U–Pb dating of zircons from tuff layer,sandstone and tillite samples in the uppermost Liantuo Formation and the lowermost Nantuo Formation in Three Gorges area,South China |
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| Institution: | 1. State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, China;2. State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China;3. Department of Earth Sciences, University of St. Andrews, North Street, St. Andrews KY16 9AL, UK;4. School of Earth and Environment, University of Western Australia, WA 6009, Australia |
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| Abstract: | Uranium-lead (U–Pb) dating was conducted on zircons in tuff layers and sandstone samples from the uppermost Liantuo Formation and in a tillite sample from the lowermost Nantuo Formation in Three Gorges area, South China, using SHRIMP and LA-ICP-MS techniques. Zircons from these samples yielded age spectrum (within 1000 Ma) of ～890, ～830, ～780, ～730, and 646 Ma. Zircons from the Liantuo tuffs have a weighted mean 206Pb/238U age of 734.1 ± 8.1 Ma (2σ, n = 7, MSWD = 0.48), which was regarded as the best estimation of the upper boundary age of the Liantuo Formation. Combining with previous geochronologic data, the Liantuo Formation was proposed to be a pre-Chang′an glaciation unit, and it is comparable to the middle-upper Banxi/Danzhou Group in South China. |
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| Keywords: | U–Pb dating Zircon Liantuo Formation Three Gorges South China |
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