Eruption ages of younger-stage lava flows and olderstage pyroclastic cones on the northeastern foot of Fuji Volcano, Japan.

Abstract

Columnar sections of several trenching sites and outcrops on the northeastern foot of Fuji Volcano were prepared with the results of the identification of widespread tephras and radiometric carbon dating. The results are as follows: Older-stage pyroclastic cones (Shin-Fuji) at the Oshino village (Kousu, Usukubo-bashi and Ousu) erupted during 12,000 and 9,000 years ago in ascending order. They are the farthest lateral eruption sites on the northeastern side of the summit crater. Several younger lava flows (Shin-Fuji) were reliably dated. The scoria fall just below the Nakanochaya lava is dated as 1,430±40 yBP. The Gannoana-marubi lava is dated as 1,520±40 yBP and 1,590±60 yBP, and the scoria fall just below the lava is dated as 1,590±40 yBP. The results showed that the above products were effused in a series of eruptions. The Tsuchi-marubi lava is dated as 2,220±40 yBP. The scoria fall just below the Hinoki-marubi-2 and Taka-marubi lava is dated as 1,260±40 yBP. These ages of scoria fall and the proceeding lava effusion support the correlation to the eruption event that occurred in A.D. 800-802 and is recorded in old documents.