Early Cretaceous non-marine mollusc faunas of Japan and Korea

A biostratigraphic correlation of Early Cretaceous marine and non-marine mollusc faunas of south-west Japan and exclusively freshwater faunas of Korea is proposed. The material originates from the Inner Zone of central Japan (Tetori, Sanchu), the Outer Zone of south-west Japan (Kyushu, Shikoku, Kii Peninsula), and the Kyongsang Basin of south-west Korea. It includes new collections of freshwater molluscs from the Monobegawa Group (Shikoku). The alternation of well-dated marine strata with non-marine beds in Kyushu, Shikoku and central Honshu (Sanchu area) provides accurate age constraints to the well-studied non-marine faunas. In the Inner and Outer Zones of Japan, four non-marine bivalve associations alternate with marine faunas: (1) Hauterivian: brackish–freshwater Hayamina naumanni–Unio ogamigoensis Assemblage of the Tatsukawa faunal association; (2) Hauterivian: brackish Hayamina carinata–Isodomella matsumotoi Assemblage of the Shobu faunal association; (3) Barremian: marine Yabea shinanoensis, Pterotrigonia kawaguchiensis and Nanonavis yokoyamai, with the ammonite Shasticrioceras nipponicum and radiolarians (Archaeodictyomitra pseudoscalaris assemblage); (4) Late Barremian: brackish Hayamina matsukawai, Costocyrena radiatostriata, and Pulsidis tashiroi of the non-marine Sebayashi faunal association, with Nippononaia ryosekiana in Sanchu, passing upwards to marine deposits with ammonites; (5) Early Aptian: brackish Costocyrena minor, and Pulsidis rostratus of the non-marine Hibihara faunal association, passing upwards to marine Pterotrigonia pocilliformis and Goshoraia minor, with the ammonite Cheloniceras sp.; (6) Middle Albian: marine Inoceramus anglicus, and Parvamussium tosaense, with ammonites, radiolarians an