Chemical Compositions of Obsidian in Japan -An Approach to Archaeological Provenience Studies

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This report presents the research results of the characterization of geological source obsidian in Japan on the basis of the chemical compositions (concentrations of major and trace elements) as a scientific approach to the archaeological studies in the identification of provenience.Instrumental neutron activation analysis (INAA) was used to determine 15 trace elements in 370 samples of obsidian from geological outcrops of 50 localities in Hokkaido, Honshu, Okinawa, and northern Kyushu.The principal constituent elements were determined by the energy dispersive X-ray fluorescence (EDXRF) analysis, which is entirely nondestructive method. Thus, the samples of obsidian from geological sources and artifacts were mounted on the sample stage without any processing.On the basis of the multivariate analyses, (factor analysis, cluster analysis) using concentrations of 12 trace elements as variables 370 samples of geological source obsidian have been classified into the geological outcrops of localities.The concentrations of 12 trace elements measured in obsidian artifacts by INAA can be used as "fingerprint" to match the artifacts to geological sources of obsidian. Thus, the cluster analysis of each of obsidian artifacts from various sites of Prehistoric age (the Preceramic period and the Jomon period) in Japan together with the geological source obsidian of 50 localities was carried out. The sourcing of the obsidian artifacts has been achieved successfully.