Knowledge Resource Center for Ecological Environment in Arid Area
| 淮北平原晚新生代（8 Ma 以来）沉积地层与古环境变化 | |
| 其他题名 | The late Cenozoic (since 8 Ma) stratigraphy and paleoenviroment change of the Huaibei Plain in the eastern China |
| 张磊 | |
| 出版年 | 2016 |
| 学位类型 | 博士 |
| 导师 | 刘嘉麒 ; 秦小光 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 摘要淮北平原地处我国东部半湿润区，又是在我国南北方气候、地貌、植被过渡带上，其沉积物记录了晚新生代以来中国东部气候环境变化以及东亚季风的形成演化等信息。另外，淮北平原又是我国重要的粮食和能源生产基地，而且是人口密集区，其环境变化深刻影响着当地人的生产生活。因此，深入研究淮北平原晚新生代以来的气候环境演化不仅具有重要的科学意义，而且具有重要的现实意义。晚新生代以来的古环境、古气候的研究，不仅对从长时间尺度理解古环境、古气候变化特征、规律和机制具有特别重要的意义，而且对于理解当前全球气候变暖的驱动机制及发展趋势具有重要意义。然而我国对于长尺度的气候环境变化研究主要集中在西部黄土高原和青藏高原周边以及南海等地，东部地区长尺度的古气候古环境研究非常缺乏，在半湿润区几乎是空白。这阻碍了我们对东部地区晚新生代以来气候环境演化的认识。针对上述问题，本文对淮北平原中部的一根钻孔（淮南钻孔，进尺481.45 m）开展了包括沉积学、层序地层学、磁性地层学、地球化学、古气候学（粒度、磁化率、色度等指标）等的研究，主要得到以下认识：（1） 建立了淮北平原晚新生代沉积8 Ma以来的古地磁年代框架和时间序列。根据古地磁测量结果与古火山喷发记录，首次建立了中国东部半湿润区淮北平原晚新生代481 m长岩芯的年代框架和时间序列：钻孔新生代底界年龄大约为8 Ma，说明淮北平原中部新生代沉积始于8 Ma前后。第四纪底界（2.588 Ma）深度在132 m，上新世与中新世界限（5.33 Ma）深度为286.1 m；B/M界限（0.78 Ma）在孔深72 m处，G/G界限（高斯/吉尔伯特界限3.58 Ma）见于200.0 m深处。（2）建立了中国东部半湿润区淮北平原481 m长岩芯的详细完整的沉积地层序列，并进行了沉积相古环境分析，发现淮河盆地第四纪以前主要以河流-河滨湖滨交替环境为主，第四纪以来主要以泛滥平原环境为主。重建了淮北平原晚新生代（8 Ma）以来的气候环境变化序列，大致可以分为8个大的阶段：I、8.0-7.8 Ma 氧化环境，气候较干热，冲洪积相；II、7.8-7.1 Ma 深水湖环境，气候非常湿润，为深湖相；III、7.1-3.7 Ma 长周期的河流-河滨湖滨交替环境，气候为稳定的长周期的湿润-干旱交替波动，为河流-河滨湖滨相特征；IV、3.7-2.7 Ma 河流-河漫滩环境，是气候快速波动的转型过渡期，总体上从相对湿润、降雨量较多转变为降雨量减少、气候向干旱化方向发展；V、2.7-1.7 Ma 气候剧烈频繁波动，为气候快速波动情况下的河流相沉积环境；VI、1.7-0.75 Ma 气候相对稳定，相对干旱的气候背景；VII、0.55-0.75 Ma 湖沼环境沉积，为冷湿的气候环境，植被生长茂盛，为湖沼相；VIII、0-0.55 Ma 泛滥平原沉积，为相对干旱的气候环境。（3） 首次发现中国东部半湿润区（淮北平原）8 Ma以来在构造尺度上具有与西北干旱半干旱区（黄土高原）基本同步的相似古气候波动特征。晚新近纪（7.1-3.7 Ma）中国东部半湿润区与西北部半干旱区气候均存在相对稳定的长周期的湿润-干旱波动特征，而且几乎同步波动；3.7-2.7 Ma为气候转型期，气候环境在快速剧烈波动中从湿润气候向相对干旱气候转型过渡；第四纪（2.6 Ma）以来东部半湿润区与西北部干旱半干旱区均具有干旱化加强趋势。其原因可能是：晚新近纪（7.1-3.7 Ma）中国从东部半湿润区到西部干旱-半干旱区气候都主要受稳定的东亚夏季风控制，而3.7 Ma以来，由于北极冰盖的形成与发展，季风增强，使得中国东、西部日趋干旱化。（4） 首次发现了史前大约13.2 ka BP前后“黄河入淮”事件的地质证据。通过对淮南钻孔顶部8 m岩芯详细的地球化学分析，发现0-2 m的沉积物的TiO2/Al2O3、SiO2/ TiO2、Th/Nb、La/Nb、Zr/10-Th-Sc以及稀土配分组成都与中国北方黄土基本一致，指示该层为黄泛层。黄泛沉积的风化程度比北方黄土高，比南方黄土低。黄泛沉积的底部年龄为13200 BP，说明黄河至少在13200 BP （末次冰消期）可能就已经改道进入淮北平原，这比历史记录的最早的“黄河入淮”（361 BC）早10000多年。黄河在末次冰消期改道进入淮北平原，可能是黄河上游冰川融水增加与下游降雨量增加共同作用导致的。 |
| 英文摘要 | AbstractThe Huaibei Plain is located in semi humid area in eastern China, and is a climate, vegetation, and geography transition zone of China. The sediments from this area recorded paleoclimate change and the East Asian monsoon formation and evolution information since the late Cenozoic in eastern China. In addition, the Huaibei plain is an important food and energy production base in eastern China, and it is a densely populated area. The environment change has a profound impact on the local people’s life. Therefore, it is a great scientific significance and practical significance to study the evolution of climate and environment in Huaibei Plain since the late Cenozoic era. To study the late Cenozoic palaeoenvironment and palaeoclimate change, which is not only important for understanding the characteristics, law and mechanism of the long time scale paleoenvironment and paleoclimate changes, but also has a great significance for understanding the drive mechanism and development trend of current global warming. However, long time scale climate change researches are mainly concentrated in the Western Loess Plateau, Tibet Plateau surrounding and the South China Sea in our country, long time scale paleoclimate and paleoenvironment research are very lack in east China and is almost blank in semi humid area. This has hindered us to understanding the climate and environment evolution of the eastern China since the late Cenozoic era. In view of the above problems, we drilled a core which is 481.45 m long from Huainan city in the center of Huaibei Plain. We carried out sedimentology, sequence stratigraphy, magnetostratigraphy, geochemistry and paleoclimate (grain size, magnetic susceptibility, chromaticity etc.) analysis and research to this core. We mainly get the following conclusions:(1) The geomagnetic age framework and time series of the Huainan core (HN core) since the late Cenozoic (about 8 Ma) was established. According to the geomagnetic results and the records of the volcanic eruption, the age frame and time series of the late Cenozoic 481 m long core of the semi humid region of eastern China (Huaibei plain) were established for the first time. The basal age of the borehole is about 8 Ma, which indicates that the Cenozoic sediments in the central of Huaibei Plain began around 8 Ma. The depth of Quaternary and Pliocene boundary (2.588 Ma) is in 132 m, the depth of Pliocene and Miocene boundary (5.33 Ma) is in 286.1 m; B/M boundary (0.78 Ma) is in 72 m, G/G (Gauss/Gilbert boundaries 3.58 Ma) limits found in 200.0 m depths.