Hydrogeology of the city of Rome

The hydrogeologic framework of the area around Rome is chharacterized by a Pliocene-Lower Pleistocene marine calystone bedrock, which is the amjor regional aquiclude underlying the shallow shallow hydrogeologic units; the claystone bedrock is hundreds of meters thick and has a very lowpermeability. The nearly impermeable bedrock is overlain by Lower to Middle Pleistocene marine to continental sediments which are in turn overlain by and partly interfingered with Middle to Upper Pleistocene volcanic deposits from the Sabatini volcanic complex to the north and the Colli Albani volcanic complex to the south. Holocene alluvial sediments cap the stratigraphic sequence along the present day river system. All rock sequences overlying the claystone bedrock are aquifers, the geometry and circulation of which are controlled by both the evolution with time of the paleotopographic setting and the vertical and lateral variations of lithologies, each with different permeabilities. Other locally important hydrogeologic units, only present in the urbanized areas, are the backfilled deposits accumulated during 3000 yr of human civilization in the Roman area