||Permian–Cretaceous radiolarians from Ie Island, Okinawa Prefecture, Japan
Ito, TsuyoshiMatsuoka, Atsushi
Science reports of Niigata University. (Geology)
136 , 2017-10 , 新潟大学理学部
InterRed XV in Niigata 2017 Niigata University (JAPAN) Oct/22-Oct/27, 2017
Ie Island in northwestern Okinawa Prefecture, Japan, mainly comprises of basement rocks (Gusukuyama Formation of the Southern Chichibu terrane) and the overlying Pleistocene Ryukyu Group. The bedded cherts of the Gusukuyama Formation in Mt. Gusuku in the central part of Ie Island have yielded radiolarians ranging from the Neoalbaillella optima Zone (Changhsingian, Lopingian, Permian) to the Kilinora spiralis Zone (JR6: Oxfordian, Upper Jurassic). Siliceous mudstones in the southern flank of Mt. Gusuku have yielded radiolarians of the Pseudodictyomitra carpatica Zone (KR1: uppermost Jurassic–lowermost Cretaceous). This age difference is assumed to indicate the presence of a thrust between Mt. Gusuku and the southern flank of the mountain. Red chert clasts are contained in the Pleistocene Ryukyu Group at Waji on the north coast of Ie Island, and Permian radiolarians have been obtained from chert clasts. In addition, a red bedded chert boulder at Waji yielded Cisuralian (Early Permian) radiolarians including dimorphic pair of Albaillella sinuata Ishiga and Watase.