Magnetic and geoelectrical measurements on the eastern hill of the archaeological site of Selinunte

Geophysical research into the archaeological site of Selinunte involved magnetic and geoelectrical investigations, which were based on knowledge of the characteristics of coeval settlements found at other archaeological sites. Detailed surveys were carried out in two areas suggested by the archaeologists. The main goal of these investigations was to test the reliability of the methods and to find the magnetic and geoelectric response of the shallowest materials in the eastern hill of Selinunte. The magnetic gradient maps show the signals from buried magnetic sources, which cannot generally be identified; however, a correlation can be established between the natural local background disturbed only in some spots, with weak and variable intensity, which correspond to the surficial features of the agricultural terrain. The very low values of the measured magnetic susceptibility do not reveal any significant magnetization of the surficial materials. The resistivity contour maps show a resistivity decrease towards the east, with scattered maxima which do not show any particular pattern. The maps of data collected from electrodes 1, 2 and 3 meters apart show that lithological and structural variations extend downwards. The geoelectrical section highlights three main levels: (a) a first layer, composed of surficial agricultural soil and containing remnants of the underlying bedrock; (b) biocalcarenite composed of cemented and very porous sediments, and (c) argillites underlying the biocalcarenites and occurring at limited depths (4-5 m). From a geoelectrical point of view, the general behaviour of the areas under investigation shows a resistivity decrease with depth. However, in the horizontal direction the situation is extremely variable and suggests the occurrence of more complex structures.