Abstract: Based on a lot of outcrop geological surveys, we discussed the thrust fault belt in the front of the east section of Kalpintag in Kalpin area and found many evidences, including the fault incising the surface of diluvium and fluvial channel sediments and terraces, and also the fracture and subsection character of the faults. The evidences indicate that the frontal fault of the Kalpintag is an active thrust-fault of low angle. According to the interpretation and analysis of the satellite image and field investigation, we analyzed the geometry structure of the fault. Many samples in several trenches are used to date the diluvium and fluvial channel sediments and terraces and the sections of the fault scarps at 7 observation points in the field were measured too. Using these data we estimated the slip rate of the fault. The research results implicate that the front edge fault of the east section of kalpintag is divided into two arc segments: from west to east, the first segment is from Bachulinkuang to Sanchakou, and the other segment is from Sanchakou to east of Qionggemandaoban. The Wudaoban, Sanjianfang and Dashankoudaoban are at the crest of the arc of the fault which incises the surface of T₁ and T₂ diluvium and terraces, the horizontal averaged shortening rate of the fault is 0.35～0.44mm/a since Holocene and 0.16～0.30mm/a in the late Pleistocene to Holocene. The neotectonic movement at these sites is strong. Whereas the fault only incises T₃ diluvium at such sites as Bachulinkuang, the north of Sanchakou and Dashankou which are not at the crest of the arc of the fault. The horizontal averaged shortening rate in these areas is 0.05～0.07mm/a since late Pleistocene, being smaller than that of other sites.

Key words: Kalpintag, thrust fault, late Quaternary, fault scarp

摘要： 柯坪塔格前缘断裂东段是柯坪推覆构造系前缘的一条活动断裂,野外调查获得了其晚第四纪错断洪积扇、冲沟阶地面的证据,实测了变形地貌面上的断层陡坎,分析了断层的形变量,通过采样测年估算了断层的缩短速率。由7个观测点的断层陡坎剖面测量,计算了观测点处断层的水平缩短速率,结果表明,断裂弧顶部位的五道班、三间房以西及其大山口道班附近,断层错断了Ⅰ级和Ⅱ级洪积扇(阶地)。断层在这些地点最新活动强烈,水平缩短平均速率全新世以来为0.35～0.44mm/a,更新世晚期末以来为0.16～0.30mm/a,而在非弧顶部位的巴楚磷矿、三岔口以北及大山口北断层只错断了更新世晚期Ⅲ级洪积扇,且水平缩短速率较小,断层水平缩短平均速率更新世晚期以来为0.05～0.07mm/a。

关键词: 柯坪塔格, 逆冲断裂, 晚第四纪, 断层陡坎