柴西南新生代沉积和构造特征及其与祁漫塔格的构造耦合

发布时间：2018-04-27 11:59

本文选题：柴达木盆地 + 祁漫塔格　；参考：《浙江大学》2017年博士论文

【摘要】：青藏高原北缘祁漫塔格-柴达木盆地西南(简称"柴西南")地区,西北部以阿尔金断裂为界,南部紧邻东昆仑构造带,处于青藏高原大地构造的关键部位,是青藏高原内部最大的地形高差所在之地,由此可见其新生代以来构造活动之强烈、差异隆升之显著。因此理清柴西南地区的沉积构造演化特征及其与祁漫塔格地区的耦合关系对于探究整个青藏高原隆升机制和演化模型具有重要意义。本文基于柴西南地区的沉积构造响应以及祁漫塔格地区低温热年代学研究来探讨柴西南及邻区新生代的演化过程,并初步得到以下认识:(1)柴西南被一些主要断裂分成若干个不同的构造单元,这些次级单元具有不同的沉积构造演化历史。西部的格斯凸起为中生代晚期就已经存在的古隆起,分割着两侧的阿拉尔凹陷与切克里克凹陷;自新生代早期开始,地层不断向其超覆沉积,并最终与两侧的凹陷连通。西北侧的阿拉尔凹陷和红狮斜坡在路乐河组沉积时地层向阿尔金山前变厚,说明当时的阿尔金山未隆起,柴达木盆地可能与塔西南相连;自下干柴沟组沉积时期开始,沉积中心逐渐向东迁移,形成鼻状隆起,下油砂山组时期隆起范围最大并遭受剥蚀;自上油砂山组沉积开始,红狮地区又变为简单的向东南倾的斜坡形态。中部的跃进-乌南地区同样是继承晚中生代古地形发育而来,新生代早期表现为一整体向东倾的斜坡,直到下油砂山组末期由于断裂强烈活动才开始出现分异,形成跃进斜坡、切克里克凹陷、扎哈泉凹陷和鸟南斜坡。南部紧邻祁漫塔格的昆北地区沉积特征受盆地内北西向断裂控制作用最为明显,下油砂山组及以上地层在其东部大范围缺失,可能意味着这一时期祁漫塔格地区发生强烈活动。东南端的弯西地区在新生代早期一直稳定接受沉积,直到下油砂山组末期发生强烈变形,可能与祁漫塔格的活动有关;北东侧的英雄岭背斜构造带新生代以来一直是柴西南的沉积中心所在,在狮子沟组沉积末期(～3Ma)发生强烈褶皱隆升,成为现今盆地内最大、活动性最强的背斜带。(2)通过柴西南地区大量的地震剖面刻画了该地区断裂的几何学、运动学特征以及其随时间的传播演化规律。该地区主要发育NW向和少量的N-S向断裂。断层陡直,大都切穿基底,除逆冲分量外,NW向断裂还具有一定的左旋走滑分量,而N-S向断裂则具有一定的右旋走滑特征,但走滑量相对于逆冲量来说可以忽略不计。研究区内最老的断裂为阿拉尔断裂、昆北断裂、昆北1号断裂以及茫南断裂,它们在整个新生代都持续活动,推测可能是前新生代的老断裂重新活动的结果。这些断裂在新生代整体不断向北,向东传递,可能与其南侧祁漫塔格的冲断以及西侧阿尔金断裂系的活动有关。(3)祁漫塔格地区磷灰石裂变径迹以及(U-Th)/He结果表明祁漫塔格整体新生代初期已经存在显著隆升。热史模拟显示祁漫塔格在新生代经历了两次快速隆升事件,第一期自新生代初期开始一直持续到40 Ma左右,之后进入缓慢隆升阶段;第二期自20 Ma开始,祁漫塔格地区再次进入到强烈隆升阶段。晚中新世以后,由于变形快速向北传递,祁漫塔格现今隆升已非常微弱。此外,磷灰石(U-Th)/He结果也表明祁漫塔格南峰(阿达滩断裂以南)一直处于整体稳定抬升状态,受局部构造活动影响较小,而北峰(阿达滩断裂以北)明显受局部断裂影响较大,可能与它们经历了不同的前新生代构造变形历史有关。(4)柴西南与祁漫塔格之间的接触关系在西边为超覆不整合,向东则变为断裂接触。结合前人的研究结果,本文提出了柴西南及邻区的演化模型:①古新世至中始新世时期,盆地整体属于填平补齐阶段,盆地范围在不断扩大,柴西南地区一些北西向的老断裂开始活动,但活动强度不大。阿尔金山还未隆升,祁漫塔格为晚古生代的继承性局部隆起,为柴西南地区提供物源,部分分割了柴达木和库木库里盆地;②晚始新世时期(～47-35.5Ma,盆地范围达到最大,水体加深,同时南山强烈隆升剥蚀,为其北侧的柴西南地区提供充足的物源;③渐新世-旱中新世时期(～35.5-15.3Ma),阿尔金山开始显著隆升,导致邻近的红柳泉、七个泉一带发生强烈的断裂活动,形成了上、下油砂山组之间的角度不整合,与此同时祁漫塔格地区处于相对构造平静期;④中中新世时期(～15.3-8Ma),阿尔金断裂、东昆仑断裂开始大规模走滑,导致青藏高原北缘发生一起构造调整,祁漫塔格再一次快速隆升,表现为其东段向北冲断至柴西南新生界之上;⑤上新世-至今(8-0Ma),变形开始由盆地周缘向盆地内部快速扩展,表现为在盆地内部发育了大量NNW向背斜构造和断裂,最强烈的变形发生在英雄岭位置,致使英雄岭地区由原始沉积坳陷转变为大型的隆起区。
[Abstract]:The northern margin of the Qun tge Qaidam Basin in the northern margin of the Qinghai Tibet Plateau is the area in the southwest of Qaidam Qaidam Basin. The northwest is bounded by Altun fault, and the south is close to the East Kunlun tectonic zone. It is the key site of the Qinghai Tibet Plateau geotectonics and the largest terrain elevation difference in the Qinghai Tibet Plateau. This shows that its tectonic activity since the Cenozoic era is strong and poor. The characteristics of the sedimentary tectonic evolution and the coupling relationship with the Qiman area are of great significance to the exploration of the uplift and evolution model of the whole Qinghai Tibet Plateau. This paper is based on the sedimentary tectonic response and the low temperature thermal chronology in the Qiman area. The evolution process of the Cenozoic in the southwest and its adjacent areas has been preliminarily recognized as follows: (1) the southwest of Qaidam is divided into several different tectonic units, and these sub units have different sedimentary tectonic evolution history. The Gus uplift in the west is a paleo uplift which has already existed in the late Mesozoic, and the alar sag on both sides is divided. Since the early Cenozoic, the formation of the strata has been overoverlying and eventually connected to the depression on both sides. The alalin and honglion slopes in the northwest side of the lelehe formation thickened to the AlTiN mountain, indicating that the Altun mountain was not uplifted at that time, and the Qaidam basin may be connected to the Southwest of the tower; from the lower dry wood ditch. At the beginning of the sedimentary period, the sedimentary center gradually migrated eastward to form a nose like uplift, and the lower oil sand mountain group had the largest uplift range and suffered erosion. Since the deposit of the upper oil sand mountain group, the Red Lion area changed into a simple and southeastern slope. In the early period of the generation, it showed an overall eastward slope, until the end of the lower oil sand mountain formation began to differentiate, formed a leap slope, the kkkkkk sag, the Zaha spring sag and the southern slope of the south. The absence of the sand mountain formation and the above strata in the East may mean a strong activity in the Qun Tagge area in this period. The southeastern corner of the southeastern end of the Cenozoic has been steadily deposited until the early stage of the lower oil sand