A new 3D model of the base Quaternary for northwestern Lower Saxony (Germany)

The base Quaternary in northwestern Lower Saxony is characterised by an undulating surface that is intersected by a complex network of buried tunnel valleys. Their development is mainly associated with the Elsterian glacial stage. The Quaternary sediments contain minable sand and gravel deposits, and host most of the groundwater reservoirs. The incision depth of tunnel valleys is a relevant parameter for the countrywide ongoing search for a suitable site for radioactive waste storage. To date, comprehensive information for the base Quaternary in Lower Saxony is available from a 30-year-old contour map, but more recent data are available. Thus, a revision of the base Quaternary as a 3D geological model is essential to support strategies for sustainable resource extraction and land use.

The new 3D model covers approximately 11,800 km². It has been compiled in Aspen SKUA® and is based on a broad dataset: The existing contour map of the base Quaternary has been combined with more recent data, especially seismic data (2D/3D) and extensive borehole data. Additionally, we considered information from geological cross sections and regional 3D models. Several previously unknown tunnel valleys were discovered. Seismic data proved to be extremely valuable to map their course and geometry over tens of kilometres. Our model indicates that erosion depths may reach up to -415 m NHN, which is more than 50 m deeper than previously assumed.

The 3D model will be available via the NIBIS® mapserver (https://nibis.lbeg.de/cardomap3). Work on the 3D model will be continued for other parts of Lower Saxony.