新潟県蒲原山地の足尾帯泥岩から見出された前期ジュラ紀放散虫化石 Early Jurassic radiolarian fossils from mudstone of the Ashio Terrane in the Kambara Mountains, Niigata Prefecture, Japan
Early Jurassic radiolarian faunae were extracted from mudstone samples collected at three localities (Se1, Ik1, and Jo2) in an accretionary complex within the Ashio Terrane in the Kambara Mountains, Niigata Prefecture, Japan. The faunae of both Se1 and Ik1 are dominated by <i>Canoptum</i> species, in association with two characteristic species belonging to <i>Gorgansium</i> (<i>G</i>. sp. A and <i>G</i>. sp. B) for Se1, and species belonging to <i>Parahsuum</i>, <i>Lantus</i>, and <i>Helvetocapsa</i> for Ik1. The fauna in Jo2 consists mainly of the species of <i>Parvicingula</i>, <i>Zhamoidellum</i>, and gen. et sp. indet. B.<br>Based on a comparison of these radiolarians with those from North America, Europe, and Southwest Japan, the ages of the faunae from Se1, Ik1, and Jo2 are Hettangian, Late Pliensbachian, and Middle to Late Toarcian/Aalenian?, respectively.<br>This is the first report of radiolarian fossils from terrigenous clastic rocks (mudstone) in the Kambara Mountains; thus, this result contributes to reconstructions of oceanic plate stratigraphy in the region and to correlating the area with other accretionary complexes in the Ashio Terrane.
地質学雑誌 116(8), 441-446, 2010
The Geological Society of Japan