Discovering the source of obsidian tools from Neolithic archaeological sites of Catalonia by LA-HR-ICP-MS

Abstract

During the last decades, the use of LA-ICP-MS for the characterization and identification of the source of archaeological samples is being increased due to the limited amount of sample necessary for this technique, and the low visual impact of the ablation crater produced during the geochemical analysis. In this work, we analyzed obsidian samples by LA-HR-ICP-MS from several archaeological sites of Catalonia (Spain) in order to identify the source of this geological material, which was used to manufacture different tools. The sites where they were recovered correspond to the Middle Neolithic (4100-3500 cal BC), and recent studies associated these obsidians with the same source area and time, i.e., with the highest diffusion period of the Sardinian obsidian distribution around the Mediterranean coasts in the beginnings of the 4th millennium cal BC. The LA-HR-ICP-MS analyses were carried out using a NewWave Research UP 193 excimer laser ablation system coupled to an Element XR HR-ICP-MS (Thermo Scientific). A whole of 50 isotopes (major and minor elements), among them Zr, Y, Nb, Ba, Sr, Ce, La and Ti, could give us information about the source of the raw material. NIST 612, CORN-B, CORN-D and 2402 (as internal reference material) were used as reference materials. Obsidian samples of outcrops from Lipari, Palmarola, Sardinia (Monte Arci) and Pantelleria were used to compare their geochemical composition versus the studied archaeological samples. All the studied archaeological obsidian samples show similar composition, and once plotted on the diagram of Y/Zr versus Nb/Zr overlap the composition of the Sardinian obsidian. These results allow us to confirm the known maximum distance reached during the distribution of the Sardinian obsidian (not less than 1200 km).