【作者】 廖林；

【导师】 杨树锋； 陈汉林；

【作者基本信息】 浙江大学 ， 构造地质学， 2010， 博士

【摘要】 受印度-欧亚板块的碰撞和持续的汇聚作用,位于帕米尔东北缘的西昆仑造山带在新生代重新活化,并向塔里木板块强烈冲断挤压。对其开展新生代构造活动过程及其沉积响应的研究可以为揭示青藏高原的演化、印度-欧亚板块碰撞的远距离效应以及大规模的陆内俯冲作用等提供重要参考。本文对西昆仑山前带新生代构造变形特征及演化规律分析、新生界沉积学特征及构造-沉积响应关系分析的进行了研究,结合前人热年代学成果,初步获得如下认识：1、中新世末期-上新世早期的构造事件造就了研究区现今的构造格局,山前冲断带在空间结构特征上存在着“东西分段、南北分带、深浅分层”的特点,自西向东可划分为以第四纪背驮盆地和下伏冲断变形发育为特征的乌泊尔走滑-逆冲构造段、以堆垛式三角带构造和宽缓的北翼为特征的齐姆根走滑-冲断构造段、以冲断型三角带构造和高陡的北翼为特征的棋北-柯克亚逆冲构造段和以外来远距离推覆体和深浅两个地层系统叠加为特征的皮山-和田推覆构造段。2、在变形时间上,表现为由造山带向前陆方向逐渐变新的“前展式”变形：山前第一排背斜带开始形成于上新世阿图什组沉积早期,而第四排背斜带至更新世晚期才开始形成。同时,在同一排背斜带中变形起始时间存在着由西自东逐渐变新的特点,表现为生长地层底界的位置由西向东逐渐抬高。3、在变形强度上,具有乌泊尔构造段和棋北-柯克亚构造段的新生代总缩短量和缩短率大于齐姆根构造段以及上新世早期变形强度大于后期的特征。同时,同一期变形也存在着由西向东强度逐渐变小的特征。4、塔里木西南缘新生代沉积演化可划分为五个阶段：古新世-渐新世中期的稳定期、渐新世晚期-中新世早期的局部不稳定期、中新世中期的相对稳定期、中新世晚期-上新世早期的相对不稳定期以及上新世中期以来的极不稳定期。其中,渐新世晚期-中新世早期的局部不稳定沉积表现为同由路克以西地区克孜洛依组平行不整合于下伏巴什布拉克组,以及山前西带克孜洛依组发育扇三角洲沉积而东带则以曲流河沉积为主；中新世晚期-上新世早期的相对不稳定沉积表现在粗碎屑与细碎屑沉积物不等厚互层组成多个向上变细的沉积韵律,局部层段不稳定重矿物富集,花岗岩砾石开始出现及其区域古水流方向在中新世末期-上新世早期发生改变；自上新世中期以来的极不稳定沉积表现在冲积扇沉积体系和砾质粗碎屑的广泛发育,以及西域组与下伏阿图什组、乌苏群与下伏西域组之间区域不整合接触关系。5、山前各地层单元沉降中心既存在由造山带向盆地方向的迁移,还存在平行造山带走向的迁移,反映西昆仑山前存在由造山带向盆地方向的生长和侧向上由NW向SE的扩展。其表现在古近系沉降中心呈E-W向分布于合1井-皮山一线,而新近系已迁移至固3井-固2井-叶城一带呈三角状分布。6、山前带沉积记录、构造变形特征和热年代学成果反映西昆仑造山带的新生代主要存在如下几期活动：渐新世晚期-中新世早期的局部隆升期(～20±2Ma)；中新世晚期的脉冲式构造活动期(～10±2Ma)；中新世末期-上新世早期的强烈隆升期(～5Ma)；上新世中晚期以来的快速隆升期(<3.6Ma)。其中,渐新世晚期-中新世早期,西昆仑造山带西段隆升活动导致同由路克以西地区克孜洛依组与巴什布拉克组间的平行不整合以及克孜洛依组中的砾质粗碎屑沉积；中新世晚期,造山带脉冲式构造活动导致山前粗碎屑与细碎屑交替沉积和局部层段出现的高含量不稳定矿物；中新世末期-上新世早期的强烈隆升活动,导致乌泊尔断裂上盘上新统不整合于下伏古近系,棋北-柯克亚构造段东部阿图什组不整合于下伏帕卡布拉克组,地层中花岗岩砾石开始出现以及区域古水流方向的急变,本期构造活动奠定了现今盆山格局,造成山前带在空间结构特征上存在着“东西分段、南北分带、深浅分层”和在时间演化上呈现为由造山带向盆地方向逐渐变形的特点；而上新世中晚期以来的快速隆升活动,导致西域组与阿图什组之间、乌苏群与西域组之间的区域性不整合以及普遍发育冲积扇沉积体系。更多还原

