【作者】 程波；

【导师】 陈发虎；

【作者基本信息】 兰州大学 ， 自然地理学， 2006， 博士

【摘要】 共和盆地位于青藏高原东北边缘，处于现代亚洲季风影响的北界和中国干旱与半干旱气候的过渡地带，独特的地理位置和脆弱的生态系统使其对气候变化极其敏感，是研究区域气候对全球变化响应的理想地点。 在共和盆地中的沙珠玉河尾闾湖泊——达连海获取40.92m长的湖泊岩芯（DLH钻孔）。选用岩芯中植物残体作为测年材料，利用AMS ¹⁴C测年技术获得达连海钻孔10个绝对年龄，结合前人研究建立的达连海湖相沉积物¹³⁷Cs时标，估计其¹⁴C年龄的碳库为380年，在扣除碳库之后建立了达连海地区晚冰期14.6 Cal ka BP以来可靠的年代序列。对达连海钻孔岩芯样品进行孢粉分析（200个样品，70年分辨率）为主，粒度（1025个样品，15年分辨率）和碳酸盐含量分析（1029个，15年分辨率）为辅的多指标分析，重建共和盆地末次冰消期以来的古植被和古环境。 达连海钻孔高分辨率的孢粉分析显示，整个岩芯孢粉组合从下至上可划分为八个孢粉带。不同孢粉带变化的特征主要是以乔木花粉和草本与灌木花粉含量彼此消长为特点的，其中第Ⅰ、Ⅳ、Ⅴ和Ⅵ孢粉带，即14.6～12.3 Cal ka BP和8.9～3.4 Cal ka BP时段乔木花粉含量较高，以针叶树的云杉和松花粉为主，但草本和灌木花粉含量也较高；第Ⅱ、Ⅲ、Ⅶ和Ⅷ孢粉带，即12.3～8.9 Cal ka BP和3.4～0 Cal ka BP时段草本和灌木花粉占绝对优势，并以藜科、蒿属、禾本科和麻黄属为主要成分，乔木花粉含量较少。粒度分析结果显示达连海钻孔除13.10—14.53m（4.4-3.8 Cal ka BP）和39.16—40.90m（14.1-14.6 Cal kaBP）层位平均粒径＞100μm外，多数样品平均粒径变化在5.0—50.0μm之间，说明达连海钻孔样品主要以细颗粒为主。碳酸盐含量分析结果显示达连海钻孔沉积物的碳酸盐含量很低，除了两个平均粒径较大的砂层和19.85m—15.89m层位（6.8-5.0 Cal ka BP）碳酸盐含量变化幅度较大外，其他层位的含量变化较小。 通过孢粉及粒度与碳酸盐含量的多指标分析，重建末次冰消期以来共和盆更多还原

【Abstract】 Gonghe Basin is located on the northeast edge of Tibet Plateau and the northwest margin of modern summer monsoon where is the transitional boundary of arid and semiarid regions of China. Due to its unique geographical location and fragile ecological system, the basin is a suitable place for the research of regional climate in response to the global climate change.A 40.92m long core (DLH) was drilled in a terminal lake—Dalianhai Lake in Gonghe Basin. The preliminary chronology of which was established by AMS C-14 dating on several plant remains from the sediment. In combination with Cs-137 timescale of former study, the carbon reservoir effect of 380 yrs was deducted to give the final credible chronology of Dalianhai Lake since the late glacial. On the basis of this reliable chronology, the evolutionary history of palaeovegetation and palaeoenvironment in Gonghe basin during the late glacial and Holocene was reconstructed mainly by pollen analysis (200 samples with 70-yr resolution) and other proxies such as grain size (1025 samples of 15-yr resolution) and carbonate content (1029 samples with resolution of 15 yrs) as complement as well.The result of pollen analysis shows there are eight pollen zones can be partitioned in the whole pollen assemblages, and each zone is mainly characterized with the growth and decline of arbor or herbaceous pollen percentage. The arbor pollen percentages are relatively high in zone I, IV, V and VI, namely 14.6-12.3 Cal ka BP and 8.9-3.4 Cal ka BP, dominated by conifer pollen such as Picea and Pinus, but meanwhile the herbaceous and shrub pollen percentage are not very low. In Zone II, III, VII and VIII, around 12.3-8.9 Cal ka BP and 3.4-0 Cal ka BP, the更多还原