河套盆地第四纪晚期不整合面的时代厘定及其构造意义讨论

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白鸾羲, 徐锡伟, 罗浩, 李康, 李梦妮, 魏雷鸣, 王启欣, 赵俊香. 河套盆地第四纪晚期不整合面的时代厘定及其构造意义讨论[J]. 地震地质, 2020,42(4): 806-824.
BAI Luan-xi, XU Xi-wei, LUO Hao, LI Kang, LI Meng-ni, WEI Lei-ming, WANG Qi-xin, ZHAO Jun-xiang. DISCUSSION ON THE TIMING AND ITS TECTONIC SIGNIFICANCE OF ANGULAR UNCONFORMITY IN HETAO BASIN IN THE LATE QUATERNARY SEDIMENTS[J]. SEISMOLOGY AND GEOLOGY, 2020,42(4): 806-824. 复制到剪切板

DOI:10.3969/j.issn.0253-4967.2020.04.003
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河套盆地第四纪晚期不整合面的时代厘定及其构造意义讨论

白鸾羲¹⁾, 徐锡伟^2),^*, 罗浩³⁾, 李康²⁾, 李梦妮¹⁾, 魏雷鸣¹⁾, 王启欣²⁾, 赵俊香^2,⁴⁾

1)中国地震局地质研究所, 地震动力学国家重点研究室, 北京 100029

2)应急管理部国家自然灾害防治研究院, 北京 100085

3)中国地震灾害防御中心, 北京 100029

4)中国地震局地壳动力学重点实验室, 北京 100085

*通讯作者: 徐锡伟, 男, 研究员, E-mail: xiweixu@ies.ac.cn。

〔作者简介〕白鸾羲, 女, 1991年生, 2017年于中国地震局地质研究所获构造地质学硕士学位, 主要从事活动构造等方面的研究, 电话: 13718261956, E-mail: blx0101@126.com。

收稿日期: 2019-12-20

基金项目: 中国地震行业科研专项(201508010)、国家自然科学基金(91214201)和国家重点研发计划项目(2018YFC1504105)共同资助

摘要

由于受到青藏高原隆升和东部多板块持续俯冲作用的影响, 鄂尔多斯块体周缘在新生代不同时期发生了不同强度的断陷活动。河套盆地是鄂尔多斯块体北缘与阴山山脉之间的新生代断陷盆地, 其内广泛分布着第四纪中晚期的湖相地层沉积。壕赖沟剖面、边墙壕剖面和狼山剖面位于河套盆地内, 通过分析其上更新统地层剖面的岩性和结构可知, 在厚约10m的湖相地层沉积中记录了1~2期角度不整合面。研究壕赖沟剖面、边墙壕剖面和狼山剖面的测年结果可知, 80ka以来形成了不整合面。

关键词: 壕赖沟剖面; 边墙壕剖面; 边墙壕剖面; 狼山剖面; 第四纪中晚期; 河套盆地

中图分类号:P315.2 文献标志码:A 文章编号:0253-4967(2020)04-0806-19

DISCUSSION ON THE TIMING AND ITS TECTONIC SIGNIFICANCE OF ANGULAR UNCONFORMITY IN HETAO BASIN IN THE LATE QUATERNARY SEDIMENTS

BAI Luan-xi¹⁾, XU Xi-wei²⁾, LUO Hao³⁾, LI Kang²⁾, LI Meng-ni¹⁾, WEI Lei-ming¹⁾, WANG Qi-xin²⁾, ZHAO Jun-xiang^2,⁴⁾

1)State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, China

2)National Institute of Natural Hazards, MEMC, Beijing 100085, China

3)China Earthquake Disaster Prevention Center, China Earthquake Administration, Beijing 100029, China

4)Key Laboratory of Crustal Dynamics, China Earthquake Administration, Beijing 100085, China

Abstract

The interaction between the continental-continental collision of the Indian-Eurasian plate and the westward underthrusting of Pacific plate is generally considered to be the cause of the destruction of North China Craton. At present, there are still doubts in the researches worldwide about the dynamic mechanism of the formation and evolution of the Ordos peripheral fault-depression system and the contemporary tectonic stress field.
The Hetao Basin is a Cenozoic fault basin located between the Ordos block and the Yinshan Mountains. Due to the effect of uplift of the Tibet Plateau and the continuous subduction of the Pacific plate, graben faulting of different intensities occurred in different periods of Cenozoic around the Ordos block. Late Quaternary lacustrine facies sedimentary strata are widely developed in Hetao Basin. The Haolaigou profile, Bianqianhao profile and the Langshan profile in this study are all located in Hetao Basin. According to the lithology and structural analysis of the upper Pleistocene series in the three profiles, angular unconformities of phase 1-2 are recorded in the lacustrine facies sediments with a thickness of about 10m. The dating results of the Haolaigou profile, Bianqianhao profile and Langshan profile show that the formation time of both unconformities is 80ka BP.
Using the tectonic geology, Quaternary geology, stratigraphy, sedimentology and a variety of dating methods, we also carry out a comprehensive study and obtain the following results:
(1)The analysis of lithological and structural features of Haolaigou profile, Bianqianghao profile and Langshan profile in the Hetao Basin shows that multi-phase angular unconformities events are recorded in the lacustrine strata of a thickness of nearly 10m. These unconformities represent the tectonic movement in the late Pleistocene period since the 80ka BP and they may be widely distributed in the North China region. They are probably the direct products of the latest tectonic movement in the Quaternary period.
(2)The present tectonic movement initiates at about 80ka BP. It not only causes multiple angular unconformity events, but also leads to the disappearance of the Hetao ancient lake. The rapid regional epeirogenetic uplifting of the Ordos block since 76.4ka BP should also be the specific manifestation of this tectonic movement. Because of the influence of the accelerated uplifting and eastward spreading of the Qinghai-Tibet plateau in the late Quaternary, the NEE thrusting effect of the Ordos block is enhanced and affected.

Keyword: Haolaigou profile; Bianqianghao profile; Langshan profile; angular unconformities; the Mid-Late Quaternary; Hetao Basin

文章图片

0 引言

由于受到青藏高原隆升和东部多板块俯冲作用的持续影响, 鄂尔多斯块体周缘于新生代不同时期发生了不同强度的断陷活动, 形成了一系列断陷盆地(邓起东等, 1999; Yin, 2010)。河套盆地是鄂尔多斯块体北缘与阴山山脉之间的新生代断陷盆地(图1), 主要在NEE向最大主压应力场作用下于渐新世开始发育, 新近纪早期以来持续接受沉积, 第四纪时期构造活动强烈, 周缘山地缓慢抬升, 强震活动频繁(国家地震局 “ 鄂尔多斯周缘活动断裂系” 课题组, 1988; 邓起东等, 1999; 冉勇康等, 2003; 陈小斌等, 2005; 何仲太等, 2007; 聂宗笙等, 2010; 刘群, 2012; 朱日祥等, 2012; 韩晓明等, 2013; 酆少英等, 2015)。河套盆地内广泛分布着第四纪中晚期湖相地层沉积(聂宗笙等, 1988; 贾铁飞等, 2001; 李建彪等, 2007; 陈发虎等, 2008), 记录了末次间冰期晚期到末次冰期早中阶段河套古大湖的形成与消亡历史, 认为由于距今120ka前青藏高原共和运动引起鄂尔多斯高原隆升以及鄂尔多斯北缘断裂、和林格尔断裂等强烈活动导致黄河外流受阻而成, 其消亡也主要受构造运动的影响(程绍平等, 1998; 李建彪, 2006; 陈发虎等, 2008)。

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	图1 河套盆地主要断裂带分布(据国家地震局 “ 鄂尔多斯周缘活动断裂系” 课题组, 1988修改) a 壕赖沟剖面; b 边墙壕剖面; c 狼山剖面Fig. 1 Distribution of major active faults in Hetao Basin(adapted after the Research Group on Active Fault System around Ordos Massif, SSB, 1988).

尽管前人已对河套盆地第四纪中晚期古大湖地层的沉积年代进行了一定的分析, 但是对河套盆地在第四纪时期的构造演化、沉积历史缺乏系统研究。近期对河套盆地北缘山前断裂进行考察的过程中, 在包头市壕赖沟村北、边墙壕村北部以及狼山等地区的古大湖湖相沉积物中发现了一系列时代不明的角度不整合面, 进一步证实在这一区域可能存在一期最新构造活跃期。对古大湖沉积地层进行高精度年代学测试以厘定其起始时间, 有利于深化认识河套盆地的构造演化过程以及新构造运动特征。

基于以上现状, 本文首先简要介绍研究区的新构造运动背景, 在此基础上着重描述不整合面所在的湖相地层层位及其上、下地层的沉积时代, 以确定最新构造运动的起始年代。

1 新构造运动背景

位于鄂尔多斯块体北缘的河套盆地南北宽40~80km, 东西长约440km, 总体走向近EW, 自西向东由临河盆地、西山咀隐伏凸起、白彦花盆地、包头凸起和呼包盆地等左行右阶形成一条左旋剪切拉张带, 单个盆地呈北深南浅的箕状, 分别受控于狼山-色尔腾山山前断裂、乌拉山山前断裂和大青山山前断裂等左旋走滑正断层(图1); 盆地地表由全新世沉积物所覆盖, 形成广阔的黄河冲积平原, 更新世地层仅在盆地边缘或正断层下盘的狼山、色尔腾山、乌拉山和大青山等山麓地带出露(国家地震局 “ 鄂尔多斯周缘活动断裂系” 课题组, 1988; 梁金鹏等, 1997; 马保起等, 2000; 冉勇康等, 2002; 范俊喜等, 2003; 李建彪等, 2005)。已有的地质资料表明, 鄂尔多斯块体南北两侧的河套盆地和渭河盆地最早形成于古新世末期至始新世早期, 银川盆地形成于始新世中期, 山西地堑系最晚形成于上新世, 其中河套盆地和渭河盆地为左旋剪切拉张带, 而银川盆地和山西地堑系为右旋剪切拉张带。该地的构造背景源于青藏高原东北隅六盘山地区的E向挤出引起鄂尔多斯块体的逆时针转动效应, 秦岭北缘断裂带的左旋及其向E的扩展, 并叠加局部上地幔隆升作用(Tapponnier et al., 1982; 国家地震局 “ 鄂尔多斯周缘活动断裂系” 课题组, 1988; Xu et al., 1992; 徐锡伟等, 1994; Northrup et al., 1995; Schellart et al., 2005; 韩鹏等, 2008; 李三忠等, 2011); 也有人认为鄂尔多斯周缘断陷系的形成与太平洋板块向欧亚大陆的俯冲作用有关, 属于弧后盆地(Tian et al., 1992; Northrup et al., 1995; Schellart et al., 2005), 或者鄂尔多斯周缘的断陷系是二者共同作用的结果(张岳桥等, 2006)。震源机制解显示, 河套盆地目前处于NEE-SWW向挤压和NNW-SSE向拉张的区域应力场作用下(邓山泉等, 2015), 为典型的左旋剪切拉张带。

2 湖相地层沉积学与构造年代学特征

研究区自东向西沿河套盆地北部边缘分布, 可见构造-地层被大青山山前断裂、乌拉山山前断裂和狼山-色尔腾山山前断裂切割, 在断裂南侧(上盘)深埋河套盆地中, 北侧(下盘)出露地表并组成山前台地。这些山前台地根据地貌特征可大致分为高、低2类台地, 其中高台地记录了河套古大湖的发育过程, 而低台地的沉积特征反映了河套古大湖消退过程和最新构造运动的基本信息(吴卫民等, 1996; 马保起等, 2004; 李建彪等, 2005, 2007; 陈发虎等, 2008; 公王斌等, 2013)。

研究区主要沿河套盆地北缘分布, 我们对其中位于大青山山前断裂的壕赖沟剖面(图1a)、边墙壕剖面(图1b)和狼山山前断裂的狼山剖面(图1c)进行了年代样品采集。

2.1 壕赖沟剖面

2.1.1 壕赖沟剖面的沉积特征

研究区位于大青山山前包头壕赖沟村(图1a), 地理坐标(40° 34'57.94″N, 110° 5'33.77″E), 海拔1 063m。剖面走向N, 高约9m, 长约50m, 位于断层下盘。剖面整体由湖相沉积地层组成, 中间存在着1个连续的角度不整合面, 不整合面的倾角约为3° 。不整合面的下部为中粗砂层与黏土层互层, 自下而上粒度逐渐增粗, 在砂土层中间夹有钙板层, 指示1次湖退过程。下部地层倾角约为7° , 自北向南地层逐渐增多, 说明在湖退过程中地层依然在增长。角度不整合面的上部地层以粉细砂层为主, 指示静水沉积环境(图2)。

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	图2 壕赖沟采样剖面地层的特征Fig. 2 Stratigraphic section of Haolaigou profile.

