Paleomagnetic direction and fission-track age of the Fugenji volcanic ash at the Takatsuka trail in Joyo city, Kyoto prefecture

摘要

We made paleomagnetic study and fission-track dating of a volcanic ash layer at the Takatsuka Trail in Joyo City, Kyoto Prefecture, which resembles the Fugenji Volcanic Ash of the Osaka Group in lithological features. This correlation is confirmed by analyses of mineral composition and refractive index of glass shards. Fission-track data of 30 zircon crystals are determined by using external detector method with ζ- calibration, yielding an average age of 1.80±0.24 Ma (1σ). Alternating-field demagnetization experiments reveal that this ash layer has stable remanent magnetization of reversed polarity, which is consistent with the Fugenji and its correlative ash layers.