Knowledge Resource Center for Ecological Environment in Arid Area
| 全新世呼伦湖区水文和气候变化的介形类记录 | |
| 翟大有 | |
| 出版年 | 2011 |
| 学位类型 | 博士 |
| 导师 | 肖举乐 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 未来全球变暖将对我国北方半干旱区的水循环产生何种影响，是学术界关注的热点问题。本文详细分析了内蒙古呼伦湖HL06沉积岩芯的介形类组合及介形类壳体地球化学特征，基于AMS 14C年代标尺，恢复了全新世呼伦湖水位、盐度及水温的变化过程。结果表明：距今11,100–8300日历年前，喜淡/冷水的史氏达尔文介繁盛，喜冷的疏忽玻璃介和侯氏玻璃介（比较种）较丰富，喜暖的土星介稀少，浅水种未出现，Mg/Ca和Sr/Ca比值低，δ18O偏轻，说明湖泊水位高，湖水淡而冷。8300–6200年前，土星介丰富，史氏达尔文介急剧减少，浅水种稀少，Mg/Ca和Sr/Ca比值低，δ18O偏轻，反映湖泊水位仍高，盐度仍低，但湖水转暖。6200–4300年前，浅水种频繁出现，土星介大量减少，Mg/Ca和Sr/Ca比值持续升高，表明湖泊逐渐收缩，盐度升高，湖水变凉。4300–3350年前，浅水种繁盛程度达全新世之最，说明湖泊水位大幅度下降。3350–1900年前，浅水种几乎消失，土星介显著增加，Mg/Ca和Sr/Ca比值呈降低趋势，δ18O逐渐变轻，说明水位回升，湖水变暖。1900–500年前，湖泊基本保持前一阶段的水文状况，但在1100–800年前，湖面降低，盐度升高，湖水变暖。最近500年，浅水种较少，Mg/Ca和Sr/Ca比值逐渐降低，δ18O逐渐变轻，说明湖泊逐步扩张，湖水变淡。呼伦湖介形类记录暗示，东亚夏季风直到约8300年前才显著增强，这可能是早全新世北半球高纬残存冰盖抑制了季风雨带北进的结果。4300–3350年前，季风降水显著减弱，可能与低纬西太平洋海表温度下降有关。 |
| 英文摘要 | More and more attention is being paid to the effect of future global warming on the hydrological cycle in the semi-arid area of northern China. In this study, a sediment core recovered in the central part of Hulun Lake in northeastern Inner Mongolia was analyzed for the species assemblage and shell geochemistry of ostracodes. AMS 14C time series of the proxy data documents a detailed process of changes in the water level, salinity and temperature of the lake during the Holocene. During the early Holocene between ca. 11,100 and 8300 cal yr BP, fresh/cold-adapted D. stevensoni was abundant, warm-adapted Ilyocypris was scarce, littoral ostracodes were absent, and Mg/Ca, Sr/Ca and δ18O were low, indicating high stands and cold/fresh waters of the lake. From 8300 to 6200 cal yr BP, Ilyocypris flourished, D. stevensoni declined, and Mg/Ca, Sr/Ca and δ18O were still low, implying that the lake succeeded high levels but shifted to warm/fresh waters. The lake began to contract and the water became cool/brackish 6200–4300 cal yr BP as suggested by the appearance of littoral ostracodes, decline of Ilyocypris and high elemental ratios. During the interval of 4300–3350 cal yr BP, littoral ostracodes flourished, marking an extreme drop in the lake level. Littoral ostracodes almost disappeared, Mg/Ca and Sr/Ca decreased and δ18O became light 3350–1900 cal yr BP, denoting a recovery of the lake level. The lake maintained the status of the preceding stage during the episode of 1900–500 cal yr BP although the lake assumed relatively lower stands and higher salinities 1100–800 cal yr BP. During the recent 500 yr, reduced littoral ostracodes and decreased Mg/Ca, Sr/Ca and δ18O demonstrate that the lake expanded gradually and the water was freshened. Based on the ostracode data, the author suggests that the East Asian summer monsoon wasn’t intensified until 8300 yr ago, which might result from the restrained northward penetration of the monsoon rainfall belt by the remnant ice sheets in the Northern Hemisphere during the early Holocene. An obvious weakening of the monsoon precipitation 4300–3350 cal yr ago might be related to a decrease in the temperature of the surface waters in the western tropical Pacific. |
| 中文关键词 | 呼伦湖 HL06岩芯 ; 介形类 ; 湖水盐度 ; 水温 ; 东亚季风 ; 全新世 |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 第四纪地质学 |
| 来源机构 | 中国科学院地质与地球物理研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/286905 |
| 推荐引用方式 GB/T 7714 | 翟大有. 全新世呼伦湖区水文和气候变化的介形类记录[D]. 中国科学院大学,2011. |
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