四国東部の南部黒瀬川帯（坂州帯）坂州層群（新称）の層序と放散虫年代

The post-Norian and pre-Hauterivian cover formation of the Permian accretionary complex is investigated in the lithostratigraphy and radiolarian ages in the Sakashu Belt (South Kurosegawa Terrane), East Shikoku. The cover formation, proved to be the Lower Jurassic-earliest Cretaceous fore-arc basin-deposits, is newly named the Sakashu Group. The group is composed of the Lower Jurassic Hirose Formation (new name), and the Middle Jurassic-earliest Cretaceous Kurisaka Formation (revised). The Hirose Formation unconformably overlies the Carnian and Norian shallow-marine formations. The Kurisaka Formation is unconformably overlain by the Shobu Formation of the Takegatani Group (brackish Hauterivian). The Hirose Formation initiates in the radiolarian Parahsuum simplum Zone. The middle to upper part of the Kurisaka Formation at least ranges from the Tricolocapsa conexa to the Pseudodictyomitra primitiva zones. The Sakashu Group provably encircles the upper Lower Jurassic beds. Because the submarine-slide beds, being intercalated in the Kurisaka Formation, contain the mudstone block of the Trillus elkhornensis Zone. The Sakashu Group is correlative with the Kawamata and the Ashikita groups in Kyushu. The Naruho and Kagio formations in West Shikoku, and the Nakanose and Birafu formations in Central Shikoku are correlative to the formations of the Sakashu Group. The fore-arc basin-formations were formed on the Permian accretionary complex of the Kurosegawa Terrane from earliest Jurassic to earliest Cretaceous. The sedimentation was after the deposition of the Triassic shelf-deposits (Zohoin and Kochigatani groups), and before the initiation of Hauterivian delta-sedimentation (Shobu Formation of the Takegatani Group).