Rotation of slip direction of the Atokura Nappe viewed from microstructural analyses of brittle shear zones in the Sambagawa belt, Southwest Japan

The Atokura Nappe is mainly composed of Late Cretaceous fore-arc sediments (Atokura Formation) and overlies the Mikabu greenstones of the Sambagawa belt in the Kanto region, Southwest Japan. Meso- and microstructures of the foliated cataclastic fault rocks along the base of the nappe (klippes) are described, and slip directions are determined. Movement of the nappe is divided into three stages based on a difference in fault rocks. The-slip direction of the nappe has rotated clockwise from WNW (subparallel to the trend of geologic belts) to N (perpendicular to the trend). Movement of the Atokura Nappe may have changed from a strike-slip to an extensional tectonic setting.