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黄河中上游河段是横贯整个“柴达木 -祁连山活动地块”的贯流水系。通过对青海共和至宁夏石嘴山段长约 180 0km的黄河中上游阶地的系统考察、阶地剖面实测和年代测定 ,绘制了该河段的阶地纵剖面图。综合分析各段的阶地级数、高度、年代及变形特征得到以下认识 :该流域可划分为若干个次级活动地块 ,表现在不同地块之间的阶地抬升幅度和速率存在较大差别 ;活动地块内部在较大程度上具刚性特征 ,表现在块体内部阶地级数、高度和形成年代基本相当 ;阶地纵剖面反映的本区活动地块自 1.6MaB .P .以来的抬升量大于 3.6~ 1.6MaB .P .的抬升量 ;柴达木 -祁连山活动地块距今 1万年以来和 15~ 2 0万年间存在 2次强烈的构造抬升运动 相似文献
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位于帕米尔前缘逆冲推覆体(Pamir Front Thrust,PFT)东端的木什滑脱背斜,是帕米尔弧形推覆构造带最前缘和最新的变形带。对地形横剖面、纵剖面和水系发育特征的分析表明,木什背斜总体上具有由西向东扩展生长的特征。在背斜核部及北翼发育数级开阔平坦的沿轴向展布的河流阶地,阶地可划分为4期。利用阶地堆积细颗粒石英光释光测年获得阶地面T2a、T3和T4的形成年龄分别为(15.8±2.40)ka、(55.1±10.3)ka、(131.4±23.9)ka。伴随背斜的生长扩展,河流阶地面发生了横向和纵向掀斜,并形成断层陡坎和褶皱陡坎。木什背斜晚第四纪的缩短和隆升主要是通过褶皱翼旋转机制进行的,估算其最小缩短速率为(1.6±0.3)mm/a,最小隆升速率为(1.9±0.3)mm/a。与此同时,沿轴向背斜发生了向东的侧向迁移和旋转。根据背斜垂直隆升与侧向扩展之间的关系,估算背斜在131~16ka期间向东的侧向迁移扩展速率较快,为 (14.6±3.6)mm/a; 自16ka至今,侧向迁移扩展速率迅速减小至(1.7±0.3)mm/a,背斜向东的迁移扩展可能已基本停止,而以侧向旋转为主。 相似文献
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发育在褶皱区的河流阶地作为一种发育广泛、易于定年的被动变形的地貌标志物,已越来越多地被应用到活动逆断层相关褶皱晚第四纪变形的研究中;结合前生长地层和生长地层,可限定褶皱缩短总量和变形起始时间等参数,恢复从开始生长至晚第四纪以来完整的生长演化历史。文中对正弦曲线状和尖棱状弯滑褶皱模型、经典断弯褶皱模型和纯剪切断顶褶皱模型进行了总结和讨论。这些模型的提出为限定褶皱变形提供了很好的方法,但不能完全概括自然界中的褶皱模型,这就需要更多的野外地质、数值模拟和实验模拟工作。 相似文献
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褶皱在三维空间的生长包括横向缩短、垂向隆升和侧向扩展.沿褶皱走向不同位置这3个分量的比重是不同的:在背斜中段以缩短和隆升为主;靠近背斜端部,在缩短和隆升的同时也会发生强烈的侧向扩展.前人研究主要集中在褶皱中段,对端部这一相对独特的构造位置研究较少.那么褶皱端部是如何生长变形的,与褶皱中段有何不同,伴随褶皱生长同步变形的河流阶地具有怎样的发育特征?对帕米尔-天山对冲带明尧勒背斜西南倾伏端的研究表明,研究区内的4期河流阶地在垂直褶皱轴向上均发生了强烈反向掀斜,越老的阶地面掀斜角度越大,背斜在西南端的生长是以翼旋转机制进行的.据T2b,T3b,T4a的细颗粒石英光释光年龄及下伏基岩的磁性地层年龄可得46°等斜岩区在距今约0.35Ma、(93.9±18.7)ka、(82.6±16.5)ka和(19.4±2.9) ka时期旋转角度大致呈抛物线曲线函数递减,平均旋转速率依次为>(0.13±0.01)°/ka、(0.08±0.02)°/ka、(0.05±0.01)°/ka和(0.04±0.01)°/ka,呈明显减小趋势,但该等斜岩区吸收的缩短速率大致保持恒定.河流阶地在发生掀斜和抬升变形的同时,也发生了向西的侧向扩展变形:由东向西,T3a和T4a阶地面上冲沟密度、宽度和下切深度明显减小,阶地拔河高度、陡坎高度和旋转角度也呈减小趋势,这些均反映了背斜向西的侧向扩展.据喀浪勾律克河谷和背斜西南剖面的磁性地层年代学结果,背斜向西侧向加长的速率恒定为16.0 ~ 16.8mm/a. 相似文献
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受新生代印度-欧亚板块碰撞的远程效应影响,西准噶尔地区平行斜列的走滑断裂系统被重新激活。托里断裂作为其中重要的组成部分,获取其晚第四纪构造变形特征对于认识和理解天山以北区域的构造变形和地壳缩短吸收方式都具有重要意义。文中基于野外调查结果和无人机三维重建技术分析了托里断裂晚第四纪的构造变形特征,并利用光释光测年方法对托里断裂的地貌面期次进行定年,进而通过冲沟和阶地陡坎等标志性地貌的位错量和地貌年龄计算托里断裂的晚第四纪活动速率。研究结果表明:托里断裂由东、西2支分支断裂构成,均以左旋水平走滑为主。东支断裂使喀普舍克河T3和T2阶地分别产生了(89±31) m和(39±13) m的水平位错量,结合T3阶地(52.9±5.1) ka和T2阶地(23.4±1.5) ka的形成年龄,计算得到其活动速率约为(1.7±0.8) mm/a;西支断裂使铁斯巴汗河T2阶地产生了(34.0±6.8) m的水平位错量以及喀普舍克河T3阶地上最大为(37.5-4.1/+2.7) m的冲沟水平位错量,结合T2阶地(18.8±1.3) ka的形成年龄,计算得到其活动速率为(1.8+0.5/-1.3) mm/a。结合... 相似文献
