The Roman aqueduct of Nora (Sardinia, Italy): archaeometric characterisation of stone and mortar-based building materials.

This study proposes to investigate the Roman aqueduct of the ancient city of Nora (2nd-3rd c. AD) in Sardinia (Italy) through a multi-analytical characterisation of its building materials, specifically mortars and stones of the main preserved structural portions (e.g. opus caementicium pillar cores, brick arches and specus coatings). Around 50 samples between mortar and stone elements were analysed combining Transmitted Light Optical Microscopy on 30 µm thin sections (TL-OM), Scanning Electron Microscopy coupled with X-Ray Spectroscopy (SEM-EDS) and Quantitative Phase Analysis X-ray Powder Diffraction (QPA-XRPD). Moreover, X-ray fluorescence (XRF) analyses were carried out on non-local volcanic clasts, such as pumices and tuffs, to define their provenance through the comparison with geological data from an in-house UNIPD reference database. The detailed archaeometric investigation of the materials provided further data about the construction techniques of the aqueduct, the provenance of geo-materials and their selective utilization in construction. Based on these data, the re-assessment of the previous construction phasing and chronology of the hydraulic infrastructure has been proposed.