【作者】 钱程；

【导师】 朱大岗；

【作者基本信息】 中国地质科学院 ， 构造地质学， 2011， 硕士

【摘要】 近年来,随着全球环境变迁与气候变化研究力度的加大,古近纪和新近纪的沉积演化及其环境研究也引起国内外地学界关注。榆社盆地位于华北地区中部的晋东榆社地区,盆内新近纪河湖相沉积发育,古生物化石丰富,是研究本区乃至华北地区新近纪沉积环境和构造演化的最佳选择。本论文以榆社盆地新近纪河湖相沉积为主要研究对象,在详细野外地质调查的基础上,综合前人材料,以沉积环境演化为研究主线,进行了沉积地层、古气候变化、地层年代、物质来源、构造地貌、盆地性质及构造演化等研究,理清了河湖相地层的沉积序列,恢复了榆社盆地新近纪的古环境、古气候,分析了盆地的构造演化特征,并探讨榆社古湖的演化及其构造意义。取得的主要认识如下：榆社盆地为NE-NNE向碟形展布的围椅状盆地。盆内地势北西高南东低,地势平坦,地表坡度较缓;呈现一核三环带的高程分布特征；河谷宽大平坦,沟壑纵横发育。盆内广泛分布浊漳河上游水系,处于老年期的初期阶段。大地构造上,榆社盆地位于山西地块中部裂陷带以东的隆起地区,属于沁水向斜沾尚-武乡-阳城北北东向褶皱带的中-东北部,基底地层主要为三叠系。盆地为新生代形成的山间同生断陷盆地,受控于东侧太行山大断裂和西侧汾渭裂陷系东侧的张性断裂带。榆社盆地新近系分布广泛,与盆地的展布形态一致,地层呈叠瓦式叠覆展布。这套沉积可划分3个组、3个段、10个岩性段、66层,总厚度为476m。形成时间上,马会组为13.01～5.25Ma,属新近纪中新世晚期；高庄组为5.25～3.08Ma,属新近纪上新世早期,其中桃阳段、南庄沟段和醋柳沟段分别为：5.25～4.50Ma、4.50～3.89Ma和3.89～3.08Ma；麻则沟组为3.08～2.43Ma,属新近纪上新世晚期。榆社盆地新近系的物质来源以母岩风化的陆源物质为主体,兼有少量生物物质,陆源区为盆地四周的山体,物质主要为基底的二叠系和三叠系。中新世晚期,形成马会组,源区水系和滨湖沉积环境,气候较为湿润,森林草原环境。上新世早期,形成高庄组,滨湖、浅湖和半深湖交替变化的沉积环境,气候以湿热为主,存在多次干旱性事件,呈现森林、灌丛、草原交混的植被。上新世晚期,形成麻则沟组,浅湖和滨浅湖三角洲沉积环境,气候逐渐变干变冷,植被为以针叶林为主的草原针阔混交林。榆社古湖存在湖泊形成期、湖泊发展期和湖泊消亡期三个湖泊演化阶段。榆社古湖形成期为中新世晚期,由源区的水系发育到汇水成湖,盆地演化进入初始断陷阶段。榆社古湖发展期为上新世早期,水体演化呈现了3次稳定增加-波动性增加的周期性变化,大致对应盆地加速断陷阶段、断陷止息阶段和二次加速断陷阶段3个盆地演化阶段。榆社古湖的消亡期为上新世晚期,水体稍有减少,盆地演化进入末次断陷阶段,末期,盆地断陷作用停止,相对抬升,湖泊外流作用增强,水体迅速减少,古湖消亡。更多还原

【Abstract】 In recent years, as the researches on Global Environmental Change and Global Climate Change are gathering momentum, researches on the sedimentary and environmental evolutions of Paleogene and Neogene are attracting the attention from geologists both at home and abroad. Yushe Basin is located in eastern Shanxi in the middle of North China. It has Neogene fluvial-lacustrine deposition and a multitude of fossils, and therefore it is the best choice for studying Neogene sedimentary environment and tectonic evolution.With Yushe Basin Neogene fluvial-lacustrine deposition as the main research subject and based on detailed field geological surveys as well as previous studies, this thesis centers around sedimentary environment evolution, and researches into sedimentary formation, palaeoclimatic changes, formation age, sources, tectonic geomorphology, basin characteristics and tectonic evolution, etc. It works out the sedimentary sequence of the fluvial-lacustrine formation, reconstructs the palaeoenvironment and palaeoclimate of Yushe Basin in Neogene, analyzes the characteristics of basin tectonic evolution, and discusses the evolution of Yushe Fossillake and its tectonic meaning. The major conclusions are as follows:Yushe Basin was in the shape of an armchair and had a NE-NNE trend, with its northern and western part higher than its southern and eastern part. It had a flat relief with gradual slope. Its distribution of altitude figures was in the shape of three rings with a core inside. Its valley was wide and flat with gullies. The basin was widely scattered with up courses of Zhuzhang River and was in the early stage of agedness.Yushe Basin was located in the uplift areas to the east of the rift zone in the middle of Shanxi plate and was the central and northeastern section of the Zhanshang-Wuxiang-Yangcheng NNE fold belt in the Qinshui Syncline. Its basal formation was mainly Triassic. It was an intermontane graden basin formed in Cenozoic, and was highly affected by Taihang Mt. Fault in the east and Shearfault in the east margin of the Fenwei Graben system in the west.Yushe Basin Neogene was widely distributed and was consistent with the distribution of the basin, with its stratum in imbricate overlap. This series of deposition can be divided into 3 formations,3 sections, 10 lithologic units and 66 layers, with a total thickness of 476m. As for the time of formation, Mahui Formation is 13.01～5.25Ma, which belongs to the older Miocene; Gaozhuang Formation is 5.25～3.08Ma, which belongs to the early Pliocene, of which Taoyang Section, Nanzhuanggou Section and Culiugou Section are 5.25～4.50Ma,4.50～3.89Ma and 3.89～3.08Ma; while Mazugou Formation is 3.08～2.43Ma and belongs to the late Pliocene.The sources of Yushe Basin Neogene were mainly terrestrial matters from the weathering of rocks, together with a bit of biological substances. Its sourceland was the mountains surrounding the basin, with Permian and Triassic in its main basal formation as the major matter.Mahui Formation came into being in the older Miocene with its sourceland in a drainage and shore lake sedimentary environment. The climate was moist as in the forest and grassland. Gaozhuang Formation came into being in the early Pliocene with a frequent change among shore lake, shallow lake and half-deep lake sedimentary environment. The climate was mainly hot and humid. It underwent a number of droughts, and had a mixed vegetation of forests, bushes and grassland. Mazugou Formation came into being in the late Pliocene, with a shallow lake and shore lake delta sedimentary environment. The climate was becoming dry and cold and the vegetation was mainly grassland mixed coniferous broad leaved forests with conifers as the major trees.Yushe Fossillake fall into three phases of limnological transformation:limnological formation phase, limnological development phase and limnological declining phase. Yushe Fossillake came into being in the older Miocene; as the waters in the sourceland developed into a lake, the basin entered its initial faulted stage. Yushe Fossillake’s development phase was in the early Pliocene, and it underwent 3 seasonal changes of water level from steady increase to wavy increase, which corresponded with the accelerated faulted stage, the cutting in heart stage and the second initial faulted stage. The third phase was in the late Pliocene. The water in the lake slightly became less and the basin entered its final faulted stage. At the end of this phase, the lake experienced an increase of water outflow. As a result, its water decreased rapidly and the fossillake finally disappeared.更多还原