Fig. 6

Proposed geometry of the top basement based on a comparison with well data and interpretations by Sommaruga (2011) and Sommaruga et al. (2012, 2017). See Fig. 1 for a map view. The wells are projected into the section with an azimuth of 60°, parallel to the fold axes. The greyed-out wells lie more than 45 km to the west of the Pontarlier fault system. The top basement horizon from Sommaruga et al. (2017) represents the situation interpreted 14 km west of the study area. The blue error bars represent the depth uncertainty of ± 300 m discussed in the text. We can observe that the “Near Base Mesozoic” horizon from Sommaruga et al. (2012) in the Molasse Basin, the wells Treycovagnes-1 and Buez-1 and the interpretation proposed herein are consistent. The dip of the top basement interface increases towards the SE from 1.7° in the Internal and External Jura to approx. 3.6° under the Plateau Molasse. The topographic slope of the Jura Mountains is 1° toward the north