A comparison of quartz OSL and isothermal TL measurements on Chinese loess

Abstract

The reliability of equivalent doses (De) from Chinese loess, measured using isothermal thermoluminescence (ITL) is tested. Dose calculations use the single-aliquot regenerative-dose (SAR) procedure. Despite good reproducibility of laboratory-induced signals and negligible response at zero dose, a significant overestimation of De is observed, compared with OSL measurements. Measurement of a known laboratory dose administered after optical bleaching, but before any heating, demonstrates that the first heating during measurement of the natural signal causes a significant sensitivity change, undetected by SAR. Using the single-aliquot regeneration and added (SARA) dose procedure, which allows for initial sensitivity change, good agreement with OSL is obtained after allowance is made for initial incomplete bleaching. It is concluded that SAR-ITL, in its present form, is not a suitable method for dating Chinese loess; it is very important to undertake a dose recovery test before any TL procedure is used to date sediments.

Determining the cooling age using luminescence-thermochronology

“…3), such as thermally-transferred OSL (Wang et al, 2006) and isothermal TL (ITL) (e.g. Buylaert et al, 2006).In light of our results, a promising candidate in luminescence thermochronology is feldspar.Photostimulation of feldspars can be achieved using both visible and infrared wavelengths (Hütt et al, 1988).The IRSL signal from feldspars is particularly useful for dating because it has several advantages over the OSL signal of quartz. Firstly, it is commonly observed that the IRSL signal from feldspar does not saturate until much higher doses than those found for the quartz OSL signal; thus it has the potential for extending the time frame for thermo-chronology.…”

“…3), such as thermally-transferred OSL (Wang et al, 2006) and isothermal TL (ITL) (e.g. Buylaert et al, 2006).…”

The development and application of luminescence dating to loess deposits: a perspective on the past, present and future

“…Unlike SAR (Murray & Wintle 2000), SARA (Mejdahl & Bøtter‐Jensen 1994) is not strictly a ‘single‐aliquot’ technique, because it requires at least two aliquots to yield a D e value; however, the benefit of SARA is that it can be used to obtain reliable D e values irrespective of the sensitivity changes which might occur during measurement of an aliquot. Buylaert et al (2006) concluded that measuring ITL using a SARA technique potentially offered a large increase in the dose range compared to measurements made using OSL, and showed consistency between the SARA‐ITL and SAR‐OSL D e values in regions where the OSL signal is not saturated. However, in contrast to Choi et al (2006), the use of a SAR‐ITL protocol gave significantly higher D e values than using SAR‐OSL, due to large sensitivity changes occurring during the first heating applied to measure the natural signal (Buylaert et al 2006).…”

“…Buylaert et al (2006) concluded that measuring ITL using a SARA technique potentially offered a large increase in the dose range compared to measurements made using OSL, and showed consistency between the SARA‐ITL and SAR‐OSL D e values in regions where the OSL signal is not saturated. However, in contrast to Choi et al (2006), the use of a SAR‐ITL protocol gave significantly higher D e values than using SAR‐OSL, due to large sensitivity changes occurring during the first heating applied to measure the natural signal (Buylaert et al 2006). Interestingly, use of the SARA‐ITL in the study by Huot et al (2006) did not give results which were in agreement with known age samples; this study is worth mentioning in this review because, although it was not conducted on loess, it noted the important point that a SARA approach is inherently less useful in the strongly non‐linear region of the growth curve, which is of course the region of interest for extending the dating range.…”

“…The loess samples in this study were beyond the limits of conventional OSL dating; however, Choi et al (2006) concluded that having measured a D e value of 550 Gy for the oldest loess sample, ITL offers a potential means of extending the age range of luminescence dating. Measurements of quartz ITL and OSL were carried out by Buylaert et al (2006) for Chinese loess using both SAR and single aliquot regeneration added dose (SARA) techniques. Unlike SAR (Murray & Wintle 2000), SARA (Mejdahl & Bøtter‐Jensen 1994) is not strictly a ‘single‐aliquot’ technique, because it requires at least two aliquots to yield a D e value; however, the benefit of SARA is that it can be used to obtain reliable D e values irrespective of the sensitivity changes which might occur during measurement of an aliquot.…”