【作者】 陈英玉；

【导师】 蒋复初；

【作者基本信息】 中国地质科学院 ， 第四纪地质学， 2009， 博士

【摘要】 共和盆地位于我国西南季风、东亚季风和西风的交汇带以及干旱半干旱地区过渡带,荒漠化十分严重,特殊的地理位置和脆弱的生态环境对全球变化非常敏感。开展对青藏高原东北缘的共和盆地的气候环境演变研究不仅了解共和盆地的历史,而且对准确评估气候变化和人类活动对我国荒漠化的影响制定对策提供科学依据。本文选择位于共和盆地东部的达连海湖泊（现已干涸）为研究对象,在湖心取得2个深度分别为2.52m（达连海Ⅰ剖面）和2.60m（达连海Ⅱ剖面）的浅井剖面。其中Ⅰ剖面AMS¹⁴C年测年表明底部年代为5600 cal a BP。选取湖泊沉积物的粒度、磁化率、碳酸盐含量以及色度等作为环境代用指标。达连海环境指标分析显示,沉积物细,反映水动力较弱,反之就较强;磁化率和中值粒径有较好的对应,反映在气候温暖湿润时,磁化率高,气候变凉变干时,磁化率较低;达连海的碳酸盐含量较低,也与中值粒径对应较好;色度的L^*和碳酸盐含量之间的相关性不明显,与有机质含量关系密切;L^*与a^*、b^*之间也不存在相关性,但a^*、b^*之间存在正相关,后二者均反映出温湿—冷干的波动。达连海自中全新世以来的气候环境演变可划分为以下四个阶段:Ⅰ阶段:5600～5100cal a B.P.期间,气候温暖湿润,为全新世气候环境条件最好的阶段,有机质含量丰富,Ⅱ阶段:5100～2500cal a B.P.期间,温度有所降低,气候温凉偏干,有机质含量较多;Ⅲ阶段:2500～800cal a B.P.期间,温度有所回升,降水有所增加,有机质含量少;Ⅵ阶段:800～0cal a B.P.期间,气候表现为寒冷干燥。研究表明,达连海所反映的中、晚全新世以2500 cal a B.P.为界线;在中全新世气候温暖湿润期内,存在大致3700～4100 cal a B.P.干冷气候事件。在晚全新世发生了明显的几次冷干事件,其中最后1次对应于小冰期;大约在800～1200 a A.D达连海记录到中世纪暖期的存在。共和盆地近代气候变化分析表明,从20世纪60年代以来一直是逐渐升温的,各季节气温和降水变化趋势不一致,进一步表明西南季风减弱的可能,共和盆地目前降水偏少的暖干环境与地面大气环流形势变化有关,而太阳活动可能是驱动短期温度变化的主要因素。更多还原

【Abstract】 Gonghe Basin located in the transition zone of the westerly,Asian southeastern and southwestern monsoons, and between arid and semi-arid places, Where desertification is very serious. Being Special location,The fragile ecological environment attributed to more sensitive to global climatic changes.Therefore,studying on the paleo-climate and paleo-environment of Gonghe Basin not only help to clarify the environmental drying history of past in Gonghe Basin But also for the accurate assessment of climate change and human activities on desertification in China that may affect further to combat desertification, dust storms reduce hazards, the development of adaptation and mitigation of global climate change to provide a scientific basis.This article choose two shallow profiles from Dalianhai Lake for studying , respectively , Dalianhai profile I is 2.52m , Dalianhai profile II is 2.60m . Based on AMS¹⁴C dating and chronological study, the bottom ages of Dalianhai profile I is about 5600 cal a B. P. Combine with grain-size ,magnetic susceptibility,CaCO₃ content and color of Lacustrine sediments as environmental proxies. the result showing after analysis that Fine sediments reflecting on weak hydrodynamic,while the coare one indicate strong;The magnetic susceptibility is Better Corresponds to the medium grain-size of Lacustrine sediments, when warm ahd wet,. The value of High magnetic susceptibility is high ,contray to Cool and dry environment ; The CaCO₃ content is better sensitive to the regional climate change;The L^* of color,is less Corresponds to CaCO₃ content, but close relationship with organic matter, a^*and b^* of color, Consistent with c environment changes, both are reflecting on climatic changes of warm-wet and cold-dry.The climate and environment changes of Dalianhai Lake In Gonghe Basin since the Mid-Holocene can be divided into the following four stages:Ⅰ5600-5100cal a B.P., the mildest climate conditions with a warm and humid, Richer in organic matter;Ⅱ5100-2500cal a B.P., lower temperature, a cool but arid stage,the organic matter is rich.Ⅲ2500-800cal a B.P., warmer than the previous stage ,the precipitation is increase a little, the organic matter is less.Ⅳ800-0cal a B.P., a cold and dry arid stage.The results also indicate of all environmental proxies that 2500 cal a B.P. is the boundary of the Middle and the Late Holocene in Dalianhai lake, there is a colder and drier climatic event about 3700-4100 cal a B.P. in The Mid-Holocene , And the several times obvious cold events in the Late Holocene , Among them the last one corresponds to the Little Ice Age（LIA）. About 800- 1200 a A.D The Medieval Warm Period was recorded in Dalianhai Lacustrine sediments which provide the evidence of existence in the western region of China.By analysis modern climate changes of Gonghe Basin,the temperature is Gradual increased began in 60’s During the 20th century,.The seasonal changes in temperature and precipitation trends are inconsistent, The southwest monsoon probabily weakening gradually, Now, the warmer and drier environment in Gonghe Basin with low precipitation corresponds to the atmospheric circulation, The solar activity may be the main Driving factors at the short-term temperature changes更多还原