The choice of Equivalent Dose Fitting Function in ESR Dating of Old Fossil samples

Subjects: Nuclear Science and Technology >> Other Disciplines of Nuclear Science submitted time 2024-06-24

谢君绮 韩非 柳华霖 黄曼琛 高峰

Abstract： [Background]: In ESR dating of old fossils, the Double Saturation Exponential (DSE) function is often used for the equivalent dose (D_E) determination, it generally requires more than 15 dose points and the maximum irradiation dose (D_max) of ＞20kGy to ensure the fitting accuracy, which limit the practical application of dating old fossils by ESR method with insufficient sample size. [Purpose]: This study attempts to explore the feasibility and reliability of using the single saturation exponential (SSE) fitting function to fit fewer dose points with lower D_max to obtain the D_E values of the fossil teeth from pre-Early Pleistocene sites, and compared with the ones determined by DSE function of 17 fossil samples from the late Miocene to the early Pleistocene. [Methods]: First, we compared the D_E values obtained by three fitting functions (DSE, SSE and EPL-exponential plus linear) by the additional dose method. Then, the influence of different D_max on the D_E results is investigated. Finally, the artificially regenerative dose-response curves fitted by the three functions with the weighted mean ESR signal intensity of the dose points were compared. [Results]: This study showed that (1) the D_E results of SSE and EPL functions are systematically higher than those of DSE function under the same condition as D_max=50kGy and 15 dose points, and the fitting accuracy of former two functions is better than that of DSE function in general. (2) For samples with D_E＞4500Gy and D_E＜4500Gy, the results of SSE and DSE are basically consistent within the error range under the conditions of D_max≥6.5*D_E and 1.3*D_E＜D_max＜2.2*D_E, respectively, which can provide the recommended dose value of D_max for samples with D_E＞2000Gy when using SSE function. (3) For fossil samples with D_E＜4500Gy, the SSE function can be used to fit the 11 dose points with D_max≤10kGy, and the D_E results are generally consistent with the DSE function within the error range. (4) The artificially regenerative dose-response curves of the weighted mean ESR signal intensity of the sample dose points showed that the DSE function had the best goodness of fit at 15 dose points, and the goodness of fit between the SSE and DSE function tended to be close at 11 dose points. [Conclusions]: Based on our study, it is viable to use SSE function to perform D_E fitting on old fossil samples under certain D_max/D_E conditions. In the further study, we will try the fragmental analysis of the fossil teeth for D_E determination and to establish the standard growth curve of old fossils established by the D_E values obtained by SSE and DSE functions and compared with conventional additive dose method to explore its feasibility.

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