祥云地区三叠系层序地层学研究

【作者】 张福神；

【导师】 张世涛；

【作者基本信息】 昆明理工大学 ， 矿产普查与勘探， 2010， 硕士

【摘要】 祥云地区处于川滇台背斜、丽江台缘皱褶带、兰坪-思茅坳陷三个二级构造单元结合部位,因其构造演化的复杂性和特殊性,该地区三叠系地层的沉积环境和层序地层研究颇为粗略、模糊。本文在大量查阅研究区区域地质资料和前人研究成果的基础上,经过长期的野外填图,层型剖面勘测及室内主要剖面、地球化学数据精细研究,以沉积学、地层学、层序地层学、大地构造学、古生物地史学及盆地分析原理等理论为指导,结合区域地质背景和沉积岩石地球化学特征,对祥云地区三叠系沉积地球化学特征、沉积环境、沉积体系、层序地层等方面的研究,进而对沉积盆地演化特征进行了研究。1、通过古生物、岩性特征、沉积构造等对研究区内三叠系地层进行了沉积相和沉积环境划分。2、对研究区三叠系地层进行了常量、微量、稀土元素沉积地球化学研究。同时通过常量、微量、稀土元素地球化学特征从古气候、古盐度、氧化还原、古水深、源区分布5个方面研究了工区晚三叠世古环境。3、根据层型剖面岩石组合,沉积序列,沉积构造、生物组合和沉积岩矿成分和地球化学特征,将该区三叠系四个组地层划分为7种沉积体系：①半深海体系(罗家大山组第二段)；②陆棚体系；③碳酸盐台地；④滨海体系；⑤三角洲体系；⑥湖泊体系；⑦河流体系。并详细分析了各沉积体系特征。4、在沉积环境和沉积体系分析研究的基础上,运用层序地层学的原理,对研究区上三叠统的三级层序界面特征、界面的成因类型进行了深入研究。工区内三级层型界面类型有Ⅰ型和Ⅱ型,分为：沉积间断面(SB11)、古风化面(SB12、SB23、SB14)、底砾侵蚀面(SB,5)。将工区上三叠统划分为5个三级层序,即卡尼阶两个(TSQ1、TSQ2),诺利阶二个(TSQ3, TSQ4),瑞替阶1个(TSQ5).5、分析了各个三级层序内部构成：体系域的类型和特征。TSQl和TSQ2缺失了低位体系域(LST), TSQ3、TSQ4、TSQ5内三种体系域(LST、TST、HST)发育完整。共出现5次海侵,其中三级层序TSQl和TSQ3内的海侵速度和幅度均很大。详细分析了构造、海平面变化、气候因素、沉积物供给四种因素对研究区层序发育的控制作用。6、晚三叠世时期,祥云地区在丽江地块和康滇古陆之间的分离裂陷和挤压逆冲作用影响下,形成了复合盆地；为前期分离裂陷作用下发育的裂陷盆地和后期挤压逆冲作用下发育的前陆盆地。盆地基底经历了裂陷-稳定-裂陷-挤压逆冲(折返)四个阶段。盆地充填序列演化经历了海相(磨拉石建造、复理石建造、碳酸盐建造)-海陆交互相(含煤砂泥岩建造)-陆相(河湖含煤泥质、砂质岩建造)这一转换过程。更多还原

【Abstract】 Xiangyun locates in the middle part of, chuandian platform anticline, Lijiang platform margin fold belt, Lanping-Simao depression binding sites of three secondary structure units, because of its tectonic evolution of the complexity and particularity, the deposition of Triassic strata environment and sequence stratigraphy of the rather rough and fuzzy. This inspection of the study area in a large number of regional geological data and the results of previous studies, based on over a long period of geological mapping, surveying and interior stratotype section the main section, the detailed study of geochemical data, to sedimentology, stratigraphy, sequence stratigraphy science, geology, tectonics, paleontology, historical and basin analysis theory and other theories as a guide, combined with regional geological setting and geochemical characteristics of sedimentary rocks, and Triassic sedimentary geochemical characteristics of clouds, depositional environment, depositional systems, sequence stratigraphy, etc. research, and study the evolution of sedimentary basin characteristics of the area.1, Through paleontology, lithology, sedimentary structures of Triassic strata of the study area was divided into sedimentary facies and depositional environment.2, Triassic strata of the study area were constant, trace, rare earth element geochemistry. Same time, through constant, trace, REE geochemical characteristics of the ancient climate, ancient salinity, redox, water depth, source distribution of five aspects of the work area the Late Triassic paleoenvironment.3, under the stratotype section of rock composition, sedimentary sequence, sediments, biological composition and mineral composition and geochemical characteristics of sedimentary rocks, the Triassic strata are divided into four groups of seven kinds of depositional systems:①semi-deep system (Luo the second paragraph of the mountain group);②shelf system;③carbonate platform;④coastal system;⑤delta system;⑥lake system;⑦river system. And a detailed analysis of the sedimentary system.4, in the depositional environment and depositional systems analysis, based on the use of the principles of sequence stratigraphy, the study area of the Upper Triassic of the three characteristics of sequence boundaries, the interface of genetic types in depth. Workers in the region three layer-type interface typesⅠandⅡ, divided into:sedimentary discontinuity (SB11), weathering surface (SB12, SB23, SB14), the end gravel erosion surface (SB15). The work area of the Upper Triassic is divided into five three sequence that Carnian 2 (TSQ1, TSQ2), Norian 2 (TSQ3, TSQ4), Rhaetian 1 (TSQ5).5, analysis of the internal structure of all three sequences:the type and characteristics of the domain system. TSQland TSQ2 missing the LST (LST), TSQ3, TSQ4, TSQ5 three systems within the domain (LST, TST, HST) complete development. Transgression occurred 5 times, including three sequences TSQ1 and TSQ3 transgression within the range of both speed and great. Detailed analysis of the structure, sea-level change, climate, sediment supply four factors in the study area controlling sequence development.6, Late Triassic period, XiangYun area in the separation and compression under the influence of thrust between Lijiang tableland and Kangdian Ancient land, forming a composite basin; for the effect of early separation of rifting and development of rift Basin and thrusting under the late development of the foreland basin. Basement through the rift-stability-rift-Extrusion and Thrust (returned) four stages.Basin-fill sequence.evolution experienced marine facies(molasse, flysch, construction, carbonate rock build)-and sea cross each other facies(the construction of coal-bearing sandstone and mudstone)-continental facies(fluvial coal-bearing shale, sandy rock build) the conversion process.更多还原