古地理学报2018，Vol.20Issue(3)：477-488,12.DOI:10.7605/gdlxb.2018.03.035
黄河晋陕峡谷1.1Ma阶地的形成及其构造背景
Formation of the Yellow River terrace about 1.1 Ma along the Shanxi-Shaanxi Gorge and its tectonic background
摘要
Abstract
Detailed field investigation on river terraces was carried out in Hequ,Heiykou,Yanshuiguan,and Hukou along the Shanxi-Shaanxi Gorge of the Yellow River.Three terrace staircases and one strath were found in the Hequ area.The strath was formed during the Neogene (Tangxian Age) and hence is named Tangxian Strath,whereas the terraces were formed during the Quaternary based on the overlapped aeolian deposits.The altitude of the Tangxian Strath is about 1000 m (150 m above local modern Yellow River).Heights of three terraces above local modern Yellow River are 110 m,80 m and 12 m.Development of five terrace staircases below the Tangxian Strath was also found in the Heiyukou area.The Tangxian Strath is higher on the western bank and lower on the eastern bank and has an altitude ranging from 940 m to 970m.The heights of these five terraces above modern Yellow River are 130 m,80 m,50m,12 m,and 4 m.Six terrace staircases are present in the Yanshuiguan area.The heights of these terraces above local modern Yellow River are 180 m,130 m,95 m,50 m,20 m,and 4 m.Eight terrace staircases were counted in the Hukou area.The heights of river terraces in this area are 260 m,210 mm,180 m,120 m,80 m,60 m,35 m,and 15 m.In both Yanshuiguan and Hukou areas,all the terraces were formed during the Quaternary.Stratigraphic studies at the Hukou area indicate that the topmost terrace is overlain by a layer of loess which is about 110 m in thickness.Oriented loess samples were also collected from the highest terrace in the Hukou area.Twelve paleosols were counted,and L13 is recognized in the lowest part of the section.Magnetostratigraphic analysis indicates that the terrace was formed around 1.1 Ma B.P.Three stages of the Yellow River can be divided during the development of the river terraces and Tangxian Strath along the Shanxi-Shaanxi Gorge.Firstly,Ordos Block experienced a long stable phase before 3.3 Ma B.P.,when the Tangxian Strath formed.Dominant processes of the Yellow River during this stage was lateral cutting with minimal downcutting.The second stage was during 3.3 Ma B.P.to 1.1 Ma B.P.The stable Ordos Block was probably disrupted,and the Yellow River experienced a slight downcutting.After 1.1 Ma,the Yellow River suffered significant downcutting.The Yellow River terrace about 1.1 Ma and the Shanxi-Shaanxi Gorge were formed due to a quick uplift of the Ordos Block during this period.关键词
晋陕峡谷/黄河/河流阶地/阶地年代/黄土Key words
Shanxi-Shaanxi Gorge/Yellow Rive/river terrace/terrace age/loess分类
天文与地球科学引用本文复制引用
刘运明..黄河晋陕峡谷1.1Ma阶地的形成及其构造背景[J].古地理学报,2018,20(3):477-488,12.基金项目
国家自然科学基金项目(编号:40901006)资助.[Financially supported by the National Natural Science Foundation of China (No.40901006)] （编号:40901006）
