宁绍平原末次冰消期以来的地貌和环境演化研究

发布时间：2018-03-10 12:07

  本文选题：XRF岩芯扫描　切入点：粒度　出处：《南京师范大学》2017年硕士论文　论文类型：学位论文

【摘要】：末次冰消期以来海平面上升,对人类尤其是沿海地区人们的生活环境产生较大的影响。海平面变化的研究已经成为全球变化研究的热点问题之一。长江三角洲因其重要的经济地位和独特的自然地理位置成为我国学者研究中国东部海平面变化的重要区域。长江三角洲处于构造沉降带,同时接收来自长江和钱塘江的河流沉积物,形成了一个广阔的近海平原。由于该区域地势平坦,极其容易受海面变化的影响,因此难以获得连续的、高分辨率的沉积序列。针对上述问题,本研究选取长江三角洲南侧的宁绍平原作为研究区域,以研究区内的自然钻孔HMD1401为研究对象,该区域受到东部舟山群岛和北部慈南山脉的屏障作用,沉积环境稳定,沉积地层连续,岩性单一,对研究长江三角洲的地貌演化具有重要的参考价值。本文通过对HMD1401孔的沉积相分析、年代框架的建立、粒度特征分析、典型元素地球化学分析,探讨宁绍平原末次冰消期以来的地貌与环境演化过程,主要得出以下结论:(1)末次冰消期以前(10.7kaB.P.):宁绍平原属于混杂的坡积物,沉积环境变化较大。古土壤层(第一硬粘土层)发育于厚约80cm的砂层之上,极有可能形成于水动力不强的静水环境。(2) 10.7～9.1 kaB.P.:这个时期为潮间带沉积环境,水动力较强,沉积环境逐渐由陆相沉积转化为海相沉积,宁绍平原由此逐渐进入浅海阶段。初期10.7～9.6kaB.P.之间应属于偶尔受海水影响的浅水洼地环境。9.6～9.1kaB.P.之间该区域可能处于近岸海湾环境。(3)9.1～6.5 kaB.P.:该阶段是海面上升的全盛时期,海平面快速上升,达到距今海平面至少-3 m左右的位置。陆源物质的输入也并不是稳定的,存在一定的沉积周期。海水淹没了整个宁绍平原,仅剩的一些低山和岛屿为河姆渡文化的发展提供了有限的生存空间。河姆渡早期人类就是在这样的地貌环境下生产和生活。(4) 6.5kaB.P.以后:该阶段宁绍平原海平面上升速度下降,但沉积物供给仍然丰富,最后成陆作用逐渐超过了海平面上升的速度,逐渐由海相沉积转变为陆相沉积。这为河姆渡文化的进一步壮大和繁荣提供了广阔的空间。并且我们认为在6.5 ka B.P.以后多次受到咸潮入侵的影响,而咸潮的入侵对河姆渡文化的发展必然会产生一定的负面影响。为保证研究结果的准确性,本文将HMD1401钻孔的元素扫描研究结果与HMD03的藻类、孢粉数据进行对比,发现海相性元素指标Ca和Mn尤其是Ca与沟鞭藻、藜科的变化具有较高的相似性;此外,将HMD1401的元素扫描结果与TLS13孔的XRD矿物鉴定结果进行对比,发现Ca和Mn的变化特征与蒙脱石具有一致性。
[Abstract]:Sea level has risen since the last ice age, The study of sea level change has become one of the hot issues in the study of global change. The Yangtze River Delta because of its important economic status and unique self. However, geographical location has become an important area for Chinese scholars to study sea level changes in eastern China. The Yangtze River Delta is located in a tectonic subsidence zone. Receiving river sediments from both the Yangtze and Qiantang rivers at the same time, forming a vast offshore plain. Because the area is flat and extremely vulnerable to changes in the sea, it is difficult to obtain continuity. High-resolution sedimentary sequence. In view of the above problems, the Ningshao Plain in the southern side of the Yangtze River Delta is selected as the study area, and the natural borehole HMD1401 in the study area is taken as the research object. The area is protected by the Zhoushan archipelago in the east and the Zinan Mountains in the north. The sedimentary environment is stable, the sedimentary strata are continuous, and the lithology is single. In this paper, the sedimentary facies of the HMD1401 pore, the establishment of the age frame, the grain size characteristics, the geochemistry of typical elements, and the analysis of the sedimentary facies of the HMD1401 pore are analyzed, which are important for the study of the geomorphological evolution of the Yangtze River Delta. The geomorphology and environmental evolution of Ningshao Plain since the last ice age are discussed. The main conclusions are as follows: before the last ice elimination stage, there were 10.7ka B.P.: Ningshao Plain belongs to mixed slope deposits. The paleosol layer (the first hard clay layer) developed above the sand layer about 80 cm thick, and most likely formed in the hydrodynamic hydrostatic environment.) 10.79.1 kaB.P.: this period is an intertidal sedimentary environment, and the hydrodynamic environment is relatively strong. The sedimentary environment gradually changed from continental to marine. Therefore, the Ningshao Plain gradually entered the shallow water stage, between 10.7 and 9.6kaB.P., which belongs to the shallow water basin environment, which is occasionally affected by seawater. The area may be in the coastal bay environment of 6.5kaB.P.: this stage is the heyday of sea level rise, and the sea level rises rapidly. At least 3 m above sea level, the input of land-based materials is not stable, and there is a certain period of sedimentation. The sea water inundated the whole Ningshao Plain. The remaining low mountains and islands provided a limited living space for the development of the Hemudu culture. It was in this geomorphological environment that the early Hemudu people produced and lived in such a geomorphological environment) 6.5kaB.P.After this stage, the sea level in the Ningshao Plain fell at a rate of decline. But the sediment supply is still abundant, and eventually the land-based process gradually exceeds the rate of sea-level rise. The gradual transition from marine to continental sediments provides a vast space for the further growth and prosperity of the Hemudu culture. And we believe that the saltwater intrusions have affected many times since 6.5 ka B.P. In order to ensure the accuracy of the research results, the elemental scanning results of HMD1401 boreholes are compared with the algae and sporopollen data of HMD03. It was found that the changes of Ca and mn, especially Ca and Verbenidae, were similar to those of Chenopodiaceae. In addition, the elemental scanning results of HMD1401 were compared with the results of XRD mineral identification in TLS13 pore. It is found that the change of Ca and mn is consistent with that of montmorillonite.
【学位授予单位】：南京师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P931;P736.2

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