【作者】 王伟涛；

【导师】 张培震； Eric Kirby；

【作者基本信息】 中国地震局地质研究所 ， 构造地质学， 2011， 博士

【摘要】 印度板块与欧亚板块在60-50 Ma的碰撞不仅造成了喜马拉雅造山带的形成,还导致了自印度与欧亚板块缝合带以北2000 km宽的广大地区逐步隆升,形成号称“世界屋脊”的青藏高原。青藏高原的形成对欧亚大陆的构造格局、中亚地区乃至全球的气候变化产生了深远的影响。除此之外,高原的隆升及其构造变形过程也是研究陆-陆板块碰撞的动力学机制、大陆内部构造变形样式以及气候变化的天然实验室。介于东昆仑断裂、阿尔金断裂和祁连山—海原断裂之间的青藏高原东北缘地区是青藏块体向北东方向挤压扩展的最前缘部位,是正在形成的高原。新生代以来该区经历了强烈的构造变形、地壳缩短,并且伴随着垂直隆升作用,致使这一区域发育众多的近东西向山脉,同时还形成了大量的新生代沉积盆地。这些新生代沉积盆地与周围狭长的山脉间隔分布,构成了青藏高原东北缘地区独特盆—岭地貌。青藏高原东北缘广泛分布的新生代沉积盆地是在变形过程中形成,与此同时,地壳因逆冲-褶皱变形而强烈缩短形成山脉,山脉的隆升总是伴随着风化、剥蚀作用,河流将造山带内的侵蚀产物搬运到山脉周边的盆地中沉积下来,于是,沉积盆地记录了其在接受沉积物充填过程中的动力学性质和周围造山带的构造活动特征与气候变化信息。因此,以青藏高原东北缘新生代盆地为研究对象,以盆地中沉积物为纽带,建立盆地与周围山脉的耦合关系,是了解高原隆升和高原向内陆扩的重要途径。宁夏南部地区因广泛出露第三系沉积物,而被命名为宁夏南部新生代盆地。该盆地位于现今青藏高原东北缘的边界断裂,祁连山—海原断裂的东端(东经105°00′~106°40′,北纬35°~37°30′),向南收敛于六盘山,向西北撒开,构成“扫帚”状;面积约1万平方公里;地貌上,东南高,西北低,属于青藏高原与鄂尔多斯地块的过渡区域。宁夏南部盆地处于青藏高原的最前缘,西南方向以海原-六盘山弧形断裂带以及黄家洼山-西华山-南华山-六盘山为界,分割于陇中盆地;向东北方向香山-天景山活动断裂带、烟筒山活动断裂带、罗山-牛首山活动断裂带呈弧形切割宁夏南部盆地,形成了一个局部的弧形盆-山构造体系。宁夏南部盆地,在上述断裂带的活动过程中形成、发育、消亡和改造,在此过程中,盆地沉积了巨厚的陆相地层,保存了大量的海原-六盘山断裂带、香山-天景山断裂带、烟筒山断裂带、罗山-牛首山断裂带的几何学、运动学信息以及与断裂带相关的造山过程和构造变形信息。通过研究宁夏南部盆地的几何形态、构造属性和演化历史,我们可以揭示上述这些断裂带或者断裂的性质,活动期次、运动方式,进而,重塑青藏高原东北缘的变形和隆升历史,探讨青藏高原在向北东扩展的运动学和动力学机制。本次研究我们选择了宁夏南部盆地作为重点研究区,通过对盆地内新生代沉积物,以及盆地内的断裂带进行沉积演化与构造变形的研究,明确盆地与断裂之间的相互关系。根据我们所获得的相关资料,结合青藏高原东北缘地区已有的构造变形、新生代沉积地层年代等方面的资料,本文取得的主要结论如下:宁夏南部盆地西南隅,寺口子剖面新生代地层出露连续并且齐全,本文在张广良博士年代研究的基础上,对寺口子剖面进行了详细的沉积序列研究,并在中国科学院地质与地球物理研究所朱日祥院士的亲自指导下重新系统地测试了张广良博士采集的古地磁样品,用以建立精确的地层时间序列。在古生物(Plesiaceratherium sp.)的控制下,寺口子剖面由下向上依次划分为:寺口子组,其时代划归为晚渐新世(E3S),~29-25 Myr;上覆清水营组属于早中新世(N11),清水营组与寺口子组之间存在约1.5 Myr的沉积间断,其底界年龄大约为23.8 Myr,顶界年龄为16.7 Myr;清水营组之上的红柳沟组被划归为中中新世(N12),16.8-5.4 Myr之间;干河沟组为上新世沉积(N2),时代5.4-2.5 Myr之间;干河沟组之上的沉积物划为第四系(Q)沉积时代为2.5-0.5 Myr。宁夏南部盆地内寺口子组岩性变化明显,盆地南部靠近六盘山,马东山地区主要为厚层紫红色含砾长石石英粗砂岩、厚层—巨厚层紫红色长石石英中砂岩夹细砂岩薄层,盆地北部主要为紫红色厚层砾岩夹紫红色泥岩,粉砂岩以及砂岩薄层。尽管寺口子组岩相由南向北剧烈变化,但是寺口子组顶部发育一套厚约3-10 m以钙质结核、生物钙质铸模、钙质胶结的砾岩等为特征的古风化壳,代表了寺口子组与清水营组之间经历较长时间的沉积间断。清水营组在研究区分布最为广泛,岩性主要由薄层—中厚层暗紫红色粉砂岩、粉砂质泥岩、泥岩,薄层-厚层绿色-灰白色石膏以及中厚层灰白色的砂岩组成,由南向北石膏层厚逐渐增厚。红柳沟组岩性主要为桔红色厚层—中厚层泥岩、粉砂质泥岩、泥质粉砂岩,夹有薄层灰色中细砂岩、粉砂岩等。干河沟组以土黄色、浅黄绿色砾岩为主,夹薄层或透镜状砂岩、粉砂岩以及泥岩,第四纪松散砾石堆积。2007-2009年,我们在宁夏南部盆地内固原寺口子剖面红柳沟组底部处采集到大量的Plesiaceratherium sp.,海原天子埫剖面红柳沟组底部采集到Kubanochoerus sp.,中宁红柳沟剖面红柳沟组中部采集到Platybelodon sp.等化石。在上述化石与已发现的同心丁家二沟动物群,海原袁家窝窝动物群,寺口子组顶部的古风化壳(古土壤)、区域可供对比的厚层石膏等标志层的基础上,以寺口子剖面磁性地层学年代为约束,我们通过盆地内新生代沉积物的颜色、岩相对比,将整个盆地内寺口子组厘定为晚渐新世(E3S);清水营组为晚渐新世-早中新世(N11);红柳沟组厘定为中中新世沉积(N12);干河沟组为上新世(N2)。寺口子组作为宁夏南部盆地内的第一套新生代沉积物,代表了盆地的开始。晚白垩纪以来,宁夏南部地区一直处于剥蚀状态,直至晚渐新世寺口子组的沉积,这是否意味着构造事件的发生?这一事件与青藏高原的隆升及其向北东的扩展是否存在着内在的联系呢?钻井剖面、野外实测剖面揭示寺口子组由南向北沉积相变化非常剧烈,呈现出南部粒度细,北部粒度粗的特点。同时穿过寺口子盆地的反射地震剖面,揭示宁夏南部盆地的寺口子组受控于盆地北部的天景山断裂和烟筒山断裂。厚度超过800 m厚的寺口子组位于紧邻天景山断裂的南西一侧,向西南方向寺口子组厚度迅速减薄,盆地的构造属性表现为典型的半地堑。寺口子组沉积时期,位于烟筒山断裂上盘的沉积中心也显示出类似的特征,证明宁夏南部地区在晚渐新世可能处于局部伸展的构造背景之下,这与鄂尔多斯盆地西缘一系列的地堑,半地堑(河套盆地、银川盆地、渭河盆地)构造背景相似,却与以挤压为特征的青藏高原变形样式存在显著的区别。因此,寺口子组沉积时期宁夏南部盆地的成因可能与鄂尔多斯块体的南西向运动紧密相关,而与印度-欧亚板块的碰撞并无直接关系。