剖面上部为棕黄色、黄绿色粉细砂与黏土互层, 地层平均产状为2.5° , 为浅湖-深湖相沉积地层; 下部为灰色中粗砂夹灰白色钙板层, 内含有砾石层, 地层平均产状约为7° , 自下而上粒度逐渐变粗, 为浅湖-滨湖相沉积。根据岩性及沉积构造特征, 自下而上可分为10层:

①0~0.80m, 褐色黏土质砂砾石, 为残留坡积层, 砾石有一定的磨圆。

②0.80~2.20m, 棕黄色含砾粉砂质黏土, 局部夹有透镜状砾石层, 底部含有20cm的砾石层, 为顶部坡洪积物堆积, 与下伏湖相地层呈角度不整合接触, 地层产状为103° ∠0.5° 。

③2.20~2.79m, 黄棕色与灰绿色粉砂质条带互层, 每层厚约4cm, 顶部15cm处夹有灰白色黏土条带, 内含极厚的泥质条带。

④2.79~4.88m, 棕红色、棕黄色中细砂与灰白色泥质条带互层, 泥质条带厚0.5~1cm, 地层产状为190° ∠2.5° 。

⑤4.88~6.08m, 深黄棕色含砾粉细砂与青灰色黏土质粉细砂互层, 局部含砾石透镜体, 顶部含有钙板层, 厚约0.5cm。

⑥6.08~6.28m, 浅灰黄色含砾中粗砂, 交错层理发育, 内含钙质条带(钙板层), 底部为一连续的钙板层, 厚2cm, 钙板顶部产状为144° ∠2.5° 。

⑦6.28~6.92m, 与上覆地层呈角度不整合接触, 地层倾角约7° , 厚6~7cm的黄褐色粗砂层与厚1~2cm的灰白色半胶结黏土质中砂层互层, 底部砾石含量增加, 粒径为0.2~2cm, 磨圆较好, 地层产状为116° ∠8.5° 。

⑧6.92~7.40m, 黄褐色中细砂层, 顶底各加1层砾石层, 粒径0.5~2cm, 磨圆较好, 砾石多呈次圆状, 地层产状为183° ∠6° 。

⑨7.40~7.83m, 上部为黄棕色中细砂与青灰色黏土质细砂互层, 下部为土黄色砂质黏土, 底部7.72~7.77m处夹粗砂砾石层, 砾石磨圆好。

⑩7.83m以下, 浅灰色中细砂夹厚1~3mm的钙板。

从以上地层岩性分析可知, 壕赖沟剖面广泛出露湖相地层沉积, 自下而上可分为10层, 其中第6、 7层之间呈角度不整合接触, 2、 3层为平行不整合接触; 剖面自下而上整体为湖相地层沉积, 中间夹杂滨湖相沉积。剖面底部(6.92m以下)为浅灰色中细砂与棕黄色中细砂互层, 中间夹杂浅灰色泥质条带, 为浅湖相沉积, 顶部有1层砾石层, 为浅湖相沉积环境; 埋深6.28~6.92m为黄褐色粗砂与厚1~2cm的灰白色半胶结黏土质中砂层互层, 底部砾石含量较多, 为滨湖相沉积; 埋深6.28m以下的地层与上覆地层呈角度不整合接触, 地层角度约为7° , 自下而上表现为1次湖退的过程。剖面向S地层逐渐增多, 表明在湖退过程中地层依然在沉积。剖面不整合面上部为连续的湖相沉积, 沉积物粒度自下而上逐渐变细, 表现为1次湖进过程, 至埋深2.20m处湖相沉积地层消失, 与上覆地层假整合接触。埋深2.20m以上至顶部地层主要为坡洪积棕黄色、褐色含砾黏土。

2.1.2 壕赖沟剖面地层的年代学特征

由于壕赖沟剖面以湖相地层为主, 夹杂一些滨湖相沉积, 沉积物颗粒较粗, 最老年龄估计约可达100ka, 因此使用ESR测年方法对该地区样品进行年代测量。在PM-1剖面上采集ESR样品22个, 采样位置位于不整合面附近, 约每隔0.5m取1个样品。在采样和实验过程中严格遵守操作流程。所有ESR样品均在中国地震局地质研究所电子自旋共振实验室进行ESR测年, 测试结果见图3。

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	图3 壕赖沟剖面测年结果剖面埋深与年代关系分析图Fig. 3 The analysis of relationship between the buried depth and ESR dating results of Haolaigou profile.

从测年结果可以看出, 单个样品(16311((33± 6.6)ka)和16318((52± 9.3)ka))的测试结果分析较可靠(图4), 尽管ESR测年结果也存在个别倒转现象, 但整体符合沉积年代变化规律。通过与包头地区标准钻孔^①(① 包头市地震局, 中国地震灾害防御中心, 2016, 包头城市活断层探测与地震危险性评价。)和华北地区标准地层萨拉乌苏组(孙继敏等, 1996)等沉积环境、沉积相、地层岩性和测年结果的对比可知, 壕赖沟地层剖面角度不整合面的上部为59ka BP堆积的湖相地层, 区域上对应于晚更新世上部城川组(70~10ka BP)(表1); 角度不整合面下部为79ka BP之前堆积的湖相地层, 区域上对应于晚更新世萨拉乌苏组(136~70ka BP)(表1), 是河套古大湖主体堆积地层(Chadin et al., 1924; 孙继敏等, 1996; 苏志珠等, 1997; 李建彪, 2006)。

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	图4 部分样品测试结果分析 a 16311号样品; b 16318号样品Fig. 4 Analysis of the ESR dating results of partial samples.

表1 壕赖沟剖面不同层位ESR测年结果 Table 1 ESR dating result of the Haolaigou profile

2.2 边墙壕剖面

2.2.1 边墙壕剖面的沉积特征

边墙壕剖面(40° 42'56.80″N, 109° 50'40.60″E, 海拔1 130m)位于河套盆地北缘乌拉山山前断裂最东端(图1b)。剖面高约5m, 剖面不整合面下部为滨湖相沉积, 多为中粗砂与黏土层互层, 与上部湖相地层沉积呈角度不整合接触, 地层倾角约为31° (图5)。根据岩性及沉积构造特征, 自下而上可将其分为8层:

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	图5 边墙壕采样剖面地层的特征Fig. 5 Stratigraphic section of Bianqianghao profile.

①黄土层覆盖层。

②灰黄色粗砂层。

③砾石层。

④灰黄色黏土层, 具水平层理。

⑤中砂层, 内夹小砾石。

⑥细砂层, 向下逐渐变粗, 底部含砾石。

⑦砾石层, 中间夹少量黏土层。

⑧中砂层与黏土层互层出现, 与上覆地层呈角度不整合接触, 地层产状为135° ∠31° 。

2.2.2 边墙壕剖面地层的年代学特征

边墙壕剖面以湖相沉积为主, 但沉积物颗粒较粗, 预估年龄在100ka以内, 故在细砂层中采集光释光样品进行年龄测定。在边墙壕剖面上采集了2个光释光样品, 分别位于不整合面上、下的湖相层中。在采样过程中, 使用内径约5cm、长约25cm的无缝钢管进行采样; 采集前在采样位置先将表层剥去30cm后, 再将一端塞有黑塑料袋和锡箔纸的采样管用橡胶锤垂直砸入新鲜面, 取出钢管的同时用黑塑料袋叠加锡箔纸迅速塞紧钢管另一端, 并用胶带将钢管两端包紧, 写上样品编号; 在实验过程中严格遵守实验操作流程。所有样品均在中国地震局地壳动力学重点实验室进行光释光测年, 测试结果见表2。

表2 边墙壕剖面的测试结果 Table 2 OSL dating result of the Bianqianghao profile

从测年结果可以看出, 不整合面上、下2个样品之间存在近10ka的沉积间断。与壕赖沟剖面进行对比可知, 边墙壕剖面的地层沉特征与壕赖沟剖面下部不整合面uc1之上的地层沉积特征相似, 位于城川组内部, 整个剖面均为城川组地层, 不整合面的形成时间为47~38ka BP。

2.3 狼山剖面

2.3.1 狼山剖面的沉积特征

狼山剖面(40° 47'29.20″N, 106° 32'59.40″E, 海拔1 266m)位于河套盆地北缘狼山山前断裂(图1c), 剖面出露高8m, 未见底。剖面不整合面的上部为砾石层堆积, 自上而下砾石粒度逐渐变细, 顶部为1层坡积物杂乱堆积, 地层近水平; 不整合面的下部为棕黄色、灰黄色粉细砂层、黏土层, 为浅湖-滨湖相沉积, 地层的倾角为15° (图6)。根据岩性及沉积构造特征, 自下而上可将其分为9层:

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	图6 狼山采样剖面地层的特征Fig. 6 Stratigraphic section of Langshan profile.

①杂色黏土层。

②灰黄色粉砂层。

③杂色黏土层。

④灰黄色粉砂层。

⑤棕红色粗砂层, 含细砂, 地层产状为240° ∠15° 。

⑥粉细砂层。

⑦黏土层夹粉砂层, 具水平层理。

⑧棕黄色粗砂层, 含砾石。

⑨黏土层, 具水平层理, 中间夹15cm厚的粉砂层, 顶部夹薄层的粗砂, 地层产状为235° ∠11° 。

2.3.2 狼山剖面地层的年代学特征

狼山剖面以湖相沉积为主, 沉积物颗粒较细, 预估年龄在100ka以内, 故选择光释光测年方法对该地区的样品进行年代测量。在狼山剖面上采集了8个光释光样品。采样位置多位于不整合面的下部, 每隔约1.0m取1个样品。在采样过程中, 使用内径约5cm、长约25cm的无缝钢管进行; 采集前在采样位置先将表层剥去30cm后, 再将一端塞有黑塑料袋和锡箔纸的采样管用橡胶锤垂直砸入新鲜面, 取出钢管的同时用黑塑料袋叠加锡箔纸迅速塞紧钢管另一端, 并用胶带将钢管两端包紧, 写上样品编号; 在实验过程中严格遵守实验操作流程。所有样品均在中国地震局地壳动力学重点实验室进行光释光测年, 测试结果见表3。

表3 狼山剖面测试结果 Table 3 OSL dating result of the Langshan profile

从测年结果可以看出, 尽管个别样品存在年龄结果倒转的现象, 但整体趋势符合沉积年代变化(规律图7)。与壕赖沟剖面的结果对比可知, 狼山剖面的地层沉积特征与壕赖沟剖面相似, 但狼山剖面的不整合面并不位于萨拉乌苏组与城川组的交界处, 而是位于城川组内部, 不整合面上、下部均为城川组地层, 不整合面的形成时间为16~12ka BP。

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	图7 狼山剖面的埋深与年代关系分析图Fig. 7 The analysis of the relationship between the buried depth and OSL dating results of Langshan profile.

