長門構造帯産石炭紀新世・ペルム紀古世放散虫とその地質学的意義  [in Japanese] Late Carboniferous and Early Permian radiolarians from the Nagato Tectonic Zone and their implication to geologic structure of the Inner Zone, Southwest Japan  [in Japanese]

Ages of some undated sedimentary rocks in the Nagato Tectonic Zone in the western Chugoku district, Southwest Japan, were examined by virtue of radiolarian biostratigraphy. The newly obtained micro fossil data strongly support the recent understanding that the Nagato Tectonic Zone is continuous with the Hida Marginal Zone in central Japan, in conjunction with the occurrence of coeval high P/T schist in both zones. Late Carboniferousradiolarians were found out from anandesitictuffaceous mudstone of a sedimentary unit previously called "undated Paleozoic formation" in the Dai area, Mine City. Such kind of andesitic tuffaceous mudstone is not known at all in the Chugo-ku district but in the Hida Marginal Zone. This unit is newly designated as the Higashi-hirano Formation. Early Permian radiolarians were found out from an allochthonous block of bedded chert, which is contained in coarse-grained clastic rocks called the Toyohigashi Group in the Toyogadake area, Toyota-cho. Judging from the age and mode of occurrence of the chert block, and the total lithologic assemblage of the unit, this group can be properly correlated with the Middle-Late Permian accretionary complex of the Akiyoshi Belt, which is distributed not merely in the east of the Nagato Tectonic Zone but also in the Hida Marginal Zone.