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    长江安庆段河谷区第四系沉积特征与古河道演化

    Quaternary sedimentary characteristics and paleochannel evolution in the Anqing valley of the Yangtze River

    • 摘要: 长江安庆段NE向河谷中发育河流相与山麓相两套沉积体系。文章基于实测第四系钻孔资料,通过构建NW向、NNE向钻孔对比剖面,揭示了该区长江冲积平原、岗地等地质地貌单元地层组合特征;结合区域新构造运动特征、气候变化等资料分析,探讨了长江河谷古河道演化历程。研究结果表明:长江安庆段河谷区发育了至少2个由含砾粗砂到含粉砂黏土的河流沉积旋回,两侧岗地同期沉积了下蜀组及戚家叽组山麓相地层;第四系沉积物由河流冲积、风成堆积等多种成因类型组成,经历了早中更新世冲洪积,中晚更新世风成堆积、河流下切侵蚀与充填等地质过程;新构造运动、冰期-间冰期气候旋回波动、海平面升降等因素共同影响了长江安庆段古河道演化历程。

       

      Abstract: Two sets of sedimentary systems, fluvial facies and piedmont facies, are developed in the NE trending valley of the Anqing section of the Yangtze River. Based on the measured Quaternary boreholes, through comparing cross sections of the NW and NNE directional boreholes, this paper revealed the stratigraphic combination characteristics of geological and geomorphic units, such as the alluvial plain and hillock of the Yangtze River. Then, we discussed the evolution process of the paleochannel in the Yangtze River valley in combination with the regional neotectonics characteristics, climate change and other information. The results show that there are at least two river sedimentary cycles developed in the Anqing valley along the Yangtze River, ranging from gravelly coarse sand to silty clay. The Xiashu Formation and Qijiaji Formation were deposited simultaneously on both sides of the hilly land. Quaternary sediments are composed of river alluvium, aeolian sediments and other genetic types, and have experienced geological processes such as early-middle Pleistocene alluvial-proluvial process, middle-late Pleistocene aeolian accumulation, river undercutting erosion and filling. Neotectonics, climate changes during the glacial to the interglacial, sea level eustacy and other factors jointly affect the evolution of the ancient channel in the Anqing section of the Yangtze River.

       

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