Investigating the provenance of Italian archaeological obsidian tools based on their magnetic properties

Reconstructing the distribution of ancient obsidian tools is one of the few ways to trace ancient trade routes during the Neolithic. The use of magnetic properties for obsidian provenance studies has already been applied as a useful inexpensive and non-destructive tool. It is mainly based on the variation of the type, concentration and grain size of the magnetic particles within the vitreous matrix coming from different sources. In this study, we present the results of a rock magnetic investigation carried out on archaeological obsidian tools collected from six Neolithic sites situated in Northern Italy (Castello d’Annone, Brignano Frascata, Cascina Chiappona, Casalnoceto, Garbagna and Parma). A total of 57 archaeological samples were analysed by measuring several magnetic parameters such as low-field and anhysteretic susceptibility, saturation isothermal remanent magnetization at room and liquid nitrogen temperature, remanence and saturation magnetization from hysteresis cycles and anisotropy of low-field susceptibility. The obtained results were compared with the magnetic properties of geological samples from five Mediterranean islands (Lipari, Sardinia, Palmarola, Pantelleria and Melos). Cluster analysis was applied to the whole set of parameters, allowing the correlation of the pertinent group of artefacts and geological obsidians. Such analysis shows that most of the studied archaeological tools come from Lipari, with few exceptions consisting of samples coming from Pantelleria and Sardinia. Our results are in good agreement with other studies based on chemical analyses that also show that Lipari is the most common Neolithic obsidian source in Northern Italy, despite its longer distance in respect to other obsidian sources.