摘要
黄河在宁夏沙坡头形成了"几"字形河曲地貌,并在河曲凸岸发育了3级河流阶地。本文针对沙坡头大弯河流阶地特征、阶地年龄,以及大拐弯的成因进行了分析,探讨本区地貌发育的机制。结果表明:(1)沙坡头大弯3级河流阶地形成的主要原因是构造抬升作用,气候变化对此处阶地形成的作用不明显。在区域新构造活动强烈的背景下,约中更新世末期中卫盆地开始抬升,黄河河道被固定,河流下切形成本区的最高阶地T3;约在70kaB.P.、8kaB.P.形成T2、T1阶地。(2)沙坡头黄河大拐弯是由香山—天景山断裂左旋走滑位错,以及水流受地球自转偏向力的河流内生动力共同作用的结果,并且河流的内生动力作用远大于前者的贡献。
The Shapotou area is located in Zhongwei city in the Ningxia Hui Autonomous Region,which is also situated in the arc area on the northeastern side of the Qinghai-Tibet plateau with very active neo-tectonic movements in China's Mainland.The Yellow River crosses the Xiangshan -Tianjingshan fault and flows through the Shapotou.The Xiangshan-Tianjingshan fault is mainly a left-lateral strike-slip.The Yellow River formed a beautiful geomorphological meander,the Big Bend,which is similar to the ＂Ω＂ type.It developed three river terraces on the convex bank since it turns around in the Shapotou area.Over the past few decades,geologists have conducted many studies in this strong neo-tectonic movement and special tectonic setting,concerned with active faults,the tectonic deformation process in the Quaternary,the scales and rates of active fault displacement,and the causes of the Shapotou Big Bend.However,there is not a comprehensive analysis of the origins of the Big Bend.The research on the river terrace is one of the most important topics in geomorphology.River terraces are the most reliable records of river histories.The meandering river is ubiquitous in nature; meandering is a natural property of rivers.This paper focuses on the characteristics and ages of river terraces and analyzes the causes of the Big Bend to explore the causes of landforms in this area from the vertical and horizontal directions.Based on field investigations and comparisons to former studies,three terraces were revealed.The formation age of the highest terraces is ～170 ka B.P.The T2 and T1 terraces were subsequently formed at ～70 ka B.P.and 8 ka B.P.,respectively.The three river terraces in the Shapotou Big Bend formed mainly due to tectonic uplift,while the impact of climate change is not obvious on the formation of the terraces.Climate change is not the only element that controls river incisions：the terraces in this area depend on tectonic uplift.In the context of strongly regional neo-tectonic activities,when the Zhongwei Basin was e
出处
《地震工程学报》
CSCD
北大核心
2013年第3期631-640,共10页
China Earthquake Engineering Journal
基金
国家自然科学基金(批准号:40972118)
关键词
黄河
沙坡头
河流阶地
大弯
成因
The Yellow River
Shapotou
river terrace
big bend
genesis
