| 元素地球化学揭示的长江中游鄱阳湖地区中更新世以来粉尘堆积的物源特征及其环境意义 |
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| 引用本文： | 凌超豪,张智,贾玉连,薛滨,申洪源,钟巍,龙桂铃.元素地球化学揭示的长江中游鄱阳湖地区中更新世以来粉尘堆积的物源特征及其环境意义[J].第四纪研究,2019,39(5):1103-1115. |
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| 作者姓名： | 凌超豪 张智 贾玉连 薛滨 申洪源 钟巍 龙桂铃 |
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| 作者单位： | 江西师范大学地理与环境学院,鄱阳湖湿地与流域研究教育部重点实验室,江西南昌330022;中国科学院南京地理湖泊研究所,湖泊与环境国家重点实验室,江苏南京210008;中国科学院大学,北京100049;江西师范大学地理与环境学院,鄱阳湖湿地与流域研究教育部重点实验室,江西南昌330022;中国科学院南京地理湖泊研究所,湖泊与环境国家重点实验室,江苏南京210008;临沂大学资源环境学院,山东临沂,276000;宜春学院,江西宜春,336000 |
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| 基金项目： | 江西省重大生态安全问题监控协同创新中心项目;国家自然科学基金;鄱阳湖湿地与流域研究教育部重点实验室(江西师范大学)开放基金;鄱阳湖湿地与流域研究教育部重点实验室(江西师范大学)开放基金;江西省教育厅科学技术研究项目;江西师范大学研究生创新基金 |
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| 摘 要： | 位于长江中游的鄱阳湖地区深受东亚季风影响,因其特殊的地理、地貌与水文、水系特征,自中更新世以来随着冬季风的加强,在大姑组、九江组砾石层之上风成堆积广泛发育。该区域中、上更新统表现为网纹红土、均质红土和下蜀黄土的独特沉积序列,厘清这三套独特沉积序列的物质来源对于我们认识东亚季风演化及其区域环境响应至关重要。本文选择了长江中游鄱阳湖地区10个典型剖面,基于<20μm颗粒组分的元素地球化学特征,研究了该地区中、上更新统粉尘堆积的特点,并将其与黄土高原西峰黄土和东秦岭黄土做了对比分析。研究认为,长江中游鄱阳湖地区这套独特的沉积序列,元素特征基本相似,具有贫Co、Pb,富Zr、Hf,低Eu/Eu^*(0.53~0.62)、LaN/YbN(4~8)、Ta/Zr(0~0.006)、Nb/Zr(0~0.09),高Y/Ho(28~30)、Zr/Hf(36~48)等特点,与黄土高原与东秦岭黄土有显著区别。基于Hf-Th-Co、Th-Sc-Zr/10和Th-Sc-La蜘蛛图投影分析,鄱阳湖地区第四纪粉尘物质的源岩接近于石英岩类,为被动大陆边缘构造背景下的产物,显著区别于黄土高原与东秦岭黄土(源岩接近于页岩,形成于大陆岛弧构造背景)。进一步分析认为,网纹红土、均质红土的母质均与区域下蜀黄土类似,推测它们均来自于其冬季风上风方向的长江或赣江的古河谷漫滩,这套独特的沉积序列是第四纪以来长江中游现代格局的水系贯通后,冬季风增强,吹蚀大江大河广阔的古河谷漫滩而形成的区域粉尘堆积的结果;是湿热的亚热带季风区对于中更新世以来在轨道尺度上冬夏季风均加强的背景下独特的区域响应。
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| 关 键 词： | 鄱阳湖地区 元素地球化学特征 粉尘堆积 物源示踪 东亚季风 水系调整 |
GEOCHEMICAL EVIDENCE FOR PROVENANCE OF AEOLIAN DEPOSTION FROM POYANG LAKE REGION IN THE MIDDLE REACHES OF YANGTZE RIVER SINCE THE MIDDLE PLEISTOCENE AND ITS ENVIRONMENTAL SIGNIFICANCE |
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| Ling Chaohao,Zhang Zhi,Jia Yulian,Xue Bin,Shen Hongyuan,Zhong Wei,Long Guiling.GEOCHEMICAL EVIDENCE FOR PROVENANCE OF AEOLIAN DEPOSTION FROM POYANG LAKE REGION IN THE MIDDLE REACHES OF YANGTZE RIVER SINCE THE MIDDLE PLEISTOCENE AND ITS ENVIRONMENTAL SIGNIFICANCE[J].Quaternary Sciences,2019,39(5):1103-1115. |
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| Authors: | Ling Chaohao Zhang Zhi Jia Yulian Xue Bin Shen Hongyuan Zhong Wei Long Guiling |
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| Institution: | (Key Laboratory of Poyang Lake Wetland and Watershed Research Ministry of Education,School of Geography and Environment,Jiangxi Normal University,Nanchang 330022,Jiangxi;State Key Laboratory of Lake Science and Environment,Nanjing Institute of Geography and Limnology,Chinese Academy of Sciences,Nanjing 210008,Jiangsu;University of Chinese Academy of Sciences,Beijing 100049;College of Resource and Environment,Linyi University,Linyi 276000,Shandong;Yichun University,Yichun 336000,Jiangxi) |
