The Aveiro coastal area consists mainly of Quaternary sedimentary units composed of alluvium, sand dunes, eolian sands and gravel formations of Pleistocene age, which disconformably overlie older Cretaceous sediments. The upper part of the Cretaceous formations consists of clays and clayey formations, known as Vagos Clays.
The main regional freshwater sources include a shallower unconfined aquifer of Holocene age and a semiconfined aquifer associated with Pleistocene formations of the lower Quaternary.