Differences of surface sediments in three basins of northern China and its implications
1, Ping Yan1
,2, Wei Wu1
,2, Yao Qian1
1State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, Beijing, China, 2Academy of Disaster Reduction and Emergency Management, Beijing Normal University, Beijing, China
Field investigation, topographic survey, sampling, laboratory analysis of grain size, mineral composition and chemical element were carried out on surface sediment samples from three river basins, including Keriya River in the west, Mu Bulag River in the middle, and Xi Xar Moron River in the east of northern China. The average grain size gradually coarsened from west to east for the three basins, the sorting worsened, the skewness increased, the kurtosis widened, and the hydrogenic characteristic became more obvious. In terms of mineral composition, the sediments were composed mainly of light mineral-based substances, especially quartz and feldspar, and the mineral maturity gradually decreased from west to east for the three basins. In terms of chemical elements, Si, Al, and Ca elements were dominant, and other elements were less concentrated. Compared with data of upper continental crust (UCC), most elements were depleted, with the exception of Si, Ca, and Co, and the self-enrichment level and loss level of these elements gradually increased. In addition, the variation coefficients also gradually increased from west to east for the three basins, indicating that the post-weathering effect on the three basins gradually increased. The chemical index of alteration (CIA) in the three basins was generally less than 50, and A-CN-K diagrams indicated that the three basins were in the initial chemical weathering stage and the weak loss stage of Ca and Na. Other elements did not show obvious signs of chemical weathering or migration. A-CNK-FM diagrams showed that Fe and Mg in the three basins underwent significant differentiation, and the effects of physical and chemical weathering on sediment characteristics were different. Analysis of the grain size and chemical weathering parameters showed that the grain size sensitive components, the standard deviation, the index of chemical variability (ICV), and the CaCO3 content could be used to properly distinguish the characteristic heterogeneity of the weathering of surface substances in the three basins. On the watershed scale, sorting differences of the surface sediments caused by climate-induced aeolian and fluvial interactions were a key factor in forming zonal distribution of physicochemical characteristics for the surface sediments from the three basins.