Searching for ancient pits and voids at the Ouels Mine (Castel-Minier, France) by using geophysical methods

Abstract

A map from the early twentieth century shows the relative positions of several entrances to the Ouels mining area, but it is not fully georeferenced. Some mines have been reported in the south-western part of the map and the archaeological team would like to confirm these locations. To this end, a geophysical prospection campaign was organised, which included electrical resistivity tomography (ERT) and microgravimetric profiling over the area of interest. Several anomalies were identified. Two of them, in the north, are very likely to be related to voids (robbed area), since gravimetric and electrical anomalies are superimposed. Conversely, in the southern part, where microgravimetric anomalies occur, there are no electrical anomalies, but cavities could be electrically shielded by the overburden. An additional deeper ERT shows a new but small resistivity anomaly in the upper slope, outside the area preliminarily surveyed. Although not all of the gravimetric anomalies are confirmed by the ERT, the geophysics ultimately proved very effective in supporting at least some archaeological targets in the northern part of the prospect.