祁漫塔格北缘断裂晚第四纪以来活动特征初步研究

祁漫塔格北缘断裂处于青藏高原内部造山带地区,其构造活动反映了青藏高原的构造演化特征。本文采用活动构造和构造地貌相结合的研究方法,对该断裂的活动性进行初步分析研究。首先采用航卫片解译和野外调查,发现该断裂断错了山前全新世冲洪积扇,形成的断层陡坎高度在1.5~2.5m。通过扩散方程,并参考前人研究结果,认为祁漫塔格北缘断裂晚第四纪的抬升速率初步限定在1~2mm/a。我们基于数字高程模型提取的地形高程纵剖面和面积-高程积分,其结果也支持祁漫塔格北缘存在构造活动。

Primary Study of Late Quaternary Active Features of Northern Margin Fault of Qimantag

The northern margin fault of Qiamantag is located between the Qaidam basin and the Kunlun orogen. Its active features are responses to the Tibetan Plateau uplift, which we examine in this paper to better understand the Tibetan Plateau''s tectonic evolution. To date, the northern margin fault of Qimantag has been little understood, including its active style and slip rate, which are important parameters in an active fault. To address this knowledge gap and to accurately determine the Qimantag fault''s slip rate, we used methods related to active tectonics and tectonics geomorphology. We traced fault lines based on satellite imagery interpretation and field surveys, and found the fault scarp to be discontinuous along the strike. In this paper, we examine in detail three sites from the west to the east of this segment. Our results show that the fault widely ruptured young alluvial fans in the field to form 1.5~2.5 m high scarps in the west segment. The slopes of these scarps have angles of ~30°. Due to the lack of dateable depositions in the study area, we took no geochronological samples to date the age of the alluvial fans. However, we used a diffusion equation to constrain the age of the faulted scarps. Based on our calculations, the scarp is about 1 000~15 000 years old at the Q1 site, with a height of about 2.5 m. Based on the age and height of the scarps, we calculated their uplift rate to be about (2.0±0.5) mm/a. This value is similar to the results obtained from river incision and geodetic leveling. Based on our results, we consider the uplift rate to be 1~2 mm/a. In addition, we also established elevation longitudinal profiles and the hypsometric integrals along the Qimantag Mountain. These profiles and HI values indicate that the mountain is experiencing tectonic uplift.