【作者】 王君兰；

【导师】 张家武；

【作者基本信息】 兰州大学 ， 自然地理学， 2012， 硕士

【摘要】 黑河下游额济纳绿洲的生态环境退化已经引起国内外的广泛关注,黑河尾闾湖处于东亚夏季风的尾闾和西风带的相交范围,可以敏感地响应气候环境的变化。本研究选取内蒙古额济纳盆地嘎顺诺尔GXN剖面为研究对象,对湖泊沉积物进行粒度、磁化率、碳酸盐含量、矿物含量及组成、有机碳含量、C/N比值及有机碳同位素613C值等多指标综合测试,根据代用指标及年代结果,可以将嘎顺诺尔GXN剖面近千年来的环境演化划分为三个阶段。200～110cm(约874～1364AD),剖面底部沉积特征具有明显的河流二元相沉积结构,这是由于黑河下游中部河流改道、从剖面位置附近入湖,洪水过后时较细颗粒沉积在河漫滩。该段整体为浅湖相夹杂风成砂沉积,湖水较浅,水动力较强且风沙活动频繁。气候偏干,对应中世纪暖期；110～20cm(约1364～1853AD),此时期剖面位置经近岸浅水至稳定的深水湖泊环境,湖泊面积开始扩大,入湖水量较为稳定,水动力较弱,气候相对湿润,该段对应小冰期；20～0cm(约1853～1962AD),河流来水减少,湖泊水位缓慢降低,湖泊开始退缩,最终于1962年干涸。该段气候偏干,对应20世纪以来的全球变暖。区域对比研究表明,嘎顺诺尔GXN剖面的湖相沉积很好地记录了近千年来的气候事件,以“中世纪暖期较干—小冰期较湿—近百年来暖干”为特征。这与我国西北内陆干旱区内不同地点的其它各种代用指标重建的过去千年气候变化序列整体上具有很有的一致性。尤其是在小冰期整体表现为冷湿的特征,与西北干旱区近千年来湿度变化特征相符,为探讨西北干旱区湖泊形成的原因和气候变化机制提供了重要的湖泊代用记录资料。更多还原

【Abstract】 The ecological environment deterioration of Ejin oasis at the lower reaches of Heihe River has drawn abroad attentions. The Gaxun Nur lake is situated the inland arid area in northwestern China,being sensitivity to global climate changes in this region. A2m-long section,GXN was obtained from Gaxun Nur for multiproxy analyses. Based on the lithology, chronology, and the variations of the proxies, three stages of environmental changes were recorded by lake sediments during the past millennium.The lower part of the section (200～110cm, corresponding to874～1364AD), has obvious river-binary structure, caused by river diversion of the lower reaches of Heihe River, resulting in fine-grained components deposited on the flood plain. The characteristics of the grain-size frequency curves of the lake sediments indicate that there are mixed depositions of fluvial and wind. Shallow lake deposit mingled with the aeolian sands. The climate was drier, corresponding to the Medieval Warm Period (MWP); The middle part of the section (110～20cm:1364～1853AD) indicated the environment changed from off shore shallow water to stable deep water. The lake area increased, and the climate became wetter, corresponding t the Little Ice Age(LIA); The upper section (20～0cm:1853～1962AD) indicated that the runoff reduced and the lake shrunk, finally dry up in1962.Regional comparison shows that climate events(MWP、LIA and the20century warming period) of the past millennium were well documented by the lake sediments of GXN section. The humid LIA in this region corresponds well with the characteristic of the LIA reported in northwestern China. The lake sediments of the past millennium reveals both natural environment change and human activities, since entering20centuries.更多还原