平面上,宁夏南部盆地内的寺口子组以冲积扇相和辨状河相沉积为主,盆地北部(同心以北)主要为冲积扇相,物源主要来自天景山断裂,烟筒山断裂的北东盘(断层的下盘)以及鄂尔多斯西缘的隆起地区;盆地南部(海原以南)主要为辨状河相沉积;向北,北东的古水流,显示其物质可能来自六盘山以西以及西秦岭地区;中部(同心-海原之间)则表现为冲积扇相向辨状河相的转变。垂向上,寺口子组表现为典型的由下向上粒度逐渐变细的正粒序。寺口子组等厚线显示盆地有多个沉积中心,位于宁夏南部盆地北部,靠近天景山断裂与烟筒山断裂。寺口子组的沉积环境、古水流、物源分析、地层等厚线等证据均支持天景山断裂,烟筒山断裂早第三纪可能为正断层的结论。清水营组(23.8-16.7 Myr)分布较为广泛,以石膏和细颗粒碎屑沉积物为代表。向南清水营组越过西华山-南华山与陇中盆地相连通,向北清水营组超覆于天景山断裂与烟筒山断裂之上,可能与宁夏北部的银川地堑相连通。清水营组地层厚度在宁夏南部盆地内较为稳定,沉积环境以北部的干盐湖沉积和南部的正常湖相沉积为主。干旱时期,盆地沉积范围迅速萎缩在宁夏南部盆地的中部和北部地区形成若干个干盐湖沉积环境;湿润时期湖平面上升,盆地沉积范围扩大,形成统一的泛盆地。这一时期(23.8-16.7 Myr)青藏高原东北角的构造活动较弱,气候变化可能是控制盆地沉积环境,湖平面升级的主要因素。红柳沟组中下段(16.7-10.5 Myr)是青藏高原东北缘分布最广的地层,以细颗粒的泥岩、粉砂岩、砂岩等为特征。红柳沟组中下段与清水营组相似,主要以河湖相为主。沉积相的显著变化发生在红柳沟组中段与上段之间(~10.5 Myr)。沉积环境由浅湖-滨湖相逐渐转变为扇三角洲-辨状河相,证明盆地周围开始抬升,盆地范围逐渐缩小。与此同时寺口子剖面(盆地南缘)的沉积速率由之前的~9cm/yr增加至~13 cm/yr。红柳沟组沉积相的显著变化、沉积速率的持续增加可能代表了盆地西南海原断裂、六盘山断裂此时开始向北东逆冲推覆,造成六盘山-南华山-西华山于~10.5 Myr开始快速隆升。红柳沟组地层厚度分布与清水营组地层等厚线之间存在巨大的差别,清水营组地层由南向北厚度相近,红柳沟组靠近海原-六盘山断裂带,地层厚度> 800 m,向北东方向厚度迅速减薄,至烟筒山断裂带(同心地区)厚度<200 m,显示出压陷型挠曲盆地的特征。盆地性质由清水营组时期的整体凹陷向红柳沟组晚期的挠曲盆地转变,表明盆地在晚中新世受到北东方向的挤压,这无疑与青藏高原向北东方向的推挤、扩展、隆升直接相关。因此,海原-六盘山断裂~10.5 Myr的活动以及六盘山-南华山-西华山的快速隆升,表明与印度-欧亚板块碰撞相关的,以地壳缩短为特征的构造变形样式才扩展到宁夏南部地区,使这一地区成为青藏高原的最新组成部分。干河组分布范围迅速缩小,主要沿海原-六盘山断裂带北东一侧呈带状分布,地层厚度南厚北薄,天景山弧形断裂带与烟筒山弧形断裂带地区缺失干河沟组,更北牛首山西麓一带出露干河组地层。在南西-北东向,干河沟组地层厚度变化趋势与前陆盆地前渊-前隆-隆后凹陷的几何形态极为相似。干河沟组发育典型的磨拉石建造,沉积环境主要由河流相和冲积扇相为主,显示盆地逐渐消亡。第四系与新世干河沟组靠近六盘山-马东山,天景山等地区呈角度不整合接触,向盆地方向两者表现为平行不整合及其整合接触关系。第四系以辨状河相和冲积扇相沉积环境为主,显示宁夏南部盆地在第四纪初物源区快速隆升、盆地遭受强烈构造变形,形成现今被六盘山-海原断裂、天景山断裂、烟筒山断裂以及罗山-牛首山断裂切割的小型压陷盆地。通过对宁夏南部盆地的沉积演化与构造变形研究,宁夏南部盆地在晚渐新世表现为局部伸展的断陷盆地,早、中中新世为整体的凹陷盆地,晚中新世以来才表现为压陷性质的前陆盆地。晚中新世压陷盆地的形成与海原-六盘山逆冲褶皱带北东向的挤压紧密相关,上新世-第四纪海原-六盘山断裂带以北的天景山断裂与烟筒山断裂相继开始活动,致使上新世干河组与第四系不整合接触,甚至干河组逆冲至第四系之上,宁夏南部盆地经受改造、裂解形成现今褶皱变形带与压陷盆地间隔分布的盆-山构造系统。宁夏南部盆地演化过程和模式表明,青藏高原东北缘的扩展可能是向北东方向的逐渐增生过程。生长地层是指在前陆盆地与褶皱构造变形同期沉积的地层,是识别盆地相邻造山带构造活动的重要标志。在寺口子剖面中我门识别出一套生长地层,这套生长地层开始于~5.4 Myr,一直持续至1.8 Myr.大比例尺构造填图显示寺口子剖面由寺口子背斜和一对次级的向斜和背斜组成,是构成马东山北部的主要构造。毫无疑问,寺口子剖面的生长地层反映了马东山构造变形以及寺口子背斜的形成。鉴于马东山位于海原断裂的最东端,其变形样式与六盘山截然不同,本文分析马东山可能由于吸收了海原断裂的左旋走滑量而褶皱构变形。因此,寺口子剖面生长地层较好的限定了海原断裂左旋走滑的开始时间。根据沉积盆地对区域构造的活动的响应关系,揭示青藏高原东北缘的边界断裂海原断裂晚中新世以来经历了两阶段构造演化:~10.5 Myr开始北东向的逆冲推覆,5.4 Myr北东向的逆冲逐渐转变为左旋走滑兼逆冲。同时,野外填图也表明该区域的天景山断裂、烟筒山断裂、牛首山-罗山断裂也具有上新世以来的北东向逆冲与之后的左旋走滑兼逆冲推覆。这些断裂活动的时间以及方式显示青藏高原东北角以薄皮构造的方式逐渐向北东方向扩展,新生的逆冲断裂裂解了之前广泛分布的沉积盆地,使断裂前缘挠曲下沉形成新生的类前陆盆地,断裂后缘隆升变形产生背驼盆地。更多还原

【Abstract】 The collision of the India-Eurasian not only created the Himalayan orogenic belt, but also caused a ~2000 km wide intra-continental deformation north of the collision zone that has subsequently uplifted to form the Tibetan Plateau referred as to“the roof of the world”. The uplift of the Tibetan Plateau posed significantly impacts on the tectonic framework of Eurasian continent, environments of the central Asia and global climate change. In addition, the Tibetan Plateau also provides a natural laboratory for studying the dynamics of collision between continent and continent, intra-continental deformation, and interaction between tectonics and climate change. The northeastern