柴达木盆地西北缘始新世晚期古隆起与阿尔金断裂的形成

Uplift of NW margin of Qaidam Basin in the Late Eocene: Implications for the initiation of Altyn Fault

研究阿尔金断裂的演化是理解青藏高原隆升过程的重要环节。本文以柴达木盆地西北缘的地震剖面、残余厚度图、沉积相图等资料进行沉积、构造的综合研究,揭示了柴达木盆地西北缘在始新世晚期开始抬升,因此导致柴达木盆地西北缘生长地层的发育。这种抬升作用在平面上则表现为与阿尔金断裂呈～30°相交的NWW-SEE走向古隆起,以及与之相关的如冲积扇等边缘沉积相。本文分析认为阿尔金断裂在始新世晚期开始孕育,在深部形成左旋性质的韧性剪切带,在地表则通过形成左阶雁列式褶皱(即古隆起)来调节深部的位移量。

The evolution of Altyn Fault holds a key link in understanding the formation process of Tibet Plateau. The sedimentary and tectonic study of seismic sections,strata isopach maps and sedimentary facies maps of NW Qaidam Basin reveals the initial uplifting related with Altyn Fault at the Late Eocene,which led to the formation of the growth strata at the NW margin of Qaidam Basin. While in the map view,these NWW-SEE trending uplift sintersect with Altyn Fault by an angle of ～ 30° and induce marginal sedimentary environment such as alluvial fan etc. Based on these observations,we conclude the initial development of Altyn Fault started at the Late Eocene,which may form a ductile sinistral shear zone in the deep and as a result a left-ordered echelon folding zone on the surface for accommodating the displacement.