mountain formation, which may be related to the activities of the Qun tagagu; the heroic ridge anticline structure of the north east side Since the Cenozoic era, the sedimentary center of Southwest Qaidam has been located in the southwest of Chai Chai formation (3Ma), which has become the largest and most active anticline belt in the present basin. (2) through a large number of seismic profiles in southwestern Qaidam area, the geometry, kinematics characteristics and its time propagation in this area are described. The region mainly develops NW direction and a small number of N-S trending faults. The fault is steep and mostly cut through the basement. Except for the thrust component, NW also has a certain left-hand slip component, while the N-S direction fault has a certain dextral strike slip feature, but the strike slip amount is negligible relative to the inverse impulse. The oldest fracture in the study area is not. For the alar fault, the kunbei fault, the kunbei No. 1 fault and the mannan fault, they are continuously active throughout the Cenozoic, presumably the result of the reactivity of the old Cenozoic old faults. These faults are continuously north and eastward to the Cenozoic, and may be broken down from the southern Qun tge and the activity of the Altun fault on the west side. (3) the apatite fission track in the Qiman area and (U-Th) /He results show that there have been significant uplift in the early Cenozoic of the Qimen tage. The thermal history simulation shows that Qiman tage experienced two rapid uplift events in the Cenozoic, and the first period started from the beginning of the Cenozoic to about 40 Ma, and then entered the slow uplift. During the second period, the second period began with 20 Ma, and the Qiman area again entered the strong uplift stage. After the late Miocene, the current uplift of Qiman tage was very weak because of the rapid northward transfer of the deformation. In addition, the apatite (U-Th) /He results also indicated that the Qiman (south of the A Da beach fault) had been in a steady state of stability and uplift. The northern peak (north of the ADA beach fault) is obviously influenced by the local fault, and it may be related to the different history of the tectonic deformation of the former Cenozoic. (4) the contact relationship between the southwest Chai and qununtag is the overlying unconformity in the West and the fracture contact to the East. The evolution model of Southwestern Qaidam and its adjacent areas was proposed: 1. During the period of the Paleocene to the middle Eocene, the whole basin belonged to the stage of filling and filling, the basin range was expanding, and some old faults in the North Western Qaidam area began to move, but the activity was not strong. The Altun mountain was not uplifted and the qimintage was a inherited partial uplift of the late Paleozoic. To provide material source for Southwest Chai, the Chaidamu and kuimuali basin were partially divided; (2) the late Eocene period (~ 47-35.5Ma, the basin range was the largest, the water depth was deepened, and the south mountain was strongly uplifted and denuded, providing sufficient source for the southwestern Qaidam area; (3) the Oligocene to the Miocene epoch (~ 35.5-15.3Ma), the AlTiN mountain began. The significant uplift resulted in the strong fracture activity in the vicinity of the red willow spring and the seven springs, which formed the unconformity between the upper and lower oil sand mountain groups, while the qimintag area was in the relative tectonic calm period; (4) the middle Miocene period (to 15.3-8Ma), the Altun fault and the East Kunlun fault began to slide on a large scale, leading to the Qinghai Tibet Plateau. There is a structural adjustment in the northern margin, and the qimatuge is once again rapidly uplifting, showing that the east section of its east segment has broken northward to the Cenozoic in southwestern Qaidam; (5) the Pliocene - today (8-0Ma), the deformation began to rapidly expand from the basin margin to the basin, showing that a large amount of NNW anticline structures and faults were developed inside the basin, and the most intense deformation occurred in the basin. The heroic ridge position resulted in the transformation of the heroic ridge area from the original sedimentary depression to a large uplift area.

【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：P542

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