Accretionary complexes (AC) form at convergent plate margins by the subduction of oceanic plate underneath the continental plate (Fig. 2b.1). The oceanic plate is created at the mid-oceanic ridge, and moves to the trench while accumulating pelagic sediments. After arriving at the trench, where the pelagic sediments are covered by continent-derived clastic materials, the plate is subducted and part of the sediments accrete to the continental plate, producing fault stacking and several types of mèlanges (Fig. 2b.1). The characteristic AC succession re?ects the ocean plate stratigraphy (OPS) (Matsuda & Isozaki 1991) starting with basaltic basement covered by radiolarian ribbon chert, then siliceous mudstone and ?nally coarse clastic rocks.