RECENT TILTED BLOCKS IN THE BRIANCONNAIS THRUST SHEETS, UPPER DURANCEVALLEY, FRENCH WESTERN ALPS

The Alpine thrust sheets, South of Briancon, are well known for their Jurassic extensional faulted blocks. In these units, we discovered sim ilar blocks, whose development postdated all the synschistous structur es associated to the Cenozoic Alpine uplift. They result from a late A lpine multitrend extension already recognized in the Piemont Schistes lustres, that could be related to a crustal thinning at the scale of t he internal Alpine zones. As in the Piemont zone, this late orogenic e xtension whose age remains unknown has evolved through time towards a transcurrent regime possibly similar to the present day seismotectonic regime.