Age of the Most Extensive Glaciation in the Alps

Catharina Dieleman,Christof Vockenhuber,Hans Rudolf Graf,Naki Akçar,Philip Gautschi,Marcus Christl

doi:10.3390/geosciences12010039

Catharina Dieleman, Christof Vockenhuber + Show 4 more

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https://doi.org/10.3390/geosciences12010039

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Journal: Geosciences	Publication Date: Jan 13, 2022
Citations: 7	License type: CC BY 4.0

Affiliation: ETH Zurich, University of Bern

Abstract

Previous research suggested that the Alpine glaciers of the Northern Swiss Foreland reached their maximum extensive position during the Middle Pleistocene. Relict tills and glaciofluvial deposits, attributed to the Most Extensive Glaciation (MEG), have been found only beyond the extents of the Last Glacial Maximum (LGM). Traditionally, these sediments have been correlated to the Riss glaciation sensu Penck and Brückner and have been morphostratigraphically classified as the Higher Terrace (HT) deposits. The age of the MEG glaciation was originally proposed to be intermediate to the Brunhes/Matuyama transition (780 ka) and the Marine Isotope Stage 6 (191 ka). In this study, we focused on the glacial deposits in Möhlin (Canton of Aargau, Switzerland), in order to constrain the age of the MEG. The sediments from these deposits were analyzed to determine the provenance and depositional environments. We applied isochron-burial dating, with cosmogenic 10Be and 26Al, to the till layer in the Bünten gravel pit near Möhlin. Our results indicate that a glacier of Alpine origin reached its most extensive position during the Middle Pleistocene (500 ± 100 ka). The age of the MEG thus appears to be synchronous with the most extensive glaciations in the northern hemisphere.

Highlights

The Most Extensive Glaciation (MEG), locally known as Möhlin glaciation, Hosskirch, Mindel, or Most Extensive Helvetic Glaciation (Grösste Helvetische Vergletscherung in German; GHV), is proposed to have occurred during the Middle Pleistocene (774–129 ka; [1]) [2,3,4,5,6].Previous studies reconstructed its extent by mapping erratic boulders detected beyond the extents of the Last Glacial Maximum (LGM), along with few relict glacial deposits [5,7,8]
It was suggested that this glaciation reached the interiors of the northern Alpine Foreland and advanced at least until Möhlin (Canton of Aargau), close to Basel in northern Switzerland (Figure 1), where the Rhone, Reuss, Linth, and Rhaetian paleoglaciers coalesced [9,10,11]
In Möhlin, the Bünten Till, one of the few preserved glacial relicts attributed to the MEG outcrops in a gravel pit

Summary

Introduction

The Most Extensive Glaciation (MEG), locally known as Möhlin glaciation, Hosskirch, Mindel, or Most Extensive Helvetic Glaciation (Grösste Helvetische Vergletscherung in German; GHV), is proposed to have occurred during the Middle Pleistocene (774–129 ka; [1]) [2,3,4,5,6].Previous studies reconstructed its extent by mapping erratic boulders detected beyond the extents of the LGM, along with few relict glacial deposits [5,7,8]. It was suggested that this glaciation reached the interiors of the northern Alpine Foreland and advanced at least until Möhlin (Canton of Aargau), close to Basel in northern Switzerland (Figure 1), where the Rhone, Reuss, Linth, and Rhaetian paleoglaciers coalesced [9,10,11]. In Möhlin, the Bünten Till, one of the few preserved glacial relicts attributed to the MEG outcrops in a gravel pit. This is perceived to be an important locality for reconstructing the MEG in the Swiss northern Alpine Foreland [3,6,8]. The MEG is esteemed as the first glacier advance that formed overdeepened valleys in the northern Alpine Foreland [4,12]

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