【Abstract】 By the effect of the collision and continued convergence between India and Eurasia, the West Kunlun Orogen reactivated and thrusted to the Tarim in the Cenozoic, which located in the northeastern margin of Pamir. Studies of Cenozoic tectonic events and their sedimentary records in the West Kunlun will provide important implications to the evolution of Qinghai-Tibet Plateau, the far-field effects of India-Eurasia collision, and the process of large-scale intercontinental subduction in this area.Based on the studies of Cenozoic sedimentology, structural deformation and evolution in frontal areas of the West Kunlun, combined with thermochronology, the following implications have been achieved.1. The present tectonic pattern of studying area took shape in the late Miocene-early Pliocene. On the aspect of structural style, they display characteristics of S-N zonation, E-W segmentation and vertical-layered structural variation. Four structural segments, for example, the Wupor strike-slipping segment featured by the Quaternary piggy-back basin and the underlying thrusting deformation, the Qimugen strike-slipping segment characterized by the stacking triangular zones and the gentle northern wings of the anticlines, the Qibei-Kekeya thrusting segment featured by the triangular zones and the steep northern wings of the anticlines, and the Pishan-Hetian nappe segment featured by the distanced nappe and the underlain of deep and shallow stratigraphic systems, have also been identified from west to east of the frontal areas of the West Kunlun Orogen.2. Regarding deformation timing, the anticline zones are featured by a forward-breaking propagation pattern, propagating gradually from Orogen to basin. For example, the deformation of the first anticline zones started in the early depositing period of the Atushi Formation of early Pliocene, and the fourth anticline zones began to deform during the late Pleistocene. Meanwhile, the starting deformation time of the anticlines in the same row gets younger gradually from west to east confirmed by the depth of growth strata gradually raise. 3. On the aspect of deformation intensity, the shortening values and rates of Wupor and Qibei-Kekeya segments are greater than those of Qimugen segment, respectively. The early Pliocene intensity is greater than latter stages. Also evident is that the deformation intensity in the same row becomes smaller gradually from west to east.4. Cenozoic sedimentary evolution of the southwestern Tarim Basin can be divided into five stages:the Paleocene-middle Oligocene stable marine sedimentary period, the late Oligocene-early Miocene unstable sedimentary period in west zone, the middle Miocene relative stable sedimentary period, the late Miocene-early Pliocene relative unstable sedimentary period, and post-mid-Pliocene very unstable sedimentary period.Within these sedimentary stages, the unstable sedimentary stage in the late Oligocene-early Miocene has been recorded by unconformity between Keziluoyi Formation and Bashibulake Formation, the fan delta deposits in the west passing to meandering river deposits in the east zone. The relative unstable sedimentary stage in the late Miocene-early Pliocene is featured by the upward-fining sedimentary cycles composed by the interbedded deposition of the coarse and fine clastic, the enrichment of unstable heavy mineral in some segments, the appearance of the granite gravel and the change of the regional paleocurrent directions in the late Miocene-Early Pliocene. The very unstable sedimentary records since middle Pliocene are the two regional unconformities, within which one located between Xiyu Formation and Atushi Formation and the other located between Wusu Formation and Xiyu Formation, gravelly alluvial fan system and the large-scale sediment of coarse clastic.5. Cenozoic subsidence centers do not only transfer from the West Kunlun Orogen to the Tarim basin but also parallel to the strike of the Orogen. The subsidence centers locates in the area between He-1 well and Pishan County in Paleogene, and moved to the triangular-shaped area of the Gu-3 well, Gu-2 well and Yecheng County. This indicates that the West Kunlun Orogen propagated not only from the Orogen towards the Tarim basin in the vertical direction but also from NW to SE in the lateral direction. 6. Based on the analysis of sedimentary records, structural deformation and thermochronology, following uplifting periods have been identified in the West Kunlun Orogen:local uplift in the late Oligocene-early Miocene, pulse uplift in the late Miocene, strong uplift in the late Miocene-early Pliocene, and rapid uplift since the mid-late Pliocene.In the late Oligocene-early Miocene, the uplift of western segment of the West Kunlun Orogen results to the unconformity between Keziluoyi Formation and Bashibulake Formation, and the coarse gravel sediment in Keziluoyi Formation. In the late Miocene, the pulse uplifting activity results to the coarse clastic deposition alternating with fine clastic, and the enrichment of unstable heavy minerals in some segments. In the late Miocene-early Pliocene, the strong uplifting activity leads to the appearance of the granite gravel, the change of the regional paleocurrent directions, and the unconformity between Atushi Formation and Bashibulake Formation in eastern part of Qibei-Kekeya structural segment. The present tectonic pattern in the front of the West Kunlun Orogen took shape after this tectonic period, displaying spatially S-N zonation, E-W segmentation and vertical-layered structural variation, and also the deformation getting younger gradually from Orogen to basin. Since mid-late Pliocene, the rapid uplift of the West Kunlun Orogen results to large-scale alluvial fan system and two regional unconformities, one located between Xiyu Formation and Atushi Formation while the other locate between Wusu Formation and Xiyu Formation.更多还原