| 引用本文: | 林旭，刘海金，陈济鑫，李玲玲，胡程伟，张玉芬，李长安.2022.晚更新世长江中下游沙山和黄土物质来源研究[J].地球环境学报,13(5):529-542 |
| LIN Xu, LIU Haijin, CHEN Jixin, LI Lingling, HU Chengwei1, ZHANG Yufen, LI Chang’an.2022.Provenance tracing of sand hills and loess in the middle and lower reaches of Yangtze River during the Late Pleistocene[J].Journal of Earth Environment,13(5):529-542 |
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| 晚更新世长江中下游沙山和黄土物质来源研究 |
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林旭，刘海金，陈济鑫，李玲玲，胡程伟，张玉芬，李长安
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1. 三峡大学 土木与建筑学院，宜昌 443002
2. 三峡库区地质灾害教育部重点实验室（三峡大学），宜昌 443002
3. 东华理工大学 地球科学学院，南昌 330013
4. 中国地质大学（武汉） 地球物理与空间信息学院，武汉 430078
5. 中国地质大学（武汉） 地理与信息工程学院，武汉 430078
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| 摘要: |
| 风成沉积物的产生、搬运和沉积过程是地球各圈层相互作用的产物。晚更新世末次冰期时，长江中下游广泛分布沙山和黄土，对于它们是远源搬运而来，还是近源堆积一直存有争议。对青山、九江、定山和红光这些典型沙山和黄土剖面进行碎屑锆石U-Pb年龄分析，获得346个新数据结果，将其与潜在物源区的碎屑锆石U-Pb年龄进行对比，结合这些地层的沉积时代和区域内已报道的物源示踪结果，发现在末次冰期青山沙山和九江黄土的碎屑锆石来自近源的江汉平原，定山沙山和红光黄土的碎屑锆石来自赣江。长江中下游沙山和黄土的发育属于河流搬运的碎屑物质被东亚冬季风吹拂和高大地形阻挡发生沉积的模式。 |
| 关键词: 沙山 黄土 长江 锆石U-Pb年龄 物源示踪 |
| DOI：10.7515/JEE222027 |
| CSTR：32259.14.JEE222027 |
| 分类号: |
| 基金项目:国家自然科学基金项目（41877292，41871019，41972212） |
| 英文基金项目:National Natural Science Foundation of China (41877292, 41871019, 41972212) |
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| Provenance tracing of sand hills and loess in the middle and lower reaches of Yangtze River during the Late Pleistocene |
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LIN Xu, LIU Haijin, CHEN Jixin, LI Lingling, HU Chengwei1, ZHANG Yufen, LI Chang’an
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1. School of Civil Engineering and Architecture, China Three Gorges University, Yichang 443002, China
2. Key Laboratory of Geological Hazards on Three Gorges Reservoir Area, Ministry of Education, China Three Gorges University, Yichang 443002, China
3. School of Earth Sciences, East China University of Technology, Nanchang 330013, China
4. School of Geophysics and Spatial Information, China University of Geosciences, Wuhan 430078, China
5. School of Geography and Information Engineering, China University of Geosciences, Wuhan 430078, China
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| Abstract: |
| Background, aim, and scope The generation, transport, and deposition of eolian sediments are the result of the interaction between the Earth’s atmosphere, hydrosphere, and lithosphere. The last period of prolonged and frequent climatic fluctuations occurred during the last glaciation of the Late Pleistocene (75—10 ka). Therefore, provenance tracing of well-preserved deserts or loess, reconstructing their transportation paths, and understanding the climatic characteristics of this period have important significance for the future development of human society. During the last glacial period of the Late Pleistocene, sand hills and loess were widely distributed in the middle and lower reaches of Yangtze River. Some researchers believe that they originated from the Gobi Desert and loess from Mongolia and northern China, while others speculate that they were derived from the adjacent provenance area. Thus, the origin of these eolian sediments remains controversial. In this study, we conducted detrital zircon U-Pb age analysis from the continuous distribution, and well-exposed sand hills and loess profiles along the middle and lower reaches of Yangtze River. We simultaneously collected published detrital zircon U-Pb ages from the Gobi Desert and loess of Mongolia and northern China, the Yangtze River Basin, and the Jianghan Plain. In this study, the specific source regions of the sand hills and loess were determined based on a comparison of the detrital zircon U-Pb age spectrum and