Lake Qinghai is the largest inland brackish lake in China and lies within the NE Tibetan Plateau. Our study shows that pollen assemblages in each vegetation belt are significantly correlated with the vegetation types of this area. Among the herbaceous and shrubby pollen assemblages, Artemisia is over-represented, while Poaceae, Cyperaceae and Polygonaceae are under-represented. Artemisia/ Chenopodiaceae (A/C) ratios with the regional vegetation characteristic can be used as a proper index to reconstruct the history of vegetation and climate in Lake Qinghai basin. Modern pollen in the lake mainly comes from the nearby vegetation, controlled by the directions and velocity of the wind. The distribution of modern pollen in Lake Qinghai tends to be similar in most part of the lake. The difference of pollen sedimentation process in the lake can be potentially influenced by the focusing function of the lake, river streams, and lake current.
对柴达木盆地东部尕海湖DG03孔岩芯沉积物的粒度特征的研究,结果表明:在12 800—11 800 cal a BP之间,DG03孔沉积物主要以砂为主,含少量的粉砂和粘土,表明钻孔地点的水动力条件比较强,湖泊水位较低,尕海地区经历了一次短暂的干旱事件,这一事件可能是该区域对全球性的YD事件的响应;全新世早中期(11 800—5 600 cal a BP),沉积物主要以粉砂和粘土为主,钻孔地点的水动力条件比较弱,湖泊水位较高,气候环境相对湿润;全新世中晚期以来(5 600 cal a BP以来),沉积物中砂粒组分含量越来越多,粉砂和粘土含量越来越少,平均粒径越来越大,钻孔地点的水动力越来越强,该区域经历了一个干旱化的过程。
The widely distributed red clay sediment underlying the Chinese Loess Plateau truly records the Neogene environmental evolution, and its genesis and development are intrinsically related to the uplift processes of the Tibetan Plateau and the evolution of East Asia monsoon system. In this paper, a detailed magnetostratigraphy of a loess-red clay section (107°13′E, 35°02′N) from the central Loess Plateau is reported. The loess-red clay sequence is composed of 175 m Quaternary loess-paleosol sequence and 128 m Neogene red clay sediments. Based on the correlation with the standard geomagnetic polarity time scale, the paleomagnetic results indicate that the age of Chaona red clay sequence extends to 8.1Ma, which is the older red clay deposition in the central Chinese Loess Plateau. The commencement of red clay at ～8.1 Ma may imply that the Ordos planation surface was broken by the movement of the Haiyuan-Liupanshan Faults, which was related to the uplift of the Tibetan Plateau induced by the collision of India Plate and Eurasian Plate. And the western part adjacent to the Tibetan Plateau was uplifted to form the embryo of the Liupan Shan (Mts.) and the eastern part was down-faulted to receive red clay deposition. We link this faulting to an initial uplift of the Tibetan Plateau. The undulating nature of the broken Ordos planation surface may explain the chronological differences and depth discrepancies among various cross-sections of red clay.
SONG YouguiLI JijunFANG XiaominXIA FeiDONG Hongmei
通过对德令哈盆地尕海DG03孔岩芯的岩性、年代数据分析以及与可鲁可湖HL05-2孔岩芯多个气候代用指标的综合对比,确定了DG03孔岩芯的底部年龄约为11ka BP(AMS1-4C)。根据岩性变化,整个岩芯可划分为3个阶段:晚冰期晚期(11—10 ka BP),全新世早中期(10—4 ka BP)和全新世晚期(4—0 ka BP)。岩芯记录了晚冰期晚期和整个全新世的古气候和古环境变化信息,从晚冰期晚期以来,尕海湖经历了冷干—暖干—暖湿—冷干(现代)的气候变化过程,而湖泊水位则相应为低(盐湖或高盐度湖泊)—较高(盐湖—咸水湖)—高(咸水湖—半咸水湖/淡水湖)—较低(咸水湖—盐湖)。
Thick Cenozoic deposits were shed into the foreland basin of the Tian Shan Range,providing great potential for...
Jimin Sun ~*,Zhenqing Zhang Key Laboratory of Cenozoic Geology and Environment,Institute of Geology and Geophysics,Chinese Academy of Sciences,P.O.Box 9825,Beijing 100029,China