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本文根据滦河三角洲地区野外调查和25个样品的C14年代测定结果,讨论了第四纪地层划分和对比以及近代构造运动。研究表明,滦河内迭三级冲积扇的形成年代分别为距今18000年前,11000年前和6000—3000年之间。在全新世中期,渤海湾北岸发生过海侵。三条古海岸线的年代分别为距今5500年、3700年和350年。本区地面下沉最大幅度为10米左右(姜各庄)。由于滦河最新三角洲的西部和东部地壳下沉速度不同,使滦河河道自全新世中期以来不断向东移动 相似文献
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断裂晚第四纪滑动速率及现今GPS观测揭示了青藏高原向北扩展与高原边缘隆升的运动特征.主要断裂晚第四纪滑动速率及跨断裂GPS应变速率的结果表明,青藏高原北部边缘的断裂以低滑动速率(<10 mm/a)为主,特别是两条边界断裂:阿尔金断裂和海原—祁连山断裂.两条主要边界断裂上的滑动速率分布显示了断裂间滑动速率转换及调整特征.阿尔金断裂自95°E以西的8~12 mm/a稳定滑动速率,向东逐渐降低到最东端的约1~2 mm/a,而海原断裂自哈拉湖一带开始发育后滑动速率为1~2 mm/a,到祁连一带(101°E以东)增大到相对稳定的4~5 mm/a,直到过海原后转向六盘山一带,滑动速率降低到1~3 mm/a,甚至更低.滑动速率的变化及分布特征显示,阿尔金断裂滑动主要是通过祁连山内部隆起及两侧新生代盆地变形引起的缩短来吸收的,海原—祁连山断裂的低滑动速率及沿断裂运动学特征表明断裂尾端的陇西盆地变形及六盘山的隆起是断裂左旋走滑速率的主要吸收方式.这一变形特征表明,青藏高原北部边缘的变形模式是一种分布式的连续变形,变形发生自高原内部,边界断裂的走滑被高原内部变形所吸收. 相似文献
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Tectonic deformation of Cenozoic strata,youthful tectonontorphology,and high seismicity in the western part of Sichuan and Yunnan(Southwest China)marked intensive tectonism there during the Ceno7oic.It is a good place for studying the continental geodynamics because it is far away from those active plate boundaries surrounding the East Asian continent but near the southeastern margin of the Qinghai-Xizang(Tibet)plateau.The present study discriminated two phases of tectonic deformation with quite different styles in Cenozoic.Early compression deformation,expressed by folds,thrust,and even nappe structure,mainly occurred between the middle and late Eocene.Late extension deformation expressed by block-faulting started at least in the late Pliocene.Nonconformity,absence of strata,nonsuccessive tectonism,and inverse movement of the faults in late stages illustrated that two different deformation phases should be caused by different geodynamic processes.The early compression deformation would be related to Ar 相似文献
