Triassic to Middle Jurassic radiolarians from pelagic chertsin the Nanjō Mountains, Southwest Japan – Part 2. Kanmuri Yama district

Abstract

Abstract:The Nanjō Mountains located in the central region of Fukui Prefecture, Southwest Japan, are chiefly underlain by the sedimentary complex of various rock-types such as basalt, limestone, chert, mudstone and sandstone. Among these rocks within the mountains, twenty-seven chert outcrops (localities) were explored for their radiolarian content. Twenty-six rock samples from seventeen localities in the studied Kanmuri Yama district yielded moderately-to poorly-preserved radiolarian remains as a result. Most of the samples contain Triassic to Middle Jurassic species, with Spumellaria and Entactinaria dominant among the Triassic faunas and with Nassellaria dominant among the Jurassic faunas. The description and faunal analysis of these radiolarians revealed that the cherts in the Kanmuri Yama district span a wide range of age from the Late Olenekian to Middle Bathonian stages.