Single Aliquot Regenerative Protocol Research Articles

Limitations of quartz extracted from Antarctica sediments for luminescence dating

Thermoluminescence (TL) and Optically Stimulated Luminescence (OSL) properties of quartz samples extracted from soil of Fisher Island (76° 13ʹ 23.9ʺ E, 69° 23ʹ 31.9ʺ S) in Antarctica were studied. The nature of signals indicated presence of a dominant slow component in the OSL signal. The widely utilized Single Aliquot Regenerative (SAR) protocol for dose recovery was found unsuitable for this particular sample due to the dominating slow component in the OSL signal. Efforts to minimize the effect of slow component in dose recovery by adopting procedures like, bleaching with blue light, and early background subtraction were carried out. Additionally, thermally transferred OSL (TT-OSL) studies were conducted on the natural sample and dose estimation using the TT-OSL SAR protocol was carried out.

Spatiotemporal differences in Holocene climate change in the Yarlung Tsangpo catchment, southern Tibetan Plateau, reconstructed from two sandy loess sequences

The southern Tibetan Plateau is influenced by several atmospheric circulation systems, which combined with the complex topography results in variable environmental conditions from east to west. We investigated the spatiotemporal variability of the Holocene climate of this region based on analyses of two sandy loess sequences in the complex valley environment of the upper and mid-lower reaches of the Yarlung Tsangpo (YT) catchment. OSL dating with the single-aliquot regeneration protocol was used to establish a chronological framework, and analyses of element geochemistry, grain size, magnetic susceptibility, and chromaticity were conducted to reconstruct changes in the environment and climate during the Holocene. The results show that the deposition of sandy loess deposits was widespread from east to west in the YT catchment, especially after 8.3 ka. The proxy records suggest more complex precipitation and temperature patterns in the western loess region than in the eastern loess region of the YT catchment. After 8.3 ka, loess deposition in the western valley was more strongly influenced by the westerlies, while the climate of the eastern region was dominated by the Indian summer monsoon. Our results demonstrate significant Holocene climate variability between the eastern and the western regions. We suggest that the loess deposits in the YT catchment are a potentially valuable archive of information for understanding the complex interaction between the westerlies and the Asian monsoon during the Holocene.

Exploring the application of blue and red thermoluminescence for dating volcanic glasses

Tephras are significant markers in the stratigraphic record and play a key role in establishing paleoenvironmental and paleoclimate histories worldwide. Despite burgeoning research focused on tephra characterization and correlation techniques, there are still few techniques that allow for the direct dating of tephra, particularly below the lower age limit of K/Ar and Ar/Ar dating methods. In this study, we test different thermoluminescence (TL) dating approaches on the 4–11 μm volcanic glass constituents of three different independently different tephras. By comparing against independent age control, we demonstrate the utility of both blue (320–450 nm) and red (587–651 nm) TL emissions for dating volcanic glasses using single aliquot regenerative (SAR) dose techniques. We find that both blue and red TL emissions from the volcanic glass shards are dim but reproducible and show no evidence for significant sensitivity changes occurring between the natural TL and the first test dose during the SAR protocol. Fading tests on the blue TL signal show that g-values range from 1.6 ± 1.0 to 2.9 ± 1.1%/decade and are statistically indistinguishable with zero at 2σ for the red TL. Bleaching experiments show that both blue and red TL signals are sensitive to light exposure, with sensitivity corrected signals declining by ∼40% over a 2-h period. For all three tephras, both the fading-corrected blue and red SAR-TL ages are consistent with age expectation. These successful results demonstrate the effectiveness of TL techniques for determining the eruption ages of tephra deposits in primary position between ∼1 and at least 30 ka.

