黄河下游的河浪作用及波痕特征

黄河下游受两种水动力条件——水流和风的作用。水流的作用产生各种水流波痕,包括直脊波痕、波曲波痕、舌形波痕和菱形波痕。风的作用引起河流内的波浪——河浪,并产生大量的波浪波痕。风的作用要比水流作用强度小,故波浪波痕的波长和波高均略小于水流波痕。而且在同一时期,水流主要影响主流线及其两侧的沉积物;而波浪主要影响浅水的边滩沉积物。这充分说明,在河流相沉积中也存在大量的波浪波痕。而且这些河浪产生的波浪波痕所测出的波痕要素是在海、湖相波浪波痕所属的范围之内,只不过河流相波浪波痕的大小比海、湖相小。河浪与水流对沉积物共同改造便产生干涉波痕,并分为A,B,C三种类型,且依次表明河浪作用强度增大的趋势。

FLUVIOWAVE AND RIPPLE MARK CHARACTERISITICS IN LOWER REACH OF YELLOW RIVER

The lower reach of Yellow River was under the action of twohydrodynamic factors----water flow and wind.Various kinds of water rippleswere formed on the sediments,including straight-crested,undulatory,lingoid and rhomboid ripples by the action of water flow.Fluviowave and a large amount of wave ripples were formed by the action of wind.The length and height of wave ripples were smaller than that of water ripples,because the strength of wind was smaller than that of water.Moreover,at the same period,water had an influence mainly on the sediments at the centre and two sides of the river,while fluviowave mainly on the shallow point bars.A large amount of wave ripples remained in fluviatile facies.The wave ripples produced by fluviowave were in the same range of indices as that of marine and facies,while the size of the former is smaller than that of the latter.The joint action of fluviowave and water on sediments formed the interfered ripple marks.