光释光测年中石英颗粒全球标准曲线法(gSGC)与单片再生法(SAR)等效剂量(D_e)的比对

Optical Dating Equivalent Dose (D_e) Comparison of Global Standardised Growth Curve (gSGC) and Single-aliquot Regenerative-dose(SAR) Methods for Quartz Grains

全球标准曲线法(gSGC)的提出为高效快速地测定释光样品的等效剂量(De)值提供了可能。但是由于各个实验室的放射源剂量率、操作流程、仪器误差以及选取的再归一化剂量值等不同,每个实验室得出的gSGC会有参数的不同。通过建立实验室的gSGC曲线和测试流程,并比较gSGC法和SAR法获取的De值的一致性,发现在低剂量范围内(0~100 Gy),使用gSGC法估计的De和SAR法估计的De非常接近,表明在低剂量范围内用gSGC法估计De是可靠的。这将很大程度地提高本实验室的释光测年速度,同时也为其他实验室gSGC的建立提供借鉴。在较高剂量范围(>100 Gy)与SAR方法结果比对时出现较大差别,这可能是由于研究中用于拟合gSGC的样品数量不够多,尤其是年龄较老的样品还不够多,还需在今后工作中逐步积累更多样品,完善gSGC参数,使其也能胜任较老年龄样品。

Optical dating is a method of measuring the time since the sample was buried from last thermal e- vent or light exposure. Samples such as quartz and feldspar grains are the most commonly used sediment of meas- urement. Single-Aliquot Regenerative-dose （SAR） method has become the most acceptable procedure for obtaining the equivalent Dose （D,） of a sample. The Standardised Growth Curve （SGC） method provides a possible proce- dure for measuring a large number of samples; the limitation is that the growth curve fitted by different samples or even different aliquots is divergent. The global Standardised Growth Curve （gSGC） method improves the shortage by normalizing the dose response curves using one regenerative dose OSL signal. The gSGC provides a possible method for obtaining the De value of the sample efficiently and quickly. However, due to the radiation dose rate, operating procedures and instrument error and the selected regenerative-dose normalized dose value, etc. , each la- boratory should develop their own gSGC which has unique parameters. This study established the gSGC curve and measurement process of our laboratory, and then compared the consistency of the equivalent Dose （ De ） values from gSGC and SAR methods. In gSGC procedure, the De value of an aliquot can be estimated from the nature signal, one regenerative dose signal and their corresponding test dose signal. It will speed up the optical dating measure- ment rate of our laboratory and provide reference to establish gSGC in other laboratories. It is found that in the low dose range （0 - 100 Gy） the obtained De values were well consistent by gSGC and SAR methods. There were obvi- ously differences in the higher dose range （ 〉100 Gy） compared to the SAR results. It may be due to the insuffi- cient number of older samples used to fit gSGC in this study. It is necessary to gradually accumulate more samples to improve the gSGC parameters in the future work. For some aliquots, individual quartz grains do not follow the global standardised growth curve, which leads to some deviations of De from gSGC. However, these two methods could obtain the similar average De value when multiple aliquots measuring.