the published provenance tracing results in the region. Materials and methods Four detrital samples were analyzed for zircon U-Pb ages from the Qingshan and Dingshan sand hills, Jiujiang, and the Hongguang loess distributed in the middle and lower reaches of Yangtze River. Non-metric multidimensional scaling (MDS) maps were used to visualize the similarities and diversity of complex zircon age distributions. Results The analyzed zircons were mainly magmatic. We obtained 346 new zircon U-Pb ages, and the detrital zircon U-Pb ages of the Qingshan sand hill showed five main peaks: 212 Ma, 427 Ma, 786 Ma, 915 Ma, and 1855 Ma. The detrital zircon U-Pb age compositions of the Jiujiang loess are Mesozoic (204 Ma), Early Paleozoic (434 Ma), Neoproterozoic (778 Ma and 958 Ma), Paleoproterozoic (1719 Ma and 1841 Ma), and Neoarchean (2530 Ma). The detrital zircon U-Pb ages of the Dingshan sand hill show Late Mesozoic (126 Ma), Early Mesozoic (219 Ma), Early Paleozoic (449 Ma), Neoproterozoic (822 Ma and 980 Ma), and non-significant Paleoproterozoic (1891 Ma) peak ages. The detrital zircon U-Pb peak ages of the Hongguang loess include 140 Ma, 211 Ma, 420 Ma, 807 Ma, and 980 Ma, but the Paleoproterozoic (1755 Ma) and Neoarchean (2466 Ma) peak ages were not significant. Discussion The comparison of the results shows that the detrital zircon U-Pb age spectra of the Qingshan sand hill and Jiujiang loess are consistent with that of the Jianghan Plain. The detrital zircon U-Pb age compositions of the Dingshan sand hill and Hongguang loess were similar to those of the Ganjiang River. However, they differ from the detrital zircon U-Pb age compositions of the Gobi Desert and loess in Mongolia and northern China. Combined with the MDS plot, the Qingshan sand hill and Jiujiang loess were close to the Jianghan Plain, whereas the Dingshan sand hill and Hongguang loess are closely related to the Ganjiang River. Previously published grain size studies have indicated that these are eolian sediments. During the last glacial period, the continental shelf in the eastern China sea retreated, thereby exposing the detrital material of the Jianghan Plain and Ganjiang River. The East Asian winter monsoon strengthened during this period. Blown by the East Asian winter monsoon, exposed debris was transported and deposited in the northern piedmont of the orogenic belts along the middle and lower reaches of Yangtze River. The provenance tracing results also indicate that the sand hills and loess distributed in the middle and lower reaches of Yangtze River are mainly near source materials. In contrast, the influences of the Gobi Desert and loess in Mongolia and northern China were not dominant. Conclusions By analyzing the detrital zircon U-Pb ages of the sand hills and loess from the middle and lower reaches of Yangtze River, and comparing them with the potential provenance areas, we found that the detrital zircons from the Qingshan sand hill, Jiujiang loess, Dingshan sand hill, and Hongguang loess were mainly derived from the Jianghan Plain and Ganjiang River during the last glacial period. The development of sand hills and loess in the middle and lower reaches of Yangtze River are derived by the model of river-transported detritus, which was blown by East Asian winter monsoon and blocked by tall topography for deposition. Recommendations and perspectives Although detrital zircons provided reliable results in this study, it is necessary to combine various methods to comprehensively display provenance tracing results for the sand hills and loess in the middle and lower reaches of Yangtze River in the future. |
| Key words: sand hill loess Yangtze River zircon U-Pb age provenance tracing |
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