OSL Dating Of Sediments Related To Late Quaternary Geomorphology Of Northern Piedmont Of The Hengshan Mountain

Late Quaternary geomorphological types in northern piedmont of the HengshanMountain are mainly composed of alluvial-diluvial platform, river-gully terrace andalluvial-diluvial fans formed in the same period. Late Quaternary sedment types aremainly alluvial-diluvial deposits. As long as we find suitable dating methods foralluvial-diluvial materials, we’ll obtain ages of sediments related to Late Quaternarygeomorphology in study areas. The premise of OSL dating is that the sample isbleached fully and OSL signals return to zero level before deposition and burial.Optical bleaching process is closely related to depositing environment and depositionprocess. We select a continuous alluvial-diluvial platform profile to sample for grainsize analysis. It shows that alluvial-diluvial deposits mainly consist of silt and finesand in the area. It’s depositing environment and process isn’t stable, fluctuations.Sediments may experience uneven bleaching and isn’t suitable for OSL dating insome layers in the profile.Whether or not alluvial-diluvial materals are suitable for OSL dating? In order tosolve this problem a series of experiments are carried out in the paper. We chooseriver-gully terrace and alluvial-diluvial fans in which paleosoil are developed tosystematicly collect samples. Through pretreatment, luminescence characteristicsanalysis, preheat plateau tests on representave samples we conclude that feldspar isremoved and without feldspar inclusions if samples are treated for three days withH2SiF6. The quartz purity is enough for OSL dating. The main fast component isdominant in OSL signals and meet requirement of single aliquot regenerative-dose(SAR) and simplified multiple aliquot regenerative-dose (SMAR) measurement.Preheating conditions and dating methods appropriate for the samples in the paper aregotten. Preheat temperature of natural and regenerative dose is240℃and preheatingtime is10s. Accordingly preheat temperature of test dose is200℃and preheatingtime is10s. By recycling ratio, recuperation ration, dose recovery test onrepresentative samples in fine-grained quartz SMAR/SAR and medium-grained quartzSAR protocols the results show that equivalent dose test conditions and protocolsused for the samples in the paper are appropriate. It can effectively correct OSL signalsensitivities changes during measurements.We carry out fine-grained quartz SMAR/SAR and medium-grained quartz SAR protocols for alluvial-diluvial samples collected from several river-gully terrace andalluvial-diluvial fans. Three osl ages are checked by AMS14C ages. The results showthat OSL signals can be bleached easily. Even if alluvial-diluvial depositingenvironment and process is complex, the majority of samles’ OSL signals are able tobe bleached to negligible levels before deposition and burial. We can also obtainrelatively reliable ages through the cumulative frequency method in medium-grainedSAR protocol even if individual samples experienced insufficient bleaching beforedeposition and burial. Allucial-diluvial deposits are suitable for OSL dating.We date different geomprphology units sediments related to Late Quaternary inNorthern Piedmont of the Hengshan Mountain with OSL and AMS14C methods. Agesof four geomprphology units (T3、T2、T1、T0) are obtained. That is,30～40ka、5～8ka、2～4ka and since2ka.