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题名 新疆博斯腾湖记录的亚洲中部干旱区全新世气候变化研究
姓名 黄小忠
院系 资源环境学院
专业 自然地理学
学位名称 理学博士
外文题名 Holocene Climate Variability of Arid Central Asia Documented by Bosten Lake, Xinjiang, China
第一导师姓名 陈发虎
关键词 亚洲中部干旱区;气候变化;全新世;博斯腾湖
外文关键词 Arid central Asia;climate change;Holocene;Bosten Lake
学科 理学
摘要 亚洲内陆干旱区不仅对于全球气候变化非常敏感而且对于全球气候变化有较大的贡献。博斯腾湖是我国最大的内陆淡水湖,由于其主要受到西风带来的降水的影响,因而可以良好的记录西风影响区全新世气候变化的模式和过程。本文通过对采自博斯腾湖的多个岩芯和湖泊表层沉积物的孢粉、碳酸盐、粒度、磁化率以及少量钻孔样品的介形虫及其同位素、有机质含量等多指标的分析,在岩芯进行210Pb和137Cs,AMS C-14和OSL测年的基础上,重建了区域晚冰期以来的气候环境演化过程,并通过广泛的区域对比和分析得出以下结论和初步认识: 1、 通过对湖泊表层沉积物的多指标分析结果表明,其孢粉组合的差异主要体现了近岸植被的影响,湖滨的孢粉组合主要受近岸植被的影响,而湖泊中心的花粉组合反映的是区域的植被状况;孢粉的A/C比值能够反应区域的干湿状况。沉积物中盘星藻的初步分析表明,盘星藻浓度与水深关系比较密切,当水深超过一定深度(约10 m)时,沉积物中盘星藻的浓度迅速升高。鉴于盘星藻是一种淡水藻类,其在地层中浓度的变化可能既指示盐度也指示水深。 2、 用活塞钻从博斯腾湖钻取了5组岩芯,分析表明湖相沉积物覆盖于一厚层砂层沉积之上。对其进行了可靠的定年研究;共计测量了该岩芯19个AMS C-14年代,利用其中3个陆生植物残体的年代与等深度总有机质测年的差别校正了其它总有机质测年的碳库效应(约1140年);利用OSL测年的方法对两组岩芯底部的风成砂层进行了测年。结果表明,岩芯覆盖了晚冰期以来的地层,对湖相沉积物底部岩芯的AMS C-14测年以及风砂沉积顶部的OSL测年结果表明,现代意义上的湖泊水体形成于约8400 cal yr BP左右。 3、 孢粉组合:对岩芯的孢粉分析结果表明,在砂层中没有统计到足够的孢粉,而湖相沉积物中孢粉含量丰富,孢粉的主要成分为藜科、蒿属、禾本科、麻黄属、香蒲属等花粉。钻孔中孢粉组合最显著的特征是岩芯下部麻黄属花粉的髙含量以及岩芯中上部香蒲属花粉的峰值段。对钻孔孢粉组合的主成分分析表明,第二主轴上样品的因子荷载可以代表区域湿度的变化。盘星藻浓度在钻孔下部(8.4~6 cal yr BP)较低,而在岩芯中部较高。 4、 全新世气候变化框架和模式:博斯腾湖记录的气候变化模式为晚冰期到早全新世(16~8.4 cal ka BP)气候较干旱,从8.4 cal ka BP开始博斯腾湖开始形成,代表区域气候开始变湿,但最湿的时段发生在6~2.5 cal ka BP之间。与季风区石笋记录的季风演化过程对比发现,亚洲季风强度的变化与西风区湿度的变化相反,在早全新世较强而中晚全新世变弱。与冰期、间冰期旋回两大区域的同步的冷干暖湿气候不一样,在间冰期内季风区表现为冷干暖湿,而西风区主要表现为冷湿暖干的气候配置。全新世季风、西风演化过程可能能够解释中全新世季风边缘区的气候干旱。 5、 2000年来的气候与历史:博斯腾湖多指标记录的2000年来的干湿变化与古里雅冰芯积累量对应较好,并且与历史变迁可以基本对应,表现为汉代与唐代的湿润期对应于文化的传播、丝绸之路的繁荣,而其间的干旱期则导致了楼兰古城的衰落。中世纪的干旱使得西域与中...
外文摘要 The arid central Asia is sensitive to global climate change. Bosten Lake, the largest inland freshwater lake in China, is strongly influenced by westerly and can document the model and process of the climatic variations of westerlies dominant area during the Holocene. Based on the age model constructed with 210Pb, 137Cs, AMS C-14 and OSL dating results, multiproxy analysis of core sediments and surface sediments, including pollen analysis, carbonates content, grain size, magnetic susceptibility, has been applied to reconstruct the regional climate variability since late glacial. The primary conclusions are as follows: 1. A modern process within the Bosten Lake was investigated to understand the environmental significance of the proxies. Pollen analysis of the surface sediments suggested that the main difference of the pollen assemblages within the Bosten Lake was caused by the plants on the shore, and the pollen assemblage from the center of the lake could generally represent the regional vegetation scenery. On the other hand, it is also notable to consider the river induced influence on depositional process of the pollen grains. The pollen A/C index can generally reflect the arid state of the area. Like other lakes, the pollen concentration is correlated to the water depth, having a higher concentration in the lake center than that of the shallow water area. The growth of Pediastrum algae is strongly correlated with water depth and its concentration increase rapidly when water depth exceeds around 10 meters. Because Pediastrum algae is a kind of freshwater algae, its concentration variations can generally reflect both water salinity and lake depth. The spatial distribution of other proxies of the surface sediments also showed evident patterns. Grain size is much bigger in lake surrounding area than that from the center, and it can reflect the water dynamics and regional rainfall for the core sediments from the depocenter. Caclium carbonate content distribution shows a zonal pattern, and it is low in the river mouth area and southern part of the lake. Magnetic susceptibility varies reversely to that of calcium carbonate content, which might be related to terrestrial debris input brought by river. 2. Five groups of cores were retrieved from Bosten Lake, and the stratigraphy was comparable, which indicated that the lake sediments accumulated on a thick layer of sand. An age model of BST04H core was constructed by using ...
研究领域 环境变化
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