末次冰消期以来民勤盆地沉积地层记录及年代学研究

石羊河流域位于西北干旱区河西走廊东段,是西北干旱区与东部季风区的交汇过渡地带。流域下游的民勤盆地分布有大量保存完整的湖相沉积地层和湖岸地貌,这些沉积地层和地貌景观在整个西北干旱、半干旱地区极具代表性,是进行古气候环境研究的理想场所。鉴于此,选取民勤盆地的青土湖剖面、西渠剖面、沙坑井剖面、九坨墚剖面作为研究对象,通过剖面地层对比及可靠14C测年,探讨了区域末次冰消期以来的气候变化的几个大的阶段。主要结论和认识如下:13000aBP前和9500—6700aBP两个阶段,区域沉积地层以风成砂、河流砂沉积为主,气候环境表现为干旱;13000—9500aBP和6700—1100aBP两个阶段,区域沉积地层表现为湖相沉积的粉砂沉积为主,气候环境表现为湿润;1100—0aBP风成砂等的沉积阶段,气候环境表现为干旱。

THE RESEARCH OF LACUSTRINE STRATIGRAPHIC RECORD AND CHRONOLOGY IN THE MINQIN BASIN SINCE THE LAST DEGLACIATION

The Shiyanghe River Drainage lies in east Hexi Corridor of the Northwest China and it is the interacting belt of the East Asian Summer Monsoon and the westerly line. This paper focuses on four sections (Qingtuhu section, Xiqu section, Sakengjing section and Jiutuoliang section) in the Minqin Basin. Much work was done in spot investigation, stratigraphic correlation and dependable 14C dating in order to discuss the history of climate changes in the Minqin Basin since the Last Deglaciation. The main conclusions are as follows. The sediments were mainly composed of eolian and fluvial sands and the climate was dry before 13 000aBP and from 9 500aBP to 6 700aBP. In contrast, the sediments were mainly composed of lacustrine silts coming and the climate was humid from 13 000aBP to 9 500aBP and from 6 700aBP to 1 100aBP. Finally, the sediments had been mainly composed of eolian sands and the climate was dry since 1 100aBP.