フィッショントラック法による黒曜石の噴出年代とウラン濃度の測定(第I報)

石器時代黒曜石製石器の原産地推定に関する基礎的研究

抄録

Obsidian is a volcanic glass which was widely used as an important material for making stone implements and found everywhere in archaeological sites all over Japan. As original sources of obsidian are limited to about twenty localities in number, it might be of use to trace the trading area in prehistoric Japan, if the original sources could be determined with regard to obsidian materials found from these archaeological sites.
The fundamental experiments were carried out for determining original sources of archaeological obsidian materials by means of the age of rock formation and its uranium concentration of the materials. Present paper deals with the results of these experiments together with some results of assays obtained so far on obsidian from several original sources.
Obsidian samples from four outcrops in Wada-pass in Central Honshu gave almost the same ages of formation (0.85×10⁶yr.) in good accordance with the potassium-argon dates of the same samples. Uranium contents of these samples were also almost the same (6.8 ppm py weight). On the other hand, obsidian samples from Mt. Kirigamine near Wada-pass were clearly different from those of Wada-pass in fission track dates (1.30×10⁶yr.) as well as uranium contents (3.2 ppm by weight)