Petrographic properties of three tephra layers contained in the upper part of the Fukuchiyama Formation distributing along the Yura River, northern Kinki District, western Japan, were determined for the correlation with the previously known widespread tephra layers or the tephras erupted from the Daisen Volcano in the Chugoku District. Grain and heavy mineral compositions, morphology of volcanic glass shards, and refractive indexes of glass shards and orthopyroxene, hornblende and cummingtonite phenocrysts, were analyzed for this purpose. As the results, two of the tephra layers formerly named the Monobe Volcanic Ash Bed, were correlated with the Daisen Okutsu Pumice Bed (DOP) or the hpml Pumice Bed. The other tephra is a secondary deposit that mainly includes volcanic glass shards and orthopyroxene phenocrysts derived from the Aso-1 tephra. It also contains fewer glass shards and orthopyroxene phenocrysts from the Kakuto tephra and tephra layers erupted from the Daisen Volcano, respectively. From the estimated eruption ages of the DOP, hpml and Aso-1 tephra layers, an age of the deposition of the upper part of the Fukuchiyama Formation is considered to be from more less than 270 to around 190 ka.