3 基本科学问题的讨论

3.1 角度不整合面形成的时期

为更合理地确定研究区的地层时代, 有必要将壕赖沟地区湖相与邻近区域同时代研究程度较高的地层进行对比。本文主要将其与河套盆地内部地层和华北地区晚更新世标准地层剖面萨拉乌苏组进行对比。

萨拉乌苏组标准地层位于内蒙古乌审旗萨拉乌苏河(又名红柳河)大沟湾一带的嘀哨沟湾(Chadin et al., 1924)。对萨拉乌苏河两岸的湖相沉积地层的研究以及丰富的化石及古人类活动遗迹的研究表明, 萨拉乌苏组地层的形成时代为晚更新世(136~70ka BP), 其上为晚更新世上部的城川组(70~10ka BP)(孙继敏, 1996; 苏志珠, 1997; 李建彪, 2006)。

通过对研究区地层剖面翔实的岩性描述和系统的地层样品年代学测试结果分析可知, 研究区的地层主要为萨拉乌苏组地层(图8)。

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	图8 研究区地层对比Fig. 8 Comparison of the three profiles.

壕赖沟湖相地层剖面上存在着uc1和uc2 2期不整合面(图2, 3), 边墙壕剖面上存在1期不整合面uc2(图5), 狼山剖面上存在1期不整合面uc3(图6, 7)。壕赖沟剖面埋深6~7m处附近的角度不整合面(uc1)下部为晚更新世萨拉乌苏组(136~70ka BP), 上部为晚更新世上部城川组(70~10ka BP), 据此推测该不整合面的形成时间为80~60ka BP, 除上、下2套地层之间明显缺失同期地层堆积外, 下伏萨拉乌苏组地层的倾斜程度或倾角较上覆城川组更大: 萨拉乌苏组地层的倾角约为7° , 而城川组地层的倾角约为3° , 反映出在此期间发生过1次明显的构造运动。另外, 埋深为2.2m附近的角度不整合面(uc2)发育在城川组内部, 不整合面上、下也有短时期的沉积地层缺失和地层倾角的变化: 不整合面下部地层的倾角约为3° , 而上部地层近水平(图2), 推测其形成时代为40~33ka BP。

边墙壕剖面埋深2m附近存在1个角度不整合面(uc2), 位于晚更新世城川组地层中(46.74~37.66ka BP), 据此推测该不整合面的形成时间为47~38ka BP, 下伏城川组地层的倾斜程度或倾角较上覆城川组更大: 下伏地层倾角约为31° , 而上覆地层近水平。

狼山剖面埋深2m附近存在1个角度不整合面(uc3), 位于晚更新世城川组地层中(16.19~12.05ka BP), 据此推测该不整合面的形成时间为16~12ka BP, 下伏城川组地层的倾斜程度或倾角比上覆城川组大: 下伏地层的倾角约为15° , 而上覆地层近水平。

3.2 沉积间断分布的区域普遍性问题

从壕赖沟剖面、边墙壕剖面以及狼山剖面上发现的角度不整合面可以说明, 在晚更新世以来的河套盆地存在一系列构造活动。

在大青山山前断裂土默特右旗段哈子盖村也发现一个湖相沉积剖面(图9), 地理坐标为(40° 37'6.15″N, 110° 32'36.49″E), 海拔1 053m。剖面高度> 10m, 剖面下部为滨湖相-河流相沉积, 多为粗砂砾石沉积, 地层中断层较发育, 与上部湖相地层沉积呈角度不整合接触, 砾石轻微定向, 倾角约为7° , 野外初步判断角度不整合面的上、下地层与壕赖沟村地层为同一时期堆积地层。

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	图9 哈子盖剖面Fig. 9 Hazigai profile.

此外, 通过河套盆地东部托克托台地的湖相地层剖面系统测年结果与沉积相分析可知, 托克托台地下部湖相地层沉积时代与壕赖沟剖面下部湖相地层基本一致: 剖面下部为萨拉乌苏组地层, 上部为城川组地层, 其间为厚约2.6m、含钙质结核的黄土层, OSL年龄约为82ka, 该层黄土与下伏萨拉乌苏组地层和上覆城川组地层呈不整合接触(李建彪, 2006), 且黄土堆积本身反映出萨拉乌苏组与城川组之间存在沉积地层缺失。

表4 河套盆地第四纪地层划分表 Table 4 Quaternary stratigraphic division table of Hetao Basin

鄂尔多斯块体南缘渭河盆地的断裂活动反映出在距今约120ka也存在1次强烈的断层作用, 并形成角度不整合面(田勤俭等, 2003); 晚更新世初期, 华北地区的1次构造活跃期导致河流溯源侵蚀的加速, 打开了泥河湾古湖和延怀古湖畅通的出口, 古湖消亡, 永定河水系开始出现, 大量泥砂被带到永定河出山后的平原地区, 形成了北京古洪积扇的主体, 这次构造事件发生在约100ka BP(袁宝印等, 2002)。尽管渭河盆地第四纪中晚期的构造事件以及华北平原上的构造事件在发生时间上与河套盆地不整合面的出现时间有一定的差距, 但可以推测在河套盆地发现的晚更新世湖相地层中的角度不整合面并不是局部的, 而是广泛分布于河套盆地及其邻区, 甚至鄂尔多斯块体周缘地区。

3.3 不整合面所代表的意义

地层之间的不整合接触关系是沉积地层中常见的地质现象, 是构造运动最直接证据之一。在河套盆地北缘发现的这一系列角度不整合面具有如下特点: 1)角度不整合面所代表的沉积间断时间很短, 均发生在2个连续的组与组之间, 如壕赖沟剖面的第一期不整合面的时间为萨拉乌苏组地层与城川组地层之间的沉积间断, 或在1组内的地层之间, 如狼山剖面与边墙壕剖面中的不整合面均出现在成川组地层内部; 2)角度不整合面出现在河套盆地北缘, 同时不整合面下部地层的倾斜角度沿盆地北缘自西向东逐渐变小, 至河套盆地东缘地区渐变为平行不整合接触。

河套盆地出现的不整合面在时间上刚好与76.4ka BP黄河SN向晋陕峡谷河段宽谷阶地形成以来鄂尔多斯块体区域造陆隆升速率从之前< 0.23mm/a明显加速到> 0.77mm/a的时间段相对应(程绍平等, 1998), 而这一强烈造陆加速隆升时间段与青藏高原东缘临夏附近黄河T₃阶地和湟水河(黄河二级支流)西宁至互助段T₃阶地反映出的晚更新世加速隆升时段(Li et al., 1997; 鹿化煜等, 2004), 即青藏高原物质挤出和对华北地区推挤作用加强的时段较为吻合, 但鄂尔多斯块体及其邻区的构造运动略有延迟。

因此, 在距今约80ka的晚更新世早中期, 河套盆地地区可能存在1次最新的构造运动, 可能是太平洋板块和菲律宾海板块向W俯冲、青藏高原东北部物质隆升和NEE向滑移加速对华北地区NE向推挤作用加强等共同作用的结果(常利军等, 2011; 胡亚轩等, 2011; 邓山泉等, 2015; 盛书中等, 2015; 崔笃信等, 2016)。

4 结论

本文对河套盆地3个上更新统地层剖面— — 壕赖沟剖面、边墙壕剖面以及狼山剖面进行了岩性和结构分析, 结果表明, 在厚度近10m的湖相地层中记录了多次角度不整合事件, 其所代表的构造运动发生在80ka BP以来的晚更新世时期, 并且可能广泛分布在华北地区, 它们可能是第四纪最新一期、目前正在进行中的构造运动的直接产物。这次构造活动的起始时间约为80ka BP, 它不仅使得多期不整合面下部地层发生不同程度的变形(倾斜), 还可能导致了河套盆地古大湖的最终消亡。 76.4ka BP以来鄂尔多斯块体快速区域造陆隆升运动也应该是这次构造运动的具体表现, 反映出第四纪晚期青藏高原加速隆升和向E扩展对华北克拉通破坏区鄂尔多斯块体NEE向推挤作用加强和影响的结果。

致谢吕丽星博士在野外工作中给予了帮助; 谭锡斌研究员对文章提出了修改意见; 审稿专家对本文提出了宝贵意见。在此一并表示感谢!

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2011

0.0

... 因此, 在距今约80ka的晚更新世早中期, 河套盆地地区可能存在1次最新的构造运动, 可能是太平洋板块和菲律宾海板块向W俯冲、青藏高原东北部物质隆升和NEE向滑移加速对华北地区NE向推挤作用加强等共同作用的结果(常利军等, 2011 ...

2008

0.0

陈发虎, 范育新, Madsen D

, 等. 2008. 河套地区新生代湖泊演化与 “吉兰泰—河套”古大湖形成机制的初步研究[J]. 第四纪研究, 28(5): 866—873.

CHEN

Fa-hu

, FAN

Yu-xin

, Madsen D

, et al. 2008. Preliminary study on the formation mechanism of the “Jilantai-Hetao” megalake and the lake evolutionary history in Hetao region[J]. Quaternary Sciences, 28(5): 866—873(in Chinese).

On the basis of borehole data and dating results on lacustrine sediments,we discussed the lake evolutionary history in Hetao Basin since Cenozoic and the formation mechanism of the "Jilantai-Hetao" Megalake in Late Quaternary.Our results suggest that lacustrine environments had existed in the three fault basins in Jilantai and Hetao area since Cenozoic,especially since Early Pleistocene,but there is no geological evidence indicating a unified paleo～lake.Lake sediments and OSL dating results suggest that the "Jilantai-Hetao" Megalake began to develop since ca.100ka ago and reached its highest lake level at 1080m a.s.l.About 50～60ka ago and began to contract thereafter.We believe that the rapid tectonic uplift of the northeast margin of the Ordos Plateau at ca.120kaB.P.may have blocked the outflow of the Huanghe River at "Jin-Shan" Canyon,which resulted in the development of the Megalake in Hetao Basin.The relative humid climate during the mid-last glacial period(MIS 3)was favorable for the expansion of the "Jilantai-Hetao" Megalake,which once covered most part of the Jilantai and Hetao Basins at around 50～60ka ago when the lake was at its maximum.

