福井県東部，池田町に分布する上部白亜系足羽層の年代-花粉層位学的アプローチ

抄録

A palynostratigraphic study was conducted on the Upper Cretaceous Asuwa Formation cropping out at Ikeda Town, eastern Fukui Prefecture, central Japan, to make a precise determination of its age. An abundant and diverse assemblage of palynomorphs (52 genera and 72 species) was obtained from three horizons of mudstone in the upper member (the Sarao Interbedded Sandstone and Mudstone Member). A common stratigraphic range of index angiosperm pollen belonging to the Triprojectate (5 genera and 8 species) and Oculata (1 genus and 2 species) types indicates a Maastrichtian age for the deposit. This age is concordant with that of the Omodani Rhyolite, which is located ~40 km to the east of Ikeda, and those of later stages of the Nohi Rhyolites. The results provide important constraints on the timing and western expansion of rhyolitic volcanic activity 50 km toward the Sea of Japan in western-central Japan.