喀喇昆仑断裂北段晚第四纪活动特征及其构造意义

Late Quaternary Activity Characteristics and Tectonic Significance of the Northern Karakorum Fault

右旋走滑的喀喇昆仑断裂(KKF)作为青藏高原的西部边界,在印度板块与欧亚板块碰撞引起的陆内变形过程中扮演了重要的角色。近年来KKF北段全新世以来的活动特征存在争议。通过遥感解译和野外观测,在喀喇昆仑断裂(KKF)的北段——新疆卡拉苏地区,对KKF及其两条分支断裂的几何学、运动学进行了研究,获得了现今发育的冰水扇被右旋错断和冰水扇上分布羽列式T张破裂等指示KKF右旋走滑的证据。采集了KKF控制的浅冰水湖相沉积中贝壳的AMS14C样品,获得年龄分别为(5.20±0.03)ka、(5.61±0.03)ka和(9.95±0.04)ka。表明KKF北段晚全新世以来仍在活动,其右旋走滑速率约为3.7mm/a,累计垂向滑移速率约为1.7mm/a。据前人在KKF中部的研究成果,推测KKF北段在卡拉苏地区由南东往北西右旋走滑速率有增大的趋势。

The right-lateral strike-slip Karakoram fault (KK F), as the western boundary of the Tibetan Plateau, plays an important role in the intracontinental deformation caused by the collision of the Indian plate and the Eurasian plate. In recent years, the activity characteristics of KK F since the Holocene have been controversial. Through remote sensing and field observation in the northern Karakoram fault (KK F)- Karasu region in Xinjiang, geometrical, kinematic characteristics of KK F and its two branch faults were studied, and the evidence that the developed ice water fan is broken by right-lateral strike-slip and that the distribution of plume T fracture on the ice water fan indicates the right-lateral strike-slip of KK F was obtained. AMS ^14C samples of shells in the lacustrine deposits controlled by KK F were collected, and the ages are (5.20±0.03) ka,(5.61±0.03) ka and (9.95±0.04) ka, respectively. It indicates that the northern KK F is still active since late Holocene, with a right-lateral slip rate of about 3.7 mm/a and cumulative vertical slip rate of about 1.7 mm/a. According to the previous research results in the central part of KK F, it is inferred that the right-lateral strike-slip rate of the northern section of KK F in Karasu region tends to increase from southeast to northwest.