Geomaterials and GPR Characterisation of the Castellina Fortress (Norcia, Umbria, Italy): Construction and Reconstruction from the 1500s to the Present

An integrated petrographic–geophysical workflow is applied to the Castellina Fortress (16th century AD) to investigate: the masonry texture, construction techniques and lithological provenance. The field activities focused on several architectural structures of the Castellina, including the main façade that was embedded inside the fortress out of a previous building, named Podestà Palace (13th century AD). The petrographic analyses document the use of lithoid limestones from the Maiolica, Scaglia Bianca and Scaglia Rossa Formations (Umbria–Marche Stratigraphic Succession) in the Podestà Palace, while limestone breccias can be mainly found in the cloister columns. The Ground-Penetrating Radar (GPR) data, supported by advanced numerical modelling, show a heterogeneous internal texture in the Castellina Fortress related to the use of both lithoid materials and earthquake-derived debris for the columns. The provenance analysis points out that the limestones were quarried from Monte di Colle, Monte Belvedere and Monte Poggio Vallaccone (southeast of Norcia), whereas the breccias largely derived from debris cones composed of breccia, gravel, and conglomerate deposits that still crop out today in the mountainous area surrounding the plains of Norcia and Santa Scolastica. This study demonstrates the potential of combining two different geoscience disciplines to reconstruct material supply zones and building characteristics in the field of cultural heritage.