Investigation of quartz electron spin resonance residual signals in the last glacial and early Holocene fluvial deposits from the Lower Rhine

Abstract. In this study, we examined the residual doses of the quartz electron spin resonance (ESR) signals from eight young fluvial sediments with known luminescence ages from the Lower Rhine terraces. The single aliquot regenerative (SAR) protocol was applied to obtain the residual doses for both the aluminium (Al) and titanium (Ti) impurity centres. We show that all of the fluvial samples carry a significant amount of residual dose with a mean value of 1270 ± 120 Gy for the Al centre (including the unbleachable signal component), 591 ± 53 Gy for the lithium-compensated Ti centre (Ti-Li), 170 ± 21 Gy for the hydrogen-compensated Ti centre (Ti-H) and 453 ± 42 Gy for the signal that originated from both the Ti-Li and Ti-H centres (termed Ti-mix). To test the accuracy of the ESR SAR protocol, a dose recovery test was conducted and this confirmed the validity of the Ti-Li and Ti-mix signal results. The Al centre shows a dose recovery ratio of 1.75 ± 0.18, whereas the Ti-H signal shows a ratio of 0.55 ± 0.17, suggesting that the rate of signal production per unit dose changed for these signals after the thermal annealing. Nevertheless, all fluvial sediments investigated in this study carry a significant residual dose. Our result suggests that more direct comparisons between luminescence and ESR equivalent doses should be carried out, and, if necessary, the subtraction of residual dose obtained from the difference is essential to obtain reliable ESR ages.

Holocene moisture evolution and its response to atmospheric circulation recorded by aeolian deposits in the southern Tibetan Plateau

The pattern of changes in Holocene moisture conditions in the southern Tibetan Plateau (TP) and the associated driving mechanism are still controversial. Here, we present the results of an analysis of an aeolian sedimentary sequence from the Yarlung Zangbo River valley in the southern TP, which potentially provides a record of changes in moisture conditions during the Holocene, and hence changes in the atmospheric circulation process. Optically stimulated luminescence dating with the single-aliquot regeneration protocol was used to establish the chronology for the sequence, and geochemical and granulometric measurements were used to reconstruct the Holocene moisture history. The results indicate that moisture conditions were strongly influenced by the early Holocene maximum in summer insolation (30°N) and hence by the Indian summer monsoon (ISM), under which the weathering intensity was relatively high. However, at ∼7.6 ka the climate abruptly became drier, probably due to the weakening of the ISM. Subsequently, with the further decrease in summer insolation and increase in winter insolation, the variations in ISM-related moisture delivery to the southern TP were regulated by the enhanced winter mid-latitude Westerlies (MLW), resulting in increasing weathering intensity. Thus, the Holocene evolution of moisture conditions in the southern TP was mainly controlled by changes in the relative intensities of the ISM and the winter MLW, which depended on the variations of summer and winter insolation at 30°N. Overall, our results provide an improved understanding of the driving mechanism of climate change in the southern TP during the Holocene.

Sediment dating using Infrared Photoluminescence

Abstract Infrared photoluminescence (IRPL) is a Stokes-shifted emission arising from radiative relaxation of the excited state of the principal dosimetric tap in feldspar. Recent investigations have revealed that there exist two IRPL emissions at 880 nm and 955 nm (for excitation using 830 nm laser). Since IRPL does not depend on the recombination centers, the signal can be read out non-destructively; this allows us to insert its measurement in a conventional IRSL (infrared stimulated luminescence) or post IR-IRSL single-aliquot regenerative (SAR) dose protocol. In this study, we focus on the development of a SAR protocol using the two different IRPL emission bands (~880 nm and ~955 nm) and test their potential for sediment dating with known-age samples. Our results show that accurate equivalent doses from 100 to 300 Gy (age range 20–128 ka) can be obtained using an IRPL-based SAR protocol without a fading correction.

