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黄土高原聚湫沉积旋回、土壤侵蚀及区域差异
Alternative TitleSOIL EROSION RECORDED BY DEPOSITION COUPLETS IN LANDSLIDE-DAMMED RESERVOIRS ON THE CHINESE LOESS PLATEAU AND ITS REGIONAL DIFFERENCE
金章东1,2; 王夏青1,3; 张信宝4; 肖军1; 张飞1
Corresponding Author金章东
2017
Source Publication第四纪研究
ISSN1001-7410
Volume37Issue:6Pages:1161-1171
Other Abstract

黄土高原聚湫/淤地坝内的沉积物是黄土再侵蚀搬运的直接结果,以高堆积速率和多沉积旋回为特征,是认识黄土高原地球关键带过程和历史的理想载体之一。如何鉴定并有效划分沉积旋回是利用聚湫/淤地坝沉积序列恢复流域土壤侵蚀和地表环境过程的基础。本文选取地处黄土高原中部丘陵沟壑区(陕西靖边)和高塬沟壑区(甘肃合水)的两个聚湫为代表,利用高分辨率XRF岩芯扫描仪获取两个聚湫上部近代沉积序列的元素分布,提出划分沉积旋回的地球化学指标,并识别年际冻融层,获得旋回产沙模数及年际产沙量,进而讨论土壤侵蚀与强降水频率和强度的关系及区域差异。结果表明,沉积旋回的下部粗颗粒层均以高Zr为特征,上部细颗粒层则富集Al、Fe、Rb、Ca和Sr等造岩元素,由此提出Rb/Zr比值可有效划分沉积旋回。根据Rb/Zr比值分布,靖边和合水聚湫上部4m和2m沉积序列可分别划分为35个和18个沉积旋回。结合细颗粒层的137Cs比活度分布,划分的沉积旋回个数可分别与1963年以来两个地区强降水次数一一对应。靖边聚湫的年际沉积旋回数量和产沙模数均高于合水,是黄土高原丘陵沟壑区砂黄土更易遭受侵蚀的结果;在次降水量为50mm的强度下,靖边流域的产沙模数约为合水流域的两倍左右。重要的是,两个流域的产沙模数均与强降水次数和强度紧密相关,旋回产沙模数随降水强度线性增加。聚湫沉积旋回记录的侵蚀历史及区域差异将有助于深入认识黄土高原地球关键带中侵蚀风化、水文和生态环境变化等历史与过程。

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The sedimentary sequence in the landslide- and check-dammed reservoirs is originated from reworked loess within the catchment on the Chinese Loess Plateau, which is characterized by high sedimentation rate and various deposition couplets, so that it is one of the ideal objectives to understand processes and history of the Earth's Critical Zone within a single catchment on the Chinese Loess Plateau. How to effectively identify individual deposition couplets and to build their chronology is the first-order basis for reconstructing catchment soil erosion and for understanding its Earth's Critical Zone processes and history using reservoir sedimentary sequences on the Chinese Loess Plateau. In this study, the sedimentary sequences drilled from two typical landslide-dammed reservoirs at hilly and gully region (Jingbian, Shaanxi) and highland gully region (Heshui,Gansu) in the central Chinese Loess Plateau were scanned for elemental distributions using high-resolution X-ray fluorescence (XRF) core scanning, in order to plot out deposition couplets and annual freeze-thaw layers, then to obtain the sediment yields of individual couplet and annual sediment yields, and finally to address the relationship of soil erosion and frequency and intensity of heavy rainfall and its regional difference. The Jingbian landslide-dammed reservoir (37°18'N, 108°36'E) is located at Huabaowan Village, Jingbian County and belongs to a gully of the headstream of the Wuding River (one of major tributaries of the Yellow River). It was never destroyed, so its sediment has deposited since it formed during 1851 A.D. and 1861 A.D. The Heshui reservoir (36°1 'N, 108°7'E) is located at Laocheng, Heshui County and belongs to a gully of the middle reaches of the Malian River (one of secondary tributaries of the Yellow River). Its sediment has deposited since it formed till 1996A.D. when it was brought under cultivation. The topmost 4 m and 2 m sediments drilled from the depositional centers of the Jingbian and Heshui reservoirs respectively were used to obtain for elemental and ~(137)Cs distributions. The results showed that the underlying coarse-grained layer of each couplet is enriched by high Zr and the upper fine-grained one by high lithophile elements (Al,Fe, Rb, Ca, and Sr),so that Rb/Zr ratio by high-resolution XRF core scanning can be employed as an excellent geochemical proxy to plot out deposition couplets. By combining with ~(137)Cs activity distribution of the upper fine-grained layers in each couplet and identification of annual freeze-thaw layers among the couplets, there is consistent one-to-one correspondence between frequency of heavy rainfall and deposition couplets identified by Rb/Zr ratios since 1963A.D. The number of deposition couplets and erosion flux reflect frequency and intensity of heavy rainfall respectively, with a good correlation between rainfall intensity and the erosion flux of each couplet in respective sedimentary sequences. The erosion fluxes within the Jingbian catchment are double relative to the Heshui one at a 50 mm rainfall condition, the former with higher sediment yield under same rainfall intensity resulting from easily eroded sandy loess on the hilly and gully region of the Chinese Loess Plateau. On the other hand, sediment yield is closely correlated with frequency and intensity of heavy rainfall in both catchments, behaving a linear increase in sediment yield with increasing rainfall intensity. These observations of soil erosion and regional difference recorded by deposition couplets from both landslide-dammed reservoirs highlight the Earth's Critical Zone processes and history of erosion, weathering, hydrology, and eco-environmental changes on the Chinese Loess Plateau at decadal timescale.

Keyword聚湫 地球关键带 土壤侵蚀 降水强度和频率 黄土高原
Subject AreaX144
DOI10.11928/j.issn.1001-7410.2017.06.01
Indexed ByCSCD ; 北大中文核心
Language中文
CSCD IDCSCD:6106431
Funding Organization中国科学院重点部署项目(批准号:KZZD-EW-04-02) ; 中国科学院地球环境研究所黄土与第四纪地质国家重点实验室开放基金项目(批准号:SKLLQG1622)
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Document Type期刊论文
Identifierhttp://ir.imde.ac.cn/handle/131551/20875
Collection山地表生过程与生态调控重点实验室
Affiliation1.中国科学院地球环境研究所, 黄土与第四纪地质国家重点实验室
2.西安交通大学, 全球环境变化研究院
3.湖南文理学院资源环境与旅游学院
4.中国科学院水利部成都山地灾害与环境研究所
Recommended Citation
GB/T 7714
金章东,王夏青,张信宝,等. 黄土高原聚湫沉积旋回、土壤侵蚀及区域差异[J]. 第四纪研究,2017,37(6):1161-1171.
APA 金章东,王夏青,张信宝,肖军,&张飞.(2017).黄土高原聚湫沉积旋回、土壤侵蚀及区域差异.第四纪研究,37(6),1161-1171.
MLA 金章东,et al."黄土高原聚湫沉积旋回、土壤侵蚀及区域差异".第四纪研究 37.6(2017):1161-1171.
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