Compositional Features of Fine Sediments Involved in the Montescaglioso Landslide (Southern Italy)

This paper presents the multidisciplinary study of the southern Italy Plio-Pleistocene sediments involved in the large Montescaglioso Landslide. The principal aim of the work is to assess the compositional characters (i.e., grain-size, mineralogy, petrography and geochemistry) and some rheological features (Atterberg's limits, plasticity index and activity) of these sediments to enrich our knowledge about the Montescaglioso fine sediments and correlation among the lithological properties studied. Two types of sediments, from a deep geognostic borehole and from the surrounding landslide area, were collected and analysed. No significant compositional differences have been found between the core and landslide area sediments. Conversely, some changes have been detected in sediments along the core. Particularly, the -15 to -20 m lithostratigraphic level hosts the highest percentages of phyllosilicates and clay fraction (CF), commonly considered as possible hazard factors for the landslide triggering. Further more, in the studied core sediments, the CF contents correlate with the Atterberg's liquid and plastic limits and a CF value of about 38% was suggested as threshold value for the changing of index properties of sediments. Other factors, such as the weathering degree and clay mineral type, do not show significant correlations with the rheological properties of sediments here studied.