黄河下游原阳段沉积物粒度特征与沉积环境分析

为探究现代黄河下游沉积环境演化，在原阳段钻取了两个钻孔岩芯(YHX-1、YHX-2),通过对钻孔沉积物粒度测试与分析，运用沉积物粒度参数、频率曲线与概率累积曲线，结合沉积物岩性及周边钻孔年代信息，划分研究区钻孔地质年代，揭示研究区沉积水动力条件及环境演化历史。结果表明：YHX-1分为7个沉积段，YHX-2钻孔为11个阶段，中更新世时期，两根钻孔以中细砂为主，沉积相以河床亚相为主；晚更新世时期，钻孔经历短暂河漫滩微相，进入漫长的河床相沉积；全新世早期，YHX-1钻孔由湖泊沼泽沉积转变为河漫滩沉积，YHX-2钻孔为河漫滩沉积；全新世晚期，黄河改道流入当今河道，两根钻孔河床沉积相对比分析表明，改道后黄河主河道经历由北向南的变迁过程。

Grain-size characteristics and sedimentary environment of sediments in Yuanyang section of the Lower Yellow River

To explore the modern Yellow River downstream sedimentary environment evolution, two borehole were achieved in YuanYang section named as YHX-1 and , YHX-2, through the sediment grain size analysis, application frequency curve of sediment grain size parameters, and probability cumulative curves are discussed combined with sediment lithologic and area information to divide the geological age model and illustrate the sedimentary hydrodynamic conditions and environmental evolution history in the study area. The results show that YHX-1 can be divided into 7 sedimentary sections, and YHX-2 into 11 stages. In the Middle Pleistocene, the two holes are dominated by medium and fine sand, and the sedimentary facies is dominated by bed subfacies. During the late Pleistocene, the borehole shortly experienced floodplain microfacies and changed to riverbed facies deposition for a stable stage. In the early Holocene, YHX-1 was transformed from lacustrine marsh deposit to floodplain deposit, and YHX-2 was floodplain deposit. In the late Holocene, the Yellow River diverted into the current channel , and the comparative analysis of the thickness of the sedimentary facies of the two boreholes shows that the main channel of the Yellow River in the study area underwent a transition process from north to south.