【作者】 韩建恩；

【导师】 朱大岗； 孟宪刚； 邵兆刚；

【作者基本信息】 中国地质科学院 ， 构造地质学， 2006， 硕士

【摘要】 札达盆地位于西藏阿里地区西南隅,处于喜马拉雅山与阿伊拉日居山之间,为一新生代断陷盆地。盆地基底由中生界褶皱地层组成,盆地内为一套上新世—早更新世河湖相沉积地层,厚度近千米,是西藏已知新近纪地层出露最完整、最厚的地区之一,其上又被第四系下更新统冰缘堆积的碎屑岩不整合覆盖。札达盆地作为一个晚新生代喜马拉雅山碰撞造山带内部的山间盆地,其地层沉积体系,层序地层演化序列必然与喜马拉雅山的形成发展密切相关。本研究以野外调查为重点,在盆地内开展沉积相、沉积体系、层序地层、孢粉等古生物化石、粒度、碳酸盐、磁化率以及易溶岩等环境指标、古地磁、ESR等沉积年代学等研究,重点研究了盆地内陆相沉积地层的层序地层序列,进而了解盆地的演化过程,探讨盆地演化对喜马拉雅隆升的响应及其环境意义。得出的主要结论如下:1.在札达盆地开展了详细的上新统-下更新统露头剖面观测和系统采样工作,进行了沉积体系特征和沉积相分析,共划分出4个沉积相,7个沉积亚相,主要由冲积相、湖泊相、冲洪积相、冰湖相组成。2.对区内沉积层序发育的控制因素进行了探讨。本区三级层序的形成受构造活动、气候条件和物源供给共同作用,其中构造因素占主导地位。3.札达盆地上新世-早更新世构造—沉积演化可以划分为6个阶段:初始断陷阶段(托林组)、加速断陷阶段(古格组一至三岩段)、强烈断陷阶段(古格组第四岩段)、断陷止息阶段(古格组第四、五岩段)、二次初始断陷阶段(香孜组一、二岩段)、二次加速断陷阶段(香孜组三岩段)。4.在沉积特征、盆地构造演化、气候、物源以及沉积年代学的分析基础上,综合露头资料,进行了上新世-早更新世层序地层划分。在札达盆地共划分3个三级层序,建立了札达盆地上新世-早更新世层序地层格架。5.层序Sq1和层序Sq2界面为平行不整合,层序Sq2和层序Sq3界面为角度不整合,分别对应于象泉运动和古格运动。认为控制层序界面的构造运动对应于青藏运动,象泉运动(4.40MaB.P.)对应于青藏运动A幕,古格运动(2.68MaB.P.)对应于青藏运动B幕,札达盆地地势由原来的西高东低转为现今的东高西低,这次构造运动可能对应青藏运动C幕。更多还原

【Abstract】 Zanda basin is one of Cenozoic faulted basin, located in the southwestern of Ali area, Tibetan region, between the Himalayans mountain and Ayilariju mountain.Basin basement is composed of the Mesozoic fold stratum. There is a set of the Pliocene Epoch to the Eopleistocene fluviatile-lacustrine facies sedimentary stratum, the thickness of which is nearly 1,000 meters and is known as one of the most complete and the thickest stratum in Neogene Period sedimentary in Tibetan. On the top is uncomfortably covered with later-Pleistocene Ice accumulation of debris strata.Zanda basin is one of later Cenozoic fore-mountain basin that is formed when the Himalayas collides the interior of the orogenic belt. Therefore, the sedimentary system of Zanda basin and sequence stratigraphic evolution sequence must be inevitably related with the formation and the development of Himalayan formation.The study is centered on field investigation, carried out the sedimentary facies, sedimentary system, sequence stratigraphy, sporopollen and other paleontological fossils, granularity, carbonates, calculations, susceptibility, the easy-to-dissolve rocks and other environmental indicators, palaeomagnetism, ESR and other sedimentary chronology study. The study is centered on the inland basin of the sedimentary strata sequence stratigraphy sequence. Thus understand the basin evolution, discusses the relationship of the basin evolution and Himalaya uplifting and its response to environmental significance. The main conclusion is as follows:1.Zanda Basin can be divided into 4 facies which is composed of alluvial, lacustrine, alluvial-pluvial, ice-lacustrine facies and 7 subfacies. The result is basing on the detailed observation of the Pliocene Epoch to the Eopleistocene outcrop section and systematic working on samples, carrying on sedimentary system characteristics and the analysis of sedimentary facies.2.It discusses the sedimentary sequence stratigraphic control factors. 3-level sequence formed in this district by the tectonic activities, climatic conditions and source of supply, the tectonics of which is the dominant factors.3.The evolvement of the Zanda Basin can be divided into six phases: Initial fault depression phase (Tuolin Group), accelerated fault depression phase (Guge formation 1-3 rock segment ), tensional fault depression phase (Guge formation 4 rock segment ), cut into heart stage (Guge formation 4-5 rock segment), the second initial fault depression phase (Xiangzi formation 1-2 rock segment), accelerated fault depression phase (Xiangzi formation 3 rock segment).4.On the sedimentary characteristics, basin tectonic evolution, climate, source of supply, the analysis of deposit and integrated information of outcrop basis, it is working on sequence stratigraphy division. Zanda basin can be divided 3 3-level sequence, which found on the framework of sequence stratigraphy in the Pliocene Epoch to the Eopleistocene in the basin.5.The preface layer between Sq1 and Sq2 is parallel unconformity which correspond to the Xiangquan movement. The preface layer between Sq2 and Sq3 is angular unconformity which correspond to the Guge movement. The movements which control the preface layer correspond to the Qinghai-Tibet movement. Xiangquan movement (4.40MaB.P.) corresponds to the Qinghai-Tibet Movement A episode. Guge movement (2.68MaB.P.) corresponds to Qinghai-Tibet Movement B episode. Zanda basin topography from the West-high-East-low to current East-high- West-low, this tectonic movement may be counterpart Qinghai-Tibet movement C episode.更多还原