祁连山东南缘第四纪以来的隆升作用及动力学分析

Uplifting since Quaternary in Southeastern Qilian Mountains and Its Dynamic Analysis

祁连山东南缘隆升是来自印度板块挤压的远程效应与该区周边地块的存在及其活动的相互制约作用而产生的挤压隆升、伸展隆升和左旋走滑隆升共同作用的结果 .标志性构造及主应力分析表明 ,自早更新世以来 ,隆升动力机制不断发生转换 ,在早更新世早期以北东 -南西向挤压为主 ,中更新世早期至全新世早期以北东 -南西向拉张、近东 -西向的拉张为主 ,全新世晚期以北西 -南东向左旋扭动为主 .根据湟水河阶地有关数据估算出的不同时段河谷下切速率为 :1.4 1× 10 3 ～ 36 .4ka间平均速率较慢 (0 .11mm/a) ,36 .4ka至今较快 (1.5 4mm/a) ,其中 10 .5～ 3ka间最快 (2 .2 7～ 2 .80mm/a) ,显示该区自 1.4 1Ma至今构造隆升具有越来越强烈的变化趋势 .

Quaternary structures and those multipleage stress changes reveal that the uplifting in southeastern Qilian Mountains results from the long-distance effect of the Indian plate compression and multiplex uplift mechanism on the adjacent massifs, producing the compression-uplifting, extension-uplifting and sinistral strike-slip uplifting in the area. The analysis of the stress and marker structures indicates that the uplift dynamic mechanism changes have occurred since Early Pleistocene epoch. The early Early Pleistocene is mainly NE-SW direction compression, the Middle Pleistocene to Early Holocene, mainly NE-SW and approaching E-W direction extension, while the Late Holocene is mainly NW-SE sinistral strike-slip. The stream valley downcutting rate since 1.41 Ma is estimated according to relative date of terrace from Huangshui River. The average rate from 1.41 Ma to 36.4 ka is slower, 0.11 mm/a, from 36.4 ka to the present, it is 1.54 mm/a and from 10.5 ka to 3 ka is 2.27-2.80 mm/a, the most rapid. It is shown that the tectonic uplifting in the area tends to be more and more intense since 1.41 Ma.