High-resolution X-ray fluorescence core scanning of landslide-dammed reservoir sediment sequences on the Chinese Loess Plateau: New insights into the formation and geochemical processes of annual freeze-thaw layers
High-resolution X-ray fluorescence core scanning of landslide-dammed reservoir sediment sequences on the Chinese Loess Plateau: New insights into the formation and geochemical processes of annual freeze-thaw layers
复制标题
DOI：
10.1016/j.geoderma.2016.06.008
复制
发表时间：
2016-10
期刊：
影响因子：
6.1
通讯作者：
Xiaqing Wang;Zhangdong Jin;Liu-Mei Chen;J. Xiao;Fei Zhang
中科院分区：
文献类型：
--
作者：
Xiaqing Wang;Zhangdong Jin;Liu-Mei Chen;J. Xiao;Fei Zhang
中国黄土高原（CLP）普遍存在滑坡坝水库。由于季风水文气候的季节性差异，在滑坡坝水库沉积序列的特点是侵蚀黄土与每年冻融层的沉积偶，是理想的对象，重建流域侵蚀过程，水文事件，土地利用和人类活动的历史。从给定年份的沉积偶中识别年度冻融层对于确定沉积物序列和利用沉积物重建侵蚀历史至关重要，因为它们被认为是单个年份中最后一次水文事件的边界。利用高分辨率X射线荧光岩心扫描、粒度和矿物学，在中电北方和南方的靖边和合水滑坡坝水库的两个代表性岩心剖面中识别出细粒层。结果表明，由于沉积过程中的分选和分层作用，年内和年内的细粒层都具有高Ca、Fe和Mn含量，而低Si含量，以粘土、方解石和细粉砂为主。然而，钙表现出两个不同的趋势与铁（和锰）在这些细粒层从两个核心部分。它们之间的关系的陡峭的斜率反映了进一步的Ca和Fe（和Mn）的浓度，可能导致冻融过程。因此，具有高浓度的Ca和Fe和高斜率的相关性的细粒层被确定为年度冻融层。通过高分辨率XRF岩心扫描识别滑坡坝水库沉积物序列中的年度冻融层，为研究其形成和移动的元素富集过程以及沉积物序列的定年提供了新的见解。
Landslide-dammed reservoirs are widespread on the Chinese Loess Plateau (CLP). Due to the contrasting seasonality of the monsoonal hydroclimate, sediment sequences in landslide-dammed reservoirs are characterized by deposition couplets of eroded loess with annual freeze-thaw layers that are ideal objects to reconstruct catchment erosion processes, hydrologic events, land use and human activity history. Identifying annual freeze-thaw layer from the deposition couplets in a given year is crucial for dating sediment sequences and for reconstructing erosion history using sediments because they are considered to be the boundary of the last hydrological event in an individual year. Using high-resolution XRF core scanning, grain size and mineralogy, fine-grained layers were identified in two representative core sections from the Jingbian and Heshui landslide-dammed reservoirs on the northern and southern CLP. The results show that both annual and intra-annual fine-grained layers have high Ca, Fe, and Mn contents but low Si contents and are dominated by clays, calcite and fine silt as a result of sorting and stratification during deposition. However, Ca exhibits two distinct trends with Fe (and Mn) in these fine-grained layers from both core sections. The steeper slopes of the relationship between them reflect further concentrations of both Ca and Fe (and Mn) that potentially result from freeze-thaw processes. The fine-grained layers with high concentrations of Ca and Fe and high slopes of their correlations are therefore identified as the annual freeze-thaw layers. The identification of annual freeze-thaw layers in landslide-dammed reservoir sediment sequences by high-resolution XRF core scanning provides new insights into their formation and mobile elemental enrichment processes as well as dating of the sediment sequences.