Various folds (bends) with subvertical/vertical rotation axes in the pre-Neogene terranes of Southwest Japan : their significances on the Middle Miocene clockwise-rotation of Southwest Japan
Various folds (bends) with subvertical/vertical axes are widely developed in the pre-Neogene terranes of Southwest Japan. They are variable in shape, conical folds, accordion folds, megakink bands and so on, and some of them are associated with strike-slip faults. Their size ranges from several meters to 10km or more in half-wavelength. Their deformation style indicate that they were produced under a brittle condition in a shallow level of the crust. They are superimposed on the pre-existing structures, and are regarded to have been formed mostly during the Middle Miocene contemporaneously at the time of the clockwise-rotation of Southwest Japan. The presence of them, thus, suggests that the upper crust of island arc is easily deformable around subvertical/vertical rotation axes to form various folds (bends) and locally strike-slip faults during its rotation.
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