Revisiting the chronostratigraphy of Late Pleistocene loess-paleosol sequences in southwestern Ukraine: OSL dating of Kurortne section

Due to the general lack of other high-resolution paleoclimate records, loess-paleosol sequences are crucial archives for disentangling past climate variability in southeastern Europe. Here we present results of a multi proxy sedimentological and geochemical investigation of Kurortne loess-paleosol section from southwestern Ukraine, coupled with detailed optically stimulated luminescence (OSL) dating. OSL investigations were carried out on quartz grains of different grain sizes (4–11 μm, 63–90 μm and 90–125 μm), using the single aliquot regenerative (SAR) protocol. The OSL dating results are in line with previous findings on dating loess-paleosol sequences along the Black Sea shore in Romania, as well as worldwide: (i) ages obtained on different grain sizes are in agreement for equivalent doses of less than 200 Gy, whereas for higher equivalent doses 4–11 μm ages underestimate the coarser fraction ages; and (ii) an inverse correlation between dated grain size fractions and saturation characteristics is reported.Our combined dating and sedimentological approach would confirm that the investigated uppermost 4.5 m at Kurortne cover the Last Glacial Cycle, adding important data in better constraining local and regional chronostratigraphic correlations. The application of the SAR protocol on 63–90 μm quartz grains on samples collected from the lower part of S1 soil (the Kaydaky unit) and from the Kaydaky/Pryluky units boundary produced ages of 123 ± 10 ka and 85 ± 6 ka, respectively. As the temporal range covered by these units in the Ukrainian Quaternary stratigraphic framework is still debatable, our results confirm the broad correlation of the Kaydaky-Pryluky paleosol units at Kurortne with the last interglacial (i.e., MIS 5). Dating the Uday and Bug loess units produced ages corresponding to MIS 4 and MIS 2, respectively, whereas the sample collected from the Vytachiv unit provided an age of 37.7 ± 2.4 ka, assigning this paleosol to MIS 3. On the basis of trends in the magnetic enhancement, the onset of pedogenetic processes likely commenced already around 20 ka, but the formation of the topmost S0 soil has begun after 13.8 ± 1.0 ka.

Changes in the optically stimulated luminescence (OSL) sensitivity of single grains of quartz during the measurement of natural OSL: Implications for the reliability of optical ages

Abstract Single Aliquot Regeneration (SAR) protocol has been routinely used to estimate palaeodose for sediment samples. However, it was observed that significant changes in the optically stimulated luminescence (OSL) sensitivity occur during read out of the natural OSL and that the current SAR protocol does not take into account these changes (Singhvi et al., 2011). It was suggested that if not corrected, this change of OSL sensitivity would lead to substantive systematic offsets in ages based on the conventional SAR protocol. To circumvent this issue of sensitivity change of OSL, a natural correction factor based SAR (NCF-SAR) measurement protocol and a correction procedure was suggested by Singhvi et al. (2011) with an implicit but a reasonable assumption that the sensitivity of 110 °C TL peak of quartz correlates with the OSL sensitivity. Use of this correction resulted in reduced over-dispersion in paleodoses and additionally provided a satisfactory way to deal with samples, where natural signal was significantly higher than the saturation value of the regenerated signal. As a logical extension of this work, similar sensitivity changes in the OSL from single grains of quartz were examined and, their impact on the accuracy and reliability of single grain based SAR ages is discussed in this contribution. About ∼200 single grains each from 9 samples of diverse depositional environments were analysed and the NCF of each grain was measured. The single grain NCF’ [=(1/NCF)] values varied from 0.7 to 20. Of these ∼50% grains had sensitivity changes in the range of 0.7–1.3. The results indicated that, 1) the brighter grains (photon counts > 1000 c/s in a standard Risoe reader) had NCF′ closer to 1, though significant outliers did exist, 2) the distribution of NCF′ was positively skewed with significant number of values greater than one and, 3) the averaged single grain and multigrain NCF’ values were different, suggesting that in the case of multigrain aliquots, sensitivity changes of dim grains, on account of their larger numbers, collectively contributed significantly to the light sum in OSL.