1. Key Laboratory of Western China's Environmental Systems(Ministry of Education), College of Earth and Environment Sciences, Lanzhou University, Laznhou 730000; 2. Texas Archeological Research Laboratory, University of Texas, Austin, TX 78712, USA; 3. College of Earth and Environmental Sciences, Normal University of Inner Mongolia, Hohhot 010020; 4. Cold and Arid Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000

研究发现,河套地区在距今5～6万年前存在一个统一的"吉兰泰-河套"古大湖,覆盖吉兰泰和河套盆地的大部分地区。本研究试图依据钻孔资料和湖泊沉积物的测年结果,讨论新生代以来河套盆地的湖泊演化和古大湖的形成机制。结果表明,新生代以来,特别是早更新世以来吉兰泰盆地和河套平原的3个坳陷盆地就已经处于湖泊环境,但没有证据显示存在统一的湖泊。湖泊沉积及其OSL测年显示,"吉兰泰-河套"古大湖大约在距今10万年前后开始发育,至距今5～6万年之前湖面达到海拔1080m上下,随后湖泊衰退。我们认为,鄂尔多斯高原东北边缘距今12万年前后开始的快速构造隆升,可能导致了晋陕峡谷黄河外流受阻,最终在河套盆地积水形成统一湖泊,末次冰期中期(深海氧同位素3阶段)相对湿润的气候环境进一步促进了"吉兰泰-河套"古大湖的发育。

... 陈发虎等, 2008), 记录了末次间冰期晚期到末次冰期早中阶段河套古大湖的形成与消亡历史, 认为由于距今120ka前青藏高原共和运动引起鄂尔多斯高原隆升以及鄂尔多斯北缘断裂、和林格尔断裂等强烈活动导致黄河外流受阻而成, 其消亡也主要受构造运动的影响(程绍平等, 1998 ...

... 陈发虎等, 2008) ...

... 陈发虎等, 2008 ...

2005

0.0

... 陈小斌等, 2005 ...

1998

0.0

程绍平, 邓起东, 闵伟, 等. 1998. 黄河晋陕峡谷河流阶地和鄂尔多斯高原第四纪构造运动[J]. 第四纪研究, (3): 238—248.

CHENG

Shao-ping

, DENG

Qi-dong

, MIN

Wei

, et al. 1998. Yellow River and Quaternary tectonic movements of the Ordos plateau[J]. Quaternary Sciences, (3): 238—248(in Chinese).

On the base of the observation of terrace cross-sections at 21 sites and 17radiometric data this paper deals with the terrace corrolation , sequences and dating forthe fluvial terraces of the Shanxi-Shaanxi Canyon reach of the Yellow River ,demonstrates the Quaternary regional epeirogenic uplifts and local tectonic deformationfor the Ordos Plateau and further discusses the relations between the regionalepeirogenic uplift and the Qinghai-Xizang Plateau uplift the climatic change bine linesin the epeirogenic uplift landscape, and the effect of the base-level change.River terraces are landforms that were at one bine constrUcted and maintained asthe active floor of a river but are now abandoned, and their formation are envolvedin the changes of fluvial systems. The graded process of rivers provides a theoretic base for the genesis of river terrace and the reconstruction of evolutionary history ofancient channels.Increase in fluvial landscape relief emanates from rising geologic structures throughthe process of tectonically induced down cutting by streams. Strath terraces are thefundamental tectonic river terrace landform and indicate the regional epeirogenic upliftand its local tectonic deformation. The morphogenic implication in climatic change isto trigger aggradation that forms fill terrace landforms and records brief reversals oflong-term tectonically induced downcutting. The fill terraces represent a bine sequencein the regional epeirogenic uplift landscape.Six strath terraces develop along the Shanxi-Shaanxi Canyon reach of the Yellowhiver. Their ages are: 1.409 8MaB. P., 0.196 7 Ma B. P., 76 400aB. P., 44 000aB. P.,17 600aB. P. and 5 400aB. P. for T6k, T5y, T4t, T3m. T2w. and T1q respectively . Thelongitudinal profiles of the strath terraces reveal the Quaternary tectonic movementsinvolved in the Ordos Plateau, including two components: the regional epeirogenicuplift and the local tectonic deformation. The regional epeirogenic uplift divides intofive episode, with an average elevation of 25- 46m each episode. The local tectonicdeformation can be expressed by tWo patterns: the local differential uplift induced byfaulting and the nonuniform uplift including the relative strong uplift and the relative weak uplift even subsidence. The local tectonic deformation superimposes on theregional epeirogenic uplift.The downcutting induced by the regional epeirogenic uplift for the Shanxi-ShaanxiCanyon reach started after 1.409 8MaB. P., which lags behind the C phase of theQinghai-Xizang Movement for 0.25Ma ago. Increase of the regional epeirogenic upliftrate in Ordos initiated at 0.196 7Ma ago, which also lags behind for 0.113Ma sincethe Qinghai-Xizang Plateau uplift achieved the fastest rate at 0.31Ma ago.There are three episodes of the aggradation induced by climatic changes in theShanxi-Shaanxi Canyon reach. They occurred before 95 900aB.P., 44 300～36 800aB.P.and 17 300～9 300aB.P. respectively . The regional epeirogenic uplift episodes and theaggradational episodes occurred alternately, and the aggradational events become thebine sequence in the regional epeirogenic uplift landscape. Moreover, the aggradationoccurred in the regions where present relative weak uplipt even subsidence.The Weihe fault basin is the relative base-level of the Shanxi-Shaanxi Canyonreach of the Yellow River . The fault-scarps in the Hancheng Fault escarpment zone atthe northern margin of the basin record the falls of the tectonic base-level. The riverlength is limited and influenced by the base-level falling. The geomorphic effects ofboth the tectonic base-level fall and the regional epeirogenic uplift are commonly tosculpture a new graded longitudinal profile.

Institute of Geology, Seismological Bureau of China, Beijing 100029

本文通过黄河晋陕峡谷河段21个地点的阶地横剖面观察和阶地对比研究,确定出6级宽谷阶地序列,同时,依据17个放射性测年数据对阶地定年。6级宽谷阶地序列揭示了鄂尔多斯高原第四纪区域造陆隆起和局部构造变形,区域造陆隆起的发生时间比之青藏高原隆起要滞后0．113～0．25Ma,而且,平均区域造陆隆起量比之青藏高原的内部和边缘的隆起量小得多。晋陕峡谷河段发生过3期加积作用幕,指示着造陆隆起景观中的气候变化时间线。渭河盆地北缘的韩城断裂悬崖带记录着构造基准面下降,影响的河流长度仅为21～127km。

... 77mm/a的时间段相对应(程绍平等, 1998), 而这一强烈造陆加速隆升时间段与青藏高原东缘临夏附近黄河T₃阶地和湟水河(黄河二级支流)西宁至互助段T₃阶地反映出的晚更新世加速隆升时段(Li et al ...

2016

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... 崔笃信等, 2016) ...

1999

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... 0 引言由于受到青藏高原隆升和东部多板块俯冲作用的持续影响, 鄂尔多斯块体周缘于新生代不同时期发生了不同强度的断陷活动, 形成了一系列断陷盆地(邓起东等, 1999 ...

... 邓起东等, 1999 ...

2015

0.0

... 震源机制解显示, 河套盆地目前处于NEE-SWW向挤压和NNW-SSE向拉张的区域应力场作用下(邓山泉等, 2015), 为典型的左旋剪切拉张带 ...

... 邓山泉等, 2015 ...

1988

0.0

... 河套盆地是鄂尔多斯块体北缘与阴山山脉之间的新生代断陷盆地(图1), 主要在NEE向最大主压应力场作用下于渐新世开始发育, 新近纪早期以来持续接受沉积, 第四纪时期构造活动强烈, 周缘山地缓慢抬升, 强震活动频繁(国家地震局 #cod#x0201c ...

... 盆地地表由全新世沉积物所覆盖, 形成广阔的黄河冲积平原, 更新世地层仅在盆地边缘或正断层下盘的狼山、色尔腾山、乌拉山和大青山等山麓地带出露(国家地震局 #cod#x0201c ...

... 国家地震局 #cod#x0201c ...

2003

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... 范俊喜等, 2003 ...

2015

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酆少英, 刘保金, 姬计法, 等. 2015. 呼和浩特—包头盆地岩石圈细结构的深地震反射探测[J]. 地球物理学报, 58(4): 1158—1168.

FENG

Shao-ying

, LIU

Bao-jin

, JI

Ji-fa

, et al. 2015. The survey on fine lithospheric structure beneath Hohhot-Baotou Basin by deep seismic reflection profile[J]. Chinese Journal of Geophysics, 58(4): 1158—1168(in Chinese).

Hohhot-Baotou basin (referred to as Hu-bao basin) is a Mesozoic-Cenozoic fault basin, locating between Yinshan orogenic belt and Ordos block. To study the fine lithospheric structure and the relation between deep and shallow tectonic structures of faults, we conduct a 91.8 km-long deep seismic reflection profile cross Hu-bao basin in 2010 and get clearer image of the lithospheric structure along the profile.As for the data acquisition, the observing system, asymmetric receiving on both sides, is made up of 30 m group interval, 600 channel receiving and 50 covering. The recording time is 30 s and the sampling interval is 2 ms. Seismic wave explosion applies the drilling blasting to be the hypocenter which the hole depth is 25~30 m,the dose is 24 kg and 180 m shot interval. We give the priority to improving the S/N ratio of seismic data in data processing. Improvements include tomographic statics correction, amplitude anomaly elimination, spherical dispersion compensation and surface consistent amplitude compensation, time-varying band-pass filter and 2-D filter, surface consistent deconvolution, many iterations of velocity analysis and residual static correction, DMO and poststack noise attenuation. The results show that the crust and lithosphere of Hu-bao basin have clearly layered reflection features. The crustal thickness is about 45~48 km, and the lithospheric thickness is about 82~87 km. The Moho uplift occurrs about 3.5 km under the Daqingshan Mountain, which implies the uplift of the Daqingshan Mountain is not because of crust thickening, namely no existence of "the root of a hill". Hu-bao basin is a "half-graben" fault basin with the feature as shallow in the south and deep in the north. The thickest part of its sedimentary layer is located in the Daqingshan Piedmont with the thickness being about 7~8 km. As the south and north boundary faults, the fault on the northern edge of Ordos and the Daqingshan piedmont faults are showed the "Y" shaped fault structure made up of 3~4 faults in the profile. These faults have the important role in controlling the Hu-bao basin formation, sedimentary layers, basement deformation and seismic activities. The profile reveals the lithospheric deep fault is located below the Daqingshan piedmont fault, going upward into the upper crust, cutting down the mid-lower crust, the Moho and then going into the upper mantle.The deep seismic reflection profile of Hu-bao basin reveals the deep tectonic background and deep-shallow tectonic characteristics of faults, which provides seismic evidences for understanding tectonic characteristics of Hu-bao basin and coupling relations between the basin and areas around it. Hu-bao basin is located in the sewing position between Yinshan Mountains and Ordos basin, being formed and developed under the common effect of squeezing by Qinghai-Xizang block to Ordos block in the NE trending and extrusion by North Yanshan block. The existence of deep faults below the Daqingshan piedmont provides a channel for the upwelling and energy exchange of deep hot material, and the metasomatism and erosion between upwelling asthenospheric materials and lithospheric mantle lead to the lithospheric thinning. Strong arc-shape reflection of the lower crust in the deep seismic reflection profile may be the reaction to lower mantle magma swarming into it. Magma upwelling leads to the heating squeezing and lateral material migration of the corresponding position in the lower crust, and furtherly promotes the development of Hu-bao basin and expansion of the edge fault.

