本文選題：達(dá)連海　切入點(diǎn)：粒度　出處：《青海大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：青藏高原作為全球氣候變化的敏感區(qū),對(duì)于古氣候研究具有重大意義,而位于青藏高原東北部共和盆地的達(dá)連海是西風(fēng)帶與東南季風(fēng)交匯地區(qū),對(duì)氣候變化比較敏感,湖泊沉積物在記錄地球環(huán)境變遷信息方面具有連續(xù)性、敏感性和高分辨率的特點(diǎn),因此達(dá)連海是一個(gè)很好的研究地區(qū),對(duì)于了解和預(yù)測(cè)全球氣候變化有指導(dǎo)意義。本文選取共和盆地達(dá)連海湖泊沉積物為研究對(duì)象,在湖心取得深度為4m的淺井剖面,用AMS14C測(cè)年,底部年齡約3800 a B.P.,環(huán)境代用指標(biāo)粒度特征和孢粉顯示該區(qū)自3800 a B.P.以來,經(jīng)歷了由水動(dòng)力弱-強(qiáng)-弱-強(qiáng)4個(gè)階段,湖泊的水位經(jīng)歷了水位高,湖泊開闊、水位低,湖面較小、水位高,湖面開闊、干涸的過程,孢粉數(shù)據(jù)顯示景觀為草原和荒漠草原交替出現(xiàn),大約3800~2900a B.P.,氣候?yàn)闆鰸?為草原景觀,有少量的喬木植物生長(zhǎng),期間有過干旱過程;2900~1500 a B.P.,氣候干濕波動(dòng)明顯,風(fēng)砂活動(dòng)明顯,但整體上是相對(duì)寒冷干旱,景觀為荒漠草原;1500~400a B.P.,氣候逐漸好轉(zhuǎn),溫度略有上升,降水也有所增加,喬木很少,為草原景觀,期間也有風(fēng)砂活動(dòng);約400~0 a B.P.干旱加劇,湖泊變淺,風(fēng)砂活動(dòng)頻繁,植被類型為荒漠草原景觀。大約在3.0ka B.P.、2.7ka B.P.,1.6ka B.P.和0.8ka B.P.左右,四次顯示粉砂和砂組分都有明顯地增加,沉積物顆粒粗細(xì)變化大,孢粉含量減少,認(rèn)為是氣候變?yōu)槔涓墒录目赡�。位于達(dá)連海所處的共和盆地地區(qū),湖泊沉積物的沉積顆粒粗細(xì)與植被類型存在如下的關(guān)系:粗顆粒的沉積增加對(duì)應(yīng)的植被類型是以草本植物增多,細(xì)顆粒沉積增多對(duì)應(yīng)的植被類型是以木本植物增加。2900 a B.P~1500 a B.P期間,沉積顆粒粗細(xì)和植被類型變化十分明顯,表明氣候的波動(dòng)性不僅表現(xiàn)在大時(shí)間尺度(千年,百年)上,同時(shí)也反映在較短的時(shí)間(十年)尺度內(nèi)。
[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.
【學(xué)位授予單位】：青海大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：P532;P534.632

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