黄河源玛曲段全新世风成黄土-古土壤序列风化成壤特征以及古气候演变

通过对青藏高原东北部黄河源开展广泛细致的野外考察,选择位于玛曲段黄河左岸第二级河流阶地（T₂）之上,赋存典型风成黄土-古土壤序列的达尔琼东（DEQ-E）剖面进行系统采样。在室内对采集样品进行了磁化率、烧失量、吸湿水、粒度、土壤微形态、地球化学元素和光释光（OSL）测年等综合分析,结论表明：① 黄河源玛曲段DEQ-E剖面地层序列由上至下依次为现代草甸土层（MS）-全新世中期古土壤层（S₀）-全新世早期过渡性黄土层（L_t）-阶地漫滩相沉积层（T_2-al）;② 黄河源玛曲段DEQ-E剖面风成黄土-古土壤序列风化成壤强度呈现出全新世中期古土壤层（S₀）>全新世早期过渡性黄土层（L_t）>现代草甸土层（MS）的变化特征;③ 黄河源全新世的古气候演变可分为3个阶段：全新世早期（11000 a BP—9000 a BP）,西风势力减弱,东亚夏季风逐步增强,气温趋于变暖,降水有所增加;全新世中期（9000 a BP—3100 a BP）,东亚夏季风作用强盛,气候整体温暖湿润;全新世晚期（3100 a BP以来）,东亚夏季风衰退,西风势力有所增强,导致气候转向干冷。该研究成果有助于理解青藏高原东北缘的古气候演化机制,同时对于预测未来区域气候变化具有重要的科学意义。

Weathering and pedogenesis of the Holocene aeolian loess-paleosol section and paleoclimate evolution in the Maqu reach in the Yellow River source area

After extensive and detailed field investigation in the source area of the Yellow River on the northeast Tibetan Plateau, a Holocene aeolian loess-paleosol section at Daerqiongdong (DEQ-E) site on the second river terrace (T₂) of the Yellow River in the Maqu reach was selected for systematic sampling. Based on the comprehensive study on multiple proxies, hygroscopic water, magnetic susceptibility, grain-size distribution, geochemical elements and optically stimulated luminescence (OSL), the following conclusions were obtained: (1) The stratigraphic sequence of the DEQ-E profile is listed from top to bottom: modern soil (MS), mid-Holocene paleosol (S₀), early Holocene transitional loess (L_t), fluvial deposits (T_2-al); (2) The intensity of weathering and pedogenesis varies significantly in different layers and presents such a tendency of S₀ > L_t > MS; (3) Three stages of paleoclimate evolution in the Yellow River source area can be summarized as follows: in the early Holocene (11000 a BP-9000 a BP), the temperature tended to be warm, and the precipitation increased with the weakened Westerlies and strengthened East Asian summer monsoon; in the mid-Holocene (9000 a BP-3100 a BP), the climate was warm and wet with intensive East Asian summer monsoon; in the late Holocene (since 3100 a BP), the climate gradually turned to be dry and cold with weakened East Asian summer monsoon and the strengthened Westerlies. This study is helpful to understand the paleoclimate evolution mechanism on the northeast Tibetan Plateau, and has important scientific significance for predicting future regional climate change.