Exhumation process in the Western Alps: a multi-scalar approach to 3D geometrical modelling and geodynamic reconstruction along the Chartreuse-Maurienne traverse

In the framework of a new high-speed train connection across the Western Alps, between Lyon and Torino, geological studies in collaboration with BRGM led to producing 3D geometrical models in key locations. These models allowed a reinterpretation of the geometry of geological layers and the construction of a new geological section of the Maurienne Valley (section drawn by BRGM). Combined with an ECORS profile, this new section was used to build a crustal-scale section across the Western Alps. Extension of this section towards external zones, from the Belledone Massif to the foreland Basin, comes from Philippe's (1994) results. We built a series of balanced cross-sections of this traverse using detailed structural informations gathered along the transect, a compilation of Pressure-Temperature-Age path of each unit, and the timing of successive foreland formations. Peak temperature estimates measured with a Raman spectrometer on organic matter in meta-sediments (RSCM method), reveal the high resolution thermal structure of the accretionary prism from the "Ultra- Dauphinois" domain to the most internal domains. This method appears fundamental to understand exhumation mechanism of this traverse. These reconstructions lead to re-discussing i) the exhumation mechanisms of high-pressure units and ii) the interaction between main thrusts and normal faults that partially accommodate the rise ofWestern Alps deep units.