Integrated geophysical methods applied to some archaeological sites of North Sardinia

This study deals with the employment of a multimethod geophysical survey, electrical (Electrical Resistivity Tomography) and electromagnetical (Ground Penetrating Radar) carried out on two archaeological sites near shore archaeological sites. For this purpose the settlements of Sant'Imbenia (Alghero, SS) and Santa Filitica (Sorso, SS), two Roman villas located in northern Sardinia were considered. The focus of the paper is to assess as the geophysical response of different instruments might be impacted by different moisture conditions and archaeological contexts. The electromagnetic surveys were conducted in reflection mode, using a monostatic GPR, working simultaneously by two transmitters (frequency of 200 and 600 MHz) and two receivers, while the electrical surveying was conducted with a Terrameter SAS 1000 device combined with ES 10-64 electrode selector. The 2D and 3D high-resolution models revealed a distribution of shallow anomalies that indicate the presence of buried structures (walls and filled cavities) in the surveyed areas. A comparison of the results was made, checking the relative merits and demerits of the different techniques in the two coastal archaeological sites. The integration of geophysical methods has provided useful information to design a more efficient plan for further archaeological excavations

Prospecting for clay minerals within volcanic successions: application of electrical resistivity tomography to characterise bentonite deposits in northern Sardinia (Italy)

Electrical resistivity tomography (ERT) is applied to prospect for and characterise a bentonitic clay deposit in northern Sardinia. Sardinian bentonites derived from the hydrothermal alteration of thick successions of pyroclastic flows and epiclastites are associated with the Oligo-Miocene calc-alkaline volcanic cycle. The alteration of these rocks is generally controlled by faults that control the local circulation of hydrothermal fluids. Two-dimensional ERT investigations were performed close to a faulted area to define the location, thickness and lateral continuity of the clayey body, and determine how it relates to faulting and stratigraphy. A linebased three-dimensional ERT data acquisition was carried out in a selected area to estimate the available clay reserves. The reliability of these resistivity models was assessed by comparison with local borehole data. Finally, the interpretation of the ERT results was optimised through synthetic modelling of the electrical resistivity imaging technique. The results define the extent and geometry of the bentonitic deposit with good accuracy and outline the scenarios where the ERTmethodmay provide optimal resultswhen prospecting for clay deposits