Characterization Of Complex Archaeological Sites Using 3D Electrical Resistivity Tomography

Several types of circular burial tombs, built by different populations in different ages, can bediscovered in Europe and have in common only their location inside small hills in the countryside.These mounds have lateral dimensions varying from few meters to tens of meters, and heights around 5-10 meters. Since the standard geophysical mapping measurements used by archaeologists are not wellsuited for such targets under complex topography, a method that allows accurate image reconstructionsin 3D is required.Different kind of mounds have been analyzed in this work: Etruscan (pre-Roman) burial sites,very common in central Italy, and Celtic "Princes Age" (VI century b. C.) tombs in the Western Alps,similar to sites excavated in the ’70s in southern Germany, that provide a good experimental set for thevariety of dimensions and materials used. The wood posts and stone walls surrounded by clay trenchesused in Celtic tombs create strong resistivity contrasts, while weaker anomalies are found over Etruscantombs.The paper describes the development of a specific DC measurements on electrode grids placedover the whole surface of the mounds, that provide realistic 3D pictures meant to guide drilling orexcavation and avoid collaptions. The use of fast multi-channel instruments allows the collection ofmany data points in different array configurations, while data is processed using a 3D FEM modellingand inversion routine that allows to input complex topographic information.