Morphostructural evolution of the Luberon since the Miocene (SE France)

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AbstractIn northern Provence, a major tectonic phase occurred between 10 and 6 Ma prior to the Messinian salinity crisis. It is expressed by reverse faulting reactivation of the Luberon ramp-anticline that developed initially during the Pyrenean orogeny, with most of the deformation taking place during the Eocene. This Miocene phase led to a concomitant rejuvenation of the relief, along with the development of a “Jurassian” structural morphology and drainage pattern. Its most spectacular expression is the deeply incised transverse valleys that provide evidence of powerful downcutting.The earliest occurrence of the Valensole gravels, dated to ~11 Ma, is found in the Cucuron basin in the foreland of the Luberon. The uplift of the Luberon anticline and its foreland resulted from southward propagation of thrusting, whilst the phases of high eustatic sea-level that precede and follow the ending of the Messinian salinity crisis caused an accretion of the piedmont. The Luberon Alpine structural development occurred before the Messinian salinity crisis, and took place within two distinct tectonic episodes during the Miocene: the first episode, in the Early Miocene (Langhian), mainly affected the Petit Luberon, while the second more recent episode, during the Tortonian, lead to deformation in the Grand Luberon before 5.9 Ma. These tectonic events and their large-scale morphological impacts – notably the creation of the present-day relief – indicate that the Tortonian phase was the most important of the Miocene episodes as it controlled the Alpine structural development of the Luberon and its foreland as well as the associated ranges to the south. After the Miocene, whereas the Alpine phase did not modify the morphology, deformation migrated southwards from the Luberon. Some of the faults are still active, as shown by the 1909 Lambesc earthquake (11 June 1909; 6 Mw), which triggered the reactivation of the Trévaresse fault.