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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• 作者：Dao-Hui Pi^a ; Shao-Yong Jiang^a ; ^b ; ^{shyjiang@cug.edu.cn" class="auth_mail" title="E-mail the corresponding author}
• 关键词：U&ndash ; Pb dating ; Zircon ; Liantuo Formation ; Three Gorges ; South China
• 刊名：Chemie der Erde - Geochemistry
• 出版年：2016
• 出版时间：March 2016
• 年：2016
• 卷：76
• 期：1
• 页码：103-109
• 全文大小：3521 K

文摘

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.