钻孔揭示的河套盆地新生代环境与库布齐沙漠形成演化历史

发布时间：2018-04-22 02:08

  本文选题：河套盆地 + 古环境　； 参考：《兰州大学》2016年博士论文

【摘要】：亚洲内陆沙漠的发育是新生代亚洲内陆干旱化的直接结果,对其形成发展历史的研究可以为认识亚洲内陆干旱化历史和演化过程提供最直接的证据。在这些沙漠中,黄土高原近源沙漠是黄土高原粉尘沉积的重要源区,在黄土高原形成过程中发挥了重要作用。位于河套盆地南部的库布齐沙漠是黄土高原近源沙漠之一,由于其特殊的地理和地貌条件,库布齐沙漠的形成不仅受控于亚洲内陆干旱气候的发展,同时也受黄河活动和河套盆地古环境的影响,而河套盆地古环境重建则是认识库布齐沙漠和黄河形成演化过程的关键。本文对位于河套盆地的DR01钻孔地层序列进行了总结,同时对钻探于盆地中部的WEDP05钻孔开展了系统的沉积学和年代学研究。采用电子磁旋共振(ESR)和磁性年代学方法建立了WEDP05钻孔地层的年代标尺。通过地层岩性判识、古生物证据、颗粒形态扫描电镜观察和粒度分析等多种方法恢复了 WEDP05钻孔地层的沉积相。在此基础上,利用WEDP05钻孔沉积物色度、磁化率、粒度、碳酸盐碳氧同位素、有机质碳氮同位素及总有机碳和总氮含量等环境代用指标并结合包括DR01钻孔在内的盆地多个钻孔沉积地层特征和年代序列重建了河套盆地新生代气候和古环境演化历史。最后,探讨了库布齐沙漠的形成时间及发育模式并讨论了黄河活动在盆地古环境演化和库布齐沙漠形成方面的重要作用。主要得出以下结论:1.DR01钻孔地层自底到顶可分为:晚白垩纪地层(2503.18-2125.45 m),下部主要为棕红色泥岩夹浅灰色泥岩,上部主要为棕红色泥岩、砂质泥岩夹黄色砂岩和紫色薄层泥岩。上新世地层(2125.45-1834.55 m),棕色泥岩和砂质泥岩、淡黄色、粉色砂岩偶夹紫色泥岩、砂质泥岩,与白垩纪地层之间呈不整合接触。第四纪地层(1834.55-0 m),淡黄色粉砂和细砂夹淡红色泥岩、砂质泥岩,部分层位出现青灰色、灰绿色、浅灰色泥岩,为典型的湖相沉积物。2.WEDP05钻孔地层沉积相自顶到底可划分为:0-11.3m,河流和沙漠沉积,其中顶部5.5 m以粗颗粒河流砂为主;11.3-87.51 m,湖相沉积,以细粒粘土和粉砂质粘土为主;87.51-141.63 m,风成砂层夹湖相沉积层;141.63-183.35 m,湖相沉积为主,中间夹一套风成砂层;183.35-268.14 m,风成砂层为主,中部夹厚约30米湖相沉积层;268.14-274.60 m,湖相粉砂质粘土沉积。3.WEDP05钻孔B/M界限位于143.4m处,钻孔底界年龄为～1.68 Ma。4.河套地区在新生代早期可能处于隆起状态并接受剥蚀,至少在上新世后开始沉降形成沉积盆地,盆地内发育河湖相沉积环境,第四纪时河湖和沙漠沉积环境多次交替发育。自早更新世以来盆地经历了多次的湖泊和沙漠交替扩张过程,其中～1.47-～1.30 Ma,～1.17-～1.07 Ma,～0.68-～0.60 Ma和～0.47 Ma至末次间冰期时湖泊扩张、沙漠收缩,盆地内气候相对湿润;在～1.30-～1.17 Ma,～1.07-～0.68 Ma、～0.60-～0.47 Ma和末次冰期时沙漠扩张、湖泊收缩,盆地以干旱气候为主。～0.47 Ma、～0.3 Ma和末次间冰期是盆地内湖泊扩张最为显著的三个时期;末次冰期和全新世时,湖泊萎缩消亡,库布齐沙漠显著扩张并发育大型沙丘,逐步形成现代景观格局。5.库布齐沙漠至少在早更新世～1.65 Ma时已经形成。近地面冬季风对河套盆地内裸露的河湖相沉积物的改造和搬运分选是库布齐沙漠物质的主要来源方式。黄河活动提供大量的碎屑物质是导致库布齐沙漠发育的重要原因之一,同时盆地内湖泊萎缩及区域干旱气候也发挥了重要作用。6.河套盆地内黄河古河道可能至少在上新世时就已经形成。黄河流入河套盆地并建立较为完整上游水系的时间可能发生在至少～1.6 Ma,并至少在～1.2 Ma时形成较为完整的串联河套盆地、晋陕峡谷、汾渭盆地和三门峡的现代黄河水系。差异性构造活动造成盆地出水口抬升是导致黄河形成之后在河套盆地内发育湖泊环境的主要原因,湿润的气候条件对盆地内大湖的形成起到一定的促进作用,而黄河快速侵蚀下切是造成河套盆地湖泊消亡的主要原因。
[Abstract]:The development of the Asian inland deserts is the direct result of the droughts in the new generation of Asian inland. The study of its formation and development history can provide the most direct evidence for understanding the history and evolution process of the Asiatic droughts. In these deserts, the near source desert of the Loess Plateau is an important source of dust deposition on the Loess Plateau and is formed on the Loess Plateau. The reservoir in the southern part of the Hetao Basin is one of the near source deserts in the Loess Plateau. Due to its special geographical and geomorphic conditions, the formation of the desert is not only controlled by the development of the arid climate of the Asian inland, but also influenced by the the Yellow River activities and the palaeoenvironment of the Hetao Basin, and the ancient ring of the Hetao Basin. The reconstruction of the territory is the key to understanding the evolution process of the the Yellow River desert and the Yellow River. In this paper, the sequence of the drilling strata in the Hetao Basin is summarized, and the systematic sedimentology and chronological study of drilling in the WEDP05 borehole in the middle of the basin are carried out. The electronic magnetic rotation co vibration (ESR) and magnetic chronology are used to establish the WEDP0. The age scale of 5 borehole strata has recovered the sedimentary facies of WEDP05 drilling strata through stratigraphic lithology identification, paleontological evidence, particle morphology scanning electron microscope observation and particle size analysis. On this basis, using WEDP05 drilling sediment chromaticity, magnetic susceptibility, granularity, carbon and oxygen isotopes of carbonate salts, organic carbon and nitrogen isotopes and total organic matter. The climatic and paleoenvironment evolution history of the Cenozoic era of the Hetao Basin is rebuilt with the characteristics of the sedimentary strata of the basins, including the DR01 boreholes, including the carbon and total nitrogen content, and the history of the Paleoenvironment evolution. Finally, the formation time and development model of the cubqi desert are discussed, and the