滹沱河古河道剖面粒度参数特征及沉积环境

Grain Size Character and Sedimentary Environment of Hutuo River Paleochannel Section

滹沱河平原段从20世纪70年代中期开始,河道常年干涸断流,两岸土地沙化,河流生态系统遭到严重破坏.开展滹沱河浅埋古河道研究,对于研究区水文生态环境的可持续发展具有重要意义.在高密度取样和详细测年数据的基础上,应用沉积物粒度频率分布曲线和概率累积曲线分析方法,结合剖面岩性特征,对滹沱河古河道剖面（GCA）进行沉积相分析,讨论了研究区3万年以来的沉积环境变化过程.结果表明：GCA剖面地层由两个沉积阶段组成,以1060cm为界;下段为29.4～26.9kaB.P.（1240～1060cm）期间,研究区以浅湖沼相沉积环境为主,后期转变为河漫滩相沉积环境,水动力条件弱;上段为26.9kaB.P.至今（1060～0cm）,发育了河床-心滩相沉积组合,共同构成一个较完整的辫状河道沉积序列,水动力条件强且变化大.

Hutuo River has dried up and cut off perennially because of climate drought since the mid-1 970s. The river ecosystem has suffered severe damage.It is the basis of river ecosystem recovery and wetland ecologi-cal environment reconstruction to study the shallowly buried paleochannel of Hutuo River.In this paper,the sedimentary facies of Hutuo River paleochannel are studied using the methods of grain size analysis.And the sedimentary environmental change process of the study area since 30 ka.B.P.is discussed on the basis of high density sampling and detailed data.The results show that the paleochannel section is composed of two sedimen-tary segments with the boundary of 1 ,060 cm.The lower segment is deposited from 29.4 to 26.9 ka.B.P.. Limnetic facies sediments are developed in the study area.The upper segment is deposited from 26.9 ka.B.P. to the present.Fluvial facies sediments are developed in this stage,including two kinds of fluvial subfacies.The grain size characters are changed between the two segments correspondingly.