OSL-SAR dating of sediments from Brazilian aeolian system: Dama Branca, Rio de Janeiro, morphodynamic study

It has been reported that the formation and stabilization of coastal dune fields in Brazil have a dependence on the climatic changes, Relative Sea Level (RSL) variations, etc. In this work, a dune field known as “Dama Branca”, located in the town of Cabo Frio, Rio de Janeiro, has been studied to understand its mobility, formation and stabilization. Dating by trapped charge dating techniques as Optically Stimulated Luminescence (OSL) using the Single Aliquot Regenerative protocol (SAR), helps us to understand the formation and dynamics of aeolian systems in Brazil. Samples from two positions; DB and 2DB, were collected from different heights and points for dating. The results obtained by OSL-SAR showed that ages decrease as the height from the dune base increase and older samples are found in deeper horizontal positions. The ages from the base of the studied dunes indicated that its stabilization occurred during the recess of the sea level and that erosion caused by the wind action is revealing an old generation of this dune filed.

Is there a common alpha-efficiency in polymineral samples measured by various infrared stimulated luminescence protocols?

Dating of polymineral silt-sized samples by use of post-infrared infrared stimulated luminescence (pIRIR) protocols at elevated temperature has recently gained attraction due to assumed lower rates of anomalous fading. The α-efficiency (or <i>a</i>-value) associated with the pIRIR signals as an integral part of age calculation has, however, not yet been sufficiently constrained. Here we present a set of 65 <i>a</i>-values determined for 47 samples collected across Europe with two different IRSL protocols in two laboratories. By testing the basic preconditions for application of the single-aliquot regeneration (SAR) procedure to constrain <i>a</i>-values and by comparing SAR results to <i>a</i>-values obtained by multiple-aliquot protocols, we demonstrate that SAR-derived <i>a</i>-values are reliable for the majority of samples. While aliquot size and signal resetting mode prior to α-regeneration do not appear to affect the resulting <i>a</i>-value, we detected significant differences in mean <i>a</i>-values measured in the two laboratories. For the pIRIR<sub>290</sub> signal, <i>a</i>-values average to 0.085 ± 0.010 (Bayreuth) and 0.101 ± 0.014 (Cologne), while a modified SAR protocol yields 0.081 ± 0.008 (Bayreuth). Whereas provenance-specific differences in <i>a</i>-values might be masked by overall scatter, systematic offsets between laboratories are attributed to technical issues such as heater and source calibration. Based on the present data set, use of the same routine dating equipment is strongly advised for both dose and <i>a</i>-value measurements.

Post-sterilization radiation dosimetry of commercial pharmaceuticals using optically stimulated luminescence

Sterilization with gamma irradiation has been established as an acceptable method highly advantageous compared to other methods for the sterilization of several products, including pharmaceutical preparations. However, the effects of irradiated drugs on the consumer when they are introduced in the human body are still unknown. Thus, consumers should be aware if a drug has been irradiated and freely choose whether to consume it or not. Consequently, development of drug irradiation detection methods, useful for regulatory compliance purposes, is an active area of investigation.To this respect, new OSL measurements on five commercial solid drugs (Daktarin®, Aspirin®, Panadol®, Brufen® and Procef®) for radiation doses up to several kGy were conducted in order to investigate if the OSL method can identify irradiated drugs. Dose response study, computerized curve deconvolution analysis (CCDA), fading test and sterilization dose recovery test with the SARHS protocol were conducted to investigate the optically stimulated luminescence (OSL) characteristics of the drugs and the properties of the involved traps.Results indicate that all drugs have a linear dose range up to 1–2 kGy, while the entire dose range can perfectly be fitted with an exponential decay curve. Although the fading rate varies, an appreciable signal remains unaffected even 6 months post irradiation in all drugs. The CCDA revealed that the kinetics are of second order and that all drugs have a very fast component with a lifetime of approximately 0.3–5.6 s. The single aliquot regenerative protocol for the calculation of the equivalent dose in heat-sensitive materials exhibiting sensitization (SARHS), developed in a previous work, was also tested on the solid drugs. The SARHS, which can correct for the sensitization effect without involving any heating, but introducing an optical bleaching procedure between the repeated irradiation/stimulation cycles during the construction of the calibration curve, proved capable of calculating the sterilization dose of irradiated drugs.The new findings are very promising towards the post-sterilization dosimetry of solid drugs, rendering the OSL and the SARHS protocol capable of the detection and the determination of the radiation dose applied in irradiated drugs, after the fading factor has been estimated.

