Stratigraphic Revision of the Subsoil of the Southern Turin Plain for Hydrogeologic Purposes

The paper describes the geologic and hydrogeologic framework of the subsoil of the South Turin Plain (Northwestern Italy). The analysis of borehole logs allows the construction of detailed lithostratigraphical cross sections oriented E-W and N-S; their interpretation led to the recognition of a succession of sedimentary bodies, indicated as term 1, 2, 3, 4 and 5 from the older (Lower Pliocene) to the younger (Holocene). Taking into account the literature data, their recognition has been made on the base of: stratigraphic position, texture, occurrence and distribution of fossils, compaction and color indexes. Each term is confined by erosion surfaces marked by sharp changes in lithology and occurrence of palaeosoils. From the stratigraphic reconstruction the base of the shallow unconfined aquifer has been singled out; such base is represented by the occurrence of fine-grained deposits adequately thick and continuous to provide the confinement of the underlying aquifers.