四國中央部結晶片岩地域の層序と構造

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タイトル別名
  • Stratigraphy and Geological Structure of the Crystaline Schist Region in Central Sikoku
  • シコク チュウオウブ ケッショウヘンガン チイキ ノ ソウ ジョ ト コウゾウ

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The stratigraphical and structural analysis of crystalline schist region must be based on the mapping according to original rock-species from which the crystalline shcists were formed., The identification of original rock-species is sometimes very difficult owing to the metamorphic differentiation under allochemical conditions., The crystalline schists of Central Sikoku belong to the chlorite-zone or the green-schist facies of metamorphism of a regional scale., They can be divided lithologically into the following groups and formations from the lower to the upper (Figs., 2 and 3): 1., Nisiiya Group: The component members are mainly siliceous black-schists, interbedded with several thin beds of green-schists and pinkish or greenish quartz-schists., It is supposed that the group includes some acid igneous rocks as quartz-porphyries, granite-porphyries, granites, quartz-diorites, etc., which are now represented by the pebbles in conglomerate-schists in the Oboke-Formation (This Journal, Vol., 56, No., 658, 1950, pp., 366-367)., The whole thickness of the group exceeds 800m., 2., Yosinogawa Group: 1) The lower sub-group is divided into the lower: Oboke Formation and the upper: Kawaguti Formation., Oboke Formation: The component members are sandstone-schists interbedded with thin beds of black-schists., In the middle and upper parts there are intercalated beds of conglomerate-schists 1-40m., thick., The whole thickness of the formation exceeds 1500m., The lower limit of the formation is concealed beneath the Oboke anticline., Kawaguti Formation: This formation is mainly composed of black-schists of pelitic origin, interbeded with 1-3 beds of green-schists., The whole thickness varies from 500 to 1500m., according to the change in thickness of the intercalated green-schists beds., 2) The middle sub-group is divided into the lower Koboke Formation and the upper Minawa Formation., In the region south of the Simomyo-Tuneyama fault, the Nisiiya Group is overlain by the Koboke Formation., The relation between the two rock series is a distinct clilno-unconformity, called Minamihiura Unconformity., Koboke Formation: The component members are mainly sandston-schists, interbedded with beds of black-schists and green-schists., The whole thickness varies from 200 to 400m., Minawa Formation: The formation comprises two or more beds of green-schists 100-400m., in thickness., The other members are greenish or pinkish quartz-schists (sometimes attaining to 100m., in thickness) and black-schists., The whole thickness of the formation exceeds 800m., 3) The upper sub-group is characterized by the presence of white siliceous rocks, which also characterize the non-metamorphic Palaeozoic formation in the Titibu-Zone., The other members are black-schists, green-schists, sandstone-schists, calcareous schists, and semi-schists corresponding to them., The lower and the middle sub-groups of the Yoshinogawa Group correspond respectively to the Oboke and the Bessi Series by T., Ogawa (1902)., The geological structure of the region is characterized by domes or dome-like anticlines and basins or basin-like synclines in the non-spotted schists zones and by folds of recumbent types in the spotted schists zones.,

収録刊行物

  • 地質学雑誌

    地質学雑誌 57 (668), 177-190, 1951

    一般社団法人 日本地質学会

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