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Introduction ZHANG and ZHONG (1977), ZHANG, et al (1978) and ZHANG (1984) pointed out that Chinese mainland is divided into two parts by the NS-trending tectonic belt, i.e., the eastern area and the western area, and each area is divided into tectonic blocks by faults. In the eastern area, the faults are trending NNE and NNW, mainly NNE, and the long axis strike of blocks is nearly trending NS. In the western area, faults are trending NEE and NWW, mainly NWW, long axis strike … 相似文献
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IntroductionAccording to the division of Neo-tectonically active blocks northeastern Qinghai-Xizang (abbreviated as QX thereafter) plateau is a juncture region where 3 intra-continental subplates, the Qinghai-Xizang, Xinjiang and North China subplate, meet with each other (DING, 1991). The subplates generally consist of blocks. Specifically, around the Yinchuan-Haiyuan (quasi-trijuncture( (TIAN, DING, 1998), where the 3 subplates meet, to the south locates the Gansu-Qinghai (GQ) blo… 相似文献
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Present-day tectonic movement in the northeastern margin of the Qinghai-Xizang (Tibetan) plateau as revealed by earthquake activity 总被引:2,自引:0,他引:2
Characteristics of present-day tectonic movement in the northeastern margin of Qinghai-Xizang plateau (Tibetan) are studied
based on earthquake data. Evidence of earthquake activity shows that junctures between blocks in this area consist of complicated
deformation zones. Between the Gansu-Qinghai block and Alxa block there is a broad compressive deformation zone, which turns
essentially to be a network-like deformation region to the southeast. The Liupanshan region, where the Gansu-Qinghai block
contacts the Ordos block, is suffering from NE-SW compressive deformation. Junction zone between the Ordos and Alxa block
is a shear zone with sections of variable trend. The northwestern and southeastern marginal region of the Ordos is under NNW-SSE
extension. The above characteristics of present-day tectonic deformation of the northeastern Qinghai-Xizang plateau may be
attributed to the northeastward squeezing of the plateau and the resistance of the Ordos block, as well as the southeastward
extrusion of the plateau materials.
Foundation item: State Natural Science Foundation of China (49732090) and the Development Program on National Key Basic Researches under
the Project Mechanism and Prediction of Continental Strong Earthquakes (95-13-02-05).