On the importance of grain size in luminescence dating using quartz

There are two major problems commonly encountered when applying Optically Stimulated Luminescence (OSL) dating in the high dose range: (i) age discrepancy between different grain sizes, and (ii) age underestimation. A marked and systematic discrepancy between fine-grain (4–11 μm) and coarse-grain (63–90 μm) quartz single aliquot regeneration protocol (SAR) ages has been reported previously for Romanian and Serbian loess >40 ka (De of ∼100 Gy), generally with fine-grain ages underestimating the depositional age. In this paper, we show a similar age pattern for two grain size fractions from Chinese loess, thus pointing to a potential worldwide phenomenon. While age underestimation is often attributed to signal saturation problems, this is not the case for fine grain material, which saturates at higher doses than coarse grains, yet begins to underestimate true ages earlier. Here we examine the dose response curves of quartz from different sedimentary contexts around the world, using a range of grain sizes (diameters of 4–11 μm, 11–30 μm, 35–50 μm, 63–90 μm, 90–125 μm, 125–180 μm, and 180–250 μm). All dose response curves can be adequately described by a sum of two saturating exponential functions, whose saturation characteristics (D0 values) are clearly anticorrelated with grain diameter (φ) through an inverse square root relationship, D0 = A/√φ, where A is a scaling factor. While the mechanism behind this grain-size dependency of saturation characteristics still needs to be understood, our results show that the observation of an extended SAR laboratory dose response curve does not necessarily enable high doses to be recorded accurately, or provide a corresponding extended age range.

Thermally assisted OSL application for equivalent dose estimation; comparison of multiple equivalent dose values as well as saturation levels determined by luminescence and ESR techniques for a sedimentary sample collected from a fault gouge

Equivalent dose estimation (De) constitutes the most important part of either trap-charge dating techniques or dosimetry applications. In the present work, multiple, independent equivalent dose estimation approaches were adopted, using both luminescence and ESR techniques; two different minerals were studied, namely quartz as well as feldspathic polymineral samples. The work is divided into three independent parts, depending on the type of signal employed. Firstly, different De estimation approaches were carried out on both polymineral and contaminated quartz, using single aliquot regenerative dose protocols employing conventional OSL and IRSL signals, acquired at different temperatures. Secondly, ESR equivalent dose estimations using the additive dose procedure both at room temperature and at 90K were discussed. Lastly, for the first time in the literature, a single aliquot regenerative protocol employing a thermally assisted OSL signal originating from Very Deep Traps was applied for natural minerals. Rejection criteria such as recycling and recovery ratios are also presented. The SAR protocol, whenever applied, provided with compatible De estimations with great accuracy, independent on either the type of mineral or the stimulation temperature. Low temperature ESR signals resulting from Al and Ti centers indicate very large De values due to bleaching in-ability, associated with large uncertainty values. Additionally, dose saturation of different approaches was investigated. For the signal arising from Very Deep Traps in quartz saturation is extended almost by one order of magnitude. It is interesting that most of De values yielded using different luminescence signals agree with each other and ESR Ge center has very large D0 values. The results presented above highly support the argument that the stability and the initial ESR signal of the Ge center is highly sample-dependent, without any instability problems for the cases of quartz resulting from fault gouge.

