河套盆地晚第四纪地层划分与湖泊演化历史

发布时间：2018-06-14 21:24

本文选题：河套盆地 + 晚第四纪　；参考：《中国地质大学(北京)》2017年硕士论文

【摘要】：第四纪地层是气候变化、沉积作用、地貌过程等信息的载体,也是第四纪古地理、古环境变化研究的关键。内蒙古河套地区属于新生代断陷盆地,沉积了巨厚的第四纪地层,由于岩芯材料难以获取,长期以来缺乏系统的研究。前人研究发现,河套盆地在第四纪长期发育湖泊环境,并曾经存在一个统一的古大湖。河套古湖的演变过程是河套盆地第四纪地质研究的重要内容之一,由于测年手段的限制,盆地内部的湖相沉积序列尚未明确,造成中更新世晚期以来的河套古湖的演化过程一直缺乏深入的研究。这给河套盆地及邻区中-fi更新世的地层对比、古地理和古环境研究造成了困难。因此,在第四纪地层划分和区域地层对比的基础上,重建湖泊的演化历史,具有重要意义。本文在对研究区进行大量野外调查的基础上,获取了丰富的岩芯资料、充分的年代控制和详细的气候指标,进一步细化了河套盆地第四纪地层尤其是中-晚更新世的地层划分,确立了以湖相沉积为主的地层格架,建立了多重地层划分系统;针对盆地内部湖泊演化过程中的关键科学问题,提取了湖泊沉积的空间分布、时间序列和沉积物性质反映的湖泊水位信息,划分了湖泊的演化阶段,并结合构造事件和古气候特征探讨了古湖演化的驱动因素。本文取得的主要成果有:1)通过对钻探获取的河套盆地沉积物岩性特征进行分析,结合多种测年方法及气候学方法,建立了河套盆地晚第四纪的年代地层与岩石地层、气候地层等多重地层划分系统,将地层自下而上划分为:中更新统沟子板组、上更新统萨拉乌苏组以及城川组、全新统,将萨拉乌苏组进一步分为上、下两段,并对萨拉乌苏组和城川组进行了精确的年代约束。2)根据钻孔沉积中湖相地层的分布、沉积学特征以及沉积序列和沉积相变关系,划分出盆地内部两个较大的河-湖旋回,阐明了各个时期湖泊的覆盖范围,并将古湖沉积物粒度划分为四种特征类型以说明古湖的水位变化。在此基础上重建了河套古湖的演化历史,将河套盆地300ka以来的湖泊演化过程分为五个不同的阶段:1.中更新世大湖期(320ka~160ka),发育统一的古大湖,盆地处于深水还原环境;2.晚更新世湖泊形成期(160ka~120ka),河湖共存,北部发育黄河,湖水限于盆地中部;3.晚更新世大湖期(120ka~100ka),发育统一的古大湖,为封闭型湖泊,水位不及中更新世古湖;4.晚更新世湖泊萎缩期(100ka~11ka),100kaB.P.左右黄河外流,大湖解体,山前继续沉降并发育湖泊,至11kaB.P.湖泊全部消失;5.现代黄河期(11ka~今),河泛平原上出现一系列河成、风成湖泊,与晚更新世古大湖没有继承关系。3)通过将古湖演化的阶段性特征与古气候变迁的标志性事件进行对比,分析了影响湖泊演化的气候驱动因素;通过盆缘断裂带新构造运动的相关文献资料,分析了古湖形成与消亡的构造背景。研究表明,盆地内湖泊的发育与消亡主要受控于以盆缘断裂带差异性升降为主要表现形式的新构造运动,而古气候的波动可以在一定程度上影响湖泊的水位起伏。
[Abstract]:Quaternary strata are the carrier of information of climate change, sedimentation and geomorphology. It is also the key to the study of paleogeography and paleoenvironment changes in the Quaternary period. The Inner Mongolia Hetao area belongs to the Cenozoic fault basin, which deposited huge thick Quaternary strata, because the core materials are difficult to obtain and lack systematic research for a long time. Previous studies found that The hetao basin developed a long lake environment for a long time in the Quaternary period, and there was a unified ancient great lake. The evolution process of the ancient lake in the Hetao Basin is one of the important contents of the Quaternary geological study in the Hetao Basin. The lacustrine sedimentary sequence in the basin has not been clearly defined because of the limited means of dating, which has caused the formation of the ancient lake in the late Pleistocene. There has been a lack of in-depth study of the process. This has caused difficulties in the stratigraphic comparison of the -fi Pleistocene in the Hetao Basin and its adjacent areas, and the study of Palaeogeography and paleoenvironment. Therefore, it is important to reconstruct the history of the lake on the basis of the Quaternary stratigraphic division and regional stratigraphic comparison. On the basis of the rich core data, full age control and detailed climatic indicators, the stratigraphic division of the Quaternary strata, especially the middle late Pleistocene, was further refined, and the stratigraphic framework based on lacustrine facies was established, and a multiple stratigraphic division system was established. Key scientific problems, the spatial distribution of lake deposits, time series and the water level information reflected by the nature of the sediments are extracted, and the evolution stages of the lakes are divided, and the driving factors of the evolution of the