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Recent advances of Ordovician to Cretaceous microbiostratigraphy in Japan are reviewed with special reference to the intensive research on radiolarians and conodonts. Thirty radiolarian zones of Late Carboniferous-Cretaceous ageand 27 conodont zones of Carboniferous-Triassicage have been proposed. The newly introduced biochronologic scale offers an important key to the integration of Mesozoic "geosynclinal complexes" in Japan, forexample, to the recognition of various allochthonous elements of oceanic affinity in olistostrome-melange complexes and to the elucidation of tectono-stratigraphic characteristics of various belts. Based on these analyses, it is proposed that the Mesozoic belts of Southwest Japan can be classified into three major groups from north to south: namely, (A) Oki-Hida belts, Unazuki belt, Nagato-Outer Hida-Joetsu belts and Akiyoshi-Maizuru belts, (B) Mino-Tamba-Ashio-Ryoke belts, Sambagawa-Northern Chichibu belts, Kurosegawa belt, Southern Chichibu belt and (C)Shimanto major belt including two or more belts. These three groups were incorporated in to the eastern margin of the Mesozoic Asia during (A) Triassic, (B) Jurassic-earliest Cretaceous and (C) Cretaceous-Cenozoic times, respectively.
