Abstract
Analysis of attitudes of slaty cleavage in the Mesozoic accretionary complex of the Mino-Tanba Belt in the Nosaka Mountains, north of Lake Biwa, Southwest Japan, has identified N-S trending mappable-scale chevron folds with subvertically-plunging axes. These folds were formed by horizontal buckling by cleavage-parallel compression after the formation of the regional steeply-dipping cleavages. The geometry of these folds indicates a E-W trending principal horizontal shortening of up to 25 percent or more over a distance of 6 km. They were probably formed under the same tectonic situation which formed the outcrop- and handspecimen-scale chevron folds and kinkbands with moderately- to vertically-plunging axes. This deformation mode with subvertically plunging rotation axes is believed to be one of fundamental processes in a shallow and brittle tectonic level of continental margin and/or island arc crusts which exhibit pre-existing steep planar fabrics.
