兰州盆地黄河三级阶地的光释光年龄  

Optically stimulated luminescence dating of the Huanghe river terrace in Lanzhou basin

作　　者：王萍[1] 袁道阳[2] 刘兴旺[2] 蒋汉超[3] 

机构地区：[1]中国地震局地质研究所,地震动力学国家重点实验室,北京100029 [2]中国地震局地震预测研究所兰州科技创新基地,兰州730000 [3]中国科学院地质与地球物理研究所,北京100029

出　　处：《核技术》2007年第11期924-930,共7页Nuclear Techniques

基　　金：国家自然科学基金(40472090);中国地震活断层探测技术系统-兰州市地震活断层探测与地震危险性评价(1-4-28)资助

摘　　要：对兰州盆地黄河南岸范家坪三级阶地剖面进行了观测和地层结构分析,对剖面中段细粒沉积层以2.5cm的间隔采取了粒度、磁化率样品。通过对16个光释光(OSL)样品的细颗粒石英简单多片技术的测年以及下伏早期冲积层的电子自旋共振(ESR)测年,得到三级阶地地层剖面的年代学结果:下伏早期冲积层为中、下更新统范家坪组砾石层,黄河至少于8万年前在其上开始河床沉积,约7万年左右开始堆积以冲洪积相为主的细粒层。推测黄河三级阶地形成年龄约为7万年左右,对应晚更新世末次间冰期与末次冰期之间。In this paper, profile observation and geologic strata structure analysis on the third level terrace at Fanjiaping on the south bank of the Huanghe River in the Lanzhou basin were reported, and systemically collected sampies of fluvial sediments and the overlying diluvium and aeolian loess were analyzed by optically stimulated luminescence （OSL）. The granulometric and magnetic susceptibility samples from the fine grain sedimentary layer at the middle of the profile were collected at a 2.5 cm interval. According to simplified multiple aliquot dating on fine grain quartz of 16 optically stimulated luminescence samples and electron spin resonance （ESR） dating of the underlying early fluvial layer, the following chronology results of the strata profile of the third terrace were obtained. The underlying early fluvial layer is of gravels that belong to Fanjiaping formation in early and middle Pleistogene. The river-bed sedimentation of the Huanghe River started about 80,000 years ago. The accumulation of mainly proluvial sediments started about 70,000 years ago. And the continuous loess accumulation began about 55,000 years ago. The age of formation of the third terrace of Huanghe River was estimated at about 70,000 years, corresponding to the time between the last interglacial period and the last glacial period in the late Pleistocene.

关 键 词：兰州盆地 黄河三级阶地 石英简单多片光释光测年 阶地年龄 

分 类 号：P597.3[天文地球—地球化学]