New structural constraints on the southern Provence thrust belt (France): evidences for an Eocene shortening event linked to the Corsica-Sardinia subduction

The Eocene shortening directions along the Southern Provence fold-and-thrust belt are commonly assumed to be N-S. We present here new observations and data that allow reinterpreting the structure of the La Nerthe range as a right-lateral transpressive flower structure. Structural data collected along the range argue for an Eocene N145 degrees shortening event. The age of this shortening event is constrained by the fact that faulting and folding affect the Late Cretaceous-Paleocene continental deposits along the northern flank of the La Nerthe range and is sealed by the Miocene marine deposits. Moreover striated fault planes display both horizontal and vertical striae suggesting that they were reactivated during the Oligocene extensional event. We question here the shortening directions along the Southern Provence thrust belt. Structural data suggest both N-S and NNW-SSE shortening directions during the Eocene. During the Eocene the Provence area was in the foreland of a complex orogenic belt that extended from the Betic Cordillera to the Corsica-Sardinia block. This orogenic belt developed along the subduction linked to the convergence between Africa and Eurasia. Although the convergence vector was nearly N-S the NE-SW orientation of the trench may have led to a complex deformation pattern along the orogenic belt with NW-SE and N-S shortening directions that reflected both the along-trench compression and the regional convergence.