28ka以来莱州湾南岸的沉积学记录及环境意义

发布时间：2018-02-10 04:40

本文关键词： 粒度粘土矿物风化作用 28kaB.P. 东亚季风　出处：《中国地质大学（北京）》2014年硕士论文　论文类型：学位论文

【摘要】：本文针对莱州湾南岸BH2钻孔上部14.70m岩心资料，通过年代学结果、粒度和粘土矿物的特征及其包含的环境代用指标意义的解读，对比研究区内的已有成果、其他研究材料的环境信息及全球变化特征，解释了莱州湾南岸平原28ka以来的沉积学记录，并讨论了其环境意义。主要结论如下： 1、利用光释光（Optical Stimulated Luminescence, OSL）年代学方法内插获得了BH2孔的年代学标尺。结果显示BH2孔沉积时限为28ka，5.94ka B.P沉积速率发生一次大的转折，28~5.94ka B.P.阶段沉积速率为0.14m/ka，5.94ka以来沉积速率为1.97m/ka。通过对比BH1孔和Lz908孔的沉积特征，沉积速率的转折是由于气候变暖背景下物质输运量增大，高海面期后海水对河水能量的抵消作用减弱，造成沉积物的迅速堆积。 2、粘土矿物含量具有分段性。可分为底部蒙脱石和高岭石低值、伊利石高值段，中部蒙脱石和高岭石高值、伊利石低值段，上部蒙脱石、高岭石和绿泥石低值、伊利石高值段3段。沉积物的母岩主要为极低变质作用和浅变质作用形成的岩石；黄河来源的沉积物和山东半岛黄土也可能为莱州湾南岸的两个物源。伊利石的化学指数和膨胀层的相对数量在韵律上变化相同，，但不能反映全新世变暖背景下的化学风化作用，分析是由于物质输入量的大幅增加及海面变化所导致。 3、粒度反映出沉积物类型具有分段性。不同环境的沉积物粒径大小明显不同，其中全新世之前的沉积物表现为细粒沉积，而全新世内的沉积过程形成了粗粒沉积。平均粒径和分选系数反映出了海平面变化影响下的沉积过程特征：海面升高时，海水与河水能量抵消，潮流、波浪对沉积物的淘洗和再悬浮作用强烈，反映了低速的沉积过程；海水退去时，河流快速堆积，沉积速率较大，分选较差，反映了河流沉积的特征。 4、粒度的主成分分析结果表明，第一主成分F1的方差贡献量为54.7%，控制了整个沉积物的粒度变化；第二主成分（F2）的方差为22.5%，前两个主成分涵盖了沉积物的大多数组分。F1变化与细粒组分含量相同，可以指示东亚冬季风的变率，而F2与中粗粒组分含量变化相同，可以指示东亚夏季风的变率。冬季风和夏季风在变冷过程中呈正相关关系，两者在偏暖环境下呈负相关关系。
[Abstract]:Based on the data of 14.70m core in the upper part of BH2 borehole on the south bank of Laizhou Bay, this paper compares the existing results in the study area through the interpretation of the geochronological results, the characteristics of granularity and clay minerals, and the significance of the environmental substitute indicators included in the study area. The environmental information of other materials and the characteristics of global change explain the sedimentological records of Laizhou Bay South Coast Plain since 28ka and discuss their environmental significance. The main conclusions are as follows:. 1. The geochronological scale of BH2 pore was obtained by means of optical Stimulated chronology method. The results show that the deposition time of BH2 pore is 28ka- 5.94ka B.P. the deposition rate of BH2 pore is 0.14m / Ka5.94ka B.P. By comparing the sedimentary characteristics of the BH1 pore and the Lz908 pore, The change of sedimentation rate is due to the increase of mass transport under the background of climate warming and the weakening of the counteracting effect of seawater to the river water energy after the high sea level, which results in the rapid accumulation of sediment. 2. The clay mineral content is segmented. It can be divided into low value of bottom montmorillonite and kaolinite, high value of Illite, high value of middle montmorillonite and kaolinite, low value of Illite, low value of upper montmorillonite, kaolinite and chlorite. The parent rocks of the sediments are mainly formed by very low metamorphism and shallow metamorphism. The sediment from the Yellow River and loess from Shandong Peninsula may also be two provenances from the southern shore of the Laizhou Bay. The chemical index of Illite and the relative quantity of the expander are the same in rhythm, but they cannot reflect the chemical weathering in the warm background of Holocene. The analysis is due to a large increase in material input and changes in the sea surface. 3, the grain size shows that the sediment type is segmented. The size of sediment is obviously different in different environments, and the sediment before Holocene is fine grained. The mean particle size and sorting coefficient reflect the characteristics of the sedimentary process under the influence of sea level change: when the sea level rises, the energy of sea water and river water cancel, the tidal current, and the mean particle size and separation coefficient reflect the characteristics of sedimentary process under the influence of sea level change. The washing and resuspending of the sediments by waves reflects the process of low-velocity deposition, and the rapid accumulation of the rivers when the sea water retreats, the high deposition rate and the poor separation, which reflect the characteristics of the river sediments. 4. The results of principal component analysis of grain size showed that the variance contribution of the first principal component F1 was 54.7, which controlled the grain size change of the whole sediment. The variance of the second principal component (F2) is 22.5.The first two principal components cover most of the sediment components. The changes of .F1 are the same as the contents of fine-grained components, which can indicate the variability of the East Asian winter monsoon, while the changes of F2 and the contents of the middle coarse grains are the same. The winter monsoon and summer monsoon have a positive correlation with each other in the process of cooling, and there is a negative correlation between the winter monsoon and the summer monsoon in the warm environment.
【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】：2014
【分类号】：P736.2

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