| 青海湖湖东沙地沉积记录的全新世以来风沙活动变化 |
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| 引用本文： | 吕志强,鲁瑞洁,刘小槺,杜婧,陈璐,李腾飞.青海湖湖东沙地沉积记录的全新世以来风沙活动变化[J].干旱区地理,2018,41(3):536-544. |
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| 作者姓名： | 吕志强 鲁瑞洁 刘小槺 杜婧 陈璐 李腾飞 |
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| 作者单位： | 1.北京师范大学地表过程与资源生态国家重点实验室, 北京 100875;2.北京师范大学防沙治沙教育部工程研究中心, 北京 100875;3.北京师范大学地理科学学部, 北京 100875 |
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| 基金项目： | 国家自然科学基金项目（41571184）；国家重点基础研究发展计划基金资助项目（2013CB956001） |
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| 摘 要： | 青海湖湖东沙地典型剖面的AMS14C测年数据表明该剖面记录了当地约10 ka BP的风沙活动及环境变化。对沉积物的粒度组成特征、粒度参数、粒度环境敏感指标等分析，并结合沉积物磁化率和青海湖盆地相关研究中风成砂、黄土和弱发育古土壤、古土壤的OSL、AMS14C年代数据等，进行全新世以来的风沙活动及气候环境变化讨论。结果表明：（1）粗颗粒敏感组分（138~156μm）可以用来指示风沙活动的强弱，细颗粒敏感组分（2~5 μm）可以用来指示成壤作用。（2）10~9ka青海湖盆地气候状况较全新世之前略有好转，暖湿程度增加，部分区域开始发育古土壤，但总体上古土壤、弱发育古土壤、黄土、风成砂共存；9~4.2 ka青海湖盆地水热组合条件较好，风沙活动弱，大部分沙丘固定成壤，但9~8 ka和4.2 ka左右风沙活动较为频繁的特征可能指示了8.2 ka和4ka冷事件；4.2 ka之后特别是2 ka之后风沙活动显著增强，气候朝干冷化发展。
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| 关 键 词： | 青海湖 粒度 古气候 风沙活动 |
| 收稿时间： | 2018-01-21 |
Holocene aeolian activities on sedimentary record at the east of Qinghai Lake |
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| LV Zhi-qiang,LU Rui-jie,LIU Xiao-kang,DU Jing,CHEN Lu,LI Teng-fei.Holocene aeolian activities on sedimentary record at the east of Qinghai Lake[J].Arid Land Geography,2018,41(3):536-544. |
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| Authors: | LV Zhi-qiang LU Rui-jie LIU Xiao-kang DU Jing CHEN Lu LI Teng-fei |
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| Affiliation: | 1.State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, Beijing 100875, China;2.MOE Engineering of Desertification and Blown sand Control, Beijing Normal University, Beijing 100875, China;3.Faculty of Geographical Science, Beijing Normal University, Beijing 100875, China |
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| Abstract: | Qinghai Lake Basin is located in the joint zone of the Asia monsoon region of eastern China, the arid region of northwestern China and the cold region of Qinghai-Tibet Plateau. It is a natural barrier to prevent the land desertification from spreading eastwards and help maintain the ecological security in the northeastern Qinghai-Tibet Plateau. Its special geographical location and its high elevation makes itself highly sensitive to the climatic changes. The aeolian deposits are widely distributed around Qinghai Lake which can serve as a source of palaeoclimatic information and provide the important evidence for aeolian geomorphology and aeolian activity processes. In the stratum, aeolian sand represents dune-field expansion and/or dune buildup, whereas paleosols indicate stabilization of dunes, accompanied by ameliorated vegetation coverage. We used 4 conventional radiocarbon dates to construct chronological frameworks for QHH sections, and all of the 14C ages occur in stratigraphic order within the limits of the analytical error. The grain size distribution and parameters were analyzed to extract the sensitive components of Aeolian deposits. The results showed that medium and large sand fractions (138-156 μm) were used for indicating the strength of aeolian activity, and the fine sand component(2-5 μm)might be influenced by the formation of paleosol. The variations of the proxy indicators measured in the laboratory were largely consistent with the lithofacies variations of QHH sections. The aeolian sand in the field showed little or no evidence of pedogenic alteration, and it had a relatively coarse mean grain size(Mz), and low magnetic susceptibility(MS). In contrast, in the field the paleosols were more compact than the aeolian sand, and they have a finer Mz and much higher MS. In addition, we collected the previously published OSL and AMS14C ages of aeolian deposits in the Qinghai Lake Basin. Combined with the ages in this study, 59 ages in total of 20 sites were plotted to extract paleoenvironmental information using a probability density function (PDF) which indicated a transitional period from last glacial period to Holocene occurred in 10-9 ka, when the climate was slightly warmer and wetter but variable, as indicated by the distributions of ages of the paleosol, weak paleosol, loess, and aeolian sand. From 9-4.2 ka, the number of PDF was relatively small during the midHolocene, indicating a mid-Holocene Climatic Optimum with weak aeolian activity. After 4.2 ka, the climate tended to be dry with frequent fluctuations. Since a drier climate occurred and the Aeolian activity strengthened again the previously stabilized dunes reactivated again especially after 2 ka. However, there is considerable disagreement about the nature of centennial-scale climatic variations during the late Holocene in the region, even between studies of the same geological archive and therefore this topic requires further investigation. |
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| Keywords: | Qinghai Lake grainsize paleoclimate aeolian activity |
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