Thrust tectonics at the front of the western Alps: constraints provided by the processing of seismic reflection data along the Chambéry transect

Abstract

The processing of a seismic acquisition made in the 1960s provides new constraints regarding the structure of the tectonic front of the western Alps between the autochthonous foreland and the Belledonne crystalline massif. These seismic data show: ( i) that the Subalpine frontal thrust is responsible for a large tectonic displacement (about ten kilometres), ( ii) that the basement is not involved in the deformation westward of the Isère valley, ( iii) that the molasse formations that are underthrust beneath the Subalpine front are thinning eastward, at depth, and ( iv) that there is no evidence of salt tectonics on the transect studied, whereas it is the case northward under the Jura and the Molasse Basin.