Late to post-metamorphic cross-section trough the Piedmont Zone in the lower Susa Valley (Western Alps)

Stefano Ghignone (a) & Marco Gattiglio (a)
(a) Dipartimento di Scienze della Terra, Università di Torino, Via Valperga Caluso 35,10125 Torino, Italy. E-mail: stefano.ghignone@studenti.unito.it

A structural transept, EW oriented, through the Pennidic Domain, in the lower Susa valley, between the Dora Maira and Ambin crystalline massifs, takes into account the relationship between the late doming of the two crystalline massifs and the deformation of the overlaid Piedmont Zone. The regional foliation and kinematic indicators, show that the entire Puys-Venaus unit is deformed in a regional asymmetric synform structure. This is linked to the doming of the two underlying crystalline massifs. The Puys-Venaus Unit is bordered, in the footwall, by two shear zones, with regional importance; the Susa Shear Zone, with top to W shear sense, in the eastern sector, and the Venaus Shear Zone, with top to E shear sense, in the western sector. In both Susa and Venaus Shear Zones, are present old top to SE shear sense, testifying the development of pre-doming extensional shear zones that allow the differential diachronic exhumation of HP units, moving from internal sector of the chain to external ones.

Extensional tectonic, Susa Shear Zone, Venaus Shear Zone, Western Alps