甘肃省双龙砂金矿床成因的研究

本文通过对双龙砂金砂床的地貌、沉积物、金的粒度及形态、矿床产出特征的研究，认为该矿床是在中晚更新世及全新世初期的冰川（水）的作用及化学作用下而形成的冰水堆积－阶地型砂金矿床。     

Glacial distribution and mass balance in the Yarlung Zangbo River and its influence on lakes

Glaciers in the Yarlung Zangbo River witness severe glacial retreat nowadays, which gives important influence on lake processes in the region. We have studied glacial distribution, glacial mass balance and found large deficit in glacial mass and its impact in the region. Our study also integrated the variation in glacial-fed lakes of the Nam Co and Ranwu Lake, and presented an initial assessment of the impact of glacial mass balance on lakes. The study has shown a significant contribution of glacial melting to recent lake expansion and lake level rising.     

青藏高原冰川退缩对河水径流的影响

青藏高原发育着36 793条现代冰川,冰川面积49 873.44 km2,冰储量4 561 km3,分别占中国冰川总条数的79.5%,冰川总面积的84%和冰储量的81.6%。进入20世纪以来,随着全球气候的波动变暖,特别是进入20世纪80年代以来的快速增温,使得大多数冰川处于退缩趋势。20世纪上半叶是冰川前进期或由前进期转为后退的时期;50年代至60年代冰川出现大规模退缩,但并未形成冰川全面退缩;60年代末至70年代,许多冰川曾出现前进或前进迹象,前进冰川的比例增大,退缩冰川的退缩幅度减小; 80年代以来,冰川后退重新加剧;90年代以来冰川退缩强烈。现在虽仍有个别冰川在前进,但高原冰川基本上转入全面退缩状态,这是20世纪90年代以来冰川变化的一个重要特征。 青藏高原哺育了亚洲的十多条河流,包括长江、黄河、恒河、印度河、雅鲁藏布江、怒江和澜沧江等七条最重要的河流。近数十年来,在全球变暖和冰川退缩加快的大背景下,青藏高原七大江河径流量亦呈现出不稳定的变化。从趋势上看,短期内冰川退缩将使河流水量呈增加态势,但亦会加大以冰川融水补给为主的河流或河段的不稳定性;而随着冰川的持续退缩,冰川融水将锐减,以冰川融水补给为主的河流,特别中小支流将面临逐渐干涸的威胁。     

南海海盆演变与深部海流

 南海在距今34 Ma之前的始新世从陆地变为海洋,古水深不断加深,至距今24 Ma之前的中新世/渐新世之交,由于T60构造运动,南海海盆整体进入深海环境。但是,自中新世以来随着吕宋岛弧向欧亚板块碰撞,南海海盆的半封闭程度在距今10.0、6.5、3.0和1.2 Ma之前加剧,导致南海深部海水只能来自巴士海峡海槛深度2600 m以浅的太平洋。此后,巴士海峡两侧的南海与太平洋深部海水交换,由于全球海平面变化,呈现冰期/间冰期模式。     

Change of bacterial community in the Malan Ice Core and its relation to climate and environment

In order to understand the relationship between the community structure of bacteria in ice core and the past climate and environment, we initiated the study on the microorganisms in the three selected ice samples from the Malan ice core drilled from the Tibetan Plateau. The 16S ribosomal DNA (rDNA) molecules were directly amplified from the melt water samples, and three 16S rDNA clone libraries were established. Among 94 positive clones, eleven clones with unique restriction pattern were used for partial sequence and compared with eight reported sequences from the same ice core. The phylotypes were divided into 5 groups: alpha, beta, gamma proteobacteria; CFB, and other eubacteria group. Among them, there were many “typical Malan glacial bacteria“ pertaining to psychrophilies and new bacteria found in the ice core. At a longer time scale, the concentration distribution of “typical Malan glacial bacteria“ with depth showed negative correlation with temperature variations and was coincident with dirty layer. It implied the influence of temperature on the microbial record through impact on the concentrations of the “typical Malan glacial bacteria“. In addition, the nutrition contained in ice was another important factor controlling the distribution of microbial population in ice core section. Moreover, the result displayed an apparent layer distribution of bacterial community in the ice core section, which reflected the microbial response to the past climatic and environmental conditions at the time of deposition.     

冰蚀湖相沉积物的环境磁学特征

以云南拱王山冰蚀湖(3579ma.s.l.)相沉积物为研究对象,对沉积物的磁化率进行实测研究,并与黄土、非冰川作用区的湖相沉积物相互校验,结果显示:冰蚀湖相沉积物的质量磁化率变化幅度大,老碳房剖面磁化率值介于 1.40～6.3333μm3·kg-1之间;频率磁化率普遍偏低,介于 0.011～0.2688 (μm3·kg-1)之间。对影响冰川作用区磁化率变化的因素进行了深入探讨,并阐述了运用磁化率变化反演环境变化的问题。     

Variations of organic carbon isotopic composition and its environmental significance during the last glacial on western Chinese Loess Plateau

The last glacial period is characterized by a cold and dry climate with low atmospheric CO2 concentration. The relatively arid climate and low CO2 concentration are favorable to the growth of C4 plants, but the low temperature limits the development of th…     

New evidence of deposition under cold climate for the Xieshuihe Formation of the Nanhua System in northwestern Hunan,China

Yangjiaping section is located in Hupingshan Town, Shimen County, Hunan Province. The section has been intensively studied since 1980. However, The paleoclimate during the deposition of the Xieshuihe Formation remains controversial. Based on chemical analysis of sedimentary clastic rocks of the unit, the resulting CIA (the chemical index of alteration) values of the Xieshuihe Formation are similar to those of the overlying Gucheng Formation (also called the Dongshanfeng Formation). It indicates that the sedimentary rocks of the Xieshuihe Formation and Gucheng Formation underwent the similar degrees of chemical weathering before deposition. Therefore, the Xieshnihe Formation was also likely to be deposited under a cold climatic condition, which probably belongs to a part of the record of glaciations.     

田桓铁路大前石岭隧道进口块碎石冻土成因机理

田桓铁路大前石岭隧道进口发现岛状多年冻土,该区域现在不具有发育多年冻土的气候、地理条件。根据对研究区的冰缘地貌现象分析,并对冻土采用不平衡U系法测年得知该冻土非现在气候条件下形成,而是形成于晚更新世末次冰期冰盛期,年龄为(12 279±79)年。现场对冻层测温表明该冻土是由于表面块石层气冷作用得以保持其热稳定性并保存至今,冻土表面7 m厚的块石层气冷作用使冻土温度平均降低约1. 5℃。开挖可能会破坏现有的热平衡体系,建议减少表层块石、碎石层的开挖。冻土测温加冻冰测年的方法为类似冻土研究提供了借鉴和参考,本研究成果可为田桓铁路建设提供了重要参数。     

末次冰盛期青藏高原冰川变化对亚洲气候的影响

以末次冰盛期(约2.6~1.9万年前)的气候为背景, 利用大气模式CAM4耦合陆面模式CLM4, 对青藏高原冰川规模扩大对气候产生的影响进行研究。结果表明, 末次冰盛期青藏高原冰川对北半球夏季的气候影响较显著, 除在冰川分布区引起显著的降温外, 通过遥相关作用, 还使得白令海峡附近显著升温。另外, 冰川产生的扰动会显著地增强南亚夏季风, 增加南亚地区降水。对比末次冰盛期与工业革命前时期不同气候态下青藏高原冰川规模扩大对气候的影响, 发现工业革命前时期的影响显著小于末次冰盛期, 说明青藏高原冰川对气候的影响与背景气候态有关。