【作者】 刘晓丽；

【导师】 杨太保；

【作者基本信息】 兰州大学 ， 自然地理学， 2010， 硕士

【摘要】 本文通过对处于青藏高原腹地BDQ0608钻孔106m岩芯高分辨率的孢粉指标的分析,结合磁化率、粒度、TOC等指标,运用磁性地磁学建立了BDQ钻孔的年代框架,尝试运用对水动力的变化较为敏感的0.2-7.5μm悬浮物质与深海氧同位素曲线进行对比,初步建立了BDQ钻孔的年代标尺。通过对BDQ钻孔环境代用指标的综合分析建立了可可西里地区中更新世以来的环境演化序列。根据地质调查分析和孢粉浓度与TOC、MS的关系对比,初步认为它们之间有很好的相关性,当孢粉百分含量很高时,TOC的曲线也处于一高值。后来又根据百分比花粉谱中的针叶林、阔叶林、草本和灌木植物各种类之间的相对含量关系的变化特征,结合聚类分析谱系,分为4个大带7个亚带。据此重建了古植被及古气候演化过程序列。730-700ka,旱生灌木和草本植物突然下降,如麻黄属、蒺藜科、蓼科等已经消失。针叶林云杉属增加幅度很大,花粉的总浓度达到了本岩芯的最大值159077.46粒／克。孢粉组合变化指示半荒漠草原处于一极度退化的阶段,而周围山地森林的退化开始缓解,气候冷湿。植被和孢粉气候指数变化均指示气候趋向一种冷湿的环境。700-455ka,孢粉组合变化指示半荒漠草原还是处于一种扩张的状态,而附近的山地森林不断退化,孢粉温度指数增加,湿度指数降低。植被和孢粉气候指数变化均指示气候趋向暖干。455-375ka,孢粉组合中藜科和蒿属有所下降,松属和云杉属有明显的增加,森林得到发育,半荒漠草原略有退化。375-345ka,针叶林的森林退化严重,植被类型以草原植被为主,气候干旱。345-265 ka,孢粉组合中旱生草本植物藜科和蒿属达到了极值,森林退化,半荒漠草原进一步发育,气候干旱。265-210ka,针叶林的松属和云杉属达到了本岩芯的峰值,气候针叶林得到扩张,面积达到了最大值,气候更加的湿冷。210-160ka,孢粉组合中藜科和蒿属含量降低,针叶林的松属和云杉属陡然上升,半荒漠草原退化,针叶林扩张,气候湿冷。160-25ka,孢粉组合主要以旱生草本植物藜科和蒿属为主的半荒漠草原为主,气候暖干。对研究区的岩芯的中值粒径、TOC、磁化率等综合指标曲线相对比有很好的对应性,存在一定的差异,但是此差异性是不能避免的,因为各个指标受控的因素不同。通过孢粉恢复的植被和气候具有高分辨率,结合其它的代用指标的对比,可以达到一个很高的准确率。更多还原

【Abstract】 Based on the qinghai-tibet plateau the thesis analysed many indicators of a 106-meter-long lake sediment of BDQ0608 core, established the date of BDQ core using magnetic geomagnetism,and tried to establish the time scale of the BDQ core,by contrast of the suspended material of 0.2-7.5μm which was more sensitive to the change of water power and deep-sea oxygen isotope curve.The author established the Hoh Xil region’s environmental evolution sequence through a comprehensive analysis of proxy climate indicator. According to geological survey analysis and pollen concentration in contrast to TOC and MS, the author viewed that they had a good correlation:the pollen concentration was very high,TOC curve had a high value. Later,the percentage pollen diagram was divided into four pollenassemblage zones, with seven subzones when necessary, based on stratigraphically constrained cluster analysis, according to the relative content of various types of relationships and changes in the concentration of pollen diagram characteristics of the percentage of pollen diagram in the coniferous forest, broadleaf forest, herbaceous plants and shrubs.730-700ka, there was a sudden drop in dry herbaceous plants such as Artemisia, Ephedra, while other dry herbaceous Ranunculaceae, Zygophyllaceae, Polygonaceae had disappeared.This sub-zone Picea had increased significantly.At this time the total concentration of pollen was up to the maximum of this profile 159,077.46 grain/gram. Pollen assemblage changes directed that a semi-desert steppe retreated, whereas,the forests on the surrounding mountain began to increase.Pollen temperature index decreased and humidity index increased.Pollen indicated that climate became cool and wet gradually.700-455ka, Pollen assemblage changes directed that a semi-desert steppe was still expanding, but forest was degenerate continuously on the mountains near the lake. Pollen temperature and the humidity index decreased.Vegetation and pollen climate index changes directed that the climate became warmer and drier.455-375ka, Chenopodiaceae and Artemisia decreaseed in the pollen assemblage, Picea increased significantly,and forests were developed,semi-desert steppe degenerated slightly. 375-345ka coniferous spruce genera and reduction, the core of a running, and herb’s chenopodiaceae and artemisia content is higher, the other representatives of thistles and drought in certain ephedra genera and peak. Thus, the coniferous forest may have deteriorated, vegetation types in grassland vegetation, dry climate.345-265ka, arid herb as Artemisia and Chenopodiaceae in the pollen assemblage was up to the maximum, and forest was degenerate,desert steppeland had the further development with an arid climate.265-210ka, coniferous forest of Pinus and Picea reached the maximum value of the pollen diagram, coniferous forests further significant expanded and reached the maximum, the climate was even colder and weter. 210-160ka, Chenopodiaceae and reduced in pollen assemblage, the coniferous forest of Pinus and Picea increased sharply, desert steppe retreated, coniferous forest prevailed, and the weather became cool.160-25ka, pollen assemblage was dominated by desert steppe plant including Artemisia and Chenopodiaceae, the climate was mainly warm and dry.To study the area size of the core, comprehensive, magnetic susceptibility TOC index curve is relatively good correspondence, there are some differences, but the difference is unavoidable, because each index controlled different factors. Through the pollen of vegetation restoration and climate with high resolution, combined with other substitution indexes, can achieve a high contrast the accuracy.更多还原