摘要
文章提出了青藏高原东缘南北向河流系统的概念,该系统包括岷江、青衣江、大渡河、鲜水河、雅砻江等总体呈现南北走向的河段,指出南北向河流系统的形成演化具有构造和气候双重意义。晚更新世以来,南北向河流系统发生多次堵江事件,形成数套堰塞湖沉积。选取岷江上游、青衣江上游、大渡河上游3个古堰塞湖进行沉积、构造及年代学研究。结果表明,岷江上游叠溪一带于71ka左右发生了大面积堵江事件,形成了上游长约30km的堰塞湖,堰塞坝位于叠溪以南的下游河谷,沿江分布约10km;该堰塞湖持续了60ka,于11ka左右彻底溃坝。青衣江上游五龙乡古堰塞湖85ka前形成,35ka前溃坝,规模不详。大渡河上游开绕村古堰塞湖长于5km,堵江时间不明,20～17ka间溃坝,堰塞坝位于色玉村一带。依据这些古堰塞湖的沉积,构造,关键层位光释光测年数据,结合前人研究成果,划分出青藏高原东缘晚更新世中、晚期存在85～70ka,43～30ka和20～10ka的3个构造活跃期,可对应于青藏高原古里雅冰芯δ^(18)O曲线体现出的C_(1),C_(3)和C_(4)的3次气候冷暖转变期。指出大规模堵江事件是快速的能量物质转化过程,地震释放强大内能,气候因素使得物质得以积累,深切河谷是堵江的有利场所。构造-气候耦合促使大型洪积扇发育、大规模堵江事件发生,进而改变河流动力、塑造河谷地貌。
The meridional river system（MRS） defined in this paper refers to the south-north segments of rivers such as the Minjiang,Qingyijiang, and Daduhe River on the east margin of the Tibetan Plateau. Since Late Pleistocene, there had been many damming events to happen in these river systems, forming many sets of dammed lake deposits. The Diexi dammed lake extended over 30km along the Minjiang River upstream and was formed by a big catastrophic event around 71kaB. P. Its dam, 10km long,is located south of Diexi. This dammed lake lasted about 60ka and was broken about 11 kaB. P. The Wulong dammed lake in the upstream of the Qingyijiang River was formed approximately 85kaB. P. and broken about 35kaB. P. The Kairao dammed lake extended 5km along the Daduhe River, with its dam being at Seyu village, and was broken between 20kaB. P. and 17kaB. P. Through comparison of the structures,deposits and OSL dating results,three tectonic phases were recognized in these three dammed lakes： 85 -70ka,43 -30ka, and 20 -10ka. They can be correlated to those three cold-warm climate charges of C1 ,C3 ,and C4 reflected in the 6180 curve of the Guliya ice core form the Tibetan Plateau. A large-scale damming event needs not only strong energy,but also a lot of loose materials. Such energy can be provided by a large earthquake, while such materials can be related to some appropriate climate conditions. In the MRSs mentioned above,incised deep valleys are favorite sites for damming. Therefore,those dammed lakes in the MRSs should be results of tectonic-climate coupling.
出处
《第四纪研究》
CAS
CSCD
北大核心
2010年第4期812-824,共13页
Quaternary Sciences
基金
国家重点基础研究发展规划项目(973项目)“龙门山地质构造断裂带及其与汶川蕴震动力条件分析”(批准号:2008CB425702)资助
关键词
南北向河流系统
晚更新世
古堰塞湖
构造-气候耦合
光释光测年
meridional river system （MRS） , coupling,optically stimulated luminescence dating（OSL） Late Pleistocene, ancient dammed lake, tectonic-climate
