Holocene slope dynamics in the area of Corvara in Badia (Dolomites, Italy): chronology and paleoclimatic significance of some landslides

CORSINI A. , MARCHETTI M. & SOLDATI M. , Holocene slope dynamics in the area of Corvara in Badia (Dolomites, Italy): chronology and paleoclimatic significance of some landslides. (IT ISSN 0391-9838, 2001). The area of Corvara in Badia, located in the Dolomites (NE Italy), is characterised by mountain groups over 3000 m high (Sella and PuezGardenaccia) which are connected to valleys located at about 1500 m in altitude by means of steep slopes. Besides the lithological, neotectonic and climatic characteristics of the area, the high relief energy has favoured intense gravitational slope modelling throughout the Holocene. The study, which aimed at the reconstruction of the geomorphological evolution of the slopes surrounding the village of Corvara in Badia, has implied the geomorphological, stratigraphic and chronological analysis of landslide processes, in particular of those affecting the Col Alto-Pralongià slope, situated uphill of the village. The research has also investigated lacustrine deposits found in the surroundings of Corvara in Badia and downstream of the village, which are due to events of valley damming linked to a landslide detached form the Puez-Gardenaccia group (Col Maladat landslide). In particular, the analysis has made use of stratigraphic data obtained from boreholes, and of chronological data derived from radiocarbon dating of wood and peat remnants collected from the cores and from excavations carried out close to the surface. The study has pinpointed that the triggering of the large complex landslides affecting the Col Alto-Pralongià slope (Col Alto landslide, Arlara landslide and Corvara landslide) occurred in the early Holocene and that subsequent phases of intense slope movements took place on the same slope during the Subboreal-Subatlantic. The 14C data gathered from landslides affecting the Col Alto-Pralongià slope have also permitted the various areas progressively involved in the movements to be identified and the chronology of deposits making up actual landslide accumulations to be reconstructed. Finally, it was also proved that the plain of Corvara in Badia was affected by lacustrine deposition during the Preboreal-Atlantic and again, but to a lesser extent, during the Subboreal-Subatlantic. The evidence of a significant temporal correlation between the development of mass movements on the Col Alto-Pralongià slope and the evolution of the Col Maladat landslide was therefore proved. Even if the landslides investigated are clearly influenced by geological factors, a cause-effect relationship seems to exist between the phases of slope dynamics outlined by the research and the climatic and environmental changes which have characterised the Holocene. The age of trigger of the landslides investigated corresponds to the early Holocene, a period that many Authors consider to be characterised by a rapid increase of temperature (followed by permafrost melting) and of precipitation. In the study area, this climate change caused in-depth infiltration and percolation of water, also favoured by the geological nature of the bedrock. A subsequent phase of slope instability, witnessed by the dating of several landslide events, corresponds to the climatic deterioration of the Subboreal early Subatlantic periods, which has probably caused a large amount of meteoric water to be available on slopes.