Structural analysis of roches moutonnées in Western Orobic Alps (Lombardia)

Abstract

The structural characters of the roches moutonnées have been studied within four cirques of the Western Orobic Alps, for the purpose of identifying the relationship between structures and observed morphologies. The meso-structural analysis of the area has led to the identification and the chronological ordering of six deformation phases (three pre-Alpine and three Alpine) represented by many different structures both ductile (folds and foliations) and brittle (faults and cataclasites). Each exposed surface of the roches moutonnées has been analysed on the base of this structural model and the correspondence between morphological and structural characters has been evident. The investigated cases demonstrate that the exposed surfaces of the roches moutonnées are, in reality, structural surfaces. Therefore, it would seem that their moutonnée appearance is not of glacial origin alone. The glacial action is likely to be limited to the removal of the higher rock portion weathered during interglacial periods.