Geophysical Prospecting Center, China Earthquake Administration, Zhengzhou 450002, China

跨呼和浩特-包头盆地(以下简称"呼包盆地")完成的91.8 km长的深地震反射剖面,揭示了呼包盆地的岩石圈精细结构和断裂的深、浅构造特征.结果表明,本区地壳和岩石圈具有清晰的层状反射结构特征,其中,地壳厚度约45~48 km,岩石圈厚度约82~87 km.莫霍面在大青山之下出现约3.5 km的抬升,暗示大青山的隆升不是因为地壳物质增厚所致,即大青山可能不存在"山根".呼包盆地为南浅、北深的"箕状"断陷盆地,盆地沉积层最厚处位于大青山山前,其厚度约为7~8 km.鄂尔多斯北缘断裂和大青山山前断裂作为呼包盆地的南、北边界断裂,在剖面上均表现为由3~4条断裂组成的"Y"字形断裂构造,它们对呼包盆地的形成、地层沉积、基底变形和地震活动都有重要的控制作用.剖面揭示的岩石圈深断裂位于大青山山前断裂的下方,该断裂向上进入上地壳,向下切割中-下地壳、莫霍面,进入上地幔.深断裂的存在为深部热物质的上涌与能量强烈交换提供了通道,而上涌的软流层物质与岩石圈地幔发生交代和侵蚀作用导致岩石圈减薄.

... 酆少英等, 2015) ...

2013

0.0

... 公王斌等, 2013) ...

2008

0.0

... 韩鹏等, 2008 ...

2013

0.0

... 韩晓明等, 2013 ...

2007

0.0

何仲太, 马保起, 卢海峰. 2007. 大青山山前活动断裂带分段与潜在震源区划分[J]. 地震地质, 29(4): 765—775.

Zhong-tai

, MA

Bao-qi

, LU

Hai-feng

. 2007. Active fault segmentation and the identification of potential seismic zones alone the Daqingshan piedmont fault[J]. Seismology and Geology, 29(4): 765—775(in Chinese).

Identification of potential seismic zone follows the earthquake structure analogy and seismic activity repetition principles at present.Active fault segmentation is an important aspect and should be considered when identifying potential seismic zones.There are three different segmentation plans along Daqingshan piedmont fault,Inner Mongolia.This article compares and analyses the segmentations and then gets a new potential seismic zone identification plan along Daqingshan piedmont fault.Identification of potential seismic zone includes the range subdivision and the estimation on the maximum earthquake magnitude of potential seismic zones.This article sub-divides the ranges of potential seismic zones according to active fault segmentation plan along the Daqinshan piedmont fault proposed by Ran Yong-kang.Ordos Massif is surrounded by depression zones which have similar earthquake structures and historical earthquake records with magnitude over 8 expect the Hu-Bao depression zone.So,this paper compares Daqingshan piedmont fault with other depression zones around Ordos Massif,especially the Huashan piedmont fault,and gets the conclusion of the maximum earthquake magnitude of Daqingshan potential seismic zones.

Institute of Crustal Dynamics, China Earthquake Administration, Beijing 100085, China

潜在震源区的划分主要包括潜在震源区范围的划定以及震级上限的确定,目前遵循地震构造类比和地震活动重复等原则。而活断层的分段特性也是潜在震源区划分时必须考虑的一个重要因素。大青山山前断裂带至今有3种不同的分段方案,文中比较分析了前人对大青山山前断裂带的分段,并在此基础上对大青山及山前盆地的潜在震源区作了新的划分。鄂尔多斯块体周缘被拉张性断陷盆地围绕,这些断裂系地震构造相似,且除呼包盆地外均有历史8级以上地震记录。文中将大青山山前断裂带与鄂尔多斯块体周缘断裂系进行了构造对比,特别是与华山山前断裂进行了断裂活动性定量对比,得出雪海沟到土左旗段的震级上限为8级,断裂两端潜源震级上限均为7.5级。

... 何仲太等, 2007 ...

2011

0.0

胡亚轩, 崔笃信, 季灵运, 等. 2011. 鄂尔多斯块体及其周缘上地幔各向异性分析研究[J]. 地球物理学报, 54(6): 1549—1558.

Ya-xuan

, CUI

Du-xin

, JI

Ling-yun

, et al. 2011. Seismic anisotropy of upper mantle in Ordos block and adjacent regions[J]. Chinese Journal of Geophysics, 54(6): 1549—1558(in Chinese).

Based on the polarization analysis of teleseismic SKS waveform data recorded at 90 broadband stations in Ordos block and adjacent regions, the splitting parameters of fast polarization direction and delay time between the fast and slow shear waves are determined at each station using the minimum transverse energy method, and the image of upper mantle anisotropy was acquired. Combined with the GPS horizontal velocity field relative to the Ordos block during 1999 similar to 2007, we analyze the seismic anisotropy as well as the crust-mantle coupling in Ordos block and its adjacent regions. At last, a new understanding of the block movement and the dynamic causes of the adjacent fault zone is achieved. The results reveal that there are nulls in the block which show an obvious isotropic characteristic. The delay time of the adjacent stations is obviously greater than those in the central block, which indicates an obvious anisotropy; the fast polarization directions are compatible with the tectonic strike direction and the horizontal velocity direction, which shows the crust-mantle coupling, however, the differences between the directions at some stations may possibly be explained by early block activities. According to the SKS shear wave splitting results and the current GPS velocity field, we know that the Ordos block does not rotate. Meanwhile, the horizontal and ascending intrusion and the transverse extension of the plastic material in the upper mantle lead to the bifurcated flow along the southwestern margin of Liupanshan. One flow forms the Fenwei graben.

[Hu Ya-Xuan; Cui Du-Xin; Ji Ling-Yun; Hao Ming] China Earthquake Adm, Crust Monitoring & Applicat Ctr 2, Xian 710054, Peoples R China.

对布设在鄂尔多斯块体及其周缘的固定宽频带地震台网90个台站记录作远震SKS波形资料偏振分析,采用最小切向能量法求得每个台站的SKS快波偏振方向和快慢波时差,获得块体及其周缘上地幔各向异性图像,并结合1999~2007年相对鄂尔多斯块体的GPS水平地壳运动速度场,分析块体及其周缘的各向异性特征和壳幔耦合特征并重新认识块体的运动及周缘断陷带的动力学成因.分析结果认为,块体内部以零分裂为主,表现为各向同性特征;块体周缘台站延迟时间则明显大于块体中部,表现出明显的各向异性特征;快波偏振方向与地质构造走向、水平速度场方向基本一致,表明壳幔之间存在耦合,而个别台站在方向上与周围台站存在差异,可能与早期的块体活动有关.SKS横波分裂结果和现今GPS地壳水平运动场解释了鄂尔多斯块体没有旋转运动,在西南缘六盘山一带存在分叉绕流运动,汾渭断陷带的形成和发展是由于上地幔塑性物质沿挤出方向水平运动和沿裂隙向上入侵、横向扩张的综合演化结果.

... 胡亚轩等, 2011 ...

2001

0.0

... 贾铁飞等, 2001 ...

2006

0.0

... 李建彪, 2006 ...

... 李建彪, 2006) ...

... 6m、含钙质结核的黄土层, OSL年龄约为82ka, 该层黄土与下伏萨拉乌苏组地层和上覆城川组地层呈不整合接触(李建彪, 2006), 且黄土堆积本身反映出萨拉乌苏组与城川组之间存在沉积地层缺失 ...

2005

0.0

李建彪, 冉勇康, 郭文生. 2005. 河套盆地托克托台地湖相层研究[J]. 第四纪研究, 25(5): 630—639.

Jian-biao

, RAN

Yong-kang

, GUO

Wen-sheng

. 2005. Research on the lacustrine strata of the Tuoketuo mesa, Hetao Basin, China[J]. Quaternary Sciences, 25(5): 630—639(in Chinese).

A weathering-denuding surface separates the lacustrine strata and a thick layer of the loess in the Tuoketuo mesa. In order to ensure the environment and age of the lacustrine strata, as well as the origin and development the mesa, we chose to sample sporo-pollen by the numbers, at the same time to gather 3 samples of optically stimulated luminescence (OSL) dating, from the bottom to top of the lacustrine strata as well as at the bottom of the loess. In addition, we obtained one OSL sample in the fluvial facies, and this fluvial facies is unconformable on the Pliocene Series. Based on these new data and known data on the age of strata, sporo-pollen and the bore of hydrographic geology, we conclude: (1) the lacustrine strata formed during the early stage of the Late Pleistocene (ca.120～100kaB.P. ago), and is equal to the Salawusu Formation of its neighboring position. The loess formed during the late stage of the Late Pleistocene (after about ca.80kaB.P.). The lacustrine sediments withthe age of ca.30kaB.P. were the results of the top loess facies change in the same term. (2) The palaeoclimate change is evident during the Late Pleistocene. The climate during the early stage of Late Pleistocene (ca.120～100kaB.P.) was mild and humid, with the highest level of the lake water at 1 050～1 080m above the sea level. This ancient lake was called as “Hetao ancient lake” and different from “Salawusu ancient lake”. However, the climate during the late stage of Late Pleistocene (since ca.100kaB.P.) was dry and cold, and the level of lake water dropped; at the same time it means that the Huanghe river began to become an exterior river. The level of the lake water was 1 020m± above sea level at ca.30kaB.P. (3) The earth's surface was weathered and denuded until the forming of peneplane after the Pliocene Series had deposited and diagenesis had finished. Meanwhile, the Helingeer fault and the northern margin fault of Ordos was active and had displaced. The lacustrine sediments had deposited during the early stage of the Late Pleistocene while the displacement of the Helingeer fault stopped. The level of the lake water fell back towards the center of the Hetao basin after ca.100kaB.P., and the loess had begun to deposit since ca.80kaB.P. up to the Holocene Epoch. Until ca.30kaB.P., the displacement of the northern margin fault of Ordos had ceased, and the Tuoketuo mesa finally shaped.

1. Institute of Geology, China Earthquake Administration, Beijing 100029; 2. Seismological Bureau of Inner Mongolia Autonomous Region of China, Hohhot 010051

野外观察表明托克托台地的湖相层与上覆的黄土之间存在风化剥蚀面。文章选择了一个剖面点系统地采集了孢粉样品,同时在湖相层底部、顶部和黄土层底部采集了3个光释光样品;另外在一个观察点的不整合于上新统之上的河流相中采取了一个OSL样品。通过对这些数据结果的分析,并综合已有的地层年代、孢粉数据和水文工程地质钻孔资料,试图取得对托克托台地湖相层形成年代、环境及台地演变过程的合理认识。结果表明:1)湖相层相当于邻区的萨拉乌苏组,形成于12～10万年以前的晚更新世早期;黄土相当于邻区的城川组,形成于8万年之后的晚更新世晚期;形成于3万年左右的湖相层是晚更新世晚期同期沉积黄土相变的结果。2)古气候变化明显,晚更新世早期(12～10万年)气候温和湿润,水量充沛,推测最高湖水位介于海拔1050～1080m之间,在河套盆地形成了一个大湖泊———“河套古湖”,与“萨拉乌苏湖”是分开的;晚更新世晚期(10万年以后)气候干冷,湖水后退,同时意味着黄河开始外流,3万年时期的湖水位为海拔1020m左右。3)上新统地层遭受风化剥蚀使地表处于准平原化,在这一时期和林格尔断裂和鄂尔多斯北缘断裂发生明显位错;约12万年以后,和林格尔断裂停止位错,沉积了晚更新世早期的湖相层,约10万之后湖水向盆地中心退却,并在8万年开始沉积黄土,湖水再也未扩展到台地之上,在这期间鄂尔多斯北缘断裂继续位错直至晚更新晚期大约3万年左右停止,台地最终形成。

... 李建彪等, 2005) ...

