Testing the potential of a transferred IRSL (T-IRSL) feldspar signal for luminescence dating

Abstract

One of the major dilemmas in feldspar luminescence dating is that the infra-red stimulated luminescence (IRSL) signals are either stable and difficult to bleach when measured at elevated temperatures, or unstable and easy to bleach when measured at low temperatures. To identify a signal for sediment dating that is both stable and easy to bleach, we investigate the potential of an optically and thermally transferred IRSL (T-IRSL) signal. Based on the mechanisms described in Wang et al. (2014), we develop a T-IRSL single-aliquot regenerative-dose (SAR) measurement protocol. We investigate the a-thermal stability of six different T-IRSL signals from a sample of infinite age using fading experiments, and by comparing field and laboratory saturation levels. The T-IRSL signal measured at 125 °C (T-IRSL125) following a preheat of 280 °C, is found to be as stable as the post-IR IRSL 290 °C signal (pIRIR290). Furthermore, laboratory bleaching experiments show that the T-IRSL125 signal bleaches faster than the pIRIR290 signal, and that the corresponding residual doses are more than 40% lower. This indicates that T-IRSL signals may be superior to pIRIR methods for dating young and/or insufficiently bleached deposits. However, a SAR protocol performance test of the T-IRSL125 signal yielded a systematic underestimation of 8 ± 2%. This is possibly caused by a sensitivity change during the first preheat and requires further investigation.