地理学报 ›› 2006, Vol. 61 ›› Issue (11): 1200-1207.doi: 10.11821/xb200611009

• 环境演变 • 上一篇    下一篇

三峡库区长江阶地冲积物的年代测定

韩志勇,李徐生,任雪梅,胥勤勉,杨达源   

  1. 南京大学城市与资源学系,南京 210093
  • 收稿日期:2006-04-16 修回日期:2006-08-15 出版日期:2006-11-25 发布日期:2010-09-01
  • 作者简介:韩志勇 (1968-), 男, 江苏南京人, 副教授, 主要从事第四纪年代学研究。E-mail: zyhan@nju.edu.cn
  • 基金资助:

    国家自然科学基金项目(40272126)

Dating of River Terraces in the Three Gorges Reservoir Area

HAN Zhiyong, LI Xusheng, REN Xuemei, XU Qinmian, YANG Dayuan   

  1. Department of Urban and Resources Sciences, Nanjing University, Nanjing 210093, China
  • Received:2006-04-16 Revised:2006-08-15 Online:2006-11-25 Published:2010-09-01
  • Supported by:

    National Natural Science Foundation of China, No.40272126

摘要:

三峡库区的长江阶地是研究川江、峡江水系演变的重要证据。发育冲积物的阶地主要出现在库区西半部的川东和重庆的中低山、丘陵区,最多有6级。阶地研究中遇到的主要问题是难以确定阶地的形成时代。我们采用TL法和ESR法测量了三峡库区6个地点阶地的堆积年龄。测量数据显示,ESR法基本不适合测定三峡库区冲积物的年龄;尽管TL法本身存在缺陷,但测得的T1~T4的堆积年龄得到其他独立的测年结果的支持。阶地T1~T4的TL年龄依次为7~17 ka、28~46 ka、62~81 ka和103~105 ka。此外,根据年代地层对比的方法以及前人的古地磁测量结果,推测三峡库区第四级阶地的年龄大于101 ka,第五级阶地的年龄大于392 ka,而第六级阶地的年龄小于780 ka。从而初步建立了三峡库区阶地堆积的时间序列。

关键词: 三峡, 阶地, 热释光, 电子自旋共振, 光释光

Abstract:

The river terraces of the Changjiang River in the Three Gorges Reservoir area are key to the study on the evolution of the water system of the Chuanjiang River and the Xiajiang River. These terraces mainly develop in the western part of the reservoir area, i.e., the hill and low mountain region in the eastern part of Sichuan. Up to 6 levels of terraces are identified. The main problem encountered in terrace related studies is the lack of reliable temporal controls on the terrace formation. We measured the terrace ages by using the TL and ESR methods. The results show that the ESR method is likely unsuitable for dating fluvial sediments in the Three Gorges Reservoir area. Although the TL method has intrinsic flaws, the ages of terrace T1-T4 given by this method are supported by independent dating results. The TL ages of terrace T1-T4 are estimated to be 7-17 ka, 28-46 ka, 62-81 ka and 103-105 ka respectively. In addition, we infer that terrace T4 is older than 101 ka, terrace T5 older than 392 ka and terrace T6 younger than 780 ka based on the chronostratigraphic and the reported paleomagnetic study. Consequently, an approximate time series of terrace accumulation is established.

Key words: Three Gorges, terrace, TL, ESR, OSL