【作者】 赵俊峰；

【导师】 刘池阳；

【作者基本信息】 西北大学 ， 矿产普查与勘探， 2007， 博士

【摘要】 中生代鄂尔多斯盆地为叠加在早、晚古生代华北克拉通大型盆地之上，历经多期不同形式改造的残留克拉通内盆地。有关该盆地中生代原始沉积面貌的探讨，长期以来深受关注但认识不一。侏罗纪直罗组—安定组沉积期是盆地发展演化的重要阶段，为油气、煤等矿产形成转化的主要时期，但研究程度薄弱。本文在广泛吸收和客观分析前人研究成果的基础上，以“整体、动态、综合”三项原则和改造型盆地研究理论为指导，从今盆地及邻区残存沉积建造、现今构造格局两方面实际出发，通过系统的地层划分与对比、沉积相分析、物源综合分析和对周邻构造单元形成演化史的分析，取得对原始盆地沉积面貌的认识。受后期强烈而不均匀剥蚀改造的影响，鄂尔多斯盆地直罗组、安定组与周邻同期地层的分布和厚度均发生了较大改观：在今盆地本部，直罗组、安定组呈大范围整体分布，厚度100～750m，呈西厚东薄特点；在盆地周邻山西、河南、内蒙及宁夏贺兰山等地区同期可对比地层零星分布，厚度124～700m不等。在大量露头和钻测井资料分析的基础上，以旋回对比法为主，结合地区性标志层和岩性、颜色特征等，将盆地本部直罗组划分为上、下2段。分段制图表明，直罗组上、下段厚度展布与全组展布规律基本一致，均呈西厚东薄。通过露头和钻井沉积相分析、区域剖面对比并结合岩矿鉴定、粒度分析和地球化学等方法，在今盆地直罗组、安定组识别出冲积扇、辫状河、曲流河、三角洲及湖泊等沉积体系类型。平面制图表明，直罗组下段以辫状河、曲流河沉积为主，局部发育河流三角洲相；上段以河流、湖泊和小规模三角洲相为主；安定组延续了直罗组晚期沉积格局，但湖相范围和水深明显加大。直罗-安定期总体构成侏罗纪继富县-延安期之后的第2个沉积旋回，经历了温暖湿润→干旱炎热的古气候转变过程。今盆地直罗组、安定组普遍缺少边缘相、沉积中心靠近剥蚀东界、砂体厚度和砂地比展布规律性强等特点，为追索原始盆地沉积边界提供了依据。对周邻直罗组、安定组同期地层的野外考察和沉积相分析表明，河南义马马凹组以冲积扇沉积体系发育为特征；济源马凹组下段属冲积扇、河流相沉积，上段则属典型的淡水湖泊沉积；大同云岗组下部为冲积扇，向上演化为不同类型的河流相沉积，天池河组为氧化干燥环境下的河流相沉积：宁武静乐盆地云岗组由下向上表现为辫状河→曲流河→三角洲的演化序列，天池河组属辫状河为主的氧化环境河流相沉积；晋中榆社和晋南洪洞同期地层以近物源的河流相沉积为主；内蒙石拐长汉沟组湖相沉积发育。贺兰山北段直罗、安定组为河流、湖沼相沉积，南段直罗组为厚层冲积扇沉积。六盘山地区石砚子组为冲积扇、辫状河沉积组合。通过分析平面沉积相变关系、垂向相演化规律、沉积前古构造格局，实测古水流方向、镜下碎屑统计、石英阴极发光观察和稀土、微量及主量元素物源判识等方法，对周邻同期地层和今盆地本部直罗组、安定组进行的物源综合分析表明，山西诸沉积区、贺兰山及六盘山地区与盆地本部关联性强，显示具同一原始沉积盆地的特点：河南义马、济源及内蒙石拐与本部关联性较差。大同、宁武-静乐与今盆地东北部在源区位置、源岩类型等方面共性较大，同时又以火山碎屑含量的增多与本部有所区别，反映有东部物源加入。通过沉积相、古构造格局、裂变径迹测年和盆山耦合关系分析等表明，吕梁山的大规模隆升发生在晚白垩世末至古新世初之后，晋西地区在中侏罗世不存在分隔东西部沉积区的隆起。岩浆岩年龄和区域构造背景分析认为，太行山在直罗组、安定组沉积期已始隆升；贺兰山、六盘山的大规模隆升均发生在新生代以来。综合地层发育特征、沉积相特征、物源特征和对周邻构造单元形成演化史的分析认为，直罗组、安定组沉积期原始盆地的沉积边界大致为：东在今太行山脉以西；北在今河套盆地一带；西北部边界在狼山-巴彦浩特盆地-科学山一带；西南部边界在今六盘山西缘；南部边界在今渭河盆地一带。通过对中生代各主要时期沉积、堆积中心分布、迁移规律的剖析和沉降中心的厘定表明，中生代鄂尔多斯盆地的发育和演化受太平洋构造域、特提斯构造域等周邻板块构造活动随时间发展的消长变化及其相互作用影响，盆地的沉降与秦岭造山带会聚造山活动及其在前陆产生的挠曲沉降关系最为密切。更多还原

