内蒙古河套地区晚第四纪库布齐沙漠的形成和演化

发布时间：2019-04-02 13:16

【摘要】：库布齐沙漠位于鄂尔多斯高原东西向隆起带北部及其向河套平原过渡的坡面上,地势南高北低,其西、北、东3面均由黄河环绕,南部为构造台地,中部为风成沙丘,北部为河漫滩地,地处现代亚洲夏季风影响的边缘,属于干旱-半干旱过渡带。沙漠生态环境脆弱,对气候变化的响应敏感,库布齐沙漠的形成演化过程是河套-鄂尔多斯地区环境变化的缩影。库布齐沙漠地表发育沙漠相风成沉积物,由沙丘、丘间、沙席等风成相沉积组成。获取沙漠覆盖区第四纪沉积物记录的地质信息,探讨库布齐沙漠形成和发展过程,构建库布齐地层格架,为还原区域环境演化历提供重要证据。本文利用遥感影像、探地雷达扫描结合沙丘类型、发育成熟度,获取风向信息并联合气象数据,还原古风向和沙漠化过程。认为库布齐沙漠是西北风为主导的低风能环境,不支持远距离搬运,风沙堆积为近源。通过槽型钻、冲击钻、深钻揭露地表风成沙后,结合粒度分析、扫描电镜等沉积分析手段和OSL、14C年代约束方法,确定库布齐的基底及风沙物质来源。本文获取了库布齐下伏河流冲积体系和湖沼体系(古河道洼地盐化湖沼)的沉积层序,确定库布齐下伏埋藏有黄河古河道,并认为库布齐是在干旱河道上受风力作用就地起沙形成风沙堆积,黄河冲积物为库布齐主要物源。库布齐北缘局部发育的砾漠,实际为被风力揭露的沙丘基底,属于黄河冲积物的再风蚀相,也证明了“就地起沙”这一形成模式。通过气候环境指标分析,探讨库布齐发育和演化过程。库布齐因受河套盆地深部隐伏正断层控制,且位于早先存在的“吉兰泰-河套”古大湖区域内(整体为台陷型湖盆),以前为滨浅湖沉积。古大湖湖面退缩的过程中,16-11ka古黄河过流并冲刷侵蚀湖相沉积地层,在古湖底之上堆积冲积砾石、细砂等大量沙源基础。中全新世距今4.1ka,库布齐地区黄河古河道低洼处发育盐化沼泽,沙丘初步堆积。晚全新世距今1.44ka,风沙活化能力增强,库布齐逐步形成沙漠地貌景观。
[Abstract]:Kubuqi Desert is located on the slope of the east-west uplift belt and its transition to the Hetao plain on the east-west of the Ordos Plateau. The topography is high in the south and low in the north, surrounded by the Yellow River in the west, north and east, structural platform in the south, and wind-formed sand dunes in the middle. The northern part is floodplain, which is located on the edge of modern Asian summer monsoon and belongs to the arid-semi-arid transitional zone. Desert ecological environment is fragile and sensitive to climate change. The formation and evolution of Kubuqi Desert is the epitome of environmental change in Hetao-Ordos region. Desert facies eolian sediments are developed on the surface of Kubuqi desert, which are composed of sand dunes, sand mats and other eolian facies deposits. The geological information of Quaternary sediment records in desert-covered area is obtained, the formation and development process of Kubuqi desert are discussed, and the Kubuqi stratigraphic framework is constructed, which provides important evidence for reducing the regional environmental evolution calendar. In this paper, remote sensing images, ground penetrating radar (GPR) scanning combined with sand dune type are used to develop maturity, obtain wind direction information and combine meteorological data to restore ancient wind direction and desertification process. It is considered that the Kubuqi desert is a low wind energy environment dominated by northwest wind, which does not support long-distance transportation, and wind-blown sand accumulation is a near source. The basement and the source of aeolian sediment in Kubuqi are determined by trough drilling, impact drilling and deep drilling, combined with grain size analysis, SEM and OSL,14C age constraint method. In this paper, the sedimentary sequence of the alluvial system and lacustrine system (salinized lake marsh in ancient channel depression) of Kubuqi is obtained, and it is determined that there is an ancient Yellow River channel buried in Kubuqi. It is considered that Kubuqi is the main source of sand in Kubuqi by wind-driven sand accumulation in the area and the Yellow River alluvial matter is the main source of Kubuqi. The gravelly desert developed locally in the northern margin of Kubuqi is actually the sand dune basement exposed by wind, which belongs to the rewind erosion phase of the alluvial matter of the Yellow River, which also proves the formation mode of "on-the-spot sand rising". The development and evolution of Kubuqi are discussed through the analysis of climatic and environmental indicators. Kubuqi is controlled by deep concealed normal faults in Hetao basin and is located in the earlier "Jilantai-Hetao" paleolake area (the whole basin is platform depression type lake basin), which was previously shoreline-shallow lacustrine deposit. During the receding process of the paleolake surface, the 16-11ka paleo-Yellow River overflowed and eroded the lacustrine sedimentary strata, and accumulated a large amount of alluvial gravel, fine sand and so on top of the ancient lake floor. The middle Holocene is 4.1 ka away. Salinized swamps and sand dunes are formed in the low-lying areas of the ancient Yellow River in Kubuqi area. The late Holocene is 1.44 ka. the ability of wind-blown sand activation is enhanced, and Kubuqi gradually forms desert landscape.
【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】：P931.3;P534.63

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