张家界甘溪砾石沉积物粒度的空间变化及其原因  

Spatial variations of gravel sediment granularities and their causes in Ganxi Stream of Zhangjiajie

作　　者：王随继[1] 闫云霞[1] 颜明[1] 贺莉[1] 方海燕[1] 王彦君[1] 

机构地区：[1]中国科学院地理科学与资源研究所中国科学院陆地水循环及地表过程重点实验室,北京100101

出　　处：《地理科学进展》2014年第1期34-41,共8页Progress in Geography

基　　金：张家界世界地质公园地质遗迹保护专项基金项目

摘　　要：以往研究沉积物粒度分布规律时，主要局限于砂质沉积物，至多涉及细砾，对于卵砾、卵石、漂石等粗大砾石沉积物的粒度分布规律很少涉及。以张家界山地河流甘溪现代砾石沉积物为研究对象，样品的颗粒粒径介于23～663mm，分析了河床、心滩和河岸沉积物样品的累积频率分布曲线。结果表明，这些河流砾石沉积物具有较好的统计规律和空间变化趋势，其分布特征可以用累积频率曲线来表达，一般呈现出清晰的两段式或三段式分布特征，是对不同水位洪水动力的响应。粒度参数反映出这些砾石沉积物具有较好的分选性和球度。河道砾石的中值粒径沿程变小，反映了河流水动力沿程变小的规律。岩壁崩塌的砂岩块体短期难以受到流水的充分改造，使河流沉积物的峰态呈现多样化；漂石及卵石缝隙间拦截了低水位洪水所携带的部分较细砾石，引起河道砾石沉积物呈现负偏。该项研究对于山地河流巨大碎屑沉积物的定量研究具有启示作用。Cumulative probability curve of particle granularities is one of the methods to study the sediments. However, the sediments in the studies were mainly sands/sandstone and silts/siltstone, and granule at most in the past. Recently the rivers with large gravel bed materials including pebbles, cobbles and boulders in mountainous regions have been studied more and more. But the distribution pattern of the granularities of coarse gravels such as pebbles, cobbles and boulders has yet to be well studied. In this study, taking the modern gravel sediments of the mountainous Ganxi Stream in Zhangjiajie scenic spot as an example, the cumulative probability curves of gravel granularity were studied for the sampling on the channel bed, mid-channel bar and channel bank. The granularities of these gravel sediments ranged from 23 mm to 663 mm, with most of them being pebbles, cob- bles and boulders. The results showed that these fluvial gravel sediments followed a statistical pattern very well and exhibited a spatial variation trend that reflected the river flow hydrodynamics. For each sample the gravel granularities could be expressed by a cumulative probability curve clearly with two or three sections. The grav- els in different sections reflected different fluvial power in different flooding stages. Granularity parameters showed that the gravel sediments have higher degree of sortability and sphericity. The median diameters of the gravels on channel bed have a decreasing trend downstream, reflecting the decrease of stream power in that di- rection. The reason for the various kurtosis of the gravels is that the blocks that fell to the river from the cliffs of ＂the sandstone forest＂ had not been modified sufficiently by the stream flow. The fine gravels intercepted in the apertures of cobbles and boulders in low flooding stages resulted in negative deflection of granularity distribu- tion of the channel gravel sediments. By comparing the sphericity among different lithological gravels one can find that the gravels composed

关 键 词：山地河流 沉积物 砾石 卵石 漂石 粒度分布 张家界甘溪 

分 类 号：P512.2[天文地球—地质学]