ancient lakes are discussed in combination with the tectonic events and paleoclimate characteristics. The main achievements of this paper are as follows: 1) through the drilling of the sediments of the river basin, the sediment rocks are obtained. On the basis of the analysis of the characteristics, combined with a variety of dating methods and climatological methods, a multiple stratigraphic division system, such as the Middle Pleistocene trench plate group, the upper Pleistocene Sara Wusu formation and the city group, and the Sara Wusu formation, are set up in the late Quaternary chronostratigraphy and climate stratigraphy of the Hetao Basin. One step is divided into the upper and the lower two sections, and the exact age constraints of the Sara Wusu and Cheng Chuan formations are carried out. According to the distribution of the lacustrine strata in the drilling deposits, the sedimentological features and the relationship between the sedimentary sequence and the sedimentary phase transformation, two large river lake cycles in the basin are divided, and the coverage of the lakes in each period is elucidate, and the ancient lake is sunk. The grain size is divided into four characteristic types to explain the change of the water level of the ancient lake. On this basis, the evolution history of the ancient lake is rebuilt, and the evolution history of the lake is rebuilt. The lake evolution process since 300kA is divided into five different stages: 1. Middle Pleistocene Great Lake period (320ka~160ka), the ancient great lake of the one development, the basin in the deep water reduction environment, and 2. late more. The formation period of the Miocene Lake (160ka~120ka), the coexistence of rivers and lakes, the development of the Yellow River in the north, the lake water limited to the middle of the basin, the 3. late Pleistocene Great Lake period (120ka~100ka), the development of a unified ancient Great Lake, the closed lake, the water level less than the Middle Pleistocene lake, the 4. late Pleistocene lake atrophy (100ka~11ka), the exodus of the the Yellow River, the disintegration of the great lake, and the continuation of the mountain. Lakes all disappear and develop lakes to 11kaB.P. lakes all disappear; 5. modern the Yellow River period (11ka~ today), a series of rivers, wind lakes, and the late Pleistocene great lakes have no inheritance relationship with the modern the Yellow River period. By comparing the characteristics of the paleolake evolution with the chronoclimatic changes of paleoclimate, the climate that affects the evolution of the lake is analyzed. Through the related literature of the neotectonic movement of the basin margin fault zone, the structural background of the formation and extinction of the ancient lake is analyzed. The study shows that the development and extinction of the lake in the basin are mainly controlled by the new tectonic movement with the differential rise and fall of the basin margin fault zone as the main manifestation, and the fluctuation of the paleoclimate can be taken to a certain extent. The water level fluctuates in the lake.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P534.63;P531

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