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独山子背斜是天山北麓三排褶皱带中西北端的背斜,其北翼发育一条逆冲断层。断层的活动在奎屯河阶地和冲积扇上形成了高度小于20m的断层陡坎。陡坎上游冲积物中发育多条冲沟,冲沟根据长度可分为7组。探槽揭示了独山子背斜北翼断层最新的两次活动,其中较早的断层活动时间为3110±40aBP。根据这次断层活动触发的冲沟的平均长度得到冲沟溯源侵蚀的速率为38mm/a。由该溯源侵蚀速率,计算出每组冲沟发育的时间,分别约为1170aBP,3110aBP,7200aBP,12570aBP,14990aBP,30570aBP,37750aBP,可能代表断层多次活动的时间。断层最新一次活动的时间与本文探槽研究限定时间段相符,其他最近的三次活动时间与前人探槽研究的结果相符。说明在特定条件下,用断层上升盘冲沟平均溯源侵蚀速率推算断层活动时间是可行的。
The Dushanzi anticline is an anticline in the northwestern part of the three-row fold belt in the northern foot of the Tianshan Mountains, with a thrust fault developed in the north wing. Fault activity A fault scarp with a height of less than 20 m was formed on the Kuitun River terrace and alluvial fan. There are several gully in the alluvium upstream of the steep ridge, which can be divided into 7 groups according to the length. The trenches revealed the latest two activities in the northern wing of the Dushanzi anticline, with an earlier fault activity of 3110 ± 40 a BP. According to the average length of gully triggered by this fault activity, the gully traceable erosion rate was 38mm / a. Based on the trace erosion rate, the development time of each gully was calculated to be 1170aBP, 3110aBP, 7200aBP, 12570aBP, 14990aBP, 30570aBP and 37750aBP, respectively, which may represent the times of fault multiple activities. The latest activity time of the fault coincided with the limited time period of the trough study in this paper, and the other three recent activity times were consistent with those of the predecessor trenches. This shows that under certain conditions, it is feasible to calculate the fault activity time using the average traceable erosion rate of the gorges in the upwelling fault.