Petrographic and geochemical investigations on the volcanic rocks used in the Punic-Roman archaeological site of Nora (Sardinia, Italy)

Research focus on the geochemical and petrographic characterisation of volcanics used in the Roman city of Nora archaeological site. These rocks, belonging to the Late Eocene–Miocene orogenic magmatic activity occurred in Sardinia between 38 and 15 Ma, were used as construction materials (ashlars, decorative frame, etc.) and as aggregate in the ancient mortars of some important buildings of Nora (e.g. Roman theatre, first century AD). Several samples coming from the Roman theatre (taken as study cases) and other ancient buildings and artifacts of Nora village have been studied and chemically-petrographically analysed. To define their provenance, analytical data of major and trace elements by XRF method have been compared with those of several volcanics coming from the surrounding areas the archaeological site and Sulcis basin in which the Nora territory is included. In order to highlight the geochemical discriminant markers or affinities between the sample populations of volcanics, factorial analysis has been used, taking some significant variables: SiO2, Na2O, K2O, L.o.I, Al2O3, Rb, Ba, Sr. The results of this research allow also define the aspects of stone quarry extraction and construction technologies used in the Roman period.