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Timing of the post-LGM retreat of the Iller Piedmont Glacier (Southern Germany) based on in-situ 36Cl exposure dating of glacial erratics

The dynamic behavior of glacial retreat following the Last Glacial Maximum (LGM), which is globally diachronous, is poorly understood. Along strike of the northern Alpine margin, multiple lobes of large foreland glaciers left a complex morpho-sedimentary record. While the reconstructed LGM ice extent is laterally constant in the west, it shows significant variations in the central and eastern part. We use these local geologic variations to explore how regional climatic conditions relate to global climate during this period of rapid late Pleistocene climate change. The chronology for this interval has been well-constrained in Switzerland, but radiometric ages have only been reported for a few locations along the Alpine Foreland in Germany. In this study, we employ cosmogenic 36Cl in limestone to constrain the in-situ exposure age of glacial erratics situated on moraine walls of the Iller Piedmont Glacier. We sampled erratic boulders along a transect perpendicular to three moraine ridges previously interpreted to represent the LGM along with two post-LGM retreat stands. Our preliminary raw data show that the sampled lithology provides internally consistent, reproducible, and geologically meaningful dates. We discuss our results taking into account limestone weathering, erosion and local postglacial landscape stabilization, and apply appropriate correction factors to obtain more accurate ages. This exposure age data gives first insights into the spatio-temporal patterns of glacial retreat in the northern Alpine Foreland, which can be used to reconstruct Central European paleoclimate in the late Pleistocene.


Dominic Hildebrandt1, Florian Hofmann1, Silke Merchel2,3, Georg Rugel2, Kathrin Strößner1, Sami Akber1, Anke M. Friedrich1
1Department of Earth and Environmental Sciences, Ludwig Maximilian University Munich, Germany; 2Department Accelerator Mass Spectrometry and Isotope Research, Helmholtz-Zentrum Dresden-Rossendorf, Germany; 3Present address: Isotope Physics, University of Vienna, Austria
GeoKarlsruhe 2021