Observations on some stratified slope deposits in the Gesso Valley (Italian Maritime Alps): typology and significance

In the Gesso Valley stratified slope deposits occur on limestone and marl outcrops of Mesozoic age. Their thickness varies from a few decimetres to some metres. They overlie alluvial terraces. At present they are inactive. Sections show an alternation of grain-supported and matrix-supported layers. Sedimentological analysis indicates that these deposits are eboulis ordonnes; each layer shows its own sedimentological peculiarities, for example concerning grain size, orientation and dip, sorting within the level, relative matrix abundance, degree of cementation and nature of limits. It is impossible, therefore, to account for a true cyclical nature of the layers. The processes responsible for the genesis of this deposit are hypothesized to be congeliturbation, associated with rill episodes and gravitational displacement of gelifracts. The deposits probably formed in a periglacial environment, near the terminal part of a retreating glacier snout.