Hydrogeology of the sasso Lungo group,a dolomitic reef stock in the alpine dolomites of North Italy

The Sasso Lungo group forms an isolated mountain mass in the Italian Dolomites in the SE Alps. The group has an area of ± 9 km² and its elevation ranges from ± 2000–3000 m. The central part consists of an exhumed, dolomitized reef of Triassic age, which has subsided by gravity tectonics partly into the surrounding and underlying plastic Permian and Triassic formations. The hydrogeological characteristics of the formations are discussed. The central reef mass forms the main aquifer, and it is embedded in impervious formations. The discharge of the snowmelt water and rain takes mainly place through a few large springs around the group at some distance from the reef. The springs are hydraulically connected with low subterranean overflow points in the impervious rim of the reef through natural conduits of permeable moraines and Quaternary valley fills. The central lolomite aquifwe shows no signs of karst drainage. The water moves through a dense network of fractures and joints and it has probably a free, fluctuating water table, subdivided by groundwater divides which coincide in most cases with surface drainage divides. All springs and surface waters were mapped and sampled during the summer and fall periods from 1966 through 1968. The chemical composition of the spring waters was very useful in tracing the origin of the spring waters.