Radiolaria‐dated Lower Permian clastic‐rock sequence in the Fukuji area of the Hida‐gaien terrane,central Japan,and its inter‐terrane correlation across Southwest Japan |
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| Authors: | Toshiyuki Kurihara Masao Kametaka |
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| Institution: | 1. Graduate School of Science and Technology, Niigata University, Niigata 950‐2181 (email: tosiyuki@rj8.so‐net.ne.jp), and;2. The Nagoya University Museum, Nagoya 464‐8601, Japan;3. Present address: Dia Consultants Co. Ltd, Yoshino‐cho 2‐272‐3, Kita‐ku, Saitama 331‐8638, Japan. |
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| Abstract: | The stratigraphy and radiolarian age of the Mizuyagadani Formation in the Fukuji area of the Hida‐gaien terrane, central Japan, represent those of Lower Permian clastic‐rock sequences of the Paleozoic non‐accretionary‐wedge terranes of Southwest Japan that formed in island arc–forearc/back‐arc basin settings. The Mizuyagadani Formation consists of calcareous clastic rocks, felsic tuff, tuffaceous sandstone, tuffaceous mudstone, sandstone, mudstone, conglomerate, and lenticular limestone. Two distinctive radiolarian faunas that are newly reported from the Lower Member correspond to the zonal faunas of the Pseudoalbaillella u‐forma morphotype I assemblage zone to the Pseudoalbaillella lomentaria range zone (Asselian to Sakmarian) and the Albaillella sinuata range zone (Kungurian). In spite of a previous interpretation that the Mizuyagadani Formation is of late Middle Permian age, it consists of Asselian to Kungurian tuffaceous clastic strata in its lower part and is conformably overlain by the Middle Permian Sorayama Formation. An inter‐terrane correlation of the Mizuyagadani Formation with Lower Permian tuffaceous clastic strata in the Kurosegawa terrane and the Nagato tectonic zone of Southwest Japan indicates the presence of an extensive Early Permian magmatic arc(s) that involved almost all of the Paleozoic non‐accretionary‐wedge terranes in Japan. These new biostratigraphic data provide the key to understanding the original relationships among highly disrupted Paleozoic terranes in Japan and northeast Asia. |
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| Keywords: | Early Permian Fukuji Hida‐gaien terrane magmatic arc Mizuyagadani Formation radiolarians stratigraphic correlation |
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