山旺盆地中新世古地磁特征及充填演化分析

发布时间：2018-11-12 08:12

【摘要】：素有化石宝库之称的山旺盆地,其形成沉积时限一直模糊不清,缺乏地质时间标尺研究,盆地沉积充填演化及古环境方面的研究只得到了一些简单的认识。本文以山旺盆地景观剖面和角岩山地层剖面为研究对象。在详细的基础地质研究的基础上,首先通过对山旺盆地山旺组古地磁特征研究,确立了山旺盆地磁性地层年代,建立了准确的年代框架,分析了山旺盆地成盆前后和沉积充填阶段构造旋转量和漂移量。其次,对盆地进行充填演化分析,分析山旺盆地主要沉积地层沉积相,划分了盆地充填演化阶段,由元素地球化学特征,恢复了山旺盆地古环境。主要结论如下:(1)基础地质研究证实山旺盆地为典型的玛珥湖盆地。根据山旺组硅藻土地层精细古地磁测量数据,并结合上下地层古地磁极性,确定了山旺盆地地层磁极性变化序列,通过实测极性柱和标准极性柱进行对比,并结合纹层沉积速率,得到可靠的磁性地层年龄:山旺组二段以及上部三段的形成年龄大致从18.524 MaB.P.～18.056MaB.P.,沉积时间略小于0.468Ma。山旺组二段硅藻页岩从18.524MaB.P.开始沉积,沉积时间应该在0.20～0.30Ma之间。整个山旺盆地山旺组的沉积时间大致为18.5 Ma B.P.～17.5 MaB.P.之间。(2)由古地磁分析结果,山旺盆地构造运动活跃程度可以划分为三期:盆地喷发成盆期,郯庐断裂带频繁活跃,断裂深切地幔,形成岩浆上涌通道,火山喷发,形成火山盆地;2.盆地稳定充填时期,断裂活动减弱,沉积环境相对稳定,在火山喷发后形成的玄武岩基底上形成玛珥湖,湖中形成适合硅藻生长环境;3.盆地喷发消亡期,由于断裂活动再次活跃,岩浆喷出将山旺盆地覆盖。(3)通过剖面实测并连续测量自然伽马,发现连续自然伽马曲线与岩性具有较好的响应。依据陆相湖泊及河流沉积相划分标准,对山旺组角岩山地层和景观剖面地层进行研究。将山旺盆地山旺组一段到四段地层划分出湖泊相、河流相以及火山溢流相。根据山旺盆地地层由老到新沉积特征,将盆地沉积演化划分为四个阶段:快速塌陷成盆期、全封闭稳定发展期、半封闭淤塞充填期、消亡期。(4)古环境演化阶段和地层沉积相有较好的对应关系,在某些层位出现的地球化学指标的峰值,记录了环境的突变事件,如结核层的出现。将山旺组主要沉积地层,即山旺组二段和三段古环境划分为3个阶段,山旺盆地经历了浅水半咸湖—深水咸水湖—浅水河流的演化过程。气候变化由相对湿热变为相对干冷。
[Abstract]:The sedimentary time limit of Shanwang basin, which is known as the fossil treasure house, has always been vague, and the study of geological time scale is lacking. The study of sedimentary filling evolution and paleoenvironment of the basin has only got some simple understanding. The landscape profile of Shanwang Basin and the stratigraphic profile of Jiao Yan Mountain are taken as research objects in this paper. On the basis of detailed basic geological research, the paleomagnetic characteristics of Shanwang formation in Shanwang Basin are studied at first, and the age of magnetic strata in Shanwang Basin is established, and an accurate chronological framework is established. The tectonic rotation and drift before and after the basin formation and the sedimentary filling stage in Shanwang Basin are analyzed. Secondly, the filling evolution of the basin is analyzed, the main sedimentary facies in Shanwang basin are analyzed, and the filling evolution stage of the basin is divided. The paleoenvironment of Shanwang basin is restored by the geochemical characteristics of elements. The main conclusions are as follows: (1) basic geological studies confirm that Shanwang Basin is a typical Mar Lake basin. According to the fine paleomagnetic survey data of diatomite formation in Shanwang formation and combining with paleomagnetic polarity of upper and lower strata, the series of variation of stratigraphic magnetic polarity in Shanwang basin is determined, and the correlation between measured polarity column and standard polarity column is carried out. The reliable magnetostratigraphic age of the second and upper third member of the Shanwang formation is obtained from the deposition rate of the laminae from 18.524 MaB.P.~18.056MaB.P., to less than 0.468 Ma. The diatom shale of the second member of Shanwang formation was obtained from 18.524 Ma B.P. Start deposition, deposition time should be between 0.20~0.30Ma. The sedimentary time of Shanwang formation in Shanwang Basin is about 18. 5 Ma B.P.~17.5 MaB.P.. (2) from paleomagnetic analysis, the tectonic activity of Shanwang Basin can be divided into three periods: the basin erupts into a basin, the Tanlu fault zone is frequently active, the deep mantle is fractured, the magmatic upwelling passage and the volcanic eruption are formed. Forming volcanic basins; 2. During the stable filling period of the basin, the fault activity was weakened and the sedimentary environment was relatively stable. Maer Lake was formed on the basalt basement formed after the volcanic eruption, and the lake was formed in a suitable environment for the growth of diatoms. 3. During the extinction of the basin eruption, the magma ejected to cover the Shanwang basin due to the reactivity of the fault activity. (3) the continuous natural gamma curve and lithology were found to have a good response through the measured and continuous measurement of the natural gamma rays in the section. According to the criteria of continental lacustrine and river sedimentary facies, this paper studies the hornstone mountain strata and landscape profile stratigraphy of Shanwang formation. The strata of the first to fourth member of Shanwang formation in Shanwang Basin are divided into lacustrine facies, fluvial facies and volcanic overflow facies. According to the characteristics of strata from old to new in Shanwang Basin, the sedimentary evolution of the basin is divided into four stages: the period of rapid collapse, the period of complete closed and stable development, the period of semi-closed silting and filling. (4) the paleoenvironmental evolution stage has a good correspondence with the sedimentary facies. The peak value of geochemical indicators in some layers records the abrupt events of the environment, such as the occurrence of the nodule layer. The main sedimentary strata of Shanwang formation, that is, the second and third member of Shanwang formation, are divided into three stages. The basin has undergone the evolution process of shallow water half salty lake, deep water salt lake and shallow water river. Climate change has changed from relative humid heat to relatively dry and cold.
【学位授予单位】：山东科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P318.44;P534.621

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