Fig. 4

Geologic–tectonic map of the Mont Terri rock laboratory. The Opalinus Clay is sandwiched between the Staffelegg Formation (base) and the Passwang Formation (top). There are three different facies of Opalinus Clay: shaly, carbonate-rich sandy, and sandy facies. The mapped tectonic faults can be assigned to one of three fault systems as shown on the stereoplots (bottom left, lower hemisphere Wulff projections). The rock laboratory is intersected by a major fault, called the “Main Fault”