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| 山西河曲黄河阶地序列初步研究 | |
| 引用本文： | 邱维理,张家富,周力平,李容全.山西河曲黄河阶地序列初步研究[J].第四纪研究,2008,28(4):544-552. |
| 作者姓名： | 邱维理 张家富 周力平 李容全 |
| 作者单位： | 1. 北京师范大学地理学与遥感科学学院,北京,100875 2. 北京大学城市与环境学院地表过程分析与模拟教育部重点实验室,北京,100871 |
| 摘 要： | 黄河干流奇特的"几"字形格局是其复杂发育历史的表现。由于流域内的地质与气候条件复杂多样,分段开展深入研究是全面认识黄河的基础。晋陕峡谷是研究黄河演化的关键地段之一,河流阶地忠实地记录着河流发育的历史。文章选择山西河曲县城附近黄河阶地发育典型的河段进行研究,在实测河流阶地地貌剖面的基础上,系统采集了20个年代样品进行光释光(OSL)测年。依据地貌类型、沉积特征以及定年结果,建立了该河段黄河阶地的演化序列,得出以下结论:1)河曲地区黄河曲流凸岸形成有4级阶地,T4阶地的形成主要受构造控制,而T3,T2和T1阶地的形成主要与气候变化有关,各阶地的年龄分别是T4为90ka,T3为30ka,T2为20ka,T1为3.4ka。2)河曲地区约140ka以来河流地貌的演化经历了5个阶段,各阶段以下切侵蚀开始,结束于各阶地堆积面的塑造。约90ka以来,该地区河谷谷底下降速度和曲流可能最大侧蚀速度的平均值分别为0.9mm/a和33.4mm/a。在不同阶段,二者的大小变化及组合状况各异,在构造相对稳定条件下,河流以侧蚀作用为主,其侧蚀速度与气候和岩性条件有关。3)河曲地区的黄河曲流是在河流下切过程中逐渐侧蚀、演化而成的,具有内生曲流的特点。4)T4阶地的泥流沉积和加积堆积,可能记录了地方性气候变化,其范围和意义有待进一步研究,另外,T3,T2和T1形成过程中气候变化的作用也有待探讨。 |
| 关 键 词： | 黄河 河曲地区 河流阶地序列 光释光年代 河谷演化 |
| 收稿时间： | 2008-03-10 |
| 修稿时间： | 2008-05-04 |
PRELIMINARY STUDY OF THE TERRACE SEQUENCE OF THE HUANGHE RIVER IN HEQU AREA,SHANXI,CHINA |
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| Qiu Weili,Zhang Jiafu,Zhou Liping,Li Rongquan.PRELIMINARY STUDY OF THE TERRACE SEQUENCE OF THE HUANGHE RIVER IN HEQU AREA,SHANXI,CHINA[J].Quaternary Sciences,2008,28(4):544-552. | |
| Authors: | Qiu Weili Zhang Jiafu Zhou Liping Li Rongquan |
| Institution: | 1. School of Geography, Beijing Normal University, Beijing 100875; 2. Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing 100871 |
| Abstract: | The unique π-shaped pattern of the main course implicates a complex history of the Huanghe River.With a complicated geological background and diverse climatic conditions of the drainage basin,to have a better understanding of its geomorphologic evolution it is important to carry out profound studies by section and section of the river.The Jin-Shan Gorge is amongst the key sections and its river terraces are the most reliable records of river histories.Thus,in the north part of the Jin-Shan Gorge,the authors chose an area with typical river terraces along the convex banks of the meanders near Hequ,Shanxi Province,China,to survey.In this area,four river terraces of the Huanghe River were recognized by fluvial sediments.A geomorphologic profile was investigated in details and twenty samples were collected for optically stimulated luminescence(OSL)dating from nine sedimentary sections.The samples were dated using single-aliquot regenerative-dose method,and a luminescence chronology for the terrace sequence was established.The terrace age is referred to the formation age of terrace treads.The geomorphologic evolution of the terrace sequence was then inferred from the optical dates,the geomorphologic and sedimentary characters of the terraces.The conclusions can be summarized as follows.(1)The formation ages of the four terraces are ca.90ka(T4),ca.30ka(T3),ca.20ka(T2),and ca.3.4ka(T1),respectively.The highest terrace(T4)was formed by deep incision as the result of tectonic uplift evidenced by the high bedrock cliff beneath the alluvium.The lower terraces(T3,T2,T1)were formed by slight incisions which might be due to the river discharge changes or climate changes coupled with lateral erosion.(2)The development of river valley in Hequ area can be divided into five stages which begin with the incisions of river bed and end with the construction of terrace surfaces.The average rates of valley bottom descending and possible lateral erosion since ca.90ka ago are estimated by the terrace height,width,and age as 0.9mm/a and 33.4mm/a respectively.But in different stages these two rates varied and matched differently.The lateral erosion prevailed when tectonic uplift was relative slow.But the rate of lateral erosion was affected by climate and rock types.(3)The meanders of the Huanghe River in Hequ area were developed gradually during the down cutting processes accompanied with obvious lateral erosion.An asymmetric cross profile of the river valley was formed which features the ingrown meanders.(4)The debris flow deposit with red clay balls and the aggradational gravel layers in terrace T4 formed between 140ka and 90ka might be records of local climate changes,although the extent and significance need further studies.The role of climate change in the formation of T3,T2,and T1 is also pending further discussion. |
| Keywords: | the Huanghe River the Hequ area a terrace sequence OSL dating development of river valley |
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