The geochemistry of the major sources of archaeological obsidian on hokkaido island (Japan): Shirataki and oketo

摘要

The geochemical compositions for obsidian from two of the most important sources on the Japanese island of Hokkaido, Shirataki and Oketo, are presented. This work represents the first systematic study of obsidian geochemistry on Hokkaido from the view of modern methodological standards. The study was performed with the help of neutron activation analysis to determine the concentrations for 28 elements. The results obtained allow us to subdivide both sources into two geochemical groups (Shirataki-A and -B; and Oketo-A and -B), with each representing an individual sub-source. Obsidian from both Shirataki and Oketo sources is identified at archaeological sites located on Hokkaido, on the neighbouring Sakhalin Island and Kurile Islands, and in the lower course of the Amur River basin. The distance of obsidian transport during the Upper Palaeolithic was up to ～250km, and in the following Neolithic and Palaeometal periods up to ～1200km. This testifies to the wide distribution of Hokkaido obsidian to archaeological complexes in North-East Asia and its active transport/exchange in prehistory. The data presented here should be used as a reference for the obsidian geochemistry of Shirataki and Oketo sources from now on.