Structural investigations and U/Pb dating in the southern Paris basin do not record any Alpine deformation

Deformation of intraplate sedimentary basins essentially results from tectonic stresses that propagate from plate boundaries. Yet, the detailed characteristics of this far field propagation are often poorly constrained, especially in age. Recent developments of U/Pb dating of calcite precipitations in fault planes and veins hopefully greatly help to frame the schedule of deformation. This is the case for the Meso-Cenozoic Paris basin, liable to have recorded several Cenozoic events due to its location in the western Eurasian plate, like Pyrenean and Alpine collisions and Oligocene extension (ECRIS).

Our study focusses on the southern Paris basin area, north of the Morvan massif, where Alpine deformations are expected. Field data reveal almost exclusively strike-slip deformations with variable σ₁ direction. These results are about to be confirmed at the microscopic scale using Anisotropy of Magnetic Susceptibility and of P-Wave Velocity methods. Associated U-Pb dating of synkinematic calcites from Jurassic strata indicates distributed Eocene deformation and an absence of Oligocene or Miocene ages. Such ages suggest the record of Pyrenean and possibly ECRIS tectonic events. Strikingly, Alpine deformation and especially stress propagation leading to the growth of the Jura fold-and-thrust belt during Miocene does not imprint the studied area although the Alpine orogen is located closer than the Pyrenean belt.