Pleistocene tunnel valleys in northern Germany - Influence of the underlying geology on tunnel-valley formation and reactivation
Country / Region: Germany
Begin of project: January 1, 2021
End of project: December 31, 2025
Status of project: February 12, 2024
Reconstruction of sub-glacial tunnel-valleys at base Quaternary in northern Germany
Source: BGR
During the Pleistocene glaciations, subglacial tunnel valleys formed in large parts of northern Germany. The formation of tunnel valleys is therefore expected to take place during potential future ice ages as well. The deep erosion during the formation of such tunnel valleys can theoretically have an impact on the integrity of the geological barrier of a repository. The Site Selection Act (StandAG) defines a minimum depth of an isolation rock zone below the largest expected depth of exogenic processes, which could have a direct or indirect negative impact on the integrity of the isolation rock zone. Tunnel valleys are specified here indirectly as “intensive erosion caused by ice ages” (StandAG Section 23 (5) No. 3).
The formation of tunnel valleys from meltwater discharge under high pressure is one of the deepest erosive processes. In the zones in northern Germany affected by Pleistocene glaciations, tunnel valleys with depths of 100 to 300 m are present over wide areas, and some extend to a maximum depth of over 500 m. Despite many years of research, there are still many open questions concerning the formation and development of tunnel valleys and their infills. Tunnel valleys frequently have complex histories with repeated phases of erosion and deposition, which can extend over several ice ages.
This project looks into the formation and distribution of Pleistocene tunnel valleys in northern Germany. The aim of the project is to improve our understanding of the controlling factors for the formation and re-activation of tunnel valleys, with the ultimate aim of improving the predictability of future tunnel-valley formation.
The following key issues will be studied in this project:
- What is the impact of the geological structure (e.g., lithology, faults, salt structures) on the formation of tunnel valleys, and their properties (e.g., distribution, geometry, dimensions)?
- Which factors control the incision of tunnel valleys and their reactivation during repeated glaciations?
- How did the tunnel valleys in northern Germany and their infills develop over time?
- Is it possible to predict the formation of tunnel valleys during future ice ages?
The first results of the project were published in the "E&G Quaternary Science Journal", the journal of the German Quaternary Association (DEUQUA) (external link): The past is the key to the future – considering Pleistocene subglacial erosion for the minimum depth of a radioactive waste repository.
The state-owned company for geologic repositories, the Bundesgesellschaft für Endlagerung mbH (BGE), and the Federal Institute for Geosciences and Natural Resources (BGR), conducted a virtual workshop on “Tunnel valleys” from 9.-10.12.2021.