Newly discovered backthrust fault and related active fold scarp in the first piedmont anticline belt of the foreland thrust belt of the North Tianshan
-
摘要:
构造楔是活动挤压区重要的发震构造。北天山前陆冲断带发育复杂的挤压构造楔, 并在地表形成3~4排褶皱带, 前人普遍认为最南部的第一排山麓背斜带自第四纪以来已不再活动。野外调查发现, 第一排山麓背斜带——南安集海背斜北翼单斜区发育2条近平行排列的、向南逆冲的晚第四纪活动反冲断层(喀沙反冲断层, KBT), 断错安集海河两岸的晚第四纪地貌面, 并形成一系列坡向南的反向断层陡坎。安集海河组灰绿色泥岩沿KBT顺层向南逆冲至沙湾组砖红色砂岩之上, 造成地层的重复出露。在安集海河西岸, 南侧的KBT断层面顺层呈铲型构成断弯, 断层的持续活动使上盘阶地和基座面均发生同步弯曲, 形成向斜断弯褶皱陡坎。褶皱陡坎南侧的阶地堆积较薄, 向北明显增厚, 具有生长地层的特征, 表明KBT在阶地堆积过程中有持续活动。喀沙反冲断层陡坎及活动褶皱陡坎的发现表明, 南安集海背斜晚第四纪以来仍在活动。这些地表反冲断层及相关褶皱构造为研究准噶尔南缘构造楔的活动性提供了窗口, 为进一步限定活动构造楔的变形机制、速率和生长演化历史提供了可靠便捷的途径。
Abstract:The tectonic wedge is an important seismogenic structure in the active compression area.The foreland thrust belts of the North Tianshan developed a complex extruded tectonic wedge and formed 3~4 groups of fold belts on the surface.It was generally believed that the first group of piedmont anticline belt in the southern part had ceased to be active since the Quaternary.In the field investigation, we found that there were two nearly parallel Late Quaternary active back thrusts (Kasha backthrust fault, KBT) arranged southward in the first piedmont anticline belt, the monocline area on the north wing of South Anjihai anticline.It had faulted the Late Quaternary landform on both sides of the Anjihai river and formed a series of southward thrust fault scarps.The gray-green mudstones of the Anjihaihe Formation (E2-3a) thrust southward along the KBT bedding onto the brick-red sandstones of the Shawan Formation (E3-N1s), it causing repeated exposure of the strata.On the west of the Anjihai river, the KBT plane on the south side is shovel-shaped along the bedding to form a fault bend.The continuous activity of the fault caused the simultaneous bending of the upper terrace and the base surface, forming a slanting fault-bending fold scarp.The terraces on the south side of the fold scarp are relatively thin, and they have obvious thickening to the north.They have the characteristics of growing strata, indicating that KBT has continuous activities during the terrace accumulation process.The discovery of the Kasha backthrust fault scarp and active fold scarp indicate that the South Anjihai anticline has been active since the Late Quaternary.These backthrust faults and related fold structures provide a window for us to study the activity of tectonic wedges in the southern margin of Junggar, and provide a reliable and convenient way to further define the deformation mechanism, rate and growth history of the active tectonic wedge.