OSL studies of local bricks for retrospective dosimetric application

Luminescence properties of quartz extracted from bricks has been reported worldwide for its use in dose estimation in case of nuclear or radiological accident. Accordingly, in this study the feasibility of utilizing the optically stimulated luminescence (OSL) emission of quartz extracted from red bricks collected from three different locations in and around Mumbai, India for retrospective dosimetry was explored. Thermoluminescence and OSL characterization of the samples were carried out. The growth curve, thermal stability and equivalent dose plateau of the OSL signal suggested the signals to be well behaving. Subsequently, the dose recovery tests carried for different administered doses, using single aliquot regenerative protocol, demonstrated the feasibility of the OSL emissions of these samples for dose evaluation in retrospective dosimetry.

Reliability of single aliquot regenerative protocol (SAR) for dose estimation in quartz at different burial temperatures: A simulation study

The single aliquot regenerative protocol (SAR) is a well-established technique for estimating naturally acquired radiation doses in quartz. This simulation work examines the reliability of SAR protocol for samples which experienced different ambient temperatures in nature in the range of −10 to 40 °C. The contribution of various experimental variables used in SAR protocols to the accuracy and precision of the method is simulated for different ambient temperatures. Specifically the effects of paleo-dose, test dose, pre-heating temperature and cut-heat temperature on the accuracy of equivalent dose (ED) estimation are simulated by using random combinations of the concentrations of traps and centers using a previously published comprehensive quartz model. The findings suggest that the ambient temperature has a significant bearing on the reliability of natural dose estimation using SAR protocol, especially for ambient temperatures above 0 °C. The main source of these inaccuracies seems to be thermal sensitization of the quartz samples caused by the well-known thermal transfer of holes between luminescence centers in quartz. The simulations suggest that most of this inaccuracy in the dose estimation can be removed by delivering the laboratory doses in pulses (pulsed irradiation procedures).

Estimation of equivalent dose and its uncertainty in the OSL SAR protocol when count numbers do not follow a Poisson distribution

Abstract The current work focuses on the estimation of equivalent dose and its uncertainty using the single aliquot regenerative protocol in optically stimulated luminescence measurements. The authors show that the count numbers recorded with the use of photomultiplier tubes are well described by negative binomial distributions, different ones for background counts and photon induced counts. This fact is then exploited in pseudo-random count number generation and simulations of De determination assuming a saturating exponential growth. A least squares fitting procedure is applied using different types of weights to determine whether the obtained De's and their error estimates are unbiased and accurate. A weighting procedure is suggested that leads to almost unbiased De estimates. It is also shown that the assumption of Poisson distribution in De estimation may lead to severe underestimation of the De error.

Extending the area of investigation of fine versus coarse quartz optical ages from the Lower Danube to the Carpathian Basin

Despite the general satisfactory performance of quartz in the single aliquot regeneration protocol (SAR), previous optically stimulated luminescence (OSL) dating studies of key loess sections in Romania, Lower Danube region, revealed a disturbing disagreement among the ages obtained on fine (4–11 μm) grains and coarse (63–90 μm) grains respectively. The current study aims at expanding these investigations, both by extending the area of study from the Lower Danube Basin to the Carpathian Basin and by applying time-resolved optically stimulated luminescence (TR-OSL) on quartz, in order to gain further insights into the above mentioned behaviour. The samples from the Orlovat loess paleosol section (Vojvodina, Serbia) showed a similar behaviour to that previously reported on Romanian loess. A marked difference between the dose saturation characteristics of fine and coarse quartz OSL signals is observed for both continuous wave (CW-OSL) and pulsed OSL (POSL), where the dose response (up to 1000 Gy) is well described by a sum of two saturating exponential functions. TR-OSL measurements show one single, characteristic quartz lifetime for both natural as well as regenerative signals in the entire dose range investigated. A general disagreement between the ages obtained on the two grain sizes for samples with equivalent doses higher than about 100 Gy is reported as in the case of Romanian loess, inferring that the age discrepancy between the two grain sizes might be more widespread than previously thought.

