富山県南西部に分布する月長石流紋岩の噴出時代について
1970 年 63 巻 1 号 p. 22-27
詳細
1970 年 63 巻 1 号 p. 22-27
The welded pyroclastic deposit of moonstone rhyolite exposed in southwest Toyama Pref. has been considered to be the uppermost member of Futomiyama formation being covered by the basal conglomerate, Nirehara formation, of Neogene formations unconformably. The result of geological study by the writers shows, however, that the rhyolite is embeded in Nirehara formation representing a product of the earliest Neogene volcanism prior to the eruption of a large amount of andesite in the following Iwaine stage. The result is consistent with that of K-Ar dating which gives the mineral age of the moonstone as 24-25 m. y.
