达连海湖泊记录的晚全新世环境演变

发布时间：2018-03-20 20:58

本文选题：达连海　切入点：粒度　出处：《青海大学》2015年硕士论文　论文类型：学位论文

【摘要】：青藏高原作为全球气候变化的敏感区,对于古气候研究具有重大意义,而位于青藏高原东北部共和盆地的达连海是西风带与东南季风交汇地区,对气候变化比较敏感,湖泊沉积物在记录地球环境变迁信息方面具有连续性、敏感性和高分辨率的特点,因此达连海是一个很好的研究地区,对于了解和预测全球气候变化有指导意义。本文选取共和盆地达连海湖泊沉积物为研究对象,在湖心取得深度为4m的浅井剖面,用AMS14C测年,底部年龄约3800 a B.P.,环境代用指标粒度特征和孢粉显示该区自3800 a B.P.以来,经历了由水动力弱-强-弱-强4个阶段,湖泊的水位经历了水位高,湖泊开阔、水位低,湖面较小、水位高,湖面开阔、干涸的过程,孢粉数据显示景观为草原和荒漠草原交替出现,大约3800~2900a B.P.,气候为凉湿,为草原景观,有少量的乔木植物生长,期间有过干旱过程;2900~1500 a B.P.,气候干湿波动明显,风砂活动明显,但整体上是相对寒冷干旱,景观为荒漠草原;1500~400a B.P.,气候逐渐好转,温度略有上升,降水也有所增加,乔木很少,为草原景观,期间也有风砂活动;约400~0 a B.P.干旱加剧,湖泊变浅,风砂活动频繁,植被类型为荒漠草原景观。大约在3.0ka B.P.、2.7ka B.P.,1.6ka B.P.和0.8ka B.P.左右,四次显示粉砂和砂组分都有明显地增加,沉积物颗粒粗细变化大,孢粉含量减少,认为是气候变为冷干事件的可能。位于达连海所处的共和盆地地区,湖泊沉积物的沉积颗粒粗细与植被类型存在如下的关系:粗颗粒的沉积增加对应的植被类型是以草本植物增多,细颗粒沉积增多对应的植被类型是以木本植物增加。2900 a B.P~1500 a B.P期间,沉积颗粒粗细和植被类型变化十分明显,表明气候的波动性不仅表现在大时间尺度(千年,百年)上,同时也反映在较短的时间(十年)尺度内。
[Abstract]:As a sensitive area of global climate change, the Qinghai-Xizang Plateau is of great significance for paleoclimate research. The Dalianhai Sea, located in the Gonghe Basin in the northeast of the Qinghai-Xizang Plateau, is an area where the westerly wind belt intersects with the southeast monsoon, and is sensitive to climate change. Lake sediments are characterized by continuity, sensitivity and high resolution in recording information on the Earth's environmental changes, so the Dalan Sea is a good research area. In this paper, the sediments of Dalianhai Lake in Gonghe Basin are selected as the research objects. Shallow well profiles with a depth of 4 m are obtained in the center of the lake, and AMS14C dating is used. The bottom age is about 3800 a B.P. the grain size characteristics of environmental substitution index and sporopollen show that the area has experienced four stages from weak hydrodynamic to strong to weak to strong since 3800 years B. P. the water level of the lake has experienced high water level, open lake, low water level and small lake surface. The water level is high, the lake is open, and the process of drying up. The sporopollen data show that the landscape appears alternately between the steppe and desert steppe, about 38000.2900a B.P. the climate is cool and wet, the climate is steppe landscape, and there are a small number of Arbor plants growing. During this period, there was a drought process, with obvious dry and wet climate fluctuation and obvious wind-sand activity, but on the whole, the landscape was relatively cold and arid. The landscape was desert steppe with a 400a B.P. the climate gradually improved, the temperature increased slightly, the precipitation also increased, and there were few trees. For the grassland landscape, there are also wind-sand activities during the period, about 400A B.P. drought intensifies, lakes become shallower, wind sand activities are frequent, vegetation types are desert steppe landscape, about 3.0ka B.P. (2.7ka B.P.) 1.6ka B.P. and 0.8ka B.P. Four times it was shown that the silt and sand composition were obviously increased, the grain thickness of sediment changed greatly, and the content of sporopollen decreased, which was considered to be the possibility of climate turning into cold and dry events, which is located in the Gonghe Basin area of the Dalianhai Sea. The grain thickness of lake sediment has the following relationship with vegetation type: the increase of coarse grain sediment corresponds to the increase of herbaceous vegetation type. The vegetation type corresponding to the increase of fine grain deposition is that the variation of grain thickness and vegetation type is very obvious during the period of the increase of woody plant. 2900a B.Pf1500a B.P. it indicates that the fluctuation of climate is not only on a large time scale (millennium, hundred years), but also on a large time scale (millennium, 100 years). At the same time, it is also reflected in a relatively short time (ten years) scale.
【学位授予单位】：青海大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P532;P534.632

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