-
Keywords:
- active fold /
- backthrust fault /
- fold scarp /
- South Anjihai anticline /
- Northern Tianshan
-
致谢: 感谢天津大学胡贵明博士在野外工作中的帮助，并且开展了非常重要的讨论；感谢审稿专家提出的宝贵修改意见。
-
![]()
![]()
图 2 北天山前陆冲断带第一排昌吉-齐古山麓褶皱带地质横剖面(据参考文献[19]修改)
SJT—准噶尔南缘断裂；JBT—准噶尔反冲断层；MBT—山麓背斜带反冲断层；构造楔Ⅰ—由基底前冲断层(SJT)与顶板反冲断层(JBT)围限形成的构造楔；构造楔Ⅱ—由基底前冲断层(SJT)和顶板反冲断层(MBT)围限
Figure 2. Geological cross section of the first row (Changji-Qishan piedmont fold belt) in the North Tianshan Foreland-and-Thrust Belt (FTB)
![]()
图 3 南安集海背斜地质简图(据参考文献[23]和本研究野外填图编制)
(在博尔通古乡以西，新发现的喀沙反冲断层(KBT)断错了不同地貌面，并在地表形成了清晰的反向断层陡坎，断层陡坎在图中用齿线标注，齿位于下降盘；KBT可能仅发育在南安集海背斜范围内)
Figure 3. Geological map of South Anjihai anticline
![]()
图 4 喀沙反冲断层在地表形成反向断层陡坎(照片位置见图 3)
a—安集海河东岸KBT断错不同期次的山前冲洪积扇，形成高度不一的断层陡坎，镜向东，黄色虚线指示阶地面基座面；b—博尔通古乡西北，KBT断错山前不同期冲洪积扇面，形成反向断层陡坎，镜向北；c—南安集海背斜北翼单斜区，KBT断错不同期次阶地面，形成反向断层陡坎，在断层上盘形成向斜断弯褶皱陡坎，镜向西。E2-3a—古近纪安集海河组
Figure 4. The backthrust scarp formed at the surface by Kasha backthrust fault
![]()
图 5 南安集海背斜北翼单斜区河流阶地、反冲断层陡坎和褶皱陡坎分布(位置见图 3)
a—Google Earth影像及实测地层产状；b—阶地、断层和褶皱陡坎地貌解译图及地形测线位置，底图为20 m等高线，齿线为新发现的断层陡坎，齿指向下降盘，阴影红色间断线为新发现的褶皱陡坎；c—沿L1测线的地质剖面简图，该剖面至少发育2条反冲断层，造成地层的重复
Figure 5. The distribution of terraces, backthrust scarps and fold scarps in the northern limb of South Anjihai anticline
![]()
图 6 南安集海背斜北翼单斜区T4阶地发育的反冲断层陡坎与褶皱陡坎地质剖面(测线位置见图 5-b；地层代号同图 5)
a—褶皱陡坎和断层陡坎野外照片(镜向西)，位置见图 5，紫红色实线为阶地基座面，白色点线为地层层面；b—解译地质剖面，紫红色实线、间断线为阶地基座面、推测基座面，灰色粗线条为推测地层。地层倾角上陡下缓，倾角变化最大处所在活动褶皱枢纽对应地表的褶皱陡坎
Figure 6. The geological profile of backthrust fault scarp and fold scarp formed in the northern limb of South Anjihai anticline.
表 1 T3阶地面沉积物光释光年龄测定值
Table 1 OSL age of sediments on terrace T3
阶地 埋深/m 238U /(Bg·kg-1) 226Ra /(Bg·kg-1) 232Th /(Bg·kg-1) 40K /(Bg·kg-1) 含水量/% 内剂量/(Gy·ka-1) 环境剂量率/(Gy·ka-1) 等效剂量/Gy 年龄/ka T3 1.7 33.9±6.7 35.4±0.6 33.0±0.4 567.4±10.1 5 0.545±0.026 3.5±0.2 382.6±45.4 108.2±14.0 
下载: 导出CSV
-
Stockmeyer J M, Shaw J H, Guan S. Seismic Hazards of Multisegment Thrust-Fault Ruptures: Insights from the 1906 Mw 7.4-8.2 Manas, China, Earthquake[J]. Seismological Research Letters, 2014, 85(4): 801-808. doi: 10.1785/0220140026
Guzofski A, Shaw J H, Lin G Q, et al. Seismically active wedge structure beneath the Coalinga anticline, San Joaquin basin, California[J]. Journal of Geophysical Research Atmospheres, 2007, 112(B3): B03S05.
