飛騨ナップの形成と中生層のテクトニクス : 飛騨地域の構造発達史

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The Southwest Japan arc consists almost exclusively of a pile of accretionary complexes showing the southward younging polarity from late Paleozoicto middle Cenozoic. The accreation ary complexes are of the Cordillera type orogeny. In the eastern portion of the Southwest Japan arc, there occurs the Hida complex, an eastern end of the collision zone between the Sino-Korean and the Yangtze cratons of the early Triassic age. These orogenic belts were formed separately before Triassic, but tectonically juxtaposed to each other with the resultant formation of the Hida nappe at the late Jurassic. The Hida nappe predated the formation of the Tetori Group at late Jurassic, because the Itoshiro Subgroup of the Tetori Group and its equivalent covered both the Hida complex and the Hida marginal belt. Paleomagnetic study and flora indicate that the early Jurassic Kuruma Group on the Hida marginal belt has a paleolatitude of the equatorial area. The change of the paleolatitude indicates that the Yangtze craton along with the accretionary complexes moved northward at the middle Jurassic time. The Hida nappe was formed by the continued subduction of the eastern wing of the Yangtze craton beneath the Sino-Korean craton. This was probably because the eastern wing consists of an oceanic crust and it occurred near the triple junction with the oceanic Farallon plate, by that it suffered little physical constraint to move. The continued underthrusting of the Yangtze craton brought the uprift and erosion of the Hida complex, the Hida marginal belt and the Kuruma Group, and thereby provided vast amounts of terrigenous sediments into a nearby trench, where the Jurassic accretionary complex, the Mino belt, began to form. After the cessation of the collision with the resultant formation of the Hida nappe, the Itoshiro Subgroup of the Tetori Group covered both the Collision- and Cordillera-type orogenic belts near the triple junction.
1993-04-30

飛騨ナップの形成と中生層のテクトニクス : 飛騨地域の構造発達史

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