赤石山地の四万十帯,とくに赤石中軸帯 : 赤石山地北部の地質(その3)

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The undivided Mesozoic Group of the Shimanto belt of the northern Akaishi mountainlands is composed mainly of pelitic and psammitic rocks accompanied by a little chert, limestone, and basic volcanics including pillow lava. Deformation of these sediments is complete and the rocks are characterized generally by phyllitic texture and various folds. Major structure of the Shimanto belt of this district is characterized by the isoclinal folds of which the axial planes are steeply inclined to east or west as shown in Figs. 1 and 2. The axes of the major anticlinorium lie along the highest range of the northern Akaishi mountains, lying 5〜8 km eastward from the Butsuzo Line. Distribution of basic volcanics, limestone, and red chert is conspicuous along the axial part of the anticlinorium, because these rocks are associated mostly with the oldest formations (may be Lower Cretaceous) in this region. In the western wing of the major anticlinorium, most beds are overturned and psammitics ediments are predominant. On the other hand, most beds are in the normal order and pelitic sediments are predominant in the eastern wing. In the axial part of the anticlinorium, deformation of sediments is striking and various transposition structure are observed. Through mesoscopic structural analyses, at least two main stages of deformation can be recognized in this district. Recrystallization of basic rocks is also marked in this zone. There are some low grade crystalline schists in which chlorite, pumpellyite, stilpnomelane, epidote, carbonate, and sericite are formed, but zeolite, prehnite, and glaucophane are not found. So, the grade of metamorphismis corresponded to the pumpellyite-actinolite schist facies (HASHIMOTO, 1966). Furthermore, there occurs post-kinematic granitic intrusives in the northern extension of this zone.
日本地質学会の論文
1969-01-31

赤石山地の四万十帯,とくに赤石中軸帯 : 赤石山地北部の地質(その3)

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