Li T, Chen J, Fang L H, et al. The 2015 Mw6.4 Pishan earthquake: Seismic hazards of an active blind wedge thrust system at the Western Kunlun range front, Northwest Tibetan Plateau[J]. Seismological Research Letters, 2016, 87(3): 601-608. doi: 10.1785/0220150205
Sun J, Shen Z K, Li T, et al. Thrust faulting and 3D ground deformation of the 3 July 2015 Mw 6.4 Pishan, China Earthquake from Sentinel-1A radar interferometry[J]. Tectonophysics, 2016, 683: 77-85. doi: 10.1016/j.tecto.2016.05.051
VonHagke C, Malz A. Triangle zones-Geometry, kinematics, mechanics, and the need for appreciation of uncertainties[J]. Earth-Science Reviews, 2018, 177: 24-42. doi: 10.1016/j.earscirev.2017.11.003
Medwedeff D A. Geometry and kinematics of an active, laterally propagating wedge-thrust, Wheeler Ridge, California[C]//Mitra S, Fisher G W. Structural Geology of Fold and Thrust Belts. Johns Hopkins University Press, 1992.
Medwedeff D A. Structural analysis and tectonic significance of Late-Tertiary and Quaternary, Compressive-Growth Folding[D]. San Joaquin Valley, California: Ph. D. thesis, Princeton University, 1988: 1-184.
Shaw J, Connors H C, Suppe J. Seismic Interpretation of Contractional Fault-Related Folds[J]. An AAPG Seismic Atlas, Studies in Geology, 2005: 53.
Taborda A, Spratt D. Structural style in the Peel region[C]//Butler R, McCaffrey B, Torvela T. Mobil057-79-44: Peel Plateau; Northwest Territories. Virtual Seismic Atlas. http://www.seismicatlas.org/entity?id=5cba926c-3cbf-4de8-8861-18f3335aaede.2008.
Ortner H, Aichholzer S, Zerlauth M, et al. Geometry, amount, and sequence of thrusting in the subalpine Molasse of western Austria and southern Germany, European Alps[J]. Tectonics, 2015, 34: 1-30. doi: 10.1002/2014TC003550
Schuller V, Frisch W, Herzog U. Critical taperbehaviour and out-of-sequence thrusting on orogenic wedges-an example of the eastern Alpine Molasse Basin[J]. Terra Nova, 2015, 27: 231-237. doi: 10.1111/ter.12152
管树巍, 张朝军, 何登发, 等. 前陆冲断带复杂构造解析与建模——以准噶尔盆地南缘第一排背斜带为例[J]. 地质学报, 2006, 80(8): 1131-1140. doi: 10.3321/j.issn:0001-5717.2006.08.005 管树巍, 李本亮, 何登发, 等. 复杂构造解析中的几何学方法与应用[J]. 地球科学, 2007, 42(4): 722-739. https://www.cnki.com.cn/Article/CJFDTOTAL-DZKX200704009.htm 管树巍, 李本亮, 何登发, 等. 构造模形体的识别与勘探——以准噶尔盆地南缘为例[J]. 地学前缘, 2009, 16(3): 129-137. doi: 10.3321/j.issn:1005-2321.2009.03.009 管树巍, 陈竹新, 方世虎. 准噶尔盆地南缘油气勘探的3个潜在领域——来自构造模型的论证[J]. 石油勘探与开发, 2012, 39(1): 37-44. https://www.cnki.com.cn/Article/CJFDTOTAL-SKYK201201005.htm 管树巍, 何登发, 雷勇良, 等. 中国中西部前陆冲断带运动学分类、模型与勘探领域[J]. 石油勘探与开发, 2013, 40(1): 66-78. https://www.cnki.com.cn/Article/CJFDTOTAL-SKYK201301010.htm 李本亮, 管树巍, 陈竹新, 等. 断层相关褶皱理论与应用——以准噶尔盆地南缘地质构造为例[M]. 北京: 石油工业出版社, 2010. 李本亮, 管树巍, 陈竹新, 等. 楔形构造在山前冲断构造位移量消减中的作用——以准噶尔盆地南缘为例[J]. 地质学报, 2012, 86(6): 890-897. doi: 10.3969/j.issn.0001-5717.2012.06.004 Qiu J H, Rao G, Wang X, et al. Effects of fault slip distribution on the geometry and kinematics of the southern Junggar fold-and-thrust belt, northern Tian Shan[J]. Tectonophysics, 2019, 772: 1-14
