富山県太美山山地の地質(概報)
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概要
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Geologic succession of the area is shown. In the area, two large igneous activities are remarkable. One is the Late Cretaceous to Paleogene acid volcano-plutonic activity. Another one is the Middle Miocene intermediate volcanic activity, so called "Green Tuff". Former one is probably subdivided into two stages. Volcanic product of first stage is the Nohi Rhyolite, over 950 m in thickness, and it consist mainly of rhyolite tuff, rhyolite welded tuff and andesitic rock. The Nohi Rhyolite is intruded by the Shirakawa Granites. Volcanic product of second stage is the Futomiyama Group, about 1,000 m, it consist of rhyolite tuff and rhyolite lava flow. The Futomiyama Group probably overlie the Nohi Rhyolite and the Shirakawa Granites with unconformity. The Usunaka Moonstone Rhyolite, a small rhyolite welded tuff sheet of the Early Miocene age, and the Tori Conglomerate Formation over lie the Futomiyama Group with remarkable unconformity, and are overalin by the "Green Tuff" with unconformity. Therefore these two are not members of neither the Futomiyama Group nor the "Green Tuff". The Usunaka Moonstone Rhyolite and the Tori Conglomerate Formation are the product of the different activity.
- 1979-09-20