Luminescence dating of young coastal deposits from New Zealand using feldspar

A new measurement protocol has been tested on K-feldspars from Whanganui Inlet and Parengarenga Harbour, New Zealand. A Single Aliquot Regenerative (SAR) dose protocol, using two successive infrared (IR) stimulations (post-IR IR SAR protocol) is setup for these young (<1000 years) coastal sediments. Significant anomalous fading (g2days=7 %/decade) is observed using the conventional IR signal measured at 50°C. In contrast, the fading rate of the IR signal measured at elevated temperature (150°C) after the IR stimulation at 50°C (a post-IR IR signal) is not significant (g2days≤ 1 %/decade). Surprisingly low residual infrared stimulated luminescence (IRSL) signals were observed for a surface sample, suggesting that accurate ages as young as ∼50 years can be obtained for these recent deposits. IRSL ages ranging between 48±6 years and 1050±50 years are obtained from six samples, indicating that sediment accumulation has occurred at the two sites during the last millennia, despite a falling trend in relative sea-level in Whanganui Inlet and a stable relative sea-level at Parengarenga Harbour.

Changes in natural OSL sensitivity during single aliquot regeneration procedure and their implications for equivalent dose determination

Abstract Measurement of low temperature (90°C–120°C) Thermoluminescence (TL) sensitivity of natural quartz samples subjected to pre-heating and optical stimulation indicate that significant sensitivity changes can occur during measurement of the natural Optically Stimulated Luminescence (OSL). During the measurement of natural signal, the luminescence sensitivity of samples can change by 40%. The sensitivity changes both during the initial preheat and the measurement of natural OSL. The currently used version of Single Aliquot Regeneration (SAR) protocol measures and corrects for the sensitivity changes after preheat and readout of natural OSL. However, it does not take into account the changes in sensitivity during the readout of the natural signal. We therefore developed a correction procedure so that both the natural and the regenerated OSL intensities can be measured and plotted with the same sensitivity and suggest that in the absence of such a correction, a considerable fraction of the SAR based ages could have systematic errors. The correction for the sensitivity is based on the use of sensitivity of 110°C TL quartz peak, which is correlated to OSL signal (Murray and Roberts, 1998). The use of 110°C peak provides a reasonable measure of the changes in OSL sensitivity of quartz. A modified Natural Sensitivity Corrected-SAR (NSC-SAR) procedure, that comprises the measurement of, 1) the TL intensity of 110°C peak for a test dose on sample as received (i.e. natural sample) and, 2) the sensitivity of the 110°C peak of the same sample after the preheat and read out of the natural OSL, is proposed. This ratio, termed as Natural Correction Factor (NCF), then provides a way to correct for sensitivity changes. Results on samples from diverse depositional environments indicated that the NSC-SAR consistently (without exception) provided improved distribution in paleodoses i.e. a lower scatter compared to the standard SAR protocol. In addition, the use of this protocol also resolved anomalous cases where the intensity of natural OSL was significantly above the saturation intensity of the regenerated OSL. Implicitly, this study implies a caution on the use of palaeodoses obtained from single grains as such a correction is not possible in the currently used automated single grain OSL measurement systems. The only way now on will be to analyze aliquots with only a grain on them.

Improving the TT-OSL SAR protocol through source trap characterisation

Abstract Thermally-transferred optically stimulated luminescence (TT-OSL) extends the age range of OSL dating using quartz. A set of experiments have been undertaken to determine the kinetic parameters of the TT-OSL source traps, and this information has been used to propose an improved TT-OSL single aliquot regenerative (SAR) dose protocol. By combining together OSL and thermoluminescence (TL) measurements on fine-grained quartz, a correspondence between TL peaks and the TT-OSL signal is found. The thermal stability of the main TT-OSL trap was estimated by applying Hoogenstraaten’s method and allowing for thermal quenching; this predicts a lifetime of 4.5 Ma at 10 °C. A set of experiments were undertaken to refine the treatment needed at the end of each SAR cycle to erase the previously acquired TT-OSL signal. An improved TT-OSL SAR protocol using this treatment is proposed, and it is tested on quartz from a young Holocene sample. These tests yielded excellent recycling ratios and excellent dose recovery.