Il movimento gravitativo lento del Sass del Camin (Agordo, Belluno)

The slow gravitational movement of the Sass del Camin (Agordo, Belluno, Italy)

Abstract

Aim of this research is the study of the head areas of Missiaga and Bordina torrents, which are left tributaries of T. Cordevole near Agordo (BL). From a geological point of view, this area is characterised by the Triassic formations outcrop, that constitute a rigid-plastic contact system. In fact, the terrigenous formation of La Valle, San Cassiano and Raibl, which have a total thickness of 350-400 m, underlie the formation of Dolomia Principale, about 800 m thick in the Missiaga valley and 300 m thick in the Bordina one. Moreover, the intense Alpine tectonic activity has provided a dense network of discontinuities. The contrast of the shear strength between the formations and the disjunction of the dolomitic mass have originated different typologies of large landslides (millions of cubic meters): the Missiaga valley is characterised by some back-tiltings, whereas the watershed zone between the two valleys is affected by a slump that originated in the terrigenous formations, consequently inducing the translation of a huge dolomitic block along a pre-existing joint. The study concerns this latter movement that, due to its largeness and low velocity, has been analysed using classic methodologies including geological, geomorphologic surveys and photo interpretation. The associated smaller landslides were investigated by more specific methods: geo-mechanical survey of the rock mass at the face behind and geotechnical studies with stability analysis of terrigenous slope.