today. Based on the data obtained within this project, we will be able to compare and evaluate different age-depth-modelling approaches and discuss potential force-feedback mechanism of Upper Pleistocene climate fluctuations on the base of highresolution and independent age models from continental Europe, which are rarely available so far. Project results were reported by different media showing the relevance of our approach towards understanding past climates. The following releases appeared up to now: SWR AKTUELL RP, 29. November 2022, https://www.swr.de/swraktuell/rheinland-pfalz/sendung- 1930-uhr-vom-29112022-100.html. Ice Age temperatures and precipitation reconstructed from earthworm granules. Phys.org, 21.11.2022. Klimacode im Regenwurmkot. Bild.de, 23.11.2022. Eiszeitliche Temperaturen und Niederschläge anhand von Regenwurm-Ausscheidungen rekonstruiert. Archäologie Online, 25.11.2022 Blick in die Vergangenheit. Die Rheinpfalz, 26.11.2022. Wärmer als bislang angenommen - Wissenschaftler haben durch die Analyse von Regenwurm- Ausscheidungen Klimadaten der letzten Eiszeit ermittelt. Mit einem überraschenden Ergebnis. Frankfurter Allgemeine, Faz.net, 29.11.2022. Regenwürmer „archivierten" Eiszeitklima. Bild der Wissenschaft, 29.11.2022. Des granules de vers de terre permettent de reconstituer le climat de la dernière ère glaciaire. Radio France, 22.12.2022. Entschlüsselt – Das sagt Regenwurmkot übers Klima. Bildzeitung, 23.11.2022. Klimadaten aus Regenwurm-Kot. Rhein-Main-Zeitung. 29.12.2022.
Publications
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Millennial-scale Land-surface Temperature and Soil Moisture Reconstruction Derived From Last Glacial European Loess Sequences. (2022, 2, 2). American Geophysical Union (AGU).
Prud'homme, Charlotte; Fisher, Peter; Jöris, Olaf; gromov, Sergey; Vinnepand, Mathias; Hatté, Christine; Vonhof, Hubert; Moine, Olivier; Vött, Andreas & Fitzsimmons, Kathryn
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Millennial-timescale quantitative estimates of climate dynamics in central Europe from earthworm calcite granules in loess deposits. Communications Earth & Environment, 3(1).
Prud’homme, Charlotte; Fischer, Peter; Jöris, Olaf; Gromov, Sergey; Vinnepand, Mathias; Hatté, Christine; Vonhof, Hubert; Moine, Olivier; Vött, Andreas & Fitzsimmons, Kathryn E.