Guan S W, Stockmeyer J M, Shaw J H, et al. Structural inversion, imbricate wedging, and out-of-sequence thrusting in the southern Junggar fold-and-thrust belt, northern Tian Shan, China[J]. The American Association of Petroleum Geologists, 2016, 100(9): 1443-1468. doi: 10.1306/04041615023
Lu H H, Cheng L, Wang Z, et al. Latest Quaternary rapid river incision across an inactive fold in the northern Chinese Tian Shan foreland[J]. Quaternary Sciences Review, 2018, 179: 167-181. doi: 10.1016/j.quascirev.2017.10.017
Li Y, Wei D, Tian H, et al. 3D structural model of an out-of-sequence earthquake in China: Implication for the reactivation of positive inversion structures along the northern Tianshan fold-and-thrust belt[J]. Tectonics, 2018, 37(12): 4359-4376. doi: 10.1029/2018TC005075
邓起东, 冯先岳, 张培震, 等. 天山活动构造[M]. 北京: 地震出版社, 2000. 卢华复, 王胜利, 贾东, 等. 天山中段南麓的第四纪褶皱作用[J]. 科学通报, 2002, 47(21): 1675-1679. doi: 10.3321/j.issn:0023-074X.2002.21.015 Thompson S C, Weldon R J, Rubin C M, et al. Late Quaternary slip rates across the central Tien Shan, Kyrgyzstan, central Asia[J]. Journal of Geophysical Research, 2002, 107(B9): 2203.
陈杰, Scharer K M, Burbank D W, 等. 西南天山明尧勒背斜的第四纪滑脱褶皱作用[J]. 地震地质, 2005, 27(4): 513-529. doi: 10.3969/j.issn.0253-4967.2005.04.001 Scharer K M, Burbank D W, Chen J, et al. Kinematic models of fluvial terraces over active detachment folds: constraints on the growth mechanism of the Kashi-Atushi fold system, Chinese Tian Shan[J]. Geol. Soc. Am. Bull., 2006, 1(18): 1006-1021.
Chen Y G, Lai K Y, Lee Y H, et al. Coseismic fold scarps and their kinematic behavior in the 1999 Chi-Chi earthquake, Taiwan[J]. Journal of Geophysical Research, 2007, 112: B03S02.
Hubert-Ferrari A, Suppe J, Gonzalez-Mieres R, et al. Mechanisms of active folding of the landscape (southern Tianshan, China)[J]. Journal of Geophysical Research, 2007, 112: B03S09.
李涛, 陈杰, 肖伟鹏. 滑脱褶皱陡坎的变形特征和运动学模型: 以帕米尔-南天山前陆地区明尧勒背斜为例[J]. 地震地质, 2014, 36(3): 677-691. doi: 10.3969/j.issn.0253-4967.2014.03.011 张玲, 杨晓平, 黄伟亮, 等. 褶皱陡坎中相关断层在缩短量计算中的作用——以东秋里塔格背斜为例[J]. 地震地质, 2015, 37(3): 697-708. doi: 10.3969/j.issn.0253-4967.2015.03.003 杨纪林. 新疆北天山江南庙断层陡坎及其形成机制[J]. 内陆地震, 2000, 14(2): 128-131. https://www.cnki.com.cn/Article/CJFDTOTAL-LLDZ200002003.htm Hu G M, Chen J, Zhang W H, et al. Out-of-sequence backthrusting since the Middle Pleistocene revealed by the Jiangnanmiao thrust fault along the northern Tian Shan, China[J]. Tectonics, https://doi.org/10.1029/2020TC006662.2021.
吴传勇, 沈军, 李军, 等. 乌鲁木齐西山断层系的新构造变形特征与机制[J]. 地震学报, 2009, 31(1): 42-49. https://www.cnki.com.cn/Article/CJFDTOTAL-DZXB200901006.htm 吴传勇, 沈军, 史杰, 等. 乌鲁木齐王家沟断层组地表变形特征及强变形带宽度[J]. 地震地质, 2011, 33(1): 56-66. https://www.cnki.com.cn/Article/CJFDTOTAL-DZDZ201101008.htm 陈立春. 北天山乌鲁木齐转换区构造系晚第四纪活动性[D]. 中国地震局地质研究所博士学位论文, 2011.
计量
- 文章访问数:
- HTML全文浏览量: 0
- PDF下载量:
