黄河三角洲北部潮间带沉积物的粒度特征

根据1964－1976年在黄河河口区选取的两条潮滩断面水准测量和底质粒度分析资料，并对样品用激光粒度仪进行分析，探讨黄河三角洲北部潮滩对黄河口南迁的响应。结果表明，在开敞程度较高的断面，潮间带狭窄，水边线附近形成贝壳担，从高潮位到低潮位粒径变细、分选性变差，表现出波浪作用特征；在开敞程度较低的断面，潮间带较宽，由高潮位向中潮位沉积物逐渐变粗，再向下粒径基本不变，从高潮位到低潮位分选变好，潮流作用较为显著。此外，两断面下部均形成了波浪侵蚀陡坎。这些特征说明黄河改道后，这晨岩滩波浪作用加强，其侵蚀效应已显现出来。

GRAIN SIZE CHARACTERISTICS OF TIDALFLAT SEDI MENTS, NORTHERN YELLOW RIVER DELTA

In the present contribution, we report the coastal profile characteristics of two transections in the northern Yellow River Delta (i.e. the Yellow River mouth area from 1964 to 1976). Leveling along the profiles and sampling in 100 m intervals were carried out along the profiles. Profile P1 is 1 175 m in length (13 surficial sediment samples were collected) and Profile P2 is 2 250 m in length (23 samples collected). We analyzed these samples with a Cilas 940 L particle sizeanalyzer and computed the grain size parameters. The result shows that along P1, from the mean high water level to the lower parts, the sediment becomes finer and more poorly sorted, indicating an effect of wave action. However, along P2, from the high water downward, the sediment becomes coarser and better sorted, indicating a tidally dominated environment. Furthermore, wave induced low cliffs are formed, where abrupt changes in grain size occur, and accumulation of shell debris is present near the high water on P1. These analyses demonstrate that wave action is becoming active after the Yellow River mouth shifted to southward and wave induced erosion has begun to alter the tidalflat morphology.