衡阳地区河流阶地第四纪红土与河漫滩沉积物粒度特征对比

THE GRAIN-SIZE CHARACTERISTICS COMPARISON BETWEEN RIVER TERRACE Q LATERITE AND VALLEY FLAT SEDIMENT IN HENGYANG REGION

湘江河流阶地上第四纪红土分布广泛,本文对衡阳高兴红土剖面(GX)和吉祥河漫滩剖面(JX)样品粒度分析与对比结果表明:(1)衡阳河流阶地红土以粉砂组分为主,次为砂砾组分,粘粒组分含量最少;河漫滩沉积物以砂砾组分为主,其次粉砂组分,粘粒组分含量很少。(2)红土10μm~50μm粒组平均含量32.74%,远低于北方黄土和下蜀土等典型风成沉积物,样点散落范围较为集中,河漫滩沉积物样点相对分散,空间分布位置上有重合区域。红土既不是风力沉积物,也不完全属于流水沉积物。为搬运动力弱于河漫滩沉积的流水作用下沉积,并经历强烈化学风化作用改造而成。

There is wide distribution of Q laterite on Xiangjiang river terrace.In this paper,the grain size analysis and comparison of Hengyang Gaoxing laterite section(GX)and Jixiang valley flat section(JX)sample shows(1)the laterite on Hengyang river terrace is mainly silt,secondly sand-gravel,with the least clay particle;whereas the valley flat sediment is mainly sand-gravel,secondly silt,with a few clay particle.⑵the laterite 10μm-50μm average 32.74%far lower than the typical aeolian sediment of N loess and Xiashu loess,samples are more concentrative,the samples of valley flat are more scattered,with superimposition area in space distribution.The laterite is neither aeolian sediment nor completely water flow sediment.It is the sediment of water flow transportation weaker than valley flat sediment,and reformed by intense chemical weathering..