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| Abstract: | The Poyang Lake region is located in the middle reaches of the Yangtze River, Southeast China. Influenced by local geographical, geomorphological, and fluvial systems, dust deposits have been widely developed mantled over the gravel layers of the Dagu and Jiujiang formations since the Middle Pleistocene period for strengthened winter Asian monsoon. The regional sedimentary sequences of Middle and Upper Pleistocene are featured by thick layers of reticulated red soil, red soil and Xiashu loess for strong aeolian accumulation. It is significant implication to unravel the provenance of material origin of this set of sedimentary sequence. This paper presents and analyzes the characteristics of the trace element geochemistry in clastic component of < 20 μm grain size of reticulated red soil, red soil and Xiashu loess from 10 profiles around Poyang Lake area, with a comparison with Xifeng loess and the Eastern Qinling loess from the Loess Plateau in Northern China. We conclude that in general the element characteristics of reticulated red soil, red soil and Xiashu loess in Poyang Lake area are similar to each other with rich in Zr and Hf, depleted in Co and Pb, low in mole fraction of Eu/Eu^*(0.53~0.62), LaN/YbN (4~8), Ta/Zr (0~0.006) and Nb/Zr (0~0.09), high in Y/Ho (28~30), Zr/Hf (36~48), which largely different from Xifeng loess and the Eastern Qinling loess from the Loess Plateau. Based on the projection analysis of Hf-Th-Co, Th-Sc-Zr/10, Th-Sc-La Ternary Diagrams, the parent materials of these soil layers are deduced similar to that of quartzite, which is deemed as to develop in the passive continental margin tectonic, also significant differences from those of loess in the Loess Plateau. The parent materials of source rocks of loess in the Loess Plateau, close to the shale in spider diagrams were conformed to develop in the continental island arc tectonic. Furthermore, the similar parent material of reticulated red soil, red soil and Xiashu loess layers in Poyang Lake area suggests these aeolian deposits in Poyang Lake area enjoy the same provenance, i.e. the Ganjiang River valley and Yangtze River floodplain, we deduced. These floodplains provided abundant sandy-silty clastic materials for aeolian deposits under intensified winter monsoon and summer monsoon regimes--winter monsoon brings about strong winds;summer monsoon brings about great rainfall and leads to regionally large floods and consequently the flood plain extended largely. So, this set of sedimentary sequences around Poyang Lake areas should be the indicator of both winter monsoon and summer monsoon intensifying during mid-Pleistocene at the present-like hydrological pattern in the Yangtze River basin. |
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| Keywords: | Poyang Lake area characteristics of geochemistry provenance tracing aeolian depostion East Asian monsoon water system adjustment |
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