Fig. 1

Geographic and geological overview. a Geographical overview of the Belchentunnel location. Blue area indicates roughly the extend of the Jurassic thrust and fold belt. b simplified stratigraphic and lithologic log of the Belchentunnel succession studied by Scheuring (1970). S: Schinznach Formation, A: Asp Member, L: Lettenkohle: GM: Gansingen Member, GD: Gansinger Dolomit. c Geological cross section along the Belchentunnel after Amann et al., (2014)