Petrographic, petrophysical and engineering geological properties of stone materials employed in the Late Baroque of Val di Noto UNESCO Heritage sites (Sicily, Italy)

Abstract

The “late Baroque towns of the Val di Noto” in south-eastern Sicily, Italy, testify an outstanding post-seismic rebuilding architectonic achievement, after that an earthquake destroyed them in 1693. The reconstructed towns, characterised by “distinctive innovations in town planning and urban building” have been added to the UNESCO World Heritage list since 2022. They exhibit architectural features characterised by a close relationship between local stone, geological context and societal development. Indeed, they are characterized by the employment of two lithotypes, i.e., sedimentary (i.e. Hyblean limestones) and magmatic (i.e. Etnean lavas) rocks, resulting in an original bichromy. Nevertheless, once in the city centres, stone materials are exposed to atmospheric agents (e.g., rain, wind, solar radiation, aggressive atmospheric pollutants, freeze-thaw cycles, crystallization of saline solutions, and growth of organisms) that, over time, may trigger weathering process. In this contribution, we focused on two main lithotypes widely used as building stones and, specifically, we carried out a review on its fabric-related petrophysical properties, in terms of petrography, porosity, seismic and geo-engineering behaviour and observed the deterioration forms developed in the buildings. Our review paper aims to provide a basic tool, useful either for conserving monuments of cultural heritage and for their restoration.