... 李建彪等, 2005, 2007 ...

2007

0.0

李建彪, 冉勇康, 郭文生. 2007. 呼包盆地第四纪地层与环境演化[J]. 第四纪研究, 27(4): 632—644.

Jian-biao

, RAN

Yong-kang

, GUO

Wen-sheng

. 2007. Division of Quaternary beds and environment evolution in Hubao Basin in China[J]. Quaternary Sciences, 27(4): 632—644(in Chinese).

A borehole (40°44.343'N,111°40.171'E; 250.03m deep) has been drilled in the Hubao Basin, a subbasin of the Hetao, Inner Mongolia Autonomous Region of China. Based on systematic analysis on litho-stratigraphy, chrono-stratigraphy, and sporo-pollen of the core, which is integrated with hydrological data and previous research results of the Hetao Basin, as well as compared with the corresponding beds of the neighbouring regions, the article has drawn the following conclusions: (1) There are evidence of two disconformity interfaces in the drilling section. According to the changes of sedimentary grain size and facies, four cycles of sedimentation can be distinguished and seven sporo-pollen zones with different species and assemblages can be recognized during Quaternary in the Hubao Basin. (2) The stratigraphic units of the drilling core section may be setup from bottom as: the late stage of Early Pleistocene (1070±150~844±126kaB.P.), the Middle Pleistocene Gouziban Formation (520±78~271±40kaB.P.), the Late Pleistocene Salawusu Formation and the Chengchuan Formation (108.7±7.8~14.80±1.03kaB.P.), and the Holocene. (3) During the Quaternary, there were four lake-stages in the Hetao Basin: ①During the Early Pleistocene (1070~800kaB.P. or earlier), the basin was in a strong oxidizing environment; ②During the Early Middle Pleistocene (451~430kaB.P.), the oxidizing degree decreased; ③During the Late Middle Pleistocene (385~192kaB.P.), the basin was strong in a reducing environment; and ④During the Late Pleistocene (113~24kaB.P.), the basin was still in a reducing environment. Except for these four lake times, the Hetao paleo-lake basin might have been vanished or shrunk on a large scale. Such an alternative occurrence suggests that the Hetao Basin has had a complicated evolution history of deposition and uplift during Quaternary.

①Institute of Geology, China Earthquake Administration, |Beijing 100029; ②Guangdong Geological Suvery, Guangzhou 510080; ③Seismological Bureau of Inner Mongolia Autonomous Region of China, Huhhot 010051

通过对呼包盆地钻孔岩芯进行系统的岩石学、年代学和孢粉带的分析,综合盆地已有的研究成果,并与邻区对比,划分了盆地第四纪地层单位,同时探讨了河套古湖泊在第四纪的演化特征。结果为:1)剖面存在两个假整合接触面(Q 1 /Q 2 和Q 2 /Q 3 ),可划分为4个沉积旋回,7个孢粉带。2)剖面第四纪地层从下至上依次可划分下更新统(1070±150~844±126kaB.P.)、中更新统沟子板组(520±78~271±40kaB.P.)、上更新统萨拉乌苏组和城川组(108.7±7.8~14.80±1.03kaB.P.),以及全新统。3)河套盆地在第四纪存在4个古湖泊发育时期,即早更新世(80.0~107.0万年或更早),湖盆处于强氧化环境;中更新世早期(43.0~45.1万年),湖盆氧化强度降低;中更新世晚期(19.2~38.5万年),湖盆处于强烈的还原环境;晚更新世(2.4~11.3万年),湖盆处于还原环境。其间隔期为湖泊消亡或大规模萎缩时期,意味着盆地停止下降甚至处于上升隆起的剥蚀状态。

... 李建彪等, 2007 ...

... 李建彪等, 2005, 2007 ...

2011

0.0

李三忠, 索艳慧, 周立宏, 等. 2011. 华北克拉通内部的拉分盆地: 渤海湾盆地黄骅坳陷结构构造与演化[J]. 吉林大学学报(地球科学版), 41(5): 1362—1379.

San-zhong

, SUO

Yan-hui

, ZHOU

Li-hong

, et al. 2011. Pull-apart basins within the North China Craton: Structural pattern and evolution of Huanghua depression in Bohai Bay Basin[J]. Journal of Jilin University(Earth Science Edition): 41(5): 1362—1379(in Chinese).

There are many pull apart basins such as Shanxi graben, Jiao-Lai basin and some sags in the Bohai Bay basin within the North China craton. The Huanghua depression is such a pull apart basin located at the center of the Bohai Bay basin. It is NNE-trending depression separating the NNE-trending Jizhong depression from the NWW-trending Jiyang depression. It developed as a pull apart basin in a large-scale strike-slipping fault system. The western margin of the depression is the Cangdong fault system, which is the Lan-Liao-Yanshan-Yangerzhuang fault system. The “Great Qikou sag” is the biggest sag with sedimentary thickness of more than 11 km and under intensive extensional region of the Bohai Bay basin area. The Huanghua depression has sharp western and eastern boundary faults controlling pull apart basin. The “Great Qikou sag” is the major component of the Huanghua depression, its inner structural pattern is controlled by E-W trending structures rather than the previously known Cangdong fault. The single sag in the Huanghua depression is characterized by graben in the lower part and the half graben in the upper part. The heaves in the Huanghua depression developed in the Shayi sedimentary stage, separating “the Great Qikou sag” into several sub-sags such as the present-day Qikou sag, Banqiao sag, Qibei sag and Qinan sag. The Huanghua depression has four major faults including NNE-trending strike-slipping boundary faults, NEE-trending regional extensional faults, E-W trending secondary extensional faults and N-S trending transfer zones such as the coastal transfer zone and the Kongdian heave. The different extensional domains are controlled by the single detachment fault system in the basement. The architecture of the “Great Qikou sag” is a result of the late destruction of the North China craton under regional NNW-oriented extension. The basin underwent four stages of evolutions including Eocene propagating rifting called Kongdian event, Early Oligocene pull-apart graben called Jiyang event, Late Oligocene half-graben called Dongying event and Miocence-Pleistocene thermal depression under dish-like bukling.

1.Key Lab of Submarine Geosciences and Prospecting Techniques, Ministry of Education, Qingdao266100,Shandong,China; 2.College of Marine Geosciences, Ocean University of China, Qingdao266100, Shandong,China; 3.Dagang Oilfield Company, CNPC, Tianjin300280, China

华北克拉通内部的拉分盆地有汾渭地堑、胶莱盆地和渤海湾盆地内部一些次级拉分构造单元等。黄骅坳陷就是这样一个拉分构造，位于渤海湾盆地中心地带，整体呈北北东走向，分割西侧北北东向的冀中坳陷和东侧北西西向的济阳坳陷，是发育在一个巨型走滑构造带中的新生代拉分盆地。黄骅坳陷的西界为沧东断裂系，东界为兰聊－盐山－羊二庄断裂系，最大负向构造单元在“大歧口凹陷”，古近系最大沉积厚度达11 km以上，是渤海湾地区地壳伸展最剧烈的地区。黄骅坳陷东、西边界相对较陡，受其控制，整个黄骅坳陷表现为拉分盆地；而“大歧口凹陷”为其主体，“大歧口凹陷”内部构造样式的控制性构造为东西向的断裂，而不是传统认为的沧东断裂等；所以，黄骅坳陷内部单个凹陷具有比较独特的下部为地堑式断陷、上部叠加北断南超的箕状结构。黄骅坳陷内部的凸起是沙一期才开始出现并起分割沉积空间的作用，沙一期以前，现今的歧口主凹、板桥次凹、歧北次凹、歧南次凹、北塘凹陷等都还是统一的一个湖盆。黄骅坳陷主要构造总体可划分为北北东向盆缘走滑断裂系、北东东向区域伸展断裂系、东西向盆内次级伸展构造和南北向变换构造，其中，最为显著的分割构造就是南北走向的沿岸变换带与孔店隆起。不同的伸展构造区受统一的基底拆离构造系统控制。“大歧口凹陷”的结构构造是华北克拉通破坏晚期阶段裂解过程的直接记录，是区域北北西向伸展背景下的产物。盆地构造经历了4个重要发展阶段：始新世孔店事件形成的拓展裂解阶段、渐新世初济阳运动事件形成的地堑式拉分断陷阶段、渐新世末东营运动形成的箕状断陷阶段、中[CD1]上新世热沉降期的碟状挠曲拗陷演化阶段。

... 李三忠等, 2011) ...

1997

0.0

... 梁金鹏等, 1997 ...

2012

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刘群. 2012. 内蒙古大青山山前断裂带构造变形特征[J]. 世界地质, 31(1): 113—119.

LIU

Qun

. 2012. Structural deformation characteristics of Daqingshan piedmont fault in Inner Mongolia[J]. Global Geology, 31(1): 113—119(in Chinese).

Daqingshan piedmont faults consist of a number of stepladder high angle southward faults，extended in the Daqingshan piedmont in east-west direction，and controlling the formation of Hetao faulted basin． The fault activity is charactered by vertical differential movement with north up and south down． There is long history of formation and development of the Daqingshan piedmont faults． The faults originate in Early Cretaceous，and their evolution can be divided into five stages: the Early Cretaceous original development stage，Paleogene-Neogene，early- middle Pleistocene，late Pleistocene，and Holocene structural deformation stages． The development of Daqingshan piedmont faults were controlled by regional tectonic stress field，and extended in south-north direction to form the tensional normal faults with east-west direction．

Geophysical Exploration Institute of Heilongjiang Province，Harbin 150036，China

大青山山前断裂带沿大青山山前呈近东西方向展布，是河套新生代断陷盆地形成的主要控制断裂，由一系向南倾斜的阶梯状高角度断层组成。断裂带活动以北升南降的垂直差异运动为主，具有长期活动发展演化历史。该断裂带在白垩纪时期开始形成，其活动可划分为5 个演化阶段: 早白垩世初始形成阶段、古近纪—新近纪、早中更新世、晚更新世和全新世构造变形阶段。该断裂带的形成受区域构造应力场控制，是区域上南北向伸展而形成的近东西方向张性正断层。

... 刘群, 2012 ...

2004

0.0

... 鹿化煜等, 2004), 即青藏高原物质挤出和对华北地区推挤作用加强的时段较为吻合, 但鄂尔多斯块体及其邻区的构造运动略有延迟 ...

2004

0.0

马保起, 李德文, 郭文生. 2004. 晚更新世晚期呼包盆地环境演化与地貌响应[J]. 第四纪研究, 24(6): 630—637.

Bao-qi

, LI

De-wen

, GUO

Wen-sheng

. 2004. Geomorphological response to environmental changes during the late stage of Late Pleistocene in Hubao Basin[J]. Quaternary Sciences, 24(6): 630—637(in Chinese).

