【作者】 孙庆峰；

【导师】 陈发虎； 赵艳； Christophe Colin； 张家武；

【作者基本信息】 兰州大学 ， 自然地理学， 2009， 博士

【摘要】 本文利用青藏高原东北边缘共和盆地中的沙珠玉河尾闾湖泊——达连海获取40.92m长的湖泊岩芯（DLH钻孔）和湖岸阶地年代开展了古气候重建研究。选用岩芯中植物残体作为测年材料,利用AMS ¹⁴C测年技术获得达连海钻孔10个绝对年龄,结合前人研究建立的达连海湖相沉积物¹³⁷Cs时标,估计其¹⁴C年龄的碳库为380年,在扣除碳库之后建立了达连海地区晚冰期14.5cal kaBP以来可靠的年代序列。对达连海钻孔岩芯样品进行粘土（200个样品,70年分辨率）为主,和粒度、碳酸盐、岩相和沉积速率为辅的多指标分析,重建共和盆地末次冰消期以来的古气候和环境。达连海钻孔高分辨率粘土矿物中的伊利石、绿泥石和蒙脱石的含量与结晶度、粘土矿物比值能很好的反映气候和环境变化特征,但高岭石含量反映的变化不甚明显。结合粒度、碳酸盐、岩相和沉积速率多指标综合分析,末次冰消期以来共和盆地的古环境和气候演化历史经历了以下几个阶段:末次冰消期（14.5-11.3 cal ka BP）,伊利石和绿泥石含量、结晶度高,蒙脱石含量低,蒙脱石/（伊利石+绿泥石）和高岭石/蒙脱石比值低,气候总的特征表现为干冷,以较强的物理风化为主,达连海湖泊水位较浅,水生植物不发育。但其间气候有明显的突变,即在12.9-11.3cal ka BP之间,气温升高或湿度增加,对应Bφlling-Allerφd时期。在早、中全新世（11.3-4.5cal ka BP）期间,伊利石和绿泥石含量、结晶度变低,蒙脱石含量增高,蒙脱石/（伊利石+绿泥石）和高岭石/蒙脱石比值增高,表现为气温由低逐渐升高、湿度加大,在中全新世的6.0calka BP左右达到极盛。在此期间化学风化作用增强,湖泊水位上升,早起湖泊水位较浅,湖泊生长较多植物,湖泊堆积较多的泥炭层;但早全新世的11.3～10.0cal ka BP,气候突然变得干冷,持续大约1.0cal ka,此段为转换期;在中全新世的晚期,气候变的干旱。在晚全新世（4.5～0.0cal ka BP）粘土矿物的特征与全新世前类似,气候再次变为干冷,物理风化作用盛行,湖泊水位变浅,水生植物不发育,泥炭层堆积很少。DLH孔粘土矿物与孢粉反映的气候与环境特征对比表明,粘土矿物能和孢粉一样反映气候和环境的变化特征,二者反映的事件序列是相同的,在大的一些时段上二者反映的气候和环境是一致的。尤其在中、晚全新世期间二者反映的变化时段一致性较好,其它时段粘土矿物要比孢粉滞后大约1.0cal ka。达连海末次冰期及冰消期高湖面出现在～25-10ka,全新世的高湖面出现在中全新世的～8.0-5.0ka BP。通过与其他青藏高原研究点的末次冰期来的气候和环境变化的记录及季风代用指标的对比,发现达连海粘土所记录到的共和盆地气候变化与它们基本一致,如Bφlling-Allerφd时期,共和盆地湿润与青藏高原季风加强湿度增加相一致;新仙女木事件发生时高原许多地点湿度降低;从早全新世开始季风逐渐增强,中全新世高原季风强盛,与共和盆地周围山地森林发育、气候湿润的时期可对应;晚全新世期间共和盆地气候干旱,与青藏高原全新世季风退缩,山地森林萎缩,整体湿度降低的时间一致。西南季风对本区气候和环境具有重要影响。然而,东亚季风和南亚季风在本区所起作用的程度以及季风的机制有待进一步的研究。更多还原

