Paleogeographic reconstructions of the East Asia continental margin during the middle to late Mesozoic

The currently available paleogeographic maps of the East Asia continental margin during the Mesozoic have been recast in the light of recent research results on sediments distributed in Korea and Japan. Both the Korean peninsula and the Inner zone of Southwest Japan exchanged sediment supply during the Middle to Late Mesozoic, suggestive of a close paleogeographic relationship between the two countries at the active continental margin setting. During the latest Middle to earliest Late Jurassic the Mino-Tamba trench was developed along the southeastern Korean peninsula, from which trench-fill sediments were sourced and to which an accretionary complex was accreted. Lower Cretaceous quartz-arenite clasts of the Tetori Group in the Hida Marginal Belt of Southwest Japan were derived from pre-Mesozoic quartz-arenite strata distributed in the southern central and east central Korean peninsula, suggesting that the Tetori Basin was located close to the central eastern part of the Korean peninsula at the time of deposition of quartz-arenite clasts, contrary to conventional thought of far distance between the two areas based on paleomagnetic data. During the early Late Cretaceous radiolaria-bearing chert pebbles and sands in the northern part of the non-marine Gyeongsang Basin distributed in the southeastern Korean peninsula were derived from the uplifted Mino-Tamba accretionary complex distributed in southwest Japan, suggesting that the Mino-Tamba terrane was land-connected with the eastern Korean peninsula. These new findings suggest that in contrast to conventional thought, the collage of tectonic blocks in Southwest Japan has assembled in post-early Late Cretaceous time.