Supervisor: Prof. Michel Jayboyedoff
Expert: Andrea Pedrazzini
The present study concerns the deep-seated gravitational slope deformation (DSGSD) of the south-east slope of the Arpille massif. This rectangular mountain is part of the Aiguilles-Rouges external crystalline massif in the centre of the Swiss Alps close to the city of Martigny in the Rhône valley. Its glacial history is complex and left many traces. Two main lithologies compose the slope: crystallines rocks from Aguilles-Rouges massif, like orthogneiss and paragneiss, and limestones from the Mont-Blanc cover. In the area surrounding the tectonic contact between those two lithologies, rocks are laminated by a vertical alpine schistosity. This particularity affects the lower part of the south-east slope. This cleavage is totally toppled over the limit of the DSGSD. This is one of the main characteristics of the geometry of the Arpille DSGSD. The aim of the study is to develop a global understanding of this phenomenon. The results are based on in-situ investigations as well as geomorphological and geological analyses. Numerical and geometrical models have been developed to understand the role of pre-existent structures in the formation of the DSGSD and associated morpho-structures.