New U-Pb age constraints on the upper Banxi Group and synchrony of the Sturtian glaciation in South China |
| |
| Authors: | Gaoyuan Song Xinqiang Wang Xiaoying Shi Ganqing Jiang |
| |
| Institution: | 1. School of Earth Science and Resources, China University of Geosciences (Beijing), Beijing 100083, China;2. State Key Laboratory of Biogeology and Environmental Geology, Beijing 100083, China;3. Department of Geoscience, University of Nevada, Las Vegas, NV 89154-4010, USA |
| |
| Abstract: | The Nanhua basin in South China hosts well-preserved middle–late Neoproterozoic sedimentary and volcanic rocks that are critical for studying the basin evolution, the breakup of the supercontinent Rodinia, the nature and dynamics of the “snowball” Earth and diversification of metazoans. Establishing a stratigraphic framework is crucial for better understanding the interactions between tectonic, paleoclimatic and biotic events recorded in the Nanhua basin, but existing stratigraphic correlations remain debated, particularly for pre-Ediacaran strata. Here we report new Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICPMS) U-Pb zircon ages from the middle and topmost Wuqiangxi Formation (the upper stratigraphic unit of the Banxi Group) in Siduping, Hunan Province, South China. Two samples show similar age distribution, with two major peaks at ca. 820 Ma and 780 Ma and one minor peak at ca. 910 Ma, suggesting that the Wuqiangxi sandstone was mainly sourced from Neoproterozoic rocks. Two major age peaks correspond to two phases of magmatic events associated with the rifting of the Nanhua basin, and the minor peak at ca. 910 Ma may correspond to the Shuangxiwu volcanic arc magmatism, which represents pre-collision/amalgamation subduction on the southeastern margin of the Yangtze Block. The youngest zircon group from the topmost Wuqiangxi Formation has a weighted mean age of 714.6 ± 5.2 Ma, which is likely close to the depositional age of the uppermost Banxi Group. This age, along with the ages reported from other sections, constrains that the Banxi Group was deposited between ca. 820 Ma and ca. 715 Ma. The age of 714.6 ± 5.2 Ma from the top of the Wuqiangxi Formation is indistinguishable with the SIMS U-Pb age of 715.9 ± 2.8 Ma from the upper Gongdong Formation in the Sibao village section of northern Guangxi, South China. It is also, within uncertainties, overlapped with two TIMS U-Pb ages from pre-Sturtian strata in Oman and Canada. These ages indicate that the Jiangkou (Sturtian) glaciation in South China started at ca. 715 Ma instead of ca. 780 Ma and support a globally synchronous initiation of the Sturtian glaciation at ca. 715 Ma. |
| |
| Keywords: | Nanhua basin Wuqiangxi Formation Banxi Group U-Pb zircon ages Sturtian glaciation South China |
| 本文献已被 ScienceDirect 等数据库收录！ |
| 点击此处可从《地学前缘(英文版)》浏览原始摘要信息 |
| 点击此处可从《地学前缘(英文版)》下载免费的PDF全文 |
|
