The Shimanto Belt of SW Japan is an accretionary complex which developed between Late Cretaceous and Late Miocene. The deeper levels of this complex are exposed along the Gokase River of eastern Kyushu. Deformation in this region took place as a result of southeasterly directed accretionary thrusting, resulting in the development of folds, fabrics and mélanges. All these structures may be attributed to progressive, top to the SE shearing and the mélanges show many similarities to other rock types in fault or shear zones. It is also possible to apply shear zone models to explain extensional structures developed perpendicular to thrust transport direction. It is suggested that deformation took place during underplating beneath the developing prism.