美濃帯上麻生地域の大規模褶曲の形態と成因

概要

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The Mino Terrane in central Japan is the Jurassic typical subduction complex. The complex has been folded to form large-scale synclines and anticlines trending E-W and plunging west. Small-scale folds are commonly found in the cherts which are widely exposed in the Mino Terrane. The chert folds are considered to have been formed under the uniform stress field in subduction/accretion in Jurassic time. The regular orientation of the axes of the chert folds can be regarded as an index for analysis of the three-dimensional form of the large-scale synclines and anticlines. Judging from the change of the orientation of the axes of the chert folds, the Shimonoho syncline and the Nakanoho anticline in the Kamiaso area show asymmetrical half-basin and half-dome structures. The asymmetry of the syncline and anticline indicates that they have been formed under the remarkable sinistral simple shear. The large-scale folds are widespread over the pre-Cretaceous terranes in the Southwest Japan. The age of the formation of the large-scale folds are restricted between late Early and early Late Cretaceous time. The formation of the large-scale folds in Cretaceous time is interpreted as a result of the sinistral displacement that dominated the eastern margin of the Eurasian continent.
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