Construction of engineering-geology model of crystallinemetamorphic rock masses experiencing deep weathering processes: example of application to the Allaro and Amusa River basin (Serre Massif, Calabria, Italy)

Abstract

The study of natural slope morphodynamic represents a complex topic involving many different features, among which geological and structural settings, kinds of landform and process activity, groundwater seepage, climatic conditions and rheological behaviour of involved rock masses also related to weathering processes. Paper deals with an area located in the south-east side of Calabria (Serre Massif); in an area inclusive of Allaro and Amusa Fiumare (RC). The geological and morpho-tectonic sketch of this area is characterized by three different belts from the coastline toward inland: the coastal one (plio-pleistocenic deposits), the medium (Mio-Pliocene terrain) and the mountain one (crystallinemetamorphic rocks, Palaeozoic). In the last one, granite-granodiorite are into contact, through a thermometamorphic aureola, with biotitic schist and phyllitic unit. Slope morphogenesis, shallow and deep landslides are strongly controlled by weathered rock masses. In particular, along the thermometamorphic contact belts, deep chemical alteration has a rule on slope morphodynamic through deeply argillification processes of rocks; they contribute to Deep Seated Gravitational Slope Deformation (DSGSD) phenomena. In the first part, paper deals with local geological-stuctural and geomorphological aspects, substratum weathering profiles, as well as areal distribution of rock mass weathering degree. The second part deals with morphological features of M. Granieri-Salincriti DSGD, geomechanical properties of crystalline rocks according to influence of deep geochemical processes. Moreover a slope monitoring was started to define DSGD phenomenon and combined active and/or quiescent landslides, as well as to validate the "geological-evolutionary slope model".