Abstract
Correlation of late Miocene volcanic ash beds in the Uchisugawa and Nomura Formations composed of hemipelagic mudstone in Niigata Prefecture was attempted. Because glass shards in these ash beds are preserved from chemical alteration, their shape and chemical composition by EPMA analyses give useful criteria of tephra identification. Four volcanic ash beds distributed in each formation were well correlated ; namely (1) Kdg (in the Uchisugawa Formation) -Sng (in the Nomura Formation) beds, (2) Gtm-Stm beds, (3) Skhq-Tmhq beds, and (4) Jng-Snsg beds in ascending order.
