In optical dating, equivalent dose (D_e) values for a sample are commonly obtained from measurement of the luminescence signals of individual mineral grains or aliquots and projection of the natural signals onto the corresponding regenerative-dose response curves. A final D_e estimate is calculated by using a statistical model to combine the individual D_e values. This method can be problematic for samples that contain large numbers of ‘saturated’ grains, which may result in underestimation of the final D_e value due to truncation of the full D_e distribution at high doses. To circumvent this problem, Li et al. (2017) proposed a new method—the so-called L_nT_n method—in which the re-normalised sensitivity-corrected natural signals (L_n/T_n) are analysed for all measured grains from a particular sample, and the weighted mean re-normalised L_n/T_n value is projected onto a standardised growth curve to estimate the final sample D_e. As no grains or aliquots are rejected because they are ‘saturated’, a full (untruncated) distribution of re-normalised L_n/T_n ratios is obtained. In this study, we use numerical simulations of ‘samples’ with a variety of assigned burial dose (palaeodose) distributions to systematically investigate the shape of the resulting L_n/T_n distributions. We test application of the central age, minimum age and finite mixture models to L_n/T_n ratios (rather than to D_e values) for well-bleached, insufficiently bleached and post-depositionally mixed samples. Our results show that application of statistical models to L_n/T_n ratios from single grains or aliquots is reliable, and that the L_nT_n method can be used to date samples with D_e values up to 4 times the characteristic saturation dose (D₀), which is well above the conservative upper limit of 2D₀.

在光学测年中，样品的等效剂量（D _e）值通常是通过测量单个矿物颗粒或等分试样的发光信号并将自然信号投影到相应的再生剂量响应曲线上而获得的。通过使用统计模型来组合各个D _e值，可以计算出最终的D _e估计值。对于包含大量“饱和”晶粒的样品，此方法可能会出现问题，由于高剂量下完整的D _e分布会被截断，因此可能会导致最终D _e值被低估。为了解决这个问题，李等人。（2017）提出了一种新方法-所谓的L _n T _n方法-分析经过重新归一化的灵敏度校正后的自然信号（L _n / T _n），以分析来自特定样品的所有测得的谷物，并将经过加权平均的经过归一化的L _n / T _n值投影到标准化增长点上曲线以估计最终样本D _e。由于没有颗粒或等分试样因为它们“饱和”而被拒绝，因此获得了重新标准化的L _n / T _n比的完整（未截断）分布。在这项研究中，我们使用具有各种指定的埋葬剂量（古藻糖）分布的“样品”的数值模拟来系统地研究所得L _n / T _n的形状分布。我们测试了中心年龄，最小年龄和有限混合模型对L _n / T _n比（而不是D _e值）的应用，用于漂白充分，漂白不充分和沉积后混合的样品。我们的结果表明，将统计模型应用于单粒或等分试样的L _n / T _n比值是可靠的，并且L _n T _n方法可用于对D _e值高达特征饱和剂量4倍的样品（ D ₀），其远高于2D ₀的保守上限。