Characterization of obsidian samples from Monte Arci (Sardinia, Italy): implications for provenance investigations on obsidian artifacts

Obsidian is a volcanic glass which can be handcrafted and chipped to be used as tool. Obsidian artifacts have been utilized since prehistoric times and their diffusion spread over large areas starting from the sites where obsidian flows are located. The provenance identification of the raw material is considered significant to track the pathways of obsidian trading in those times. One of the sites where obsidian flows are located in the Mediterranean basin is at the volcanic complex of Monte Arci in Sardinia (Italy). Artifacts made by Monte Arci obsidian were found in neolithic settlements in Sardinia, northern Italy and south France. Recent investigations have shown that at least three obsidian flows can be identified in the Monte Arci area. It was considered worthwhile to characterize these sources by their minor and trace element content and eventually to find discriminating parameters useful to provenance the prime matter of obsidian artifacts and to identify the obsidian flow exploited. In the present work obsidian samples from the three Monte Arci flows (SA, SB and SC) were submitted to instrumental neutron activation analysis for the determination of a number of minor and trace elements. In addition some obsidian artifacts from two Early Neolitic settlements in Sardinia, namely Su Paris de sa Turre (Santa Caterina di Pittinuri, OR) and Coddu is Abionis (TerraIba, OR), were also investigated. Element contents are presented and discussed for their precision and accuracy. Several approaches were adopted to characterize and discriminate the three Monte Arci obsidian flows: rare-earth element patterns, the quantitative evaluation of the Eu negative anomaly, linear discriminant analysis and cluster analysis. All sources can be fully discriminated and applying the same procedures including the obsidian artifacts data, it is possible to advance a provenance assignment showing the flow from where obsidian had been quarried for artifacts manufacturing