Age of the Taishu Group,southwestern Japan,and implications for the origin and evolution of the Japan Sea |
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| Authors: | Takashi Ninomiya Shoichi Shimoyama Koichiro Watanabe Kenji Horie Daniel J Dunkley Kazuyuki Shiraishi |
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| Institution: | 1. Office for Program Promotion, Graduate School of Sciences, Kyushu University, , Fukuoka, 812‐8581 Japan;2. Department of Earth and Planetary Sciences, Graduate School of Sciences, Kyushu University, , Fukuoka, 812‐8581 Japan;3. Department of Earth Resources Engineering, Graduate School of Engineering, Kyushu University, , Fukuoka, 819‐0395 Japan;4. National Institute of Polar Research, , Tokyo, 190‐8518 Japan;5. Department of Polar Science, School of Multidisciplinary Sciences, the Graduate University for Advanced Studies (SOKENDAI), , Tokyo, 190‐8518 Japan |
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| Abstract: | The Taishu Group, a marine formation with a thickness of >5400 m, crops out on Tsushima Island, located in the southwestern Japan Sea. The group, which is generally regarded as early Eocene to early Miocene in age, provides important information about the tectonic setting of the Japan Sea. In this study, we present new SHRIMP U–Pb dates for igneous zircons from the Kunehama Tuff, which is in the basal part of the Taishu Group, and the Oobaura Tuff, which is in the uppermost part of the group. Results show that the Taishu Group was deposited rapidly, during the short interval of 17.9–15.9 Ma (early–middle Miocene), and is equivalent to other early–middle Miocene strata found in the Japan Sea region. Our results provide new constraints on the geological history of the Japan Sea and its islands. |
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| Keywords: | early to middle Miocene Japan Sea SHRIMP U– Pb dating Taishu Group |
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