OSL Dating And Experimental Conditions Study Of Medium-grain Size Aqueous Sediments Of The Ancient Da Lu Ze In Hebei Plain

The Daluze paleolake has different types of aqueous sediment which had recorded the evolution process of the Daluze paleolake and include more medium grains.At present,in the study on the historical evolution of the Daluze paleolake,the reasons for the formation and dissolution of the Daluze paleolake have been analyzed from climate and environmental changes in the results of previous studies in which the analyses of its tectonic evolution process are less.The OSL dating technique has been developed in quaternary aqueous sediment dating.For the aqueous sediment of which the fine and coarse grains are less or more difficult to separate,the medium grains have been used in OSL dating.At present,reseachers mostly have adopted fine and coarse grains to date the OSL age of aqueous depositions.The OSL dating technology of fine and coarse grains are more mature.However,for the medium grains,their OSL dating technology is relatively weak.In order to improve the OSL dating technology of the medium-grain aqueous depositions,futher determine the sedimentary stratigraphic age of the Daluze paleolake.In this paper,taking the medium-grained aqueous sediments in the Daluze paleolake for example,by doing pre-treatment experiment,discussing the reliability of OSL dating and analyzing the geological structure evolution process of the Daluze paleolake,the preliminary conclusions are following:1.By preheat-plateau test and the relationship between Ln/Tn and preheat temperature of representative sample,it shows preheat temperature of natural and regenerative dose is220?and preheating time is 10s.Accordingly preheat temperature of test dose is 180?and preheating time is 0s.2.Through a series of experiments,the problem that the dose recovery ratio meets the requirement but the value is low has been solved.By recycling ratio,recuperation ration,dose recovery test of representative samples,it is feasible to verify the preheating conditions and the SAR test process of medium-grain quartz.3.The OSL ages of medium-grained samples on the Yan Chi?YC?profile,which have been obtained by SAR method,is basically corresponding to the ¹⁴C age.It can be shown that:the OSL age of medium-grained samples obtained by SAR method is reliable.4.The Daluze paleolake at the end of the late pleistocene epoch.The two ancient flood sediments buried in 630-660cm and 745-920cm on the YC section deposited by the diversions of the ancient Yellow River which were caused by the difference construction activities.5.The Daluze paleolake at the end of the late pleistocene epoch.There are multiple faults around the Daluze paleolake.And the new tectonic activity is strong.The Yellow river,Zhanghe river and Hutuo river which were closely related to the Daluze paleolake were affected by the new tectonic fracture and sedimentation,causing the rivers to detour and flood.And the sediments silt up.The water supply of the Daluze paleolake was greatly reduced.Then the Daluze paleolake gradually decomposed until the middle of the last century it died out.