Construction of hydrostratigraphic subsurface models of the Northwest German Basin: input for numerical simulation of subglacial erosion during past and future glaciations

Large volumes of glacial meltwater drain along the interface between the ice sheet and its bed, thereby influencing glacier dynamics. It is known from the geological record and modern glacial systems that channelized subglacial meltwater discharge generates high erosion rates, leading to the formation of overdeepenings and tunnel valleys, some over 500 m deep. It is therefore essential to constrain the depth of potential subglacial erosion under future ice sheets when searching for locations of high-level radioactive waste repository sites.

The aim of this project is to quantify the meltwater-driven erosion under the past ice sheets in northern Germany and evaluate the erosion potential during future glaciations. To achieve this goal, we develop a next-generation dynamic numerical model simulating subglacial meltwater erosion on soft beds. In the first step, we built subsurface reservoir models at different scales and resolutions to examine the impact of model resolution on the subsequent erosion modelling. The 3D subsurface model approximately covers the area of the Northwest German Basin (40,000 km²), has a depth of 2000 m, and comprises lithostratigraphical units from the Permian Zechstein to the Pleistocene. The basin fill has a complex structure due to salt tectonics, and the main challenge was to generalize the complex lateral and vertical lithofacies/hydrofacies relationships.

Two large-scale, low-resolution subsurface reservoir models were constructed. The first model does not include Quaternary deposits. This model was created to simulate the formation of Middle Pleistocene tunnel valleys and compare/validate the results with the Pleistocene record of the Northwest German Basin. The second large-scale subsurface model includes the Quaternary deposits and will be used to simulate subglacial erosion during future glaciations. A smaller high-resolution subsurface model, covering an area of about 2000 km², will then be used to test the effects of model size and model resolution on the simulation of subglacial erosion.