A Study of the Correlation between and Chronology of Sites of human Habitation and Volcanic Ejecta in the Izu Islands

点击翻译按钮获取中文摘要

Buried under the volcanic ejecta of the Izu Islands there have been discovered a great many sites and relics dating from the Jomon period and later. A study of the tephrochronology of the Izu Islands was undertaken by investigating the correlation between and chronology of these remains and the ejecta. The results may be summarized as follows.1)Following an examination of widespread tephra in the Izu Islands. the stratigraphic relationship between the ejecta and Kikai-Akahoya Volcanic ash(K-Ah) on Hachijo-Jima, Miyake-jima, et.al. was clarified, and Aira-Tanzawa volcanic ash (AT) was discovered at the Hachijo-jima.2)On the basis of its stratigraphic relationship with the sites and relies discovered in ejecta on the Izu Islands. it was ascertained that Kikai-Akahoya volcanic ash represents a maker bed for the late Initial Jomon period.3)Following an examination of the history of the formation of Higashi-yama on the basis of tephra stratigraphy, widespread tephra, earthenware types and radiocarbon dating, it was established that the caldera was formed at a time extremely close to the ejection of Aira-Tanzawa volcanic ash 21,000 to 22,000 years ago.4)The rhyolite and daite volcanic ash thought to originate from Kozu-shima. Ni-Jima, Bayonnaise Rocks will in the future serve as an important marker bed in Izu Island. Tephra fall from the Izu Islands was discovered in the Izu Peninsula and in the Boso peninsula. This should prove to be of considerable assistance in studies on tephrochronology of these regions.