察尔汗盐湖雅丹地貌沉积物粒度特征研究

对雅丹地貌沉积物的研究可以判别雅丹地貌沉积物形成的沉积环境。主要采用了粒度分析方法对察尔汗盐湖雅丹地貌的沉积物进行分析研究。结果表明:①形成雅丹地貌的沉积物主要包括粉沙、极细沙、黏土和细沙;②粒度分布曲线主要有呈不对称的双峰分布、近乎对称的双峰分布和单峰分布等4种类型。呈双峰态的分布曲线,主、次峰均位于粉沙粒级和极细沙粒级,区别仅是两个粒级含量的高低;③雅丹地貌沉积物的平均粒径介于3.95～7.18 Φ之间,平均值为5.97 Φ;标准离差变化范围为1.37～2.47,平均值为1.99;偏度的变化范围为-0.27～0.58,平均值为0.10;峰态的值介于0.71～1.28之间,平均值为0.93。运用萨胡判别公式及沉积物粒度组成和粒度分布曲线特征进行判断,可知察尔汗盐湖雅丹地貌沉积物的形成环境主要为湖相、滨湖相和河流、三角洲沉积环境,同时还有浊流沉积和极少的风沙沉积环境,形成环境十分复杂。

Grain-size Characteristics of the Deposits from Yardang Landforms in the Charhan Salt Lake Area

The sediments from yardang landforms bear rich information about sedimentary environment.This paper mainly adopts granularity analysis method to study the deposits from yardang landforms in the Charhan Salt Lake area,Qinghai,China.Results indicate:(1) Main components of the deposits are silt sand,very fine sand,clay and fine sand.(2) There are 4 types of grain size distribution curves,namely asymmetric bimodal,near-symmetric bimodal,and unimodal.The main peak and the secondary peaks of the bimodal distribution curves appear in silt sand fraction and very fine sand fraction,respectively,and the only difference is the contents of the two fractions;(3)The mean size of the deposits ranges from 3.95 Φ to 7.18 Φ,and the mean value is 5.97 Φ;the standard deviation varies from 1.37 to 2.47,and the mean value is 1.99;the skewness ranges from-0.27 to 0.58,and the mean value is 0.10;the kurtosis varies from 0.71 to 1.28,and the mean value is 0.93.According to Sahu’s discrimination formula and the characters of both the grain size composition and distribution curves,it is found that the main sedimentary deposits are formed in lacustrine environment,lakeshore environment and fluvial environment,delta environment,as well as turbidity environment and a few aeolian environment.The sedimentary environments of the deposits are very complex.