Raw materials for ancient ceramic productions from Campania region: provenance studies by means of Sr-Nd isotopes

When archaeometric studies on archaeological ceramics are performed, one of the most important questions asked by archaeologists is the provenance of pottery. This is usually performed by comparing mineropetrographic and chemical composition of ceramics with that of local raw materials (clays, temper), production indicators and appropriate reference groups. Nevertheless, the commonly-used analytical techniques (e.g. OM, SEM-EDS, XRF, ICP-MS) may not always be helpful for the determination of provenance. Indeed, processing of raw materials, such as tempering or levigation, can significantly modify their original chemical composition, sometimes leading to an ineffective identification of raw material resources. For this reason, a pioneering analytical approach has been recently applied by measuring the Sr and Nd isotopic signature. Isotope analysis has largely used in archaeological sciences to date objects and identify their provenance, making it also a useful tool for the determination of provenance of ceramic vessels (De Bonis et al., 2018 and references therein). For this study, 87Sr/86Sr and 143Nd/144Nd isotope ratios were measured on archaeological pottery from Campania and raw materials (clays and volcanic temper) exploited in antiquity for producing ceramics. The analyses were focused on samples from both the Bay of Naples and Southern Campania. The isotope signatures allowed us to better discriminate among different productions and find a strong relationship between the archaeological pottery and the geological sources of raw materials. In order to validate the method, Sr-Nd isotope ratios were also measured for the first time on experimental ceramic materials that replicate archaeological pottery (De Bonis et al., 2018). It was interesting to note that synthetic mixtures used for the ceramic replicas plot exactly on the theoretical mixing curve between the clay and volcanic temper end-members. This suggests that the artificial manipulation of raw materials (firing, levigation, tempering) induces no significant variations to the Sr-Nd isotope fingerprint, which strictly depends on the geochemical affinity of the raw materials. Thus, isotopic analysis can be considered as an effective and robust method that could complement the common multi-analytical approach in order to more precisely constrain potential geological sources for ceramic materials and pottery provenance. De Bonis, A., Arienzo I., D’Antonio, M., Franciosi, L., Germinario, C., Grifa, C., Guarino, V., Langella, A. & Morra, V. (2018): Sr-Nd isotopic fingerprint as a tool for ceramic provenance: application on raw materials, ceramic replicas and ancient pottery. J. Archaeol. Sci., 94, 51-59.