Fig. 5

Example (Bremgarten profile, Sect. 2 on Fig. 1), illustrating of how we proceeded upon modelling. a The first models were accomplished considering all drilling information and assigning a bulk density of 2000 kg/m³ to the Quaternary fill of the main overdeepening and to the positive topography on the lateral margin of the overdeepening, particularly if these topographies are overlain by Quaternary sediments. For the Bremgarten profile, such a first model shows that the residual anomaly on the NE margin is well reproduced by the model, whereas the model largely overestimates the residual anomaly signal of the main overdeepening. b The use of a bulk density of 2000 kg/m³ for the uppermost part of the Quaternary fill (constrained by the good fit between the modelling results and the measured residual anomalies on the NE margin) and a slightly higher density of 2150 kg/m³ for the lower part of the section (constrained by the data from the Rehhag drilling in Schwenk et al., 2022a) improves the fit between the modelling results and the measured residual anomaly values. However, the model still overestimates the gravity signal related to the Quaternary fill of the overdeepenings. Note that we also assigned a density of 2000 kg/m³ for the Quaternary masses forming the topographies on either side of the trough. c Improvements upon fitting the modelled signal with the measured values were only possible if the widths of the prisms were reduced. We did not further increase the bulk density of the Quaternary fill because this would not be consistent with the density values measured for the Rehhag core by Schwenk et al. (2022a). In addition, such a model would predict a maximum depth for the Molasse bedrock, which would be much lower than the constraints offered by drilling information. The red broken line illustrates the bedrock topography of the model by Reber and Schlunegger (2016). The blue dots are the gravity stations, the red diamonds indicate drillings that reached the bedrock. The black rectangles show the cross sections of the prisms used for modelling. The red star denotes the projected location of the Forsthaus drilling (see Figure D.3.1 for location)