Stratigraphic reconstruction of the Lanzo Fan right sector applied to the groundwater research.

An important erosional discontinuity is recognized in the Villafranchian succession, in which the main groundwater extraction of the area is concentred; this discontinuity, non reported in the previous geologic works, allows us to distinguish two sedimentary complexes. The Lower Complex (middle Pliocene) is formed by strongly consolidated, deformed and fossil bearing silt, with subordinate gravel bodies. The Upper Complex (lower Pleistocene?) consists of prevalently small coarse gravel, with subordinate sand-silty bodies, both non containing fossil. At the top, the fluvial sediments are also distinct in five allostratigraphic units (middle-upper Pleistocene), forming five terraced surfaces: on these sediments a loess aeolian cover is developed (upper Pleistocene), that gathers the infiltration water subsequently carried to the surficial aquifer.