Fig. 6

The Bümpliz profile. a Bouguer anomalies and regional trend of the gravity field along the profile. The blue dots represent the stations where gravity data was collected for this study. See Additional file 4: Figure D.2.1 for location of stations, Additional file 1: Appendix A for gravity data and Additional file 2: Appendix B for information on the drillings. b Results of the final model for the Bümpliz profile, made with a total of 8 prisms with a density contrast of − 500 kg/m³ for the top prism and − 350 kg/m.³ for the rest of the prisms. The blue dots represent the observed residual anomaly (the dot size corresponds to the average uncertainty of ± 0.04 mGal), and the orange dots are the modelled residual anomaly values for model 8. The black bars indicate our maximum uncertainty of ± 0.13 mGal. The light blue line highlights the main anomaly. c Elevation (SwissAlti3D 2 m DEM (© swisstopo)) along the profile (blue solid line). The red broken line illustrates the bedrock topography of the model by Reber and Schlunegger (2016). The blue dots mark the locations of the gravity stations, the red diamonds indicate drillings that reached the bedrock. The black rectangles show the cross sections of the 8 prisms used for modelling. The red star is the projected location of the Rehhag drilling (see Additional file 4: Figure D.2.1 for location)