In this paper

profile observation and geologic strata structure analysis on the third level terrace at Fan- jiaping on the south bank of the Huanghe River in the Lanzhou basin were reported

and systemically collected sam- ples of fluvial sediments and the overlying diluvium and aeolian loess were analyzed by optically stimulated lumi- nescence (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 under- lying 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.