【摘要】 在西宁市区开展的钻探工作,获得了河谷平原区第四系的分布及沉积特征。通过对沉积厚度最大部位的2个钻孔岩芯的地层岩性、年代测试、孢粉组合及粒度分析等,探讨了西宁河谷平原区晚第四纪沉积与环境的关系。认为现今西宁市河谷平原内的主体沉积——低阶地沉积及上覆黄土堆积主要是末次间冰期旋回形成,在暖湿气候条件下沉积河流相砂砾石层,在干冷气候期接受风成黄土堆积,推测T3阶地形成于距今7.4万年前后气候由暖湿向干冷的过渡时期。更多还原

【Abstract】 Quaternary distribution and sedimentation of the Xining river valley plain were investigated by drilling analysis.Discussion on the relationship between the Late Quaternary deposition and environmental changes was carried out based on analyzing the stratigraphic lithology,OSL age,pollen and grain size of two cores from the thickest depositional sites.The results indicate that the main sediment in the present Xining river valley plain,mainly including lower terraces and overlying loess,has deposited since the last interglacial period.The maximum thickness is about 70m,including 25m conglomerate at maximum in the lower alluvial sediments.During the period of the past more than 100ka,three grades of terrace named as T1,T2,and T3 have formed along the Huangshui River and its distributary.Their vertical falls are 2～4m,12～14m,and 23～30m,respectively.The fluvial sand and gravel were deposited when the climate was warm and humid,during interglacial or interstadial periods,and the subsequent aeolian loess was deposited on the terraces during dry and cool period.Accordingly,T3 was formed at the climatic transition,about 74ka.Nevertheless,the detailed process of terrace formation and its correlation to other regions need further investigation.更多还原