Geophysical and Archaeological Characterization of a Modest Roman Villa: Methodological Considerations about Progressive Feedback Analyses in Sites with Low Geophysical Contrast

The low contrast in physical properties of archaeological elements compared to the host soil is a common drawback in geophysical surveys applied to subtle archaeological sites because those contrasts are usually what are being measured by most instruments. Furthermore, when archaeological elements and construction remains are placed within the same package of materials, differentiation of each can make the interpretation of geophysical data sometimes difficult. In this work we propose a dynamic, integrated approach for the characterization of an archaeological site with simple Roman construction materials in order to evaluate methodological considerations in the evaluation of this kind of sites. This approach includes: (i) a preliminary evaluation of construction material characteristics, according to the background provided by the historical and geographical context and from previous excavations, (ii) measurements of magnetic susceptibility of archaeological and natural materials in the site for direct modelling of the expected anomalies; (iii) a geophysical survey including magnetometry, multifrequency electromagnetic (EM) method and ground penetrating radar (GPR) (100, 250 and 500¿MHz centre frequency antennas); (iv) geophysical data evaluation for planning subsequent systematic surveys; (v) dynamic interpretation of geophysical results through careful data evaluation of all previous steps. The final archaeological model from geophysical data has been successful due to the manner of data interpretation looking for orthogonal patterns of geophysical anomalies that were hypothesized to be subsurface walls. Modelling was then followed by archaeological excavations consisting of three trenches where the walls were exposed. The integration of geophysical data with excavations has permitted to evaluate significance of the different geophysical analysis and to identify their archaeological meaning. The proposed sequential methodology represents an innovative manner of analysis (i) in subtle sites where construction remains are scarce and the absence of well-defined geophysical contrasts can limit the results of usual surveys and (ii) to increase the efficiency in the evaluation of more extensive survey area