The landforms on the north margin of Hubao basin are mainly controlled by the Daqingshan piedmont fault, forming a belt of conspicuous geomorphological variation. On the south slope of the Mt. Daqingshan, there ubiquitously exits a piedmont terrace north to the Daqingshan piedmont fault, the surface of which is 120m above the fan surface to the south of the fault. The terrace is composed of a set of lacustrine-stream deposits, which can be divided into a lower and an upper part. The lower part consists of grayish yellow, yellowish green silt and fine sand, containing thin layers of sand and gravel with fine horizontal bedding. This part was deposited under lacustrine environment with an age of 47-28kaB.P. The upper part consists of gravel of varying size and low psephicity with inclined bedding. This part was deposited under stream environment with an age of 28 - 22kaB.P. The synchronous deposits in the river valleys nearby form a river terrace 100m above the present stream level, the structure of which is the same as that of the piedmont terrace. The stratigraphic sections record two environmental change events, one is lacustrine-stream transition event, occurring before 28kaB.P. , when the lake of Hubao basin retrogressed; the other is aggradation-down-cutting transition event, occurring after 28kaB.P. , when the streams in the area transited to downcutting from aggradation.Stratigraphic records demonstrate that the piedmont belt undergoes different depositional environment in the late stage of Late Pleistocene. The lacustrine environment started no later than 47kaB.P. , and sustained to 28kaB.P. During this period, the lake almost covered the whole Hubao basin, and the broad valleys in the area were under lacustrine environment, too. The depositional features in both the basin and the mountain valleys show that the Daqingshan piedmont fault was inactive during 47-22kaB.P. Comparing with the environmental changes in other lakes in North China, we can infer that the lacustrine-stream transition in Hubao basin was the response to regional climate change associated with the global climatic change.From 22kaB.P. to present, the greatest downcutting depth of the rivers in the area reaches 100m. The difference of the elevation of the lacustrine deposits cross the fault is 58-136m. These features prove that the Daqingshan piedmont fault has been intensely active since 22kaB.P. , its slip rate is about 4-6mm/a.Since the late stage of Late Pleistocene in Hubao basin, the inactive stage of the Daqingshan piedmont fault was synchronous with the period of the lacustrine environment, while the active stage of the fault synchronous with the cool and dry period.Our study in the Daqingshan piedmont indicates that the integral environmental explanation resulted from both geomorphological and depositional records is more comprehensive and reliable than that from a single record for the site where both geomorphological and depositional records are well preserved.

1. Institute of Crustal Dynamics, China Seisnwlogical Bureau, Beijing 100085; 2. Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100085; 3. Seismological Bureau of Inner Mongolia Autonomous Region, Hohhot 010051

对大青山山前台地沉积地层剖面的沉积学、年代学研究结果表明,晚更新世晚期呼包盆地环境发生过两次重大转变。约47-28kaB.P.的呼包盆地湖泊水位一直维持着较高的水平,湖相沉积沿河伸入大青山内;约28kaB.P.以后,湖泊逐渐退缩,山区及山前地带沉积特征转为以河流加积为主,并一直维持到约22kaB.P.;此后山区河流由加积转变为下切,最大下切深度达100m。断裂两侧的地貌分析表明,在约22kaB.P.之前大青山山前断裂的构造活动不明显;约28kaB.P.的湖泊-河流转换事件是与区域性的气候变化有关。约22kaB.P.的环境突变事件主要由大青山山前断裂的构造活动引起,其垂向活动速率约为4-6mm/a;晚更新世晚期以来大青山山前断裂的稳定时期对应呼包盆地的湖相环境时期,而断裂的强烈活动时期对应气候的冷干时期。

... 马保起等, 2004 ...

2000

0.0

... 马保起等, 2000 ...

1988

0.0

聂宗笙, 李克. 1988. 内蒙古包头地区萨拉乌苏组的发现及其意义[J]. 科学通报, 33(21): 1645—1649.

NIE

Zong-sheng

, LI

. 1988. Discovery and significance of Salawusu formation in Baotou area, Inner Mongolia[J]. Chinese Science Bulletin, 33(21): 1645—1649(in Chinese).

包头地区位于河套盆地,第四纪地层十分发育,由于大青山山前断裂带晚更新世以来强烈活动,在东河区山前台地上,第四系出露地表,主要为河湖相和冲洪积相沉积。近两年来,在河湖相地层中采集到萨拉乌苏组重要的哺乳动物化石,进行了~(14)C年代测定、孢粉及微体的分析鉴定,取得了重大的进展。该地层可与萨拉乌苏组对比,时代为晚更新世晚期。

... 河套盆地内广泛分布着第四纪中晚期湖相地层沉积(聂宗笙等, 1988 ...

2010

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... 聂宗笙等, 2010 ...

2003

0.0

... 冉勇康等, 2003 ...

2002

0.0

... 冉勇康等, 2002 ...

2015

0.0

盛书中, 万永革, 黄骥超, 等. 2015. 应用综合震源机制解法推断鄂尔多斯块体周缘现今地壳应力场的初步结果[J]. 地球物理学报, 58(2): 436—452.

SHENG

Shu-zhong

, WAN

Yong-ge

, HUANG

Ji-chao

, et al. 2015. Present tectonic stress field in circum-Ordos region deduced from composite focal mechanism method[J]. Chinese Journal of Geophysics, 58(2): 436—452(in Chinese).

With more and more densely seismic stations deployed, a large number of P wave first motion data are observed, which provides us an opportunity to further study the tectonic stress field. In this paper, by using the 49844 P wave first motion polarity data from 8499 earthquakes, which occurred in and around the Ordos block from August 1, 2007 to July 21, 2013, we obtained the precise and detailed stress field in the study area. The composite focal mechanism method was used in this study. By fitting the focal mechanism radiation pattern with P wave polarity data from a large number of earthquakes, this method can obtain the composite focal mechanism in specific grid, and P, B, T axes can be regarded as the principal stress axes of the tectonic stress field. The grid search method is used to fit the focal mechanism radiation pattern, the focal mechanism which has the minimum contradictory ratio was regarded as the optimal solution. The inconsistent ratio is the ratio of the number of P wave first motion polarity which is inconsistent with the focal mechanism and the total number of P wave first motion polarity data, which is weighted by the distance of the earthquake epicenter to the grid point. The study results show that the stress field has the following characteristics: First, in the rift zone of the Yinchuan-Jilantai, Hetao, Daihai, Shanxi, and Weihe around the Ordos block, the main types of composite focal mechanism are normal types, and the strike of the nodal planes is consistent with the strike of the main fault which controls the boundary of the rift zone, that is, in accord with the extension regime in the rift zone around the Ordos block. Second, the main types of the composite focal mechanism are thrust, thrust-strike-slip and strike-slip types in the southwest boundary of the Ordos block, which reflects that the Ordos block is subjected to the northeastward squeezing of the Qinghai-Tibetan plateau. The principal compressive stress direction is eastward in the distance from the southwest boundary of Ordos block, that may derived from the northeastward squeezing of the Qinghai-Tibetan plateau, the principal compressive stress direction turns to NE-SW direction when near the Ordos block. Third, the P-axis azimuth shows generally regular changes except in some local areas. From south to north, the P -axis azimuth becomes more to the north direction in the west boundary of the Ordos block. From west to east, the P -axis turns more to the east direction in the north boundary of the Ordos block. In the south and east boundary of the Ordos block, the P -axis azimuth has small change and is parallel to the main fault's strike which controls the boundary of the rift zone. The dip angle of the P -axis is nearly horizontal in the southwest boundary of the Ordos block, and nearly vertical in the basins around the Ordos block. Fourth, the T -axis azimuth is NW-SE overall. The T -axis is generally perpendicular to the strike of the main fault which controls the boundary of the rift zone and the strike of the basin in the basins around the Ordos block. Fifth, under the NE pushing force from the Qinghai-Tibetan plateau and the NW-SE extension caused by the uplifting of the deep substance, the regions around the Ordos block are shear zones with extensional components, except for the compressional region in the southwest of Ordos-block; these results are consistent with the previous studies which suggest that the Circum-Ordos block is in extensional stress field, also better explain the fault basins surrounding the Ordos block, also accord with the formation of right-lateral shear zones with extension components in its western and eastern boundary and left-lateral shear zones with extensional components in its southern and northern boundary. Overall, we obtained the stress field around the Ordos block, and its general characteristics are consistent with the results of previous study, our results are more consistent with the basin structure around the Ordos block. In this study we focus on the general characteristics of our results. In the further study, we will pay more attention on the inconsistency of our study with the previous study, try to find out the reason and give a reasonable explanation; and pay more attention on the phenomenon of sudden changes in the direction of the stress axis, try to find whether it caused by the inhomogeneity of stress field, or the complex geological structure, or other reasons.

1. Institute of Geophysics, China Earthquake Administration, Beijing 100081, China; 2. Institute of Disaster Prevention, Sanhe Hebei 065201, China; 3. Lanzhou Institute of Seismology, China Earthquake Administration, Lanzhou 730000, China; 4. Nanjing Seismic Station, Nanjing 210014, China

利用2007年8月1日至2013年7月21日发生在鄂尔多斯块体周缘的8499个地震的49844个P波初动符号资料,应用综合震源机制解法获得了鄂尔多斯块体周缘0.25°×0.25°的精细地壳应力场,所得应力场结果基本上覆盖了整个鄂尔多斯周缘地区.研究结果表明鄂尔多斯周缘地壳应力场具有以下特征: (1)在环绕鄂尔多斯周缘的银川—吉兰泰断陷带、河套断陷带、岱海断陷带、山西断陷带和渭河断陷带内,综合震源机制解结果以正断层型为主,且综合震源机制解节面走向大体与控制断陷带边界的主要断裂走向相一致,与鄂尔多斯周缘断陷带现今的拉张状态相一致.(2)在鄂尔多斯西南缘,综合震源机制解类型主要为逆冲、逆冲走滑和走滑型,反映了鄂尔多斯块体在西南缘受到青藏高原北东向挤压作用.鄂尔多斯西南缘的应力场的主压应力方向在远处为东向,源自于青藏高原向东北挤压作用,靠近鄂尔多斯块体表现为北东—南西向.(3) P 轴方位在局部地区变化较大,但总体呈现规律性变化. P 轴方位在鄂尔多斯块体西缘,从南向北,主压应力轴方位更加偏北;在其北缘,由西向东,主压应力轴方位更加偏东.在其南缘和东缘,主压应力轴方位变化不大,大体上平行于控制各断陷带主要断裂走向. P 轴倾角在西南缘为近水平,在其周缘各盆地内 P 轴倾角近直立.(4) T 轴方位总体表现为北西—南东向;在鄂尔多斯周缘各断陷带内, T 轴走向大体与控制断陷带主要断裂走向以及断陷盆地走向相垂直.(5)鄂尔多斯块体在其西南角受到来自青藏高原的北东向挤压和其东北角深部物质上涌形成的北西—南东向拉张力联合作用,上述作用使得鄂尔多斯块体周缘地区除西南区为挤压区外,其余区域均为剪切拉张区,与先前研究认为鄂尔多斯周缘地区处于引张应力场作用相符合,较好地解释了环鄂尔多斯周缘的断陷盆地构造,亦符合鄂尔多斯块体东西两侧的右旋剪切拉张带以及南北两侧的左旋剪切拉张带的认识.

... 盛书中等, 2015 ...

1997

0.0

... 苏志珠等, 1997 ...

... 苏志珠, 1997 ...

1996

0.0

... )和华北地区标准地层萨拉乌苏组(孙继敏等, 1996)等沉积环境、沉积相、地层岩性和测年结果的对比可知, 壕赖沟地层剖面角度不整合面的上部为59ka BP堆积的湖相地层, 区域上对应于晚更新世上部城川组(70~10ka BP)(表1) ...

... 孙继敏等, 1996 ...

... 对萨拉乌苏河两岸的湖相沉积地层的研究以及丰富的化石及古人类活动遗迹的研究表明, 萨拉乌苏组地层的形成时代为晚更新世(136~70ka BP), 其上为晚更新世上部的城川组(70~10ka BP)(孙继敏, 1996 ...

