The geology of the Tsugaru district and the raw materials used to make Jomon pots

Abstract

The chemical composition of glass shards and clay minerals contained in Jomon pots excavated in Aomori Prefecture, northeastern Japan, was analyzed by means of an electron probe micro-analyzer (EPMA). The analysis value of glass shards of these pots indicates that these shards were derived from the Kanagi Tuff of late Miocene, the Obirakiyama Tuff of Pliocene, the Toya Tephra and the Towada-Hachinohe Tephra of late Pleistocene. These pots are generally composed of glass shards from a single tephra. This means that these glass shards were collected from an original tephra bed. Jomon pots con-taining glass shards from the Obirakiyama Tuff are found in the Shimokita district, the northern-most part of Aomori Prefecture, although the Obirakiyama Tuff is not distributed in that area. Therefore, it can be assumed that the pots were manufactured in the Tsugaru district and then transported to the Shimokita district. Clay minerals of the matrix of all these pots consist of kaolinite or halloysite or kaolinite/smectite interstratified mineral. Reflecting the geological background of the producing area of each item of pottery, small amounts of clay minerals such as illite, chlorite, illite/smectite interstratified minerals and corrensite coexist with the kaolin minerals.