青海湖细粒沉积纹层特征与其沉积环境要素耦合关系研究

The continental and lacustrine shale oil resource is abundant and has a great potential of exploration and development in China. Lamina is not only the basic unit of lacustrine fine sedimentary rock, but it is the key factor of causing the heterogeneity. The lamina formation and evolution mechanism is the important theory basis to dissect the heterogeneity of lacustrine fine sedimentary rock. Meanwhile, accurately establishing the coupling relationship between lamina characteristics and palaeosedimentary environment factors is the premise and bottleneck problem of the lamina formation mechanism research. Compared with the paleo-lacustrine lamina, the modern lake lamina holds the advantages of defined sedimentary environment, simple sedimentary evolution process and high identifying resolution. Therefore, it is better suited to the study of the coupling relationship between lamina characteristics and paleosedimentary environment factors. Lots of fine sedimentary lamina is developed in Qinghai Lake, which is the natural laboratory for the basic theory study of lacustrine lamina. Taking the fine sedimentary lamina of Qinghai Lake as the research object, putting the absolute chronology of annual lamina as the entry point, using the field observation method and high-precision testing means and in the scale of annual time resolution, this study is designed to dissect the lamina fabric and sedimentary evolution sequence, identify the lamina sedimentary environment factors and analyse the evolution regularity further, illuminate the coupling relationship between lamina characteristics, sedimentary evolution sequence and paleosedimentary environment factors, sedimentary evolution process.Ultimately establish the theoretical model. Moreover, this study is vital to offer the scientific basis and reference way for the paleoenvironmental reconstruction of continental and lacustrine lamina.

我国陆上湖相页岩油资源量丰富且勘探开发潜力巨大。纹层是湖相细粒沉积岩的基本组成单元更是造成其非均质性的关键因素。纹层的形成演化机理是解剖湖相细粒沉积岩非均质性的重要理论依据，精确建立纹层特征与古沉积环境要素之间的耦合关系是纹层形成机理研究的前提也是瓶颈问题。现代湖泊纹层相比古代湖相纹层具有沉积环境明确、沉积演化简单、识别分辨率高的特点，更适合于湖相纹层特征与其沉积环境要素之间耦合关系的研究。青海湖内发育大量的细粒沉积纹层，是湖相纹层相关基础理论研究的天然实验室。本研究以青海湖纹层为研究对象，以年纹层的绝对年代为切入点，借助野外观测和室内高精度分析测试手段，在年分辨率的时间标尺下，解剖纹层组构特征及沉积演化序列，明确湖相纹层沉积环境要素并分析其演化规律，阐明纹层组构及沉积序列与各要素及其演化过程之间的耦合关系，并建立理论模式。为我国陆上湖相纹层的古沉积环境恢复提供科学依据和借鉴思路。

我国陆上湖相页岩油资源量丰富且勘探开发潜力巨大，已经成为我国油气资源的重要接替领域。目前，在国外海相页岩油的勘探开发经验不完全适用于我国陆上湖相页岩油勘探开发的实际情况下，亟需开展湖相细粒沉积岩特征及形成机理等相关方面的基础理论研究，以便为我国湖相页岩油的勘探开发提供理论指导和技术支撑。然而，在湖相细粒沉积演化过程及形成机理研究方面遇到了其形成古沉积环境恢复不精确、不匹配的瓶颈问题，极大地限制了湖相细粒沉积岩非均质性及相关基础理论的研究。本研究采用“将今论古”之法，以青海湖细粒沉积物为研究对象，综合运用沉积学、地球化学与湖泊学理论，采用野外观测、岩心钻取及室内实验测试分析等方法和手段。刻画出了青海湖细粒沉积物的岩石组成、元素含量及其空间分布特征，明确了其分布规律及控制因素；建立了厘米级尺度下的青海湖深水区细粒沉积物的岩石成分、矿物、古水深、古盐度、古环境、古生产力等的垂向沉积演化序列，分析了其垂向演化规律及其差异性；选出了青海湖古气候判识指标，并恢复出了青海湖细粒沉积物的沉积古环境，同时，恢复出了鄂尔多斯盆地三叠系延长组长7泥页岩的形成古气候，为长7页岩油的形成机理研究提供了重要理论依据。分析了细粒沉积物与其粒度、元素等之间的耦合关系，划分了青海湖沉积相的类型及空间展布，刻画出了其细粒沉积物平面分布特征。相关研究成果和认识为我国陆上湖相泥页岩的古环境恢复、形成演化规律及机理等研究提供科学依据和可借鉴的研究思路。