Timing of Deformation in the Provence Fold-and-Thrust Belt (SE France) as Constrained by U-Pb Calcite Geochronology

A combination of fault and fracture analyses, paleostress reconstructions from calcite twins, and U-Pb dating of syn-kinematic calcite mineralization provides new insights into the Cretaceous–Tertiary tectonic evolution of the Provence fold-and-thrust belt. This approach helped unravel 90 million years of polyphase deformation in this belt, which represents the eastward continuation of the northern Pyrenees. Focusing on three main targets along an NNE-SSW transect oriented roughly parallel to the regional Pyrenean shortening (the southernmost Nerthe range, the Bimont Lake area, and the northern Rians syncline), we date a wide range of scales and natures of deformation structures such as stylolites, veins, mesoscale faults, and major thrust fault zones. The reconstructed long-lasting tectonic history includes (1) the Durancian uplift and related NNE-SSW extension (~110 to 90 Ma); (2) the ~N-S Pyrenean compression related to the convergence then collision between Eurasia and Iberia and the Corsica–Sardinia block (~80 to 34 Ma); the Oligocene E-W to WNW-ESE extension related to the West European Cenozoic Rift System (ECRIS) and the Oligo–Miocene NW-SE to NNW-SSE extension related to the Liguro-Provençal Rifting (LPR); and a middle-late (?) N-S to NW-SE Alpine compression. We show that the Pyrenean shortening in Provence occurred during two main phases, 81–69 Ma and 59–34 Ma, coeval with the inversion of the pre-Pyrenean rift and the main Pyrenean collision, separated by a tectonic quiescence as described in the Pyrenees. Together with the published literature, our U-Pb ages also support the overall northward (forelandward) in sequence propagation of Pyrenean shortening across Provence. Our U-Pb results further allow us to refine the interpretation of local and regional fracture sets and reveal unsuspected polyphase development of fractures sharing a common strike. Beyond regional implications, our study shows that sampling structures of various natures and scales for U-Pb geochronology is probably the most efficient strategy to encompass the entire time interval of deformation in fold-and-thrust belts.