Volcanic ash layer near the boundary between late and final Jomon Period from Choda and Matsukawado sites, Aichi Prefecture, Central Japan.

In 1988, a thin volcanic ash layer was found in the peat layer from nine survey areas of the Choda and Matsukawado archaeological sites, Kasugai City, Aichi prefecture.This layer, about 4mm thick, is composed of light reddish brown to pinkish white and fine to medium-grained ash. It consists chiefly of glass (mainly C-type shards with refractive index of 1.499-1.504; mode 1.501-1.502), which small amounts of plagioclase, orthopyroxene (γ=1.703-1.705), amphibole, biotite and clinopyroxene.The 14C age of the peat layer from the horizon immediately beneath the ash layer is 3, 120±120y.B.P.; this ash layer was found above a bed containing late Jomon potsherds and below a bed containing final Jomon potsherds. So it can be said that this volcanic ash fell around the fine of the boundary between the late and final Jomon Period.This is probably the first time in the lowland Kinki and Chubu district that the ash layer of this period has been recognized as a visible stratum.The authors named the ash the “Matsukawado Volcanic Ash Layer” (MT) after the layer was discovered.