摘要
对清江中游建始、巴东等地高海拔古宽谷中残留阶地堆积物的特征进行了研究。通过对堆积物的ESR测年获得了8组年龄数据,表明清江流域1 500-1 700 m高度剥蚀面可能形成于中更新世初（704±70-789±78 kaBP）,与长江三峡第五级阶地,清江第五、六级阶地为同时期形成。这可能指示在三峡地区已不存在多级夷平面,目前三峡地区的层状地貌可能是早更新世以来地壳抬升的结果。对整个流域层状地貌面堆积物年龄与海拔高度关系的分析表明,在400-1 700 m海拔高度范围,地貌面堆积物形成时代与海拔高度呈现一定的线性关系,即海拔越高,形成时代相对越老,海拔越低,形成时代越新,这反映了新构造的间歇性隆升。根据拟合直线计算出的平均抬升速率为162.14 cm/ka（100-800 kaBP）,是整个三峡河段近十万年来平均深切速率（80.15 cm/ka）的两倍,说明十万年以来,三峡地区地壳抬升幅度明显减小,新构造活动性明显减弱。
We studied characteristics of residual depositions of terraces,which developed in the high-elevation ancient dale in Jianshi and Badong areas,middle reaches of the Qingjiang River.We obtained 8 sets of age data through the ESR dating of residual depositions,and the results indicate that El.1 500 -1 700 m erosion surface in the Qingjiang River Basin may be formed in the early Pleistocene,which is the same period with the fifth terrace of the Yangtze River and the fifth terrace and the sixth terrace of the Qingjiang River.The results probably mean that there are not multiple planation surfaces,and the layered landforms may reflect the crustal uplift since the early Pleistocene in the Three Gorges region.Analysis of the relationship between deposition age and altitude in the entire Qingjiang River indicates that the deposition age and the altitude has a linear relation in El.400-1 700 m,which is the higher the altitude is,the older the formation age relatively is.This reflects the intermittent nature of the neo-tectonic uplift.The calculated average uplift rate shows that the uplift rate has been reducing significantly,and the neo-tectonic activity was weakened in evidence.
出处
《人民长江》
北大核心
2010年第8期18-20,35,共4页
Yangtze River
基金
中国地质调查局国土资源大调查项目资助(1212010814057
1212010911016)
关键词
层状地貌
堆积物
同位素年龄
地貌演化
清江流域
layered landform
deposition material
isotopic age
geomorphic evolution
Qingjiang River
