【作者】 杨怀宇；

【导师】 陈世悦；

【作者基本信息】 中国石油大学 ， 地质学， 2010， 博士

【摘要】 本论文定位于湘桂地区海相油气勘探的基础性地质研究。在对前人相关研究成果充分调研的前提下,以野外露头剖面为主要基础资料,以沉积学、构造地质学为理论指导,通过野外地质调查、镜下薄片鉴定、地球化学分析测试和岩相古地理编图等技术手段,对湘桂地区泥盆纪-中三叠世地层进行了系统的沉积学、构造古地理学研究,明确了湘桂地区泥盆纪-中三叠世的构造古地理格局及其演化历程,在此基础上详细地剖析研究区特殊的“台-槽-丘-盆”多种沉积类型对构造活动、海平面相对变化的沉积充填响应,探讨叠加、改造型的残留盆地物质充填规律及其反映的构造-古地理意义。湘桂地区晚古生代-早中三叠世地层中发育3大沉积相组、14种沉积相类型。分别为大陆相组的风化残积、冲积扇和河流;海陆过渡相组的三角洲、潮坪和泻湖相;海相组的陆源碎屑型无障壁海岸、缓坡型碳酸盐岩台地、镶边型碳酸盐岩台地、孤立碳酸盐岩台地、碎屑岩-碳酸盐岩混积台地、台间盆地、欠补偿型盆地和补偿型浊积岩盆地。湘桂地区晚古生代-早、中三叠世构造古地理表现为泥盆纪拉开,石炭纪延续,二叠纪发展和早、中三叠世统一的特征。早泥盆世晚期-晚泥盆世,湘桂地区发生伸展裂陷,总体古地理格局为北高南低,槽-台相间格局已经形成,孤立台地面积较大,钦防海槽自加里东期之后连续沉积并未间断,石炭纪时浅水碳酸盐台地范围扩大,台间深水盆地分布局限,浅滩发育,槽-台分异不明显,早二叠世发生海侵,海水淹没全区,槽-台分异明显,孤立台地范围变小;晚二叠世东吴运动造成钦防海槽关闭并褶皱回返,云开地区发生隆起,深水盆地收缩,槽-台分异明显,早三叠世碳酸盐台地转为以大面积鲕粒滩为特征碳酸盐缓坡,该时期至中三叠世滇黔桂地区各坳陷合并统一为南盘江坳陷并以巨厚的浊积盆地沉积为特征,此时孤立台地均被淹没。湘桂地区处于多种构造体系交切复合部位,经历了长期的板块构造演化和陆内造山作用过程,形成了复杂的盆山系统,并且发育了独特的“台-盆-丘-槽”沉积体系,通过研究湘桂地区残留盆地内物质充填规律及不整合面分布,以隆林孤立碳酸盐台地与南盘江坳陷生物礁为实例,探讨不同沉积类型对于构造运动、相对海平面变化的充填响应特征,综合研究认为,本区泥盆纪-中三叠世先后经历的5次构造运动及3次海侵事件控制着研究区的3次成煤期、4次造礁期、3次生物绝灭事件及2次槽-台分异明显时期和1次分异不明显时期。更多还原

【Abstract】 This paper is devoted to the basic geologic research on the marine oil and gas exploration in the regions of Hunan and Guangxi province. On the premise of the full research on the results of previous studies, using plenty of outcrop section as the main foundation data, based on the theory of sedimentology and tectonics, combining of field geologic survey, microscope section analysis, geochemical detection, and lithofacies palaeogeographic map, this paper does systematically sedimentology and tectonics study on the Devonian - Middle Triassic strata in Hunan and Guangxi Provinces, and defines the pattern and evolution of the Devonian-Middle Triassic Tectono-palaeogeography in Hunan and Guangxi Provinces. On this basis of dependent evidence, a variety of deposit types of a special platform-basin-dome-depression in the research area on the tectonic activity, relative sea level changes in the sedimentary filling response are detailedly profiled. Besides, the filling material feature of superposition and the reconstructed residual basin and its Tectono-palaeogeography significance are discussed in depth.Three major facies groups and 14 types of the sedimentary facies are recognized in the strata of Late Paleozoic to Early-Middle Triassic in Hunan and Guangxi province, including weathering residual, alluvial fan and fluvial in the continental sedimentary facies group; delta, tidal flats and lagoon in the sea-land transition facies group ; terrigenous clastic non-barrier shore, ramp carbonate platform, rimmed carbonate platform, isolated carbonate platform, clastic - carbonate mixed platform, basin between platforms, undercompensation basin and compensation turbidite basin in the marine sedimentary facies group. Evolution of the Devonian-Middle Triassic Tectono-palaeogeography in Hunan and Guangxi Provinces can be divided into two major stages, including Devonian - Early Permian extensional chasmic transgressive basin development stage and Late Permian - Middle Triassic Back-arc chasmic marine facies basin development stage. In the period of Late Devonian - Late Devonian, the regions of Hunan, Guangxi province took place extension rift. The palaeotopotraphy declined gradually from north to south, depression-platform White pattern has been formed and the area of isolated platform is larger. The Qinzhou-Fangcheng depression’s continuous deposition was not interrupted after the Caledonian period. Shallow-water Carbonate platform during the Carboniferous period was extended, and the distribution of deep-water basin between platforms was restricted. The shoal developed, and the differentiation of the depression-platform was not obvious. The Early Permian took place transgression. The water flooded the whole region. As a result, the differentiation of the depression-platform was significant and the scope of isolated platform was shrinking. In the Late Permian, the Qinzhou-Fangcheng depression closure and the fold inversion caused by the Dongwu Movement. Uplift occurred in the Yunkai Area. The deep-water basin was contraction, and the differentiation of the depression-platform was significant. In the Triassic Period, carbonate platform transferred to carbonate ramp characterized by a large area oolitic shoal. This period was until the Triassic Period, when the independently depressions in the Yunnan,Guizhou and Guangxi regions merged into the Nanpanjiang depression characterized by the thick turbidite sedimentary basin and the isolated platforms were submerged .The regions of Hunan and Guangxi, which were in the composite position intersected by a variety of Tectonic system and experienced a long-term evolution of plate tectonics and the intracontinental orogeny process, formed a complex basin-mountain system and developed a unique platform-basin-dome-depression sedimentary system. Through the research on the sedimentary filling feature and the distribution of basin unconformity of the residual basin in the regions of Hunan and Guangxi, the filling response characteristics of tectonic movements and changes in relative sea level caused by different sediment types are discussed. Comprehensive study shows that, this area in the Devonian - Middle Triassic experienced 5 tectonic movements and 3 transgression events, which controlled 3 Coal-forming periods, 4 reef-forming stages, 3 creature mass extinction events, 2 period when the depression-platform’s differentiation was obviously and 1 period when the differentiation was not significant.更多还原