SEISMOLOGY AND GEOLOGY ›› 2015, Vol. 37 ›› Issue (3): 675-696.DOI: 10.3969/j.issn.0253-4967.2015.03.002

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LATE PLEISTOCENE SHORTENING RATE ON THE NORTHERN MARGIN OF YANQI BASIN, SOUTHEASTERN TIAN SHAN, NW CHINA

HUANG Wei-liang1,2, YANG Xiao-ping1, LI An3, ZHANG Ling1, LI Sheng-qiang1, YANG Hai-bo1   

  1. 1 Key Laboratory of Active Tectonics and Volcano, Institute of Geology, China Earthquake Administration, Beijing 100029, China;
    2 Key Laboratory of Western China Mineral Resources and Geological Engineering, College of Engineering and Surveying of Chang'an University, Xi'an 710054, China;
    3 Institute of Crustal Dynamics, China Earthquake Administration, Beijing 100085, China
  • Received:2014-06-05 Revised:2015-01-08 Online:2015-09-20 Published:2015-10-20

焉耆盆地北缘和静逆断裂-褶皱带中晚第四纪变形速率

黄伟亮1,2, 杨晓平1, 李安3, 张玲1, 李胜强1, 杨海波1   

  1. 1 中国地震局地质研究所, 活动构造与火山重点实验室, 北京 100029;
    2 长安大学, 地质工程与测绘学院, 西部矿产资源与地质工程教育部重点实验室, 西安 710054;
    3 中国地震局地壳应力研究所, 北京 100085
  • 通讯作者: 杨晓平,研究员,E-mail:yangxiaoping-1@163.com
  • 作者简介:黄伟亮,男,1987年生,2015年于中国地震局地质研究所获博士学位,主要从事活动构造与古地震、新构造与构造地貌等方面的研究,电话:13379258205,E-mail:huangweiliang1987@gmail.com.
  • 基金资助:

    全国地震重点监测防御区活动断层地震危险性评价项目(1521044025)和国家留学基金委青年骨干人才培养项目(201304190004)共同资助.

Abstract:

How strain is distributed and partitioned on individual faults and folds on the margins of intermontane basins remains poorly understood. The Haermodun(Ha) anticline, located along the northern margin of the Yanqi Basin on the southeastern flank of the Tian Shan, preserves flights of passively deformed alluvial terraces. These terraces cross the active anticline and can be used to constrain local crustal shortening and uplift rates. Geologic and geomorphic mapping, in conjunction with high-resolution dGPS topographic surveys, reveal that the terrace surfaces are perpendicular to the fold's strike, and display increased rotation with age, implying that the anticline has grown by progressive limb rotation. We combine 10Be terrestrial cosmogenic nuclide(TCN) depth profile dating and optically stimulated luminescence(OSL) dating to develop a new chronology for the terraces along the Huangshui He since 550ka. Our in situ 10Be dating of fluvial gravels capping strath terraces suggests a relationship between the formation and abandonment of the terraces and glacial climate cycles since the middle-late Pleistocene. These data indicate that the formation of the four terraces occurred at ~550, ~430, ~350, and~60ka. We suggest that episodes of aggradation were facilitated by high sediment supply during glacial periods, followed by subsequent incision that led to abandonment of these terraces during deglaciation. Combining uplift and shortening distance with ages, we found the vertical uplift gradually decreased from 0.43 to 0.11mm/a, whereas the shortening rate was constant at ~0.3mm/a since the anticline began to grow. The shortening rates of the Ha anticline from geomorphology agree with current GPS measurements, and highlight the importance of determining slip rates for individual faults in order to resolve patterns of strain distribution across intermontane belts.

Key words: cosmogenic nuclide dating, Quaternary, active deformation, Hejing reverse fault-related fold, Tian Shan

摘要:

焉耆盆地为南天山内部的一个山间盆地, 盆地北缘发育1排第四纪新生褶皱带, 即和静逆断裂-褶皱带.中晚第四纪以来, 由于和静逆断裂-褶皱带的持续活动使得在褶皱生长过程中形成的多期洪积地貌面发生反向掀斜变形.利用高精度差分GPS, 对褶皱带中部哈尔莫敦背斜区内的多期变形地貌面的地形形态进行了测绘, 判定背斜的生长主要以翼旋转为主.利用背斜北翼不同地貌面的反向掀斜角度, 分别计算了不同期次地貌面的隆升和缩短变形量.结合原地宇宙成因核素深度剖面法和光释光测年法, 对背斜区内的F4, F3b, F2洪积台地面和T1阶地面的形成年龄进行了测定, 发现背斜在距今约550ka、428.3-47.2+57.6ka和354.3-34.8+34.2ka不同时段的平均隆升速率从 0.31±0.24mm/a下降至 0.15±0.02mm/a, 同时背斜北翼的翼旋转速度也呈逐渐减小的趋势.但背斜自起始变形开始, 缩短速率却大致保持恒定为约 0.3mm/a.而这一恒定的缩短速率与现今横跨和静逆断裂-褶皱带所观测的GPS速率具有很好的一致性, 说明在天山内部的哈尔莫敦背斜区, 短尺度的GPS速率可以代表长尺度的地壳应变速率, 同时反映出山体内部一系列断层和褶皱构造在吸收和调节整体变形量时也起到一定的作用.

关键词: 宇宙成因核素定年, 第四纪, 活动变形, 和静逆断裂-褶皱带, 天山

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