Particle size separation and evidence for pedogenesis in samples from the Chinese Loess Plateau spanning the past 22 m.y.
作者单位：Department of GeographyUniversity of LiverpoolLiverpool L69 7ZTUK
会议名称：《中国科学院地质与地球物理研究所2008学术年会》
会议日期：2009年
学科分类：070903[理学-古生物学与地层学(含：古人类学)] 0709[理学-地质学] 07[理学]
基 金：supported by the Chinese Academy of Sciences(KZCX2-YW-117) 973 project 2004CB720203 the National NaturM Science Foundation of China(projects 40672115 and 40730104)
关 键 词：loess pedogenesis granulometry pipette analysis magnetic properties
摘 要：A comparison between particle size distributions determined by laser diffraction and the pipette method confirms previous studies that point to a variable underestimate of the clay fraction using laser diffraction,relative to the values obtained by pipette *** order to yield four particle-sized fractions(8μm) for further analysis, the pipette method was used on loess and paleosol samples from sites on the Chinese Loess Plateau spanning the past 22 *** all cases,a subsidiary mode in the8μm fraction provides a basis for evaluating the relative contributions of pedogenic and detrital *** using acetic rather than hydrochloric acid for carbonate removal results in no significant loss of ferrimagnetic minerals and allows magnetic characterization of the separate fractions. This confirms the isolation of almost all the finest,pedogenic ferrimagnetic grains in the clay fraction and their negligible contribution to the magnetic properties of the coarse fractions in all the samples from early Miocene time *** similar conclusions may be drawn from previous studies of late Pleistocene samples from the east-central and extreme western parts of the Chinese Loess Plateau,we conclude that this approach provides a basis for separately characterizing eolian deposition and pedogenesis throughout the region and for the whole time span of loess accumulation.