Geological context of the study. (A) Simplified geological map of the Upper Rhine Graben area, after Eisbacher and Fielitz (2010) and Bossennec et al. (2018), with locations of sampled areas represented by red stars. The position of B windows is indicated in the pink rectangle. Major Variscan and Cenozoic faults are placed according to (Schumacher, 2002). BL: Badenweiler–Lenzkirch fault system; LB: Lalaye-Lubine-Baden-Baden fault system; SHB: South Hunsrück Taunus border fault system. (B) Map of the basement fault pattern in the area of Cleebourg, Karlsruhe, Speyer. (C, D) Schematic cross-sections located on Figure 1B, with indications of the current hypothesis on waters pathway infiltration and migration in the URG (Sanjuan et al., 2010; Sanjuan et al., 2016; Böcker et al., 2016; Vidal and Genter, 2018).