雅鲁藏布江断裂带昂仁段晚第四纪活动证据  

EVIDENCES OF THE LATE QUATERNARY ACTIVITY OF THE ANGREN SEGMENT OF THE YARLUNG TSANGPO FAULT ZONE

作　　者：李彦宝[1] 陈立春 王虎[3] 曾蒂 刘成龙 LI Yan-bao;CHEN Li-chun;WANG Hu;ZENG Di;LIU Cheng-long(Institute of Geology,China Earthquake Administration,Beijing 100029,China;School of Earth Science,Guilin University of Technology,Guilin 541006,China;School of Geosciences and Environmental Engineering,Southwest Jiaotong University,Chengdu 611756,China;Beijing Digital Green Earth Technology Co.LTD,Beijing 100094,China)

机构地区：[1]中国地震局地质研究所,北京100029 [2]桂林理工大学地球科学学院,桂林541006 [3]西南交通大学地球科学与环境工程学院,成都611756 [4]北京数字绿土科技有限公司,北京100094

出　　处：《地震地质》2019年第5期1091-1104,共14页Seismology and Geology

基　　金：国家自然科学基金(41372218);中国地震局地质研究所基本科研业务专项(IGCEA1709,IGCEA1418)共同资助

摘　　要：雅鲁藏布江断裂带是青藏高原南部一条规模巨大的近EW向大地构造边界,其经历了长期的构造演化,一直是地学界关注的热点。已有资料大多认为青藏高原南部地区现今的构造活动以近SN向的裂谷系为主,近EW向的雅鲁藏布江断裂带仅在东构造结部位的鲁朗一带发现有全新世活动的迹象,而米林以西段的最新活动主要发生在早、中更新世。近年来,在沿该断裂带日喀则以西段的调查过程中,在昂仁错一带发现多个断层断错晚第四纪地层的剖面,显示其晚第四纪以来仍有断错地表的活动,但活动遗迹延伸较短。综合分析认为,在区域SN向裂谷的构造环境中,被裂谷系分割的近EW向雅鲁藏布江断裂带可能具次级构造调节作用,从而表现出相对较弱或局部的断错地表活动。The Yarlung Tsangbo fault zone,one of the most important geological interfaces in the Yarlung Tsangbo suture zone which is a huge geotectonic boundary with nearly east-west-trending in southern Tibet Plateau,has undergone a long-term tectonic evolution. Studying this fault zone can help us understand the development and evolution history of the suture zone and the tectonic mechanism of subduction-collision about the Tibet Plateau,so it has always been a hot topic in the field of geology.Most of existing data suggest that the current tectonic activity in southern Tibet is given priority to the rift system with nearly north-south-trending,and the Yarlung Tsangbo fault zone with nearly east-westtrending has relatively weaker activity since late Quaternary. There are only some evidences of Holocene activity found in the Lulang town section near eastern Himalayan syntaxis,and there are few reports about the reliable geological evidences of late Quaternary activity of the section on the west of Milin County of the fault zone.Based on image interpretation,field investigation and chronological method,we found several fault profiles along the Yarlung Tsangbo fault zone near the Angren Lake in this study. These profiles reveal that loose fault gouge has been developed on the fault plane which nearly extends to the surface and offsets the loess sediments and its overlying alluvial-proluvial gravels. The loess is characterized by coarser grains,higher content of fine sand and tiny small gravels. The results of the two OSL dating samples collected in the loess are( 94. 68±6. 51) ka and( 103. 84±5. 14) ka respectively,showing that the loess revealed at the Angren site should be the middle-late Pleistocene sand loess distributed on the high-terraces along the Yarlung Tsangpo River. Consequently,the Angren segment of the Yarlung Tsangpo fault zone is active since the late Quaternary. In addition,synchronous left-lateral offsets of a series of small gullies and beheaded gullies can be seen near the profiles along the fault,whic

关 键 词：雅鲁藏布江断裂带 昂仁段 晚第四纪 弱活动 藏南裂谷系 

分 类 号：P315.2[天文地球—地震学]