黄河贯通时间的新探索

NEW DISCUSSION ABOUT THE RUN-THROUGH TIME OF THE YELLOW RIVER

石化 2井钻孔的元素地球化学研究表明 ,现代黄河三角洲地区元素组成具有明显的规律性 ,与现代黄河沉积物元素组成相比 ,埋深 2 33m之上的沉积物中大多数元素含量及元素之比与之接近 ,而 2 33m之下的沉积物元素组成则明显偏离黄河物质的化学组成。上部与下部沉积物的元素组成明显不同。判别函数及物源指数计算结合岩性、粒度分析揭示 ,黄河物质在该地区的影响深度可达 2 33m左右 ,因此 ,推测大致在早更新世时黄河贯通并流进华北平原的现代黄河三角洲地区。

Chemical compositions of the Yellow River sediments were very stable during the geologic history.The modern Yellow River area was one of the areas that influenced ancient Yellow River materials.We can compare element composition characteristics of modern Yellow River sediments to deduce the formation time of the Yellow River as a complete river emptying into the sea according to evolution regularities of chemical compositions of sediments in the river area.Elemental geochemical study of Shihua 2 Core in the Yellow River Delta reveals that there are regular element compositions in the core sediments,and compared to the modern Yellow River sediment,the upper 233 m sediments in the core have similar element compositions to it,while sediments below 233 m yield clearly different element compositions.This shows that obviously different element compositions occur between the upper sediments above 233 m depth and the lower sediments.Discriminant functions(DF)and provenance index(PI)analyses indicate that the upper 233 m sediments mainly came from the Yellow River,and lithological and granular studies also support this origin.Based on neighboring core dating data,we infer that it is about early Pleistocene when the Yellow River ran through the Sanment Gorge and flowed into North China Plain and modern Yellow River Delta area.Of course,more cores and more accurate Quaternary dating are needed to support it,but our preliminary study provides a new and original method to solve the origin of the Yellow River.