干旱区生态环境知识资源中心

Most continental sediments are polymodal, composed of overlapping components of which the grain size generally obeys some type of natural distribution. The grain-size components and their function types can be determined from frequency and cumulative curve plots in order to define the function formula of the grain-size distribution. The function parameters can be estimated by fitting a defined function formula to the measured grain-size data of the sample, which simultaneously achieves numerical partitioning of the sedimentary components. Genetic analysis of grain-size components of hydraulic and aeolian sediments demonstrates the following environmental implications: Fluvial sediment is composed of isolated saltation and suspension components. The sediments in closed lake basins are dominated by a suspension silt-clay component with a small proportion of saltation sand. The fine sand component makes up the majority of desert sand, overlapping with a small proportion of fine dust. Aeolian loess is composed of two overlapping components: a short suspension-time silt component and a long suspension-time fine component. Aeolian material in the North Pacific deep-sea sediments is dominated by long suspension-time fine dust. The fine component in aeolian sediments shows a consistent grain-size distribution and genetic connection from the desert sand, loess of northern China to the North Pacific Ocean, which is mainly transported by westerly winds and is dispersed in the atmosphere, forming a background dust. (C) 2002 Elsevier Science B.V. All rights reserved.