Radiocarbon dating of Loess-Palaeosol-Sequences from Remagen-Schwalbenberg using Earthworm Calcite Granules

• Applicants: Dr. Peter Fischer; Professor Dr. Andreas Vött
• Subject Area: Physical Geography
• Term: from 2020 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 439443769

In the frame of the DFG-funded TERRACLIME-project, precise dating of investigated Loess-Palaeosol-Sequences (LPS) from the Schwalbenberg near Remagen (Middle Rhine valley, Germany) is one of the major challenges. The Schwalbenberg is unique because it preserves a complete terrestrial record of Last Glacial climate variability in western Central Europe, and especially of Marine Isotope Stage (MIS) 3. In context to the documentation and interpretation of millennial-timescale warming periods, named Greenland Interstadials (GI) or Dansgaard-Oeschger events, and their impact on landscape formation the dating approach gains particular importance. The interstadial periods appear as soil horizons of different development degrees within the investigated sequences and can be traced precisely using the multi-proxy-approach elaborated for the TERRACLIME-project. In contrast, the exact chronostratigraphic position remains uncertain, especially due to unfavourable mineralogical characteristics and relatively large error ranges of luminescence ages, which partly exceed the duration of interstadial periods. In this context, a promising dating approach has recently been developed applying radiocarbon dating of fossil Earthworm Calcite Granules (ECG) that shows very promising results for the Nussloch type section and northwestern France (Moine et al., 2017; Prud’homme et al., 2019). This new approach is even more important as conventional 14C-datable remains are scarce in LPS hampering the development of robust radiocarbon chronologies. Within our preparatory studies, a new profile at the Schwalbenberg was prepared and sampled in high resolution (5 cm intervals, 105 samples in total). The profile is characterised by several brown soils, tundra gleys and loess deposits of MIS 3 age, showing particularly high numbers of ECG in palaeosols. First radiocarbon ages significantly improved the age model for the Schwalbenberg LPS and shows that the sampled material is suitable for 14C-dating. Thus, the main objective of this supplementary proposal is radiocarbon dating of additional 40 samples from the Schwalbenberg profile. The data will be integrated into the ongoing work of the TERRACLIME-project and help to validate luminescence ages and refine OSL protocols. Recently, isotope analyses (δ18O und δ13C) have already been conducted on all samples from the new profile. Based on these analyses and the complementary ECG dating approach, it will be possible to interpret essential palaeoclimate data against the background of a robust chronostratigraphy and to compare them to regional and global palaeoclimate archives.

• DFG Programme: Research Grants
• Cooperation Partner: Dr. Olaf Jöris