EGU21-5643, updated on 15 Aug 2023
EGU General Assembly 2021
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Early Pleistocene complex cut-and-fill sequences in the Alps

Catharina Dieleman1, Marcus Christl2, Christof Vockenhuber2, Philip Gautschi2, and Naki Akçar1
Catharina Dieleman et al.
  • 1Institute of Geological Sciences, University of Bern, Bern, Switzerland
  • 2Laboratory of Ion Beam Physics, ETH Zurich, Zurich, Switzerland

Deckenschotter (Cover Gravels in German) are Quaternary glacio-fluvial gravels, which unconformably overlie Tertiary Molasse or Mesozoic bedrock in the Northern Alpine Foreland. They comprise also the evidence of the Early Pleistocene glaciations. A significant phase of incision separated them into Höhere Deckenschotter (HDS: Higher Cover Gravels) and Tiefere Deckenschotter (TDS: Lower Cover Gravels) based on their topography. How the landscape evolved during Deckenschotter times is still not fully understood. The new cosmogenic nuclide chronology suggests that HDS deposited around 2 Ma and TDS around 1 Ma. In addition, 2 Ma old Deckenschotter are located at the same topographic elevation as the 1 Ma ones at Irchel (Canton of Zurich). This, indeed, points to cut-and-fill sequences and challenges the chronology based on the morphostratigraphy.

The aim of this study is to reconstruct the drainage patterns, base level changes, and thus the landscape evolution in the northern Alpine Foreland during the Early Pleistocene. Therefore, we focused on three Deckenschotter sites at Irchel and one in the area around Lake Constance. Sediments at these sites were analysed in detail to reveal their provenance, transport mechanism, depositional environment, and paleoflow regimes. Their chronology was established by isochron-burial dating. Our results indicate that the analysed sediments were transported from the Central and eastern Central Alps as well as from the Molasse to the foreland first by glaciers and then by rivers. They are deposited in a glacio-fluvial environment in the vicinity of a glacier. Based on the reconstructed chronology in this study and published cosmogenic nuclide ages, we propose that Deckenschotter are cut-and-fill sequences accumulated in three pulses between 2.5 Ma and 1 Ma. This cut-and-fill system implies that the regional base level was relatively constant during the Early Pleistocene. In addition, the depositional environment of Deckenschotter shows the presence of glaciers in the foreland. The 2.5 Ma old gravels, therefore, document the first advance of glaciers onto the Alpine Foreland. This seems to be synchronous with a first onset of glaciations on the northern hemisphere, which is assumed to occur at around 2.7 Ma.

How to cite: Dieleman, C., Christl, M., Vockenhuber, C., Gautschi, P., and Akçar, N.: Early Pleistocene complex cut-and-fill sequences in the Alps, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5643,, 2021.