四国東部，四万十累層群の岩相層序と放散虫年代

Lithostratigraphic classification of the Shimanto Supergroup is newly proposed on oceanic plate stratigraphy in East Shikoku. Ages of the lithostratigraphic units are discussed on their radiolarian fauna. These units are correlated with those in Central and West Shikoku on the basis of lithological and radiolarian chronological properties with their spatial arrangement. Sedimentary facies of the units are subdivided into the slope basin facies (SL), trench-fill coarse detrital facies (AT), chert-turbidite sequence facies (AC), and the accretion melange facies (AM). The Yutomaru-Yokoishi and Gamodamisaki Thrusts subdivide the North Shimanto Belt into the Minagawa, Aratano and Kainan Zones from North to South. The Kaikawa Group consists of AT with SL of Aptian - Cenomanian and Coniacian - Santonian age. The group is distributed in the Minagawa Zone. The Fukuigawa Group consists of AC and/or AM (AM after AC). Clastic sediments of the Fukuigawa Group ranges in age from Cenomanian - Turonian to Early Maastrichtian. Within the group, these sediments become younger from the northern formations to the southern ones. The Kaifugawa Group is composed mainly of Upper Campanian to Maastrichtian formations (upper Amphipyndax pseudoconulus Zone and A.tylotus Zone) of the AT facies with some older ones of the AM facies. Subduction and accretion that formed the spatial arrangement of these facies in the Shimanto Terrane started in Aptian age. Huge amount of detrital coarse sediments filled the deeper slope and trench in Late Campanian to Early Maastrichtian age.