Correlation and Tephrochronology of the Middle Pleistocene Tephra Beds around the East Foot of Yatsugatake Volcano and Kanto Plain, Central Japan

Abstract

Tephrostratigraphic study and petrographical description were carried out on the Middle Pleistocene tephra beds which were spread around the east foot of Yatsugatake volcano and in the Kanto Plain, central Japan. The stratigraphic positions and petrographic properties of three vitreous or pumiceous tephra beds (Kt-1, 2 Py. ki-Pm., B₀) intercalated in the Hirose Loam Formation, which are pyroclastic sequences around the eastern foot of the Yatsugatake volcano, are in good agreement with those of three tephra beds (Yb 1, Yb 0.5, J 4) intercalated in the Jizodo and the Yabu Formations, which are exposed marine deposits exposed in the northern part of the Boso Peninsula. In descending order, the results are as follows:
These results suggest that the J 4 (B₀) tephra bed erupted at the beginning of stage 11.3 (of δ¹⁸O stages), the Yb 1 (Kt-1) tephra bed at the end of stage 9.1, and the APm tephra beds group between stages 11.2 and 11.0.