margin of the Tibetan Plateau is defined by the Kunlun fault in the south, the Altyn Tagh fault to the west and the Qilianshan Haiyuan faults to the north. This region is the frontier of the northeastward expanding Tibetan Plateau characterized by left-lateral strike slip faulting and northeastward crustal shortening. As the newest portion of the plateau, the region has been undergone wide-spread Cenozoic tectonic deformation. As a result, a number of arcuate basin and range pairs are formed with west northwest trending in the west and gradually becoming north-sjouth orientation eastward. The arcuate ranges are tectonically controlled by high-angle reverse faults with various amounts of left-lateral strike-slip components. The materials eroded off the arcuate mountains are deposited within the adjacent basins. Thus sediments preserved in the basin documented valuable information of the tectonic deformation, mountain uplift and environmental changes during the process of basin formation. Therefore, according to the basin and range coupling relationship, the studies of sedimentary evolution and tectonic deformation in the basins adjacent to the ranges are important approaches to understand processes of uplifting and outward growing of the Tibetan Plateau .The Cenozoic sediments well crop out in the south part of Ningxia Hui Autonomous Region which is referred as to southern Ningxia basin, which is located in easternmost part of the Qilian Shan-Haiyuan fault, the present-day boundary fault of northeastern margin of Tibetan Plateau. The southern Ningxia basin is a triangular basin with an area of ~10,000 km2 situated in the transition zone between a region of the northeastern margin of the Tibetan Plateau characterized by Cenozoic shortening and a region of Cenozoic extension surrounding the Ordos plateau. The elevation of the southern Ningxia basin drops irregularly from the 2400 m in the southwest near the Liupan Shan to 1600 m along the Huang He (Yellow river) in the north. As the southwest boundary fault, the Haiyuan-Liupan Shan arcuate fault separated the southern Ningxia basin from the Longzhong basin in the south. Within the basin, a series of the arcuate fault zones (Tianjing Shan fault zone, Yanton Shan fault zone and Luo Shan-Niushou Shan fault zone) cut the southern Ningxia basin from the basement to the surface and consist of, together with the Haiyuan-Liupan Shan fault zone, the arcuate basin and range system in the northeastern margin of the Tibetan Plateau. In the process of the activation of these fault zones during the Cenozoic time, thick sedimentary sequence was accumulated to record information related to the geometry and kinematics of the faults in the southern Ningxia basin. Though analysis of the geometry, tectonic setting and sedimentary evolution of the basin, we would be able to reveal the characters, processes and kinematics of the above mentioned