Review of the Post-IR IRSL Dating Protocols of K-Feldspar

Abstract

Compared to quartz, the infrared stimulated luminescence (IRSL) of K-feldspar saturates at higher dose, which has great potential for extending the dating limit. However, dating applications with K-feldspar has been hampered due to anomalous fading of the IRSL signal. The post-IR IRSL (pIRIR) signal of K-feldspar stimulated at a higher temperature after a prior low-temperature IR stimulation has significantly lower fading rate. Different dating protocols have been proposed with the pIRIR signals and successful dating applications have been made. In this study, we review the development of various pIRIR dating protocols, and compare their performance in estimating the equivalent dose (D_e). Standard growth curves (SGCs) of the pIRIR signals of K-feldspar are introduced. Single-grain K-feldspar pIRIR dating is presented and the existing problems are discussed.

Keywords: K-feldspar; OSL dating; post-IR IRSL; single-grain; standard growth curve (SGC).

Figure 1

D_e versus IR stimulation temperature in the MET-pIRIR protocol. The sample used is 14LC-11.0, from the top of the L2 layer (second loess layer, corresponding to Marine Isotope Stage 6) in the Luochuan section, Chinese Loess Plateau (Zhang et al. [72]). Four aliquots were measured. The error bar of the average is the standard error calculated from four aliquots.

Figure 2

Characteristic saturation dose (D₀) of the pIRIR signals versus the test dose (D_t), with the SAR protocol. Data are from Table 2. A general positive relationship exists between D₀ and D_t. Please note that the pIRIR signals in this graph includes different kinds of signals, such as pIRIR_{50, 170}, pIRIR_{50, 225}, pIRIR_{50, 290}, MET-pIRIR_250/300 signals. So the D₀ is scattered even with the same D_t.

Figure 3

Comparison of D_e values obtained by the conventional SAR protocol (Li and Li [63]) and the modified ‘MAR with heat’ protocol (Li et al. [62]), with a six-step IR stimulation from 50 °C to 300 °C. (A) Sample 14LC-16.0 is from the base of the L2 layer (second loess layer, MIS 6) in the Luochuan section, Chinese Loess Plateau. The higher degree of SAR D_e underestimation compared to MAR D_e at low IR stimulation temperatures is due to the failure of sensitivity correction. Note that the D_e values are still consistent between the SAR and MAR protocols at higher IR stimulation temperatures (250 °C and 300 °C). (B) Sample B-610 is from the Jingbian section of Chinese Loess Plateau. Note that the SAR D_e values are still underestimated at high IR stimulation temperatures compared to the MAR D_e values, because D_e is already larger than 800 Gy. Figure 3B is modified from Zhang et al. [85].