Origin of Late Mesozoic Clastic Sediments in Southwest Japan

Southwest Japan in late Mesozoic times was the site of active continental margins to the northeast of the southern Korean Peninsula, analogous to a modern arc-trench system. Geotectonic features of Southwest Japan evolved from a single arc-trench system in early Cretaceous times to a double arc-trench system in the late Cretaceous. On-land and shallow marine sediments in the Inner Zone of Southwest Japan and in the Chichibu Belt of the Outer Zone were deposited on the arc massifs. Enormous thicknesses of terrigenous turbidites were accumulated in the Central Zone of intra-arc basins and the Shimanto Belt of the Outer Zone forearc basins. Those clastics originated largely in the continental massif to the north and west throughout late Mesozoic times, as Southwest Japan was located to the east of the Korean Peninsula.