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New ideas from old observations: A study from the Leinetal Graben

In the vegetated German uplands many outcrops are temporary and the information they hold is easily lost. In fortunate cases, publications give insights into outcrops long since gone and provide the opportunity to reinterpret the old observations. I report the example of a roadcut created during construction along the A7 motorway near Göttingen in the 1950s. The geology exposed is documented as detailed line drawings in a paper (Wunderlich 1959). The main feature exposed was an arched, antiformal contact between Lower Jurassic shale above and Middle Triassic Muschelkalk limestone below it. The Muschelkalk beds beneath the contact are folded and truncated against it. In the south, the Jurassic strata are overlain by Muschelkalk and upper Buntsandstein. This seemingly chaotic arrangement was interpreted by Wunderlich (1959) as the effect of a landslide that had emplaced a jumble of Triassic blocks floating in Jurassic shale over Triassic bedrock. Kinematic modelling shows that the arched contact can be interpreted as an originally planar normal fault of > 1 km displacement that was later folded together with its footwall. Folding and the Triassic rocks overlying Jurassic in the south indicate reverse reactivation of the normal fault, but also a new thrust fault splaying from it. The major normal fault modified by later shortening matches the evolution of the adjacent Lower Saxony Basin with Late Jurassic to Early Cretaceous extension and Late Cretaceous inversion. The relatively low-angle normal fault may help explain a main feature of two short, nearby seismic lines acquired for research purposes.

Details

Author
Jonas Kley1
Institutionen
1University of Göttingen, Germany
Veranstaltung
GeoSaxonia 2024
Datum
2024
DOI
10.48380/z9rg-p691