(2) We established detailed and completed stratigraphic sequence for HN core and analyzed the sedimentary facies. We discovered the palaeoenvironment of late Cenozoic in Huaibei Plain as follows: river riverside lakeside alternate environment before Quaternary, mainly extensive floodplains environment since Quaternary. We reconstructed the climatic environment change sequence since the late Cenozoic (8 Ma) and roughly divided it into 8 major stages:I 8.0-7.8 Ma, oxidation environment, the climate is dry hot, alluvial facies;II 7.8-7.1 Ma, deep lake environment, the climate is very humid, lacustrine facies;III 7.1-3.7 Ma, long period river-riverside lakeside alternating environment. The climate is stable long period of humid-arid alternate fluctuation, river riverside lake facies;IV 3.7-2.7 Ma, river-river flat environment, climate transition period with rapid climate fluctuations, change from a relatively humid, more rainfall climate to reduced rainfall and drought climate.V 2.7-1.7 Ma, climate severe frequent fluctuation, river sedimentary environment with rapid climate fluctuations;VI 1.7-0.75 Ma, climate is relatively stable, relatively dry climate background;VII 0.55-0.75 Ma, lacustrine and swamp sedimentary environment, cold and wet climate, vegetation is lush, lacustrine facies;VIII 0-0.55Ma, flood plain deposits environment, relatively dry climate.(3) We first found that the structure scale climate of the semi humid area (Huaibei plain) in eastern China has the similar fluctuation characteristics and basic synchronization to the northwest arid and semi arid area (Loess Plateau).Late Neogene (7.1-3.7 Ma) in eastern China semi humid region and northwest semi arid climate are existed relatively stable long period humid-arid fluctuation characteristics and almost synchronous fluctuation; 3.7-2.7 Ma is a climate transition period, climate and environment change from humid climate to the relatively arid climate with fast and dramatic fluctuations. Eastern semi humid region and the northwest arid semiarid area are both become arid since Quaternary (2.6 Ma). The reason is that the climate from eastern semi humid area to northwest arid-semi arid region of China since Late Neogene (7.1-3.7 Ma) are mainly affected by the stability East Asian monsoon. The climate of eastern semi humid area and northwest arid-semi arid region are both become more drought because the Artic ice cap was formatted and developed since 7 Ma and lead to the monsoon strengthened.(4) We first discovered geological evidences of the Yellow River invasion into Huaibei Plain in about 13.2 ka BP. Through detailed geochemical analysis of top 8 m sediments of Huainan core, the results is that the TiO2/Al2O3, SiO2/Al2O3, Th/Nb, La/Nb values and REE patterns in the upper core (0–2 m) are similar to those found in samples from the Chinese Loess Plateau (CLP). These results suggest that the CLP in northern China is likely to be the primary origin of the upper part (0–2 m) of the Huainan core. Compared with CLP samples, the upper part of the Huainan core exhibits lower K2O/Al2O3 values and higher chemical alteration indices. The bottom age of the Yellow River floods is 13.2 ka BP (deglaciation), indicating that the Yellow River may have migrated into the Huaihe River catchment much earlier than the earliest historical records (361 BCE) suggest. The sediments may have been transported from the CLP to Huainan as Yellow River flood events, probably during the last deglaciation (13.2 ka) as a result of increased precipitation, along with glacier and snow melt in the upper reaches of the Yellow River catchment during this period. |
| 中文关键词 | 淮北平原 ; 晚新生代 ; 磁性地层 ; 古气候 ; 8 Ma |
| 英文关键词 | Huaibei Plain late Cenozoic magnetostratigraphy paleoclimate 8 Ma |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 第四纪地质学 |
| 来源机构 | 中国科学院地质与地球物理研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287671 |
| 推荐引用方式 GB/T 7714 | 张磊. 淮北平原晚新生代（8 Ma 以来）沉积地层与古环境变化[D]. 中国科学院大学,2016. |
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