Pre-folding magnetic fabrics in fold-and-thrust belts: Why the apparent internal deformation of the sedimentary rocks from the Minervois basin (NE — Pyrenees, France) is so high compared to the Potwar basin (SW — Himalaya, Pakistan)?

The Minervois basin recorded the Pyrenean compression in the Languedoc region, at the northeastern tip of the Pyrenees (France). It exhibits tectonic magnetic fabrics characterized by a complete loss of the sedimentary heritage. By contrast, the Potwar basin, which is located at the front of the southwestern Himalaya (Pakistan), shows magnetic fabrics with preservation of the sedimentary record. Two factors can explain these differences. The first is a tectonic factor and is related to the degree of coupling between cover and basement, which is notably higher in Minervois than in Potwar. The second and probably main factor is the degree of initial anisotropy which is low in Minervois, due to the importance of pedological processes erasing the sedimentary heritage and hardening rocks before burial in the basin. By contrast, the Potwar exhibits a more classical evolution where the sedimentary signature is related to compaction during burial.