evolution of the Paleoenvironment of the Yellow River in the basin is discussed and the evolution of the Paleoenvironment in the basin is discussed. The main conclusions are as follows: the bottom to the top of the 1.DR01 borehole can be divided into the late Cretaceous (2503.18-2125.45 m), the lower part mainly of the brown red mudstone with pale gray mudstone, the upper part of the brown mudstone, the sandy mudstone with yellow sandstone and the purple thin mudstone. The Pliocene (2125.45- 1834.55 m), brown mudstone and sandy mudstone, pale yellow, pink sandstone and purple mudstone, sandy mudstone, unconformable contact with Cretaceous strata. Quaternary strata (1834.55-0 m), pale yellow silt and fine sand with pale red mudstone, sandy mudstone, gray green, gray mudstone, and typical lacustrine deposits. .2.WEDP05 sedimentary facies from the top to the end can be divided into: 0-11.3m, river and desert deposition, the top 5.5 m with coarse grain river sand; 11.3-87.51 m, lacustrine deposition, mainly fine clay and silty clay; 87.51-141.63 m, the aeolian sand layer lacustrine sedimentation layer; 141.63-183.35 m, lacustrine deposition, a set of wind in the middle. Sand formation, 183.35-268.14 m and aeolian sand layer are mainly in the middle, and the middle part is thicker than 30 Lake Myvatn sedimentary layers; 268.14-274.60 m, lacustrine silty clay deposits.3.WEDP05 borehole B/M boundary is located at 143.4m, and the age of drilling bottom boundary is 1.68 Ma.4. in the early Cenozoic, which may be in the early stage of uplift and denudation, at least after the Pliocene. The sedimentary basins are formed and the sedimentary environment of the river lacustrine facies is developed in the basin, and the sedimentary environment of the rivers and lakes and deserts develops alternately in the Quaternary period. Since the early Pleistocene, the basin has undergone several periods of alternation expansion of lakes and deserts, of which 1.47- to 1.30 Ma, to 1.17- to 1.07 Ma, to 0.68- to 0.60 Ma and to 0.47 Ma to the last interglacial period. Expansion, desert contraction, and relatively humid climate in the basin; from 1.30- to 1.17 Ma, to 1.07- to 0.68 Ma, to 0.60- to 0.47 Ma and in the last glaciation, the desert expands, the lakes shrink, the basin is dominated by arid climate. To 0.47 Ma, to 0.3 Ma and the last interglacial period is the most significant three period of Lake expansion in the basin; the last glacial and Holocene, The lake atrophy is dying out, and the reservoir desert has expanded and developed large sand dunes, and the modern landscape pattern is gradually formed in.5.. At least in the early Pleistocene to 1.65 Ma, the transformation and transportation of the bare River lacustrine sediments in the river basin are the main source of the material in the desert. The river activities provide a large amount of debris material which is one of the important reasons for the development of the the Yellow River desert. At the same time, the lake atrophy and regional arid climate also play an important role in the basin. The ancient river in the the Yellow River river basin may have been formed at least in the Pliocene. The Yellow River flows into the river set basin and establishes a more complete upstream water system. It may occur at least 1.6 Ma, and at least 1.2 Ma to form a relatively complete series of Hetao Basin, Shanxi Shaanxi Canyon, Fenwei basin and Sanmenxia's modern the Yellow River water system. Differential tectonic activities cause the basin outlet uplift is the main cause of the lake environment development in the river basin after the Yellow River formation, the humid climate. The conditions played a certain role in promoting the formation of the Great Lakes in the basin, and the rapid erosion and undercutting in the Yellow River was the main reason for the loss of lakes in the Hetao Basin.

【学位授予单位】：兰州大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：P941.73;P534.6
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本文编号：1785117