【摘要】 中滩剖面系中滩镇渭河第四级阶地上的黄土堆积,通过黄土剖面的地层结构及粒度分析表明,其形成于0.9 Ma以来,河漫滩堆积年代为0.86—0.94 Ma。在过去1 Ma以来,中滩黄土及河漫滩剖面的地层特征、粒度曲线表明其记录了9个湿热干冷气候旋回,3次冬季风强化阶段,存在着3次极端干旱事件。中滩黄土粒度特征以粉砂为其众数粒级,其次为粘土颗粒,不同于黄土高原其他地区,可能与秦岭北麓的湿润环境及六盘山对冬季风的阻挡有关。更多还原

【Abstract】 Zhongtan section is loess deposits on the fourth terrace of Weihe River in Tianshui city of Gansu province.Based on stratigraphic feature and grain size curve,the loess was formed since 0.9 Ma BP,and the floodplain was deposited during 0.86—0.94 Ma.During the last 1 Ma,Zhongtan underwent nine moist hot-dry cold cycles,three winter monsoon intensifications,and three extremely dry events.Grain size date indicates that Zhongtan loess is different from other sections in the Longxi basin,which was caused by the uplifting of Liupan Mountain and moist environment in the flank of Qinling.更多还原