Abstract
Fission-track (FT) dating was carried out on zircon crystals from four vitric tuff beds in the Mifune Group, middle Kyushu. FT ages of 93.1±4.4 Ma, 89.8±4.0 Ma for the lower part of the Lower formation, 83.6±3.1 Ma for the lower part of the Upper formation and 82.1±11.1 Ma for the upper part of the Upper formation were obtained. These data suggest that the Mifune Group ranges in age from Late Cenomanian to Early Campanian, though the upper age limit remains uncertain. The age of the vertebrate fauna from the middle part of the Upper formation is assigned to Coniacian to Campanian. This age is younger than previously estimated age obtained from paleontological studies. The Mifune Group is possibly correlated with the Onogawa Group on the basis of the present FT ages.