【Abstract】 The Mesozoic Ordos basin is a residual interior cratonic basin that superimposed on the Palaeozoic large North China craton and experienced multistaged deformation by different styles. The discussion about the primary features of this basin in Mesozoic has been paid more attention. Various conclusions have been proposed. The Zhiluo-Anding period in middle Jurassic is an important stage in the development and evolution of Ordos basin. It’s the main period for the hydrocarbon and coal seams forming and transforming, but the study about Zhiluo-Anding formations is very little. On the base of predecessor’s work, taking integrated, dynamic and comprehensive analysis and the research theories about reformed basin as guidance, starting from the nowadays’ remanent sedimentary entities and structural framework of the basin and its adjacent areas, by the systemic stratigraphic partition and compare, sedimentary facies analysis, multidisciplinary analysis of provenance, and the formation and evolution analysis of the adjacent tectonic units, the cognition about the sedimentary features of primary basin is acquired as a result.Effected by the intense and diversified denudation in later stages, the stratum distribution and thickness pattern of Zhiluo-Anding formations in Ordos Basin and it’s synchronal stratum in adjacent areas altered largely. In the residual basin, Zhiluo-Anding formations distributed extensively, the thickness is from 100m to 750m, appearing west thicker than east generally. The synchronal stratum that can be compared sparsely distributed in the adjacent areas of Ordos basin, including Shanxi, Henan Provinces, the inner Mongolia, Ningxia autonomous regions, with thickness from 124m to 700m.Based on the analysis of great deal of outcrops and well logging data, taking the cycle compare as the main method, combine with the regional marker bed and the characteristic of lithology and color characteristics, the Zhiluo formation in the residual basin is divided into upper and lower members. The thickness of both the upper and lower members is consistent with the distribution pattern of the whole formation, and both show thicker in the west and thinner in the east.According to the analysis of the well sedimentary facies, regional sections compare, and combined with other methods, such as lithology identify, grain size analysis and geochemical, such sedimentary system types as the alluvial fan, braided river, meandering river, delta and lacustrine facies are identified in Zhiluo-Anding formations in residual Ordos basin. The regional mapping show, the lower member of Zhiluo formation include mainly braided river and meandering river facies, the delta facies developed locally; while the upper member include mainly fluvial, lacustrine and small scale delta facies. The sedimentary framework of Anding formation succeeded that of upper Zhiluo member, except the sedimentary range of lacustrine and the water depth are obviously increased. Zhiluo-Anding formations formed the second cyclic sedimentation after Fuxian-Yan’an period in Jurassic, experience the transition from warm-moist to drought-torridity. Zhiluo-Anding member usually lacks marginal facies, the depocencer close with the eastern boundary of denudation, and the obvious distributing pattern of sandstone thickness and ratio in residual basin, All of these provide foundation for seeking the sedimentary boundary of primary basin.On the basis of field survey and sedimentary facies analysis, Mawa formation in Yima shows characteristcs of alluvial facies. Mawa formation in Jiyuan shows alluvial, fluvial and lacustrine facies. Yungang formation in Datong is alluvial and fluvial facies of different type; Tianchihe formation mainly has characteristics of fluvial facies in drought-torridity environment. Yungang formation in Ningwu-Jingle basin shows succession from braided-river, meandering river to delta facies. Tianchihe formation in this basin is fluvial facies. The synchronal stratum of Zhiluo-Anding formations in middle and southern Shanxi province mainly show character of fluvial facies near provenance. Changhangou formation in Shiguai has extensive lacustrine facies. Zhiluo-Anding formations in north Helanshan is fluvial and lacustrine facies. Shiyanzi formation in Liupanshan is alluvial and braided river association.According to integrated provenance analysis of sedimentary facies, paleotectonic frameworks, paleocurrent, detrital statistics and other geochemistry methods such as rare earth, minor and major elements discrimination, sedimentary entities in Shanxi province, Helanshan and Liupanshan show close relationship with the residual Ordos basin, while the sedimentary entities in Yima, Jiyuan and Shiguai have poor unification with the residual Ordos basin. The difference about provenance position and type between Datong, Ningwu-Jingle basin and the residual Ordos basin indicates that there have additional provenanve joined in former areas.The systemic analysis of sedimentary palaeogeography, tectonic framework, fission-track dating and basin-mountain coupling shows, the large scale uplift of Lvliang mountain took place after later Late Crataceous-early Paleocene, there isn’t uplift that dividing the sedimentary area into eastern and western section in Jinxi area during Middle Jurassic. Through analysis the age of magmatite and the regional tectonic setting, it is thought that Taihangshan has initially risen in Zhiluo-Anding period. The large scale uplift of both Helanshan and Liupanshan happened in Cenozonic.Combining the analysis of the sedimentary facies , provenance .nowadays’ tectonic units of its neighboring area, the boundary of the original basin during the Zhiluo-Anding period is approximately concluded: The eastern borderline is to the west of Taihangshan; the northern borderline lie is in Cenozoic Hetao basin; the north-westerm borderline lie in Langshan-Bayanhaote basin-Kexueshan; the north-easterm borderline lie in the west of the Liupanshan; the southern borderline reach to nowadays’ Weihe Cenozoic basin.Through the study on the distributing and transferring pattern of the depocenters and accumulation centers, and the determination of subsidence centers, it is show that the development and evolution of Mesozoic Ordos basin is affected by its neighboring plate tectonic actives’ decreased and increased intensity with time, such as Pacific tectonic domain and Tethys tectonic domain, including their interaction. the subsidence of the basin is related to the convergence orogenic activity of Qinling Mountain and the twisted subsidence yielding in its foreland.更多还原