fault zones, and to reconstruct the tectonic deformation and uplift history of the northeastern margin of Tibetan Plateau.This study focuses on the southern Ningxia basin. Based on the previous works, including field works from 2007 to 2010 and measurements in the laboratory, we analyzed the paleomagnetostratigraphy, depositional characteristics, sedimentary facies distribution, sedimentary basin evolution, and tectonic deformation. We summarized the primary conclusions and drew them as follows:Along the best exposed Cenozoic section (Sikouzi section in the southern basin margin) paleo-magnetic samples are collected and analyzed to build the temporal series of the Cenozoic sediments in the basin. Constrained by newly mammalian fossils directly collected in the Sikouzi section at a depth of 2010 m, the age of the section is estimated from ~29 Myr to 0.5 Myr. From the base to the top, the section is subdivided into five lithostratigraphic units: the lowest Sikouzi Formation is dated from ~29 to 25.3 Myr, and Qingshuiying Formation is estimated at 23.8-16.7 Myr. Almost a 1.5 Myr hiatus existed between Sikouzi Formation and Qingshuiying Formation. The Honliugou Formation is deposited between 16.7 Myr and 5.4 Myr and the Ganhegou Formation is estimated at 5.4-2.58 Myr. The upper-most Quaternary deposits maybe continue to 0.5 Ma or even younger.The south Ningxia basin initiated as an extensional subsidence which controlled by the arcuate Tianjin Shan fault and Yanton Shan fault in the early Tertiary. The isopach pattern of early Tertiary E3s is restored based on the measured stratigraphic sections, boreholes, and seismic-reflection profiles suggesting that the thickest Sikouzi Formation is more than 800 m near the TJSF and gradually thins southwestward. Another similar southwestward thinning depocenter is bounded by the Yantonshan fault (YTSF) in the north basin margin. Considering the southwest-dipping of TJSF and YTSF (Zhang et al., 1990; 1991), the southwestward thinning Sikouzi Formation in the hanging wall of Tianjing Shan fault and Yanton Shan fault indicate that they are probably the extensional faults when they reactivated in Oligocene time. The data that suggest initiation of basin subsidence and early basin filling was linked to extensional slip on basin-bounding faults directly contradict models for early Tertiary contractional deformation in the region. Thus, the kinematics of this period of deformation may closely relate to the motivation of Ordos block and suggest no link to deformation driven by the Indo-Asian collision. This reference is also supported by the changes of grain-size, sedimentary facies and paleocurrents from clast imbrication and cross-stratification in the Sikouzi Formation.The southern Ningxia basin expanded coeval with the deposition of Qingshuiying Formation. The basin’s depositional area extended southwestward across the Haiyun-Liupan Shan fault