Minero-petrographic caracterization of stone materials used for the Roman Amphitheater of Eporedia (Ivrea, To): a scientific-dissemination proposal in the cultural heritage

Ivrea, the ancient Eporedia founded around 100–101 B.C. by the Romans, is a town where stone has always been the most widely used building material, characterizing the architectural identity of the city. In particular, an ancient Roman amphitheater built in stone materials is still preserved. A minero-petrographic study was carried out to identify the different stone materials and their provenance areas used in the masonry of the amphitheater. The origin of rock samples resulted essentially from local or nearby geological units, except for the Bardiglio marble (from Aosta Valley) recognized and found in the portions located towards the center of the arena. Among the local materials, the most used stones were gabbronorites and diorites of the Ivrea Verbano Mafic Complex, which crops out in the city of Ivrea itself. Other rocks used were granites and meta-granophyres from the Canavese Zone; diorites, gabbronorites and websterites from the Ivrea Verbano mafic Complex; acid granulites from the II Dioritic-Kinzigitic Zone; micaschists from the Eclogitic Micaschist Complex of the Sesia Zone; calcschists from the Piemonte Zone; orthogneiss from Dent Blanche klippen; Bardiglio Marble from the External Piemonte Zone. The walls of the amphitheater therefore represents an open air petrographic collection, representative of the Alpine orogeny. For this reason, a multimedia study of this monument, was carried out with the purpose of creating a GIS-Based geo-archaeological tour to increase the value of the heritage stone outcropping in the territory of Ivrea and the lower Aosta Valley.