【Abstract】 A 40.92m long core （DLH） was drilled in a terminal lake, Dalianhai, of Shazhuyu River in Gonghe Basin, Northeast Tibet Plateau. The preliminary chronology of the core was established by AMS ¹⁴C dating on 10 plant remains from the core sediment. In combination with ¹³⁷Cs timescale of previous study, the carbon reservoir effect of 380a was deducted to give the final credible chronology of DLH core since the late glacial. On the basis of this reliable chronology, the evolutionary history of palaeoclimate and palaeoenvironment in Gonghe Basin since the late glacial and Holocene is reconstructed by clay mineral （200 samples with 70a resolution） and other proxies as grain size （200 samples with 70a resolution） , carbonate content （1,029 samples with resolution of 15 a）, Petrological face, sedimentary rate and lake retraces as well.The contents, crystallities and ratios of illite, chlorite and smectite can reflect the characters of paleoclimate and paleoenvironment changes very well, whereas, kaolinite doen’t obviously. By the mult-proxies analyses of clay minerals with grain size, carbonate, Petrological face and sedimentation together, the history of paleoclimate and paleoenvironment changes of Gonghe basin can be partioned the following stages: the late deglacial, early-middle Holocence and late Holocence. During the deglacial（14.5-11.3 cal ka BP） , the climate was generally dry and cold, with strong physic weathering, and the lake levelwas low with less hydrophytes as indicated by the high content of illite and chlorite and their crystallity, low content of smectite and the high ratios of smectite/（illite+chlorite） and kaolinite/smectite.. However, during this period an abruput climatic change occurred from 12.9-11.3 cal ka BP, where the temperatue and humity were becoming higher, which may correspond to Bφlling-Allerφd events. During the early-middle Holocences （11.3-4.5cal ka BP） , the contents and crystallities of illite and chlorite were low, the content of smectite was high, and the ratios of smectite/（illite+chlorite） and kaolinite/smectite were high, therefore, it indicates that increasing temperature and humidity, which reached Climatic Optimum at about 6.0 cal ka BP. Chemical weathering became stronger, lake water table was rising. At the beginning of this period, lake water was shallow and suitable for plants growth, much peat accumulated. But, in the time from 11.3-10.0 cal ka BP the climate beame cold and lasted for a about 1.0 ka, which may be a transition period. However, after the Climatic Optimum, from 6.0-4.5 cal ka BP the climate was very dry. During the late Holocence （4.5-0.0 cal ka BP） , the climate was similar to that of the deglacial. The cliamate was dry and cold, physical weathering prevailed, the lake water table became shallow again, less aquatic plant grew around lake shore and less peats accumulated.Compared with pollen of this core, clay minerals can reflect climate and environment very well just like pollen. Generally, they both have the same clamitic and environmental phases in long time intervals, especially in middle and late Holocene. In other stages, the change of clay minerals lagged after that of pollen about 1.0 ka.High lake levels of Dalianhai, Gonghe Basin occurred about 25-10 ka of the Last Glacial and Deglacial, and about 8.0-5.0 ka BP of Holocene.In comparison with other lake records and monsoon proxies of Tibet plateau, the records of Dalianhai evidently confirms that the consistency amongst all these records in large phases. During the Bφlling-Allerφd period, the humid climate of Gonghe Basin corresponded with the strengthening of Monsoon in other regions of Tibet Plateau. When the Young Dryas event occurred, the climate began to dry at many sites in the plateau. From early Holocence, Monsoon of the plateau began to strengthen and ameliorated at middle Holocence, which corresponreded to the expansion of forests and humid climate in the mountains around the Gonghe Basin. In late Holocene, the climate of Gonghe basin was dry and cold, that is constent with the flinches of Monsoon, forests and humity. Indian Monsoon played importamt role in climatic and invironmental changes of this area. However, the detail effects of Indian Monsoon and East Asian Monsoon on the plateau and their mechanisms are to be researched.更多还原