Black limestones used in antiquity: the petrographic, isotopic and EPR database for provenance determination

We compiled a database of some of the most important black limestone quarries used in Roman times to be able to determine the provenance of ancient artifacts. For this purpose, we adopted a multimethod approach using the techniques commonly applied to study the provenance of white marbles: petrographic observations, carbon and oxygen isotope composition, electron paramagnetic resonance (EPR) spectra characteristics. Few black limestones were quarried and traded in ancient times; indeed, the importance of most of these quarries was restricted to the areas in which they were located. In this work, we selected a limited number of quarries that produced material believed to have been exported and used throughout the Mediterranean area; most of the quarries selected are found in northern Tunisia, i.e. the Roman proconsular Africa: Djebel Oust, Djebel Azeiz, Ain al Ksir and (presumably) Thala. The “Nero Chiota” limestone quarried on the Aegean island of Chios (Greece) was also included in the database.The petrographic and physicochemical parameters used to distinguish between the different provenances of the black limestones we selected proved to be very effective. The isotope and EPR numerical data processed by means of discriminant analysis proved to be almost decisive in determining the provenance of unknown artifacts. However, the combination of these parameters with the petrographic data definitely provides a more organic characterization.