Mining landscape and mines. integrating digital aerial photogrammetry and geophysical prospecting in Gargano area (Italy)

The aim of this paper is to illustrate the results of a national research project devoted to studying both features of a prehistoric fl int mining landscape and underground mines not visible, or partially visible, on the surface. The geographical context of the project is the promontory of Gargano (south-eastern Italy), where an extraordinary abundance of fl int is associated with evidence of numerous extraction complexes (underground mines). According to the available data, the mines cover a time-span of almost three thousand years; the most important of them is the Defensola A mine, the oldest in Europe and active from roughly 5800 BC onwards. Unlike other European prehistoric mining complexes, mine entrances in Gargano are generally located on convex slopes, and have often produced extremely large cone-shaped spoil heaps outside. This suggested a method of investigation based on digital aerial photogrammetry. A DGPS survey was executed to measure ground control points, to be used for the external orientation of the photographs, as well as to obtain precise positions of the main known mines. Thanks to the stereo-interpretation it was possible to recognize key geological beds, such as limestone rich in fl int, and possible ancient entrances to mines. Sometimes anthropogenic covers (dumps and alluvial fans) near the mines were also recognized and interpreted as evidence of quarrying activity. A second level of investigation used geophysical surveys. These can determine the internal layout of each mining structure of which only the entrance is known. Moreover, geophysical prospection allowed us to verify the presence of new mining structures in cases where one or a few vertical shafts are present, which generally indicates the presence of larger mining complexes. The archaeological features of the area suggested to perform additional surveys using other geophysical methods: resistivity and ground penetrating radar. This multi-method approach allowed us to check the data from several independent measurements and to increase the amount of geometrical and physical information that can be used for the interpretation.