connecting with Longzhong basin and northeastward overlying Tianjin shan fault and Yantong Shan fault to joint with Yinchuan graben at this stage (23.8-16.7 Myr). Fine-grained deposits comprise the late Oligocene-early Miocene Qingshuiying Formation and no basin-marginal facies association, such as alluvial fan system, exposed in the present-day basin margins. Depositional environments are dominated by playa lake and shallow lacustrine from the northern to the southern basin margins suggesting a broad basin appearance in the Liupan Shan area and its adjacent region. Considering the sedimentary facies distribution and inactivation of border faults coeval with the Qingshuiying formation, we propose that the main reason caused expansion of Sikouiz basin in the late Oligocene-Miocene is climate change, which maybe also trigger the pseudo-unconformity contact between the Sikouzi Formation and Qingshuiying Formation.In a manner similar to the Qingshuiying Formation, the lower and middle subunits of Honliugou Formation (16.7-10.5 Myr) also are dominated by fine-grained sediments. The obvious change of sedimentary environment occurred at about 10.5 Myr. The sedimentary facies evolved from earlier shallow lacustrine into delta-fan and braid river environments suggesting that ranges around the basin initiated to uplift and the depositional area of the southern Ningxia basin gradually reduced after 10.5 Myr. At the same time, accumulation rates pulsed at ~10.5 Myr from ~9 cm/kyr to ~13 cm/kyr. Collectively, the sedimentary environment change and increase in accumulation rate at ~10.5 Myr probably respond to northeastward thrust of the Haiyuan fault and Liupan Shan fault.The isopach pattern of the Honliugou Formation show that more than 800 m thick Honliugou Formaiton is preserved adjacent to the Haiyuan-Liupan Shan fault, and the thickness of the Honliugou Formation gradually thins to the northeastward with less than 200 m near the Tongxi county. This phenomenon implies a possible textural subsidence due to thrusting of Haiyuan-Liupan Shan fault driven by the outward growth of the Tibetan Plateau. Therefore, the reactivation of northeastward thrusting of Haiyuan fault and Liupan Shan fault and associated uplift of Liupan Shan, Nanhua Shan and Xihua Shan probably suggest that the deformation related to the collision of Indo-Eurasia has reached the northeast corner of Tibetan Plateau at about 10.5 Myr. And this region started to became the newest component of the Tibetan Plateau in late Miocene.Depositional area of the southern Ningxia basin distinctly shrank in Pliocene time, when the Ganhegou formation was deposited in a narrow area paralleling the Haiyuan fault and the Liupan Shan fault. The maximum observable thickness of the Ganhegou Formation is > 600 m in the southwest part of the Haiyuan-Liupan Shan fault. To the north, the Ganhegou Formation is absent in the region near the