青海湖现代沉积体系研究

发布时间：2018-04-08 14:56

本文选题：青海湖　切入点：沉积体系　出处：《中国地质大学(北京)》2016年博士论文

【摘要】：形成于中新世的青海湖是中国内陆最大的断陷型咸化湖泊。这里发育了多种类型的陆源碎屑沉积,为我国东部第三纪陆相断陷湖盆的古今对比提供了理想场所。在20世纪60至70年代,前人对青海湖展开了多学科的综合研究。自此以后,对青海湖现代沉积的研究多集中在单一的沉积相上,缺乏系统的研究。本文以野外露头、探槽、水深测量、遥感影像资料和气象资料为基础,结合显微薄片、扫描电镜、粒度分析及地化测试分析等手段,开展了青海湖现代沉积体系的研究工作。通过引入“源-汇”体系的研究思路,以每个“点”上的沉积相分析为基础,建立了6个从物源区到沉积区“线”上的“源-汇”沉积体系和湖泊沉积体系,从而深入剖析了青海湖现代沉积体系“面”上的特征,并编制出新的青海湖现代沉积体系平面图。本次研究在沉积相类型和形成机制方面取得了一些新认识:提出分割青海湖和耳海的第Ⅲ道湖堤是湖平面下降和波浪及沿岸流共同作用而形成;湖滩岩的形成与微生物作用有着密切的关系;发现布哈河三角洲发育前缘斜坡;原先的沙柳河扇三角洲是由冲积扇、扇三角洲和曲流河三角洲组成;发现哈尔盖河和甘子河河口区发育有障壁岛-泻湖-三角洲、喇叭状河口和障壁岛-水道-泻湖。研究发现,青海湖现代沉积体系的形成与分布,除了受“源-汇”体系控制,还与风向和风力有关,进而提出了青海湖现代沉积体系是“风(风场)-源(物源)-湖(湖盆地貌/盆地演化)”系统综合作用下的产物。具体包括物源区的岩性特征、地形地貌、水系、植被类型和覆盖度、风场、波浪、湖流和湖平面的升降,并建立了两大沉积模式:强物源背风体系模式和弱物源迎风体系模式。强物源背风体系是由冲积扇、扇三角洲、河流、三角洲等组成。弱物源迎风体系是由风成沙丘、障壁岛、水道、泻湖、喇叭状河口等组成。两大模式体系的建立为古代陆相断陷湖盆中砂体分布预测提供了新的思路。湖盆半深湖-深湖区的细粒沉积物能够成为潜在的烃源岩。强物源背风体系中的三角洲前缘和扇三角洲前缘与弱物源背风体系中的障壁岛和风成沙丘均为潜在的优质储集体。
[Abstract]:Qinghai Lake formed in Miocene is the largest faulted lake in inland China.There are many types of continental clastic deposits, which provide an ideal place for the Paleo-modern correlation of Tertiary continental faulted lacustrine basins in eastern China.In the 1960 s-70 s, the predecessors carried out a multi-disciplinary comprehensive study of Qinghai Lake.Since then, researches on modern sediments in Qinghai Lake have been concentrated on single sedimentary facies, and lack of systematic research.Based on field outcrop, trench, bathymetry, remote sensing image data and meteorological data, combined with microslice, scanning electron microscope, particle size analysis and geochemistry analysis, the modern sedimentary system of Qinghai Lake has been studied in this paper.By introducing the idea of "source-sink" system, based on the analysis of sedimentary facies on each "point", six "source-sink" sedimentary systems and lacustrine sedimentary systems from provenance to sedimentary "line" are established.The characteristics of the "surface" of the modern sedimentary system of Qinghai Lake are deeply analyzed, and a new plan of the modern sedimentary system of Qinghai Lake is worked out.In this study, some new understandings on sedimentary facies types and formation mechanism have been obtained: it is proposed that the third lake embankment separating Qinghai Lake from Erhai Lake is formed by the combination of lake plane descent and wave and coastal currents;The formation of lacustrine rocks is closely related to the microorganism, and it is found that the front slope of Buha River delta is developed, and the former Shaliu River fan delta is composed of alluvial fan, fan delta and meandering river delta.It is found that there are barrier islands, lagoon deltas, loudspeaker estuaries, barrier islands, waterways and lagoons in the estuaries of Hargai and Ganzi rivers.It is found that the formation and distribution of modern sedimentary systems in Qinghai Lake are not only controlled by the "source-sink" system, but also related to wind direction and wind power.Furthermore, it is suggested that the modern sedimentary system of Qinghai Lake is the result of the integrated action of the "wind (wind field)-source (material source-lake (lake basin geomorphology / basin evolution)" system.The characteristics of lithology, landform, water system, vegetation type and coverage, wind field, wave, lake current and lake plane rise and fall are included in this paper, and two sedimentary models are established: strong material source leeward system model and weak material source upwind system model.The strong material source leeward system is composed of alluvial fan, fan delta, river, delta and so on.The weak source upwind system is composed of wind-formed sand dunes, barrier islands, waterways, lagoons and trumpet estuaries.The establishment of the two model systems provides a new idea for the prediction of sand body distribution in the ancient continental faulted lake basin.Fine-grained sediments in the semi-deep lake-deep lake region of the lake basin can become potential source rocks.The barrier islands and wind-formed dunes in the strong source leeward system and the fan delta front system and the weak material source leeward system are both potential high quality reservoirs.
【学位授予单位】：中国地质大学(北京)
【学位级别】：博士
【学位授予年份】：2016
【分类号】：P618.13;P512.2

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