Quartz Optical Luminescence Dating Of Old Red Sands In South China

This paper takes Southern China old red sand as the research object,using quartz particles as dating material on the coast of Southern China to tropical selection as the representative of the PQR,JSR profile,represented by subtropical QFT,YCR,a total of 20 sections of the luminescence samples its release OSL geochronology.Through the experimental research on reliability of representative samples,the following conclusions are obtained:natural and regeneration dose of Fujian old red sand's preheating temperature is 260?,experimental dose preheating temperature of 220?,natural and regeneration dose of Hainan old red sand's preheating temperature is 220?,experimental dose preheating temperature is 180 C;two sample area the IRSL/OSL ratio shows that the older Fujian sample infrared luminescence signals was significantly higher than that of younger Hainan samples,but the two ratio was less than 10%,with SAR and quartz SGC dating requirements.Through the decomposition of the samples,the following conclusions are obtained.The luminescence signal of Fujian and Hainan samples is mainly composed of fast components.The fast component signal occupies 0.64 s of the total signal above 80%before the signal channel,and it decreases to the background value at 1 s excitation time.The calculation shows that the Fujian old red sand's fast and medium component of the photoionization cross section of 2.62×10-17 cm2 and 3.24×10-18 cm2;Hainan old red sand fast and medium component of the photoionization cross section of 2.66×10-17 cm2 and 3.51×10-18 cm2.By calculating the De value of the different integral signal channels,it is found that the old red sand samples from Southern China coast are more sensitive to the selection of the integral signal channel.By comparing the De values calculated with the fast component method,compared to the traditional method of late background signal deduction,the early background signal deduction method 1 is the integral signal interval 1-2(0-0.16 s)as the fast component signal interval,and the integral signal channel 3-7(0.32-1.12 s)as the background signal interval is the closest to the De value calculated with the fast component method.More detailed case analysis shows,for the light exposure and poor exposure samples,the De value of the late background signal deduction is less systematic,the results of the early background signal deduction can be more consistent with the fast component method.For the samples with better exposure,the De values calculated by the background signal deduction method or the background signal deduction method are all consistent with the De values calculated by the fast component method.However,it is undeniable that compared with the late background signal subtraction method,the De value calculated by the early background signal subtraction method has some disadvantages in the uncertainty of the fitting error accuracy.By comparing the growth curves of different aliquots from the same section,different samples and different profiles,it is found that the standard growth curve of old red sand in Southern China coastal area can be established.By comparing the De values measured by SGC method and SAR method,the correlation between them is relatively high.Therefore,SGC method can effectively improve the efficiency of photometric dating of old red sand samples in Southern China coastal area,and quickly and accurately get the OSL age of large quantities of old red sand samples.But the old red sand samples at different latitudes of the standard growth curve are different,which may be caused by regional differences in different heat environmental dose rate,the primary geological background,quartz sand rock weathering and handling process and other factors,so the applicability of SGC method has certain restrictions on the space scale.This paper combines OSL dating data and the previous published OSL age data show that the optical use of a comprehensive analysis of the probability density curve in Fujian old red sand can be divided into to divided into 128-117 Ka,106-98 Ka-76 Ka,88 66-,54 Ka,38-28 Ka,and 15-9 Ka and these 6 development stages,broke the previous to the time frame of the Southern China old red sand,the old red sand development pushed to the last interglacial.The development of old red sand in Fujian is mainly concentrated at high sea level or high sea level.The last ice age is missing.The whole development process is closely related to sea level rise and fall.In addition,the development of Fujian old red sand is influenced by many global background factors,such as the change of East Asian monsoon,the change of solar radiation and so on.