Tianjin Shan fault and Yanton Shan fault. Further to the north, the Ganhegou Formation corps out in the west flank of Niushou Shan. This isopach pattern suggests that the southern Ningxia basin is a typical foreland basin with foredeep, forebulge and back-bulge. The Ganhegou Formation is characterized by molasse deposits indicating that the Ningxia basin was gradually dying out coeval with the deposition of Ganhegou Formation.Based on the studies of the basin evolution and tectonic deformation, the southern Ningxia basin initiated as extensional subsidence in the late Oligocene and became a widespread depression from early to late Miocene. Flexural subsidence associated with northeastward thrusting of Haiyuan-Liupan Shan fault has been developed since about ~10.5 Myr. Tectonic studies show that Tianjin Shan fault displaces the pre-Tertiary sediments over the Quaternary conglomerate suggesting that the reactivation of Tianjing Shan fault started in Quaternary. Although the onset of northeastward thrust along the Yanton Shan fault is unknown, it is clear that the reactivation of Yantong Shan is later than that on the Tianjin Shan fault. All of the data imply that the deformation progressively propagated from the southwest to the northern in the northeastern corner of the Tibetan Plateau.Growth strata are syntectonic sediments which are closely linked to folding and faulting in the foreland basin, and, thus, they can provide precise information on tectonic and depositional interaction. In the Sikouzi section, the age of inception of growth strata is at ~5.4 Ma, deformation apparently continued into the Pleistocene. The implication of this set of growth strata is that the sediments exposed along the Sikouzi section were subjected to syn-sedimentary deformation, which is closely related with the emergence of Madong Shan folds at ~5.4 Ma. Considering that the Madong Shan is located at the east tip of Haiyuan fault, we propose that the deformation in the Madong Shan is caused by the transfer of the left-slip displacement along the Haiyuan fault to shortening in the Madong Shan area. Thus, the left-slip along the Haiyuan fault may initiate at ~5.4 Ma and continue to the present-day.Following the respond of sediments to tectonic activation in the southern Ningxia basin, all of fault zones within the basin have been undergone two major deformational phases since late Miocene. The northeastward thrusting seems to be the first phase of the deformation, which is followed by left-lateral strike-slip on the east-west parts of the arcuate fault zones and the displacement on the left-lateral strike-slip fault zones were transferred to crustal shortening in the north-south trending parts of fault zones. According to the kinematics and ages of fault activations, a northeastward propagated model is propose to describe the deformational style in the northeastern corner of the Tibetan Plateau.更多还原