Human activity patterns at the Horokazawa Toma Upper Paleolithic stone tool manufacturing site in the Shirataki obsidian source area: Combining excavation with experimentation

Abstract

The Horokazawa site locality Toma (HT) is an Upper Paleolithic archeological site situated on a hillside near the Shirataki Akaishiyama obsidian source area, the largest in Japan. Excavations at HT over a period of more than 20 years have produced more than 570,000 artifacts from an area of less than 100 m2. The Horokazawa Toma lithic assemblage was characterized by the Yubetsu technique, which was used to manufacture microblades in Siberia, the Far East, and North America. The assemblage at HT has been dated to the period just after the last glacial maximum, around 15,000 years ago, and when the microblade industry was flourishing in Eastern Asia. As flakes and chips account for 98% of the lithic artifacts, the site was evidently a lithic workshop. In this study, along with examination of excavated materials we identified the source of excavated materials by macroscopic observation and nondestructive analyses, and we experimentally replicated the manufacturing technique to analyze the activities carried at this workshop and infer the distribution network of raw materials and worked stone, beginning with the acquisition of the obsidian.The obsidian came from the East Atelier and Ajisainotaki (especially) sources near the summit of Mt. Akaishiyama. Large angular and slab-like nodules from these sources were likely collected at Hidarinosawa being closer to HT, brought to HT, and processed into large bifaces and boat-shaped blanks for microblade manufacture. Many of these products were exported to other sites. We showed by experiment that the first and second spalls efficiently removed from a large biface by the block-on-block technique. A similar microblade industry based on Shirataki obsidian is found at sites in the Yubetsu River drainage, below HT, and other sites in Hokkaido. In fact, Shirataki obsidian is found at remote sites such as Akatsuki site (eastern part of Hokkaido) and Sokol site (on Sakhalin island), suggesting that raw materials were exchanged between groups of people over long distances. This large distribution network was supported by mass production of blanks for microblade manufacturing at the Toma locality of the Horokazawa site.