An age constraint on the Miocene succession in the Kinbusan area, eastern Tottori Prefecture, Japan: Uranium–lead dating of zircons from an ash-fall tuff

Abstract

We undertook U‒Pb zircon dating to constrain the age of the Miocene succession in the Kinbusan area, eastern Tottori Prefecture, Japan. The succession has been correlated with the upper part of the Iwami Formation in the upper part of the Miocene Tottori Group. Recently, a new stratigraphic interpretation was proposed that correlated the succession with the lowermost part of the formation; however, there is no chronological constraint on the depositional age of the succession in the Kinbusan area. We carried out U‒Pb analysis of zircons from an ash-fall tuff in the succession to determine the age. The analysis yielded a mean age of 17.92±0.20 Ma (2σ) from the youngest age cluster. The occurrence of the tuff, the similar optical characteristics of the dated zircons, and the consistent ages indicate the mean age represents the depositional age of the tuff. The result supports the recent stratigraphic interpretation that the Miocene succession in the Kinbusan area is correlated with the lowermost part of the Iwami Formation.