Pulsed IRSL: A stable and fast bleaching luminescence signal from feldspar for dating Quaternary sediments

Abstract

Elevated temperature post-infrared infrared stimulated luminescence (post-IR IRSL; pIRIR) dating method using feldspar has led to a significant advancement in dating Quaternary sediments, as this signal has been shown to be stable on geological time scales. In comparison to the conventional IRSL, the pIRIR signal is nearly free from anomalous fading, but it is more difficult to reset during daylight exposure; the latter characteristic may give rise to age over-estimation in some environments because of partial bleaching. The pulsed IRSL signal has also been known to be less affected by anomalous fading, when the signal is recorded during the off-time of LED stimulation pulses. In this study, we compare the signal bleachability, thermal and athermal stability, and age estimates derived using different measurement methods, i.e., pulsed IRSL measured at 50°C (pulsed IR 50 ; subscripts refers to measurement temperature), continuous wave (CW) pIRIR 225 and pIRIR 290 signals, as well as the two IR 50 signals measured as a part of the pIRIR protocols. This comparison is carried out for 3 samples taken from Late Quaternary fluvial sediments, which have independent age estimates from radiocarbon dating and tephrochronology. We observe that under exposure to solar simulator, the pulsed IR 50 signal bleaches as rapidly as the CW IR 50 , and much more rapidly than the pIRIR signals. Furthermore, the pulsed IR 50 signal is also as stable as the pIRIR signals, especially when the middle part of the decay curve is used for signal intensity calculation.

A novel coupled RPL/OSL system to understand the dynamics of the metastable states

“…Infrared stimulated luminescence (IRSL) is widely used in luminescence dating [26][27][28][29][30] . This method, however, suffers from an unexpected loss of signal (anomalous fading), a problem that has been addressed in the last decade using preferential sampling of a more stable signal.…”

Optical dating in a new light: A direct, non-destructive probe of trapped electrons

“…However, historically, this potential of IRSL has not been exploited because of the loss of trapped charge with time due to quantum mechanical tunnelling, a process commonly referred to as anomalous fading 24 , 25 ; this loss of trapped electrons gives rise to age underestimation. In recent years, the problem has been tackled with some success by correcting for the fading loss 26 , 27 , and/or selectively sampling electron-hole populations that are less prone to fading recombination 10 , 18 , 28 – 32 . It is debated whether the more stable variants of IRSL, known as post IR-IRSL (pIR-IRSL) 30 , MET-IRSL 29 , 32 or pulsed IRSL (PIRSL) 31 , 33 , exhibit fading over geological time scales or not 18 , 28 .…”

“…In recent years, the problem has been tackled with some success by correcting for the fading loss 26 , 27 , and/or selectively sampling electron-hole populations that are less prone to fading recombination 10 , 18 , 28 – 32 . It is debated whether the more stable variants of IRSL, known as post IR-IRSL (pIR-IRSL) 30 , MET-IRSL 29 , 32 or pulsed IRSL (PIRSL) 31 , 33 , exhibit fading over geological time scales or not 18 , 28 . Furthermore, pIR-IRSL and MET-IRSL signals do not reset as rapidly as IRSL on exposure to daylight, and suffer from undesirable effects such as thermal transfer during heating and optical stimulations at high temperatures (e.g., pIR-IRSL at 290 °C) 28 , 34 .…”

“…Furthermore, pIR-IRSL and MET-IRSL signals do not reset as rapidly as IRSL on exposure to daylight, and suffer from undesirable effects such as thermal transfer during heating and optical stimulations at high temperatures (e.g., pIR-IRSL at 290 °C) 28 , 34 . Pulsed IRSL does not suffer from the problems of bleachability (signal resetting by exposure to daylight) and thermal transfer 18 ; however, luminescence sensitivity is an issue here since more than 90% of the luminescence is deliberately rejected in the readout.…”

Extended-range luminescence dating of quartz and alkali feldspar from aeolian sediments in the eastern Mediterranean

“…For example, the TT-OSL signal is thermally unstable, producing therefore only minimum ages after a few hundred thousand years (Adamiec et al, 2010;Shen et al, 2011;Chapot et al, 2016;Faershtein et al, 2018); it appears that the natural growth of the VSL signal cannot be properly described with the single aliquot regenerative (SAR; Murray and Wintle, 2000) constructed dose response curve (DRC) generally used for De determination (Ankjaergaard et al, 2016;Ankjaergaard, 2019). There is evidence of age overestimation for the pIRIR 290 and athermal signal loss (termed anomalous fading) issues for the pIRIR signals measured at lower temperatures (Lowick et al, 2012;Tsukamoto et al, 2017). The potential and limits of these methods in dating early and middle Pleistocene sediments were tested in several locations around the globe (e.g.…”