"Structural and age analysis of micro and mesoscale brittle deformations in an intracontinental sedimentary basin: the Paris Basin as a case study."

Deformation of the intraplate domain is a consequence of stress transmission from continental plate boundaries. It results in lithospheric buckling, regional deformations, and micro to mesoscale fracture networks. This project focuses on the micro to mesoscale fracture network, and in the context of the BRGM project Référentiel Géologique de la France (RGF), we studied the intraplate deformations of the Paris Sedimentary Basin.

The first part focuses on structural investigations in the field. The results highlight spatial and temporal heterogeneities of fracture geometries, distribution, and kinematics. The data show that an extensive network of multi-directional brittle joints exists and is expressed at different scales. Evidences of faulting, while less common than joints, also exist in the Paris Basin. Calculated paleostress tensors indicate mostly strike-slip faulting regimes with maximum principal stress axes (σ1) roughly N-S.

The second part focuses on the absolute dating of fault activity using in-situ U-Pb dating of calcite mineralized along fault planes. The resulting ages are restricted to a time-period spanning the Late Cretaceous to the Eocene. The structural characteristics and timing of these intraplate deformations are compared with a timeline of Meso-Cenozoic geodynamic events occurring at the continental plate borders of Western Europe. The combined findings indicate that the Pyrenean Orogeny exerts a greater influence on the deformation of the Paris Sedimentary Basin than the Alpine Orogeny or the European Rift System (ECRIS).

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