|Alternative Title||SOIL 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|
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|
|Indexed By||CSCD ; 北大中文核心|
|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）|
|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.|
|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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