The Capoterra coastal plain lies on the south-western tip of the Campidano Graben, few kilometers west of Cagliari, the main town of Sardinia (Fig.1). It was originated by the ancient Santa Lucia river delta and is bounded by salt-works and lagoons on the east, the seashore on the south-east and the Paleozoic basement on the west and south-west. The surface geology of the plain is characterized by Pleistocene and Holocene sand and alluvium; the Paleozoic bedrock is mainly constituted by Carboniferous granite and Cambrian-Ordovician schist (Fig.1). Concerning hydrogeology, to date the dominant theory is that two aquifers can be distinguished: a shallow phreatic aquifer and a deeper, multilayer, locally confined aquifer. Due to the large number of incorrectly drilled water-wells, these two aquifers, laterally recharged through the fractured Paleozoic rocks, are now communicating in several areas of the plain; moreover they are affected by saltwater intrusion coming from the sea and the neighbouring salt-works. In the past, several hydrogeological and geophysical surveys were carried out in the Capoterra plain , e.g. Balia et al., 1994; Barrocu et al., 1994; Godio et al., 1999; Montaldo, 1966; Sciabica, 1994; Vernier, 1999. Referring to most recent works, Sciabica (1994) afforded the the mathematical modeling of the aquifer system based on hydrogeological and hydrogeochemical data, while Vernier (1999) conducted a more general synthesis including all available data. However the overall information on the Capoterra plain is still inadequate for a reliable modeling of saltwater intrusion and its evolutionary trend, and very important aspects such as stratigraphy of Pleistocene-Holocene sedimentary cover, relationships between phreatic and confined aquifer and depth to Paleozoic basement must be further elucidated. Hence a new campaign of geophysical surveys including a gravity survey and then some seismic reflection profiles, properly designed on the basis of gravity interpretation, and TDEM soundings has been recently planned.


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