Contribution No. 00FE2003, Institute of Geophysics, China Seismological Bureau. 相似文献
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利用滇西及周边地区中国地震台网固定台站,中国地震局地球物理研究所和中国科学院地质与地球物理研究所的临时密集台阵的地震观测数据,使用具有一致性约束的双差地震层析成像方法,联合反演了滇西地区50 km以上深度VP、VS和VP/VS的三维精细结构模型.结果显示,在本研究区域范围内,地震主要集中在高速体的薄弱区域或高低速体过渡带偏向高速体的一侧,空间分布与速度结构之间表现出了很好的对应关系.低速异常体的分布情况非常复杂,受断裂构造限制十分明显,最大控制深度甚至达到了上地幔顶部.本文的地壳结构模型显示,滇西地区的莫霍面深度东西向变化幅度较小,而北南向由深变浅,且起伏变化较大,最深处大于55 km,最浅处约为29 km.波速比存在明显的壳幔边界转换带,在地壳内部变化范围为1.5~1.9,在上地幔顶部均在1.9~2.1之间,且与莫霍面的变化趋势一致.在腾冲火山区下方存在早期火山通道内冷却固结的岩浆侵入体或难以挥发的高密度残留体表现的高速体、尚未固结的岩浆囊或部分熔融物质的低速异常体和延伸至上地幔顶部的热流通道.大理地区存在北南向低速异常条带,推测可能为青藏高原下方向南运移的地壳物质,在区域构造应力作用下,促使在高低速异常体的转换区出现频繁的地震活动.龙陵、澜沧和耿马的4次7.0级以上强震虽然相距较远,但是它们具有相同的发震结构和孕震环境.模型结果可为分析滇西更多重点区域的深部构造背景提供精细的地壳结构数据支持.
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Asymmetrical river valleys in response to tectonic tilting and strike‐slip faulting,northeast margin of Tibetan Plateau 下载免费PDF全文
The northeast margin of the Tibetan Plateau, a particularly important area to understand the mechanism of plateau formation, is characterized by large transpressional arcuate faults. There is debate on the amount of Quaternary sinistral displacement on the major Haiyuan Fault. Previously unrecognized systemic asymmetrical valleys have developed between the Haiyuan and Xiangshan faults. Southeast tilting and sinistral displacement on the northeast side of the Haiyuan Fault resulted in southeast migration of large rivers and asymmetrical widening of their valleys, leaving a systematic distribution of tilted strath terraces along their northwest sides. Where asymmetrical widening created by tilting kept pace with sinistral displacement, rivers have not been deflected, and the increase in valley width downstream from the fault should equate to total lateral displacement since river formation (e.g. Yuan River, a 7 km asymmetrical valley with a c. 2.2 Ma paleomagnetic age). Where river deflection and asymmetrical valley growth are coeval, valley width is less than total horizontal displacement (e.g. Hebao River, a c. 2.1 km asymmetrical valley with c. 2 km deflection). All rivers north of the Haiyuan Fault converge to cut across the Xiangshan Mountains as a gorge. Northeast thrusting of the upthrown side of the Xiangshan Fault has resulted in degradation and related strath terrace formation as the valleys asymmetrically widened. A probable earthquake‐induced landslide caused by movement on the Xiangshan Fault in latest Pleistocene blocked the gorge causing aggradation along all rivers and their tributaries. Deposition terraces were formed after the landslide dam was breached. Together with previous research on the Xiangshan Fault, it is concluded that there has been c. 7 km of Quaternary sinistral displacement on the Haiyuan and Xiangshan faults along the northeast margin of the Tibetan Plateau since the formation of rivers that intersect them. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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The regional geologic and geomorphic observations show that an active arcuate normal fault constitutes the main boundary fault of the Haba-Yulong Snow Mountains (HYSM). This fault is called eastern piedmont fault of Haba-Yulong Snow Mountains (HYPF). The fault consists of two segments with differential trend; the northern segment is NW-trending and NE-dipping and the southern section is S-N trending and E-dipping. Three sets of fault scarps cutting late Quaternary landforms and their dating results indicate... 相似文献