北アルプス北ノ俣岳附近の手取層群

抄録

In the western district of the Northern Alps of Japan, the Tetori groups are scattered, each in rather small area on the high mountains, such as Yakushi-dake, Kitanomata-dake, Kurobegoro-dake and others. In this paper the writer treats especially the group in the Kitanomata-dake area. The area is covered mainly by the Oritate-toge conglomerate, which is the basal one of the Itoshiro subgroup occupying the middle division of the Tetori group and is composed of the rounded pebbles of granite, gneiss, quartz-porphyry, cherty rocks, sandstone, hornfels and so on. The conglomerate along the upper drainage of the Kitanomata River, forming a monoclinic structure, is a southeastern part of the large basin structure situating in the southern district of Toyama Prefecture. On the eastern margin of this basin, the conglomerate unconformably overlies the basement of the Shimonomoto-type granitic rocks which intruded in late Palaeozoic, whereas on the southeastern margin is normal fault contact with the plutonic rocks of the same type. In the valley of the Kitanomata River the fossil plants are found, such as Cladophlbis exiliformis (Geyler), Onychiopsis elongata (Geyler), Podozarnites lanceolatus (Lindley and Hutton) and Xenoxylon latiporosum (Gramen), the discovery of the last of which is significant of its extensive distribution on the Tetori group.