巴丹吉林沙漠泥炭层年代学与环境重建研究

For this project, we select peat layers in dry lakes of the Badain Jaran Sand Sea and its adjoining areas as the study object. Using sedimentological and palaeo-climatic proxies (grain size,grayscale, TOC, loss on ignition, humification, dry density and cellulose stable isotope), we attempt to reconstruct the characteristic of the peat and mirabilite layers including lithology, sedimentary and formation scale. Moreover, we will employ 14C dating and optically stimulated luminescence dating for the peat- mirabilite layers and sand layers to establish the chronology. Inaddition, based on the dating results,we will use previous proxies to reconstruct the effective moisture and temperature variations during the formation perionds of the peat, as we describe in this project. At last, we will also discuss the mechanism of environmental evolution in the desert region. This study will fill the gaps of peat research in arid region, which could extend paleoclimate records in arid region. It will also provide scientific basis for the potential environment impact prediction and adaptation of global warming.

以巴丹吉林沙漠泥炭沉积层为研究对象，通过粒度、灰度、有机质含量、烧失量、腐殖化度、干容重、植物残体组合、孢粉、纤维素碳氧同位素、生物标志化合物等多种环境代用指标的分析，探讨泥炭层的理化性质、产状特征、发育规模、植物残体和成因类型。基于不同的环境代用指标选取泥炭层剖面适合的组分，采用AMS14-C、OSL等多种测年方法确定成炭期，建立泥炭层及其剖面的年代模式，确定其与气候突变事件和气候阶段的耦合关系。集成多类型、多来源的物理、环境地球化学、生物等代用指标，开展特征气候阶段古环境多源重建研究，确定成炭期的气候变幅和水热组合关系，并与芒硝、冰芯、黄土等地质载体进行区域对比，揭示研究区晚冰期至冰后期气候变迁模式及其机制。项目可望填补我国泥炭气候环境纪录研究的区域空白，拓展与重建干旱沙漠地区气候环境变化序列，力求在气候要素的定量重建方面取得突破，为全球变暖对干旱区环境的潜在影响预测与适应提供科学依据

本项目运用多代用指标的方法重建了全新世巴丹吉林沙漠腹地环境演变过程，巩固和丰富了巴丹吉林沙漠全新世初成炭期（准扎罕吉林期）和全新世泛湖期（巴丹吉林期）等环境演变新概念，进一步认为巴丹吉林沙漠腹地分布广泛的全新世初期埋藏泥炭，可作为晚更新世与全新世层型剖面的“金钉子”。本研究的沉积记录表明，全新世之初巴丹吉林沙漠腹地湖盆发育泥炭地，显示全新世初泥炭地形成所需的水分条件可能来自于其他区域的水分运移。通过沙漠湖泊变化过程与季风边缘区湖泊演化历史的对比，发现早全新世巴丹吉林沙漠的湿润程度与青藏高原冰冻圈的变化有关。巴丹吉林沙漠受青藏高原东北部冰雪融水经地下水远距离补给，且地下水循环过程中蒸发较弱，全新世气候环境演变与青藏高原东北缘气候干湿变化模式类似，揭示沙漠湖泊群一定程度上受青藏高原东北缘冰冻圈变化的调控。