The Optically Stimulated Luminescence Dating Of Barchan Dune In Qaidam Basin

Qaidam basin is located in the northeast of Qinghai Tibet Plateau with drought climate and strong wind.Aeolian sediments and all kinds of dunes are widely distributed in the hyper-arid Qaidam Basin.Barchan dunes are the most common forms in desert,which have been learnt for a long time.The early researches reviewed the shapes and migration,formation conditions and process,but there are few researches on chronology.Usually barchan dunes are moving along the direction of wind.The oldest age is in windward slope and the youngest age is in leeward slope.According to their shape size,larger dunes are older than smaller dunes in age.In general,the age of barchan dune is less than one hundred years.The existing dating methods most are imprecise in dating scale of one hundred.14 C dating is mainly aimed at the scope of 1950 years ago to 50 ka and the dating material is the organic matter.The optically stimulated luminescence(OSL)dating method is the best choose.In this paper,we used the method of single aliquot regeneration-dose(SAR)protocol to measure the equivalent dose(De).We found that,the quartz signal of most samples here is too weak to be dated in experiment.In order to solve this problem,we extracted K-feldspar,utilizing a higher stimulation temperature of 180? after the 50? low temperature(pIRIR)for dating.At the same time,we use remote sensing images of Google for recent years to monitor these dunes in order to verify the accuracy of the OSL age.There are some conclusions as follows:(1)The K-feldspar is more suitable for young samples because of its high signal.The methods of IRSL and p IRIR can be used to test these young samples.The difference between them is that within a 10 years old of sample,the two kinds of results are similar.while there will be a recession in the age of IRSL when samples are above 50 years old.It is necessary to carry out a series of recession correction experiments for IRSL.Due to the two infrared excitation,the signal obtained by the second excitation is almost no longer attenuated,and the age of pIRIR is closer to the real age of these dunes.Therefore,the pIRIR excitation at 180? is more suitable for young samples.(2)Through the monitoring of remote sensing images,we can see the movement of sand dunes in the past 10 years.The larger dunes moved slowly,while the small dunes moved significantly.By measuring the movement distance of sand dunes and the length of dunes,we can calculate the real age of these dune.We can use it as a yardstick to test the OSL ages.These ages of 4 dunes in RS are 55.4a,59.1a,7.3a and 9.5a;Ages in IR50 degrees are 45±7a,48±5a,7±2a and 7±2a;Ages in 180?p IRIR are 63±8a,66±11a,10±3a,7±3a.In general,ages in 180?p IRIR are more closer to the real age of these barchan dunesIn this paper,the problem of the measurement of the aeolian sand landform is solved,and the comparison between the RS images and the results shows that the results are accurate and reliable.In this paper,the IR dating and pIRIR dating of feldspar can be used as the basis for its application in young samples.This paper can solve the problem of dating young sand samples.Analysing RS image can explain the dating of OSL are accurate and reliable.Based on OSL dating,the method of IR dating and feldspar pIRIR dating can also lay a foundation for its application in young samples.