A robust feldspar luminescence dating method for Middle and LatePleistocene sediments

Abstract

Luminescence dating is used extensively to provide absolute chronologies for Late Pleistocene sediments. Nowadays, most optical dates are based on quartz optically stimulated luminescence (OSL). However, the application of this signal is usually limited to the last ∼100 ka because of saturation of the quartz luminescence signal with dose. In contrast, the feldspar infrared stimulated luminescence (IRSL) dose–response curve grows to much higher doses; this has the potential to extend the datable age range by a factor of 4–5 compared with quartz OSL. However, it has been known for several decades that this IRSL signal is unstable, and this instability often gives rise to significant age underestimation. Here we test against independent age control the recently developed feldspar post‐IR IRSL approach to the dating of sediments, which appears to avoid signal instability. A physical model explaining our observations is discussed, and the method is shown to be accurate back to 600 ka. The post‐IR IRSL signal is reduced by exposure to daylight more slowly than that from quartz and low‐temperature IRSL, preventing its general application to young (e.g. Holocene) sediments. Nevertheless, this new approach is widely applicable (feldspar of appropriate luminescence behaviour is even more ubiquitous than quartz). These characteristics make this a method of great importance for the dating of Middle and Late Pleistocene deposits.

Age of a prehistoric “Rodedian” cult site constrained by sediment and rock surface luminescence dating techniques

“…This is consistent with earlier reports that elevated temperature pIRIR signals are more difficult to bleach than the IR 50 signal (e.g. Sohbati et al, 2012c;Buylaert et al, 2012;Kars et al, 2014). On closer inspection, one can see a step in the luminescence profiles of both signals; at about ~4-5 mm for the pIRIR 225 signals and ~4-10 mm for the IR 50 .…”

“…This argument is based on the widely-observed differential bleaching rates of quartz and feldspar signals (e.g. Godfrey-Smith et al, 1988;Thomsen et al, 2008;Buylaert et al, 2012;Murray et al, 2012;Sugisaki et al, 2015;Colarossi et al, 2015) when exposed to a daylight spectrum, and helps to quantitatively address one of the main uncertainties in the application of OSL to dating.…”

On the dose dependency of the bleachable and non-bleachable components of IRSL from K-feldspar: Improved procedures for luminescence dating of Quaternary sediments

“…Sohbati et al (2012) observed an increase in the pIRIR(225) residual doses with the D e values of their samples. A similar observation was made by Buylaert et al (2012) for the pIRIR(290) signals of 15 samples, and they suggested that the residual doses at the time of burial may be smaller than the residual doses inferred from laboratory measurements. Reimann and Tsukamoto (2012) found that the residual doses associated with the 50°C IRSL and pIRIR (150) signals were the same after a prolonged bleach, although the pIRIR signal is thought to be bleached more slowly than the 50°C IRSL signal.…”

On the reconstruction of palaeo-ice sheets: Recent advances and future challenges

“…In such contexts, feldspar IRSL often provides an alternative, although this signal is known to suffer from anomalous fading, causing age underestimation (Wintle, 1973;Huntley and Lamothe, 2001). To circumvent the problem of fading, new approaches involve using a thermally-assisted IRSL measurement (post-IR IRSL; Thomsen et al 2008;Buylaert et al, 2012). However, this signal is known to bleach less rapidly and can cause ageoverestimation in proglacial environments (Blomdin et al, 2012;Lowick et al, 2012).…”