My research is interdisciplinary and concerns Basement lenses in sediments overlying the Mont Blanc and Aiguilles Rouges Massifs. Paleozoic basement s.l. slivers have been observed inside the highly deformed Mesozoic sedimentary cover along the top of the Aiguilles Rouges and Mont Blanc Massifs. in the vicinity of the main décollement level of the Helvetic Nappes. The main outcrops are in the Salanfe-Tours Salière and in the Petit Col de Ferret area. The extent of the basement slices is in the order of 10-several hundreds of meters. The origin/cause of the basement slices inside the sedimentary pile remains to be elucidated. I will use a combined sedimentological, tectonic and petrographic approach to document and discriminate the involved processes.