Zircon U-Pb Dating of a Tuff Layer from the Miocene Onnagawa Formation in Northern Japan
Geochemical Journal, Vol. 55, pp. 185 to 191, 2021 doi:10.2343/geochemj.2.0622 NOTE Zircon U-Pb dating of a tuff layer from the Miocene Onnagawa Formation in Northern Japan JUMPEI YOSHIOKA,1,2* JUNICHIRO KURODA,1 NAOTO TAKAHATA,1 YUJI SANO,1,3 KENJI M. MATSUZAKI,1 HIDETOSHI HARA,4 GERALD AUER,5 SHUN CHIYONOBU6 and RYUJI TADA2,7,8 1Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8564, Japan 2Department of Earth and Planetary Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan 3Institute of Surface-Earth System Science, Tianjin University, Tianjin 300072, China 4Geological Survey of Japan, AIST, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8567, Japan 5Institute of Earth Sciences, University of Graz, NAWI Graz Geocenter, Heinrichstrasse 26, 8010 Graz, Austria 6Faculty of International Resource Sciences, Akita University, 1-1 Tegatagakuenmachi, Akita, Akita 010-8502, Japan 7The Research Center of Earth System Science, Yunnan University, Chenggong District, Kunming, Yunnan 650500, China 8Institute for Geo-Cosmology, Chiba Institute of Technology, 2-17-1 Tsudanuma, Narashino, Chiba 275-0016, Japan (Received December 10, 2020; Accepted March 3, 2021) During the Middle-to-Late Miocene, diatomaceous sediments were deposited in the North Pacific margin and mar- ginal basins. The Onnagawa Formation is one of such deposits, which shows cyclic sedimentary rhythms reflecting oscil- lations of the marine environment in the Japan Sea. However, the age of the Onnagawa Formation is still poorly con- strained due to the poor preservation of siliceous microfossils. To better constrain its age, we performed U-Pb dating of zircon grains from a tuff layer from the middle part of the Onnagawa Formation, and obtained an age of 11.18 ± 0.37 Ma.
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