Isolating quartz-dominated OSL signal of rock slice by using pulsed stimulation: Implications for dating burial age of cobbles

Abstract

Although the OSL signal sourced from quartz is expected to be more stable and bleached more rapidly than the IRSL signal sourced from feldspar in a general sense, the former is much less investigated than the latter for rock surface related luminescence dating. It is mainly due to the difficulty in isolating quartz-dominated OSL signals from rock slices, and the low sensitivity and non-fast component dominated OSL signals for quartz in most of rocks. In merit of the sub-conduction band transition of trapped electrons of feldspar under both green light stimulation and IR stimulation at elevated temperature (Jain and Ankjӕrgaard, 2011), it is expected that the contribution of feldspars to the green light stimulated luminescence could be substantially reduced by a prior IR stimulation at elevated temperature. Meanwhile, more fast-component dominated quartz OSL signal (if there is any) could be obtained by green light stimulation (Bailey et al., 2011). Therefore, in this study, we investigated the feasibility of using the post-IR pulsed green stimulation, which is performed at 25 °C (PGLSL 25 ) following two IR stimulations (IR 50 IR 225 ), to isolate the quartz-dominated OSL signals from rock slices of granite cobbles for burial dating. The decay characteristics of stimulation curve, characteristic saturation dose and thermal stability of the pIR 50 IR 225 PGLSL 25 signal suggest that this signal is quartz-dominated, but still not fast-component dominated. We tentatively validated the equivalent dose (D e ) measurement protocol by dose recovery experiment. The luminescence-depth profiles show that the bleaching depths of pIR 50 IR 225 PGLSL 25 signals are slightly smaller than or close to that of the IR 50 signals, while they are much shallower for the pIR 50 IR 225 signals. The pIR 50 IR 225 PGLSL 25 procedure enables multiple D e values determined from luminescence signals, with different bleachabilities and stabilities, from both feldspars and quartz in one measurement, which is of potential for buried age dating of cobbles. • The pIR 50 IR 225 PGLSL 25 method could be used to isolate the quartz-dominated signal from rock slice. • The bleaching depth of the pIR 50 IR 225 PGLSL 25 signalis slightly less than or close to that of the IR 50 signal. • The pIR 50 IR 225 and the pIR 50 IR 225 PGLSL 25 D e values could be obtained in one measurement.