2003

0.0

田勤俭, 申旭辉, 冯希杰, 等. 2003. 渭河盆地断层活动反映的第四纪构造事件初步研究[J]. 地震地质, 25(1): 146—154.

TIAN

Qin-jian

, SHEN

Xu-hui

, FENG

Xi-jie

, et al. 2003. Primary study on Quaternary tectonic events based on variation of fault activity in Weihe Basin[J]. Seismology and Geology, 25(1): 146—154(in Chinese).

Recognition of major tectonic events and tectonic cycles in Quaternary is an important topic that attracts more and more attention of many geologists. Recently, the research in this aspect has focused mainly on Quaternary sedimentation and geomorphologic evolution, while little attention has been paid to the study of fault evolution, which is directly related to tectonic cycle or tectonic event. This is mainly because of the lacking of geological evidence and the limitation of dating technique. Nevertheless, significant progress has been made in loess study, especially the characteristics and dating of loess-paleosoil sequences, which provide a time scale for regional correlation and timing of loess deposits. In this paper, an attempt has been made to discuss the migration and variation of Quaternary activity of fault zone through the analysis of loess deposition along the zone by using this time scale. The main purpose of this study is to provide direct evidence for the division of tectonic cycles in Quaternary. The present study deals mainly with the Lintong-Chang'an Fault and the Lishan mountain front fault on the southern margin of Weihe basin, as well as the Kouzhen-Guanshan Fault on the northern margin of the basin. The loess deposits along these fault zones have been studied in detail, while the main unconformities in loess sequences were identified in the geological sections across the fault zones and dated by using the loess-paleosoil time scale. The results show that tectonic unconformity presents broadly along the Lintong-Chang'an Fault and the Lishan mountain front fault, appearing as discordant contact of the S 8 paleosoil layer with the underlying strata. The underlying strata are offset significantly by the fault, but the overlying strata of S 8 are offset inconsiderably. Along the Kouzhen-Guanshan Fault zone, the S 1 paleosoil layer discordantly contacts with the underlying strata, which are significantly offset by the fault, but the overlying strata of S 1 layer are inconsiderably offset. In term of the loess-paleosoil time scale, the following conclusion can be drawn from the result of this study: The activity of the Lintong-Chan'an Fault zone on the southern margin of the Weihe basin was markedly changed at 800～900ka B.P. At the same time, the migration of activity occurred along the Lishan mountain front, while strong activity started to occur along the Weinan Yuan front Fault and the whole Weinan Yuan began to be uplifted. At 120ka B.P., the activity of the Kouzhen-Guanshan Fault zone began weakened. Thus, the variation of fault activity in this area may indicate two major tectonic events in mid-late Quaternary. This result may provide basic material for regional correlation of Quaternary tectonic events and for the research of the tectonic manifestation of tectonic events.

1. Center for Analysis and Prediction, China Seismological Bureau, Beijing 100036, China; 2. Seismological Bureau of Shannxi Province, Xi'an 710068, China

研究了渭河盆地南缘和北缘几条断裂第四纪活动性的迁移变化.利用横跨断裂的构造地层剖面,结合断裂上覆黄土地层的年代学研究结果,对断裂活动强度迁移变化的演化阶段进行了研究.结果表明,在大约80～0万年前,渭河盆地南缘的临潼-长安断裂带的活动性发生了显著变化,骊山山前断裂也有活动性迁移现象,渭南塬前断裂开始强烈活动,渭南塬全面抬升;12万年前左右,渭河盆地北缘的口镇-关山断裂活动性明显减弱.该区断层活动的这些变化是对第四纪中晚期的2次重要构造事件的反映.

... 鄂尔多斯块体南缘渭河盆地的断裂活动反映出在距今约120ka也存在1次强烈的断层作用, 并形成角度不整合面(田勤俭等, 2003) ...

1996

0.0

... 这些山前台地根据地貌特征可大致分为高、低2类台地, 其中高台地记录了河套古大湖的发育过程, 而低台地的沉积特征反映了河套古大湖消退过程和最新构造运动的基本信息(吴卫民等, 1996 ...

1994

0.0

... 徐锡伟等, 1994 ...

2002

0.0

袁宝印, 邓成龙, 吕金波, 等. 2002. 北京平原晚第四纪堆积期与史前大洪水[J]. 第四纪研究, 22(5): 474—482.

YUAN

Bao-yin

, DENG

Cheng-long

, LÜ

Jin-bo

, et al. 2002. A Late Quaternary accumulation period and the prehistoric flood in Beijing plain[J]. Quaternary Sciences, 22(5): 474—482(in Chinese).

The Orient Square section and Xiaohongmen section in Beijing were studied in detail, and a accumulation picture of Beijing Plain is obtained. From 0.1 Ma to 22 000 a B.P., an alluvial fan consisting of gravel was formed in front of the Beijing mountain region. After that, Beijing Plain began to enter into its formation stage. From 22 000 a B.P. to 12 000 a B.P., the Beijing climate was dry and cold, so the water quantity of the Yongdinghe River reduced, and then the accumulated rate of Beijing Plain lowered. As a postglacial age came, the Beijing climate became warm and wet, weathering fragments formed in that glacial age were moved from the mountain region into Beijing Plain. The sediments formed are mainly of levee facies and burst fan facies. The accumulated rate obviously increased. From 8 000 a B.P. to 4 000 a B.P., an accumulation period with the maximum accumulation rate came as great flood occurred frequently. This period is just corresponding to the Prehistoric Flood in legend. After 3 000 a B.P., the climate again became dry and cold. At the same time the water quantity of the Yongdinghe River reduced again, but the human productivity raised and the ability for human to resist flood strengthened, although flood threats became relatively lower compared with the Prehistoric Flood.

1. Institute of Geology and Geophysics, Chinese Academy of Sciences,Beijing 100029; 2. Beijing Geological Survey, The Ministry of Territory and Resource, Beijing 102206; 3. Institute of Vertebrate Paleontology and Palaeoanthropology, Chinese Academy of Sciences, Beijing 100044; 4. Institute of Botany, Chinese Academy of Sciences, Beijing 100093

通过北京平原地区东方广场剖面和小红门剖面第四纪地层、年代学、环境变迁、沉积相及孢粉分析等方面的研究发现,从大约0.1MaB.P.～22000aB.P.,北京平原地区形成以砂砾石沉积为主的洪积扇,此后开始进入北京平原形成时期。22000～12000aB.P.,气候干冷,永定河水量减少,平原沉积速率较低。进入冰后期以来,气候逐渐温暖湿润,永定河水量增加,山区风化物质被搬运至北京平原堆积下来。沉积以天然堤相、决口扇相为主,沉积速率大增。8000～4000aB.P.,沉积速率达到最大,出现晚第四纪堆积期,同时洪水频繁,恰好与传说中的史前大洪水时期相当。3000aB.P.以后,气候向干冷转化,永定河水量减少,人类生产力提高,抵御洪水能力增强,洪水给人类造成的威胁相对降低。

... 晚更新世初期, 华北地区的1次构造活跃期导致河流溯源侵蚀的加速, 打开了泥河湾古湖和延怀古湖畅通的出口, 古湖消亡, 永定河水系开始出现, 大量泥砂被带到永定河出山后的平原地区, 形成了北京古洪积扇的主体, 这次构造事件发生在约100ka BP(袁宝印等, 2002) ...

2006

0.0

张岳桥, 施炜, 廖昌珍, 等. 2006. 鄂尔多斯盆地周边断裂运动学分析与晚中生代构造应力体制转换[J]. 地质学报, 80(5): 639—647.

ZHANG

Yue-qiao

, SHI

Wei

, LIAO

Chang-zhen

, et al. 2006. Fault kinematic analysis and change in late Mesozoic tectonic stress regimes in the peripheral zones of the Ordos Basin, North China[J]. Acta Geologica Sinica, 80(5): 639—647(in Chinese).

Based on detailed field observations and measurements of fault geometry, kinematics and activity phases along the southwestern boundary zone, the central W-E fault zone, the eastern boundary zone and the northeastern area of the Ordos Basin, and according to striation superimposition relationship on fault plane and regional tectonic events, this paper established late Mesozoic stress directions, stress regimes and their evolution sequence, and proposed a 4-stage tectonic evolution model with tectonic stress regimes changed alternately between extension and compression. The Basin was under extensional stress environment during the Early-Middle Jurassic, with the extension oriented in N-S to NNE-SSW. The tectonic stress regime had changed to multi-directional (W-E, NW-SE, NE-SW) compression during the period from the latest Middle Jurassic to late Jurassic and the peripheral zones of the Ordos Basin submitted to multi-directional shortening deformation. The stress regime changed again to extension during the Early Cretaceous, with the orientations of extension being NW-SE, W-E and NE-SW. It is followed from the latest Early Cretaceous to late Cretaceous by NW-SE compression. The stress field evolution and the changes in stress regimes in the peripheral zones of the Ordos Basin during the late Mesozoic not only recorded far-field effects produced by different inter-plate convergences, but also reflected changes in deep-seated thermal-tectonic regimes beneath the Ordos Basin, which caused the proto basin to have been significantly reformed.

基于对鄂尔多斯盆地西南缘构造带、中央断裂、东缘边界带和东北部地区的断裂几何特征、运动学及其活动期次的野外观察和测量,并根据断层面上滑动矢量的叠加关系和区域构造演化历史,确定了鄂尔多斯盆地周边地带晚中生代构造主应力方向、应力体制及其转换序列,提出了4阶段构造演化模式和引张-挤压交替转换过程。早中侏罗世,盆地处于引张应力环境,引张方向为N-S至NNE-SSW向。中侏罗世晚期至晚侏罗世,构造应力场转换为挤压体制,盆地周缘遭受近W-E、NW-SE、NE-SW等多向挤压应力作用。早白垩世,盆地构造应力场转换为引张应力体制,引张应力方向为近W-E、NW-SE和NE-SW向。早白垩世晚期至晚白垩世,盆地应力体制再次发生转换,从前期的引张应力体制转换为NW-SE向挤压应力体制。晚中生代构造应力体制转换和应力场方向变化不仅记录了不同板块之间汇聚产生的远程效应,同时记录了盆地深部构造-热活动事件,并对盆地原型进行了一定的改造。

... , 2005), 或者鄂尔多斯周缘的断陷系是二者共同作用的结果(张岳桥等, 2006) ...

2012

0.0

... 朱日祥等, 2012 ...

1997

0.0

1995

0.0

... Northrup et al ...

2005

0.0

... Schellart et al ...

1982

0.0

... 该地的构造背景源于青藏高原东北隅六盘山地区的E向挤出引起鄂尔多斯块体的逆时针转动效应, 秦岭北缘断裂带的左旋及其向E的扩展, 并叠加局部上地幔隆升作用(Tapponnier et al ...

1924

0.0

... 角度不整合面下部为79ka BP之前堆积的湖相地层, 区域上对应于晚更新世萨拉乌苏组(136~70ka BP)(表1), 是河套古大湖主体堆积地层(Chadin et al ...

... 萨拉乌苏组标准地层位于内蒙古乌审旗萨拉乌苏河(又名红柳河)大沟湾一带的嘀哨沟湾(Chadin et al ...

1992

0.0

... 也有人认为鄂尔多斯周缘断陷系的形成与太平洋板块向欧亚大陆的俯冲作用有关, 属于弧后盆地(Tian et al ...

1992

0.0

... Xu et al ...

2010

0.0

... Yin, 2010) ...