Multi-scale structural analysis of fracture networks in folded limestones: A case study from the Central Internal Jura, Switzerland

Fracture characterization is key to understanding deformation in fold-and-thrust belts, where fractures record paleostress states, constrain tectonic timing, and control fluid flow in low-porosity carbonates. In the context of the energy transition, this control is particularly relevant for geothermal exploration in the Swiss Jura Mountains, where Upper Malm limestones act as target reservoirs. At Creux-du-Van in the Central Internal Jura, we integrated field structural analysis, paleostress inversion, and a LiDAR-derived Digital Outcrop Model (DOM) on the cliffs to investigate fracture networks across scales, from regional strike-slip faults to meter-scale fracture corridors. Our results show that strike-slip fault zones are organized in a self-similar hierarchical Riedel system, ranging from the first-order Pontarlier Fault System ( km long) to fourth-order ( 1 km long) zones. DOM mapping revealed three main fracture sets: fold-perpendicular background fractures, diagonal conjugate strike-slip sets expressed as fracture corridors on cliffs, and fold-parallel fractures at the hinge. Paleostress analysis yields a consistent Late Miocene stress field, with trending 153–159°perpendicular to the Nouvelle Censière fold axis. Stress deviations up to 30°occur not only near major faults but also in sub-seismic third-order ( 10 km) structures, reflecting the combined influence of inherited anisotropy and reactivation. Evidence of – switching reveals alternating strike-slip and compressional stages within a single SE–NW–directed contractional phase. These findings demonstrate that hierarchical fault architecture and paleostress perturbations strongly control fracture networks, shaping preferential fluid pathways and directly influencing geothermal reservoir performance in the Upper Malm.