MULTISTEP SHORTENING IN THE PELVOUX MASSI F (WESTERN ALPS) - CASE OF THE VILLARD-NOTRE-DAME BASEMENT TRUST

As in other pinched remnants of Mesozoic cover within the Pelvoux Mass if basement, the Villard-Notre-Dame structure derives from a Liassic h alf graben, born during the Tethyan rifting. The bounding normal fault was inverted as a northward thrusting during a N-S shortening, alread y recognized along the northern limit of the massif. This shortening w as itself I,receded by a NE-SW shortening, already recognized along th e southern limit of the massif. These two ''ante-Nummulitic'' phases p redated the main E-W Alpine shortening of the Oligocene age. This chro nology, enlarged to the whole NW part of the Pelvoux massif, suggests an important, regional scale uplift, as a far distance response to the Pyrenean-Provencal collision.