Dose Recovery Tests Research Articles

OSL signal saturation and dose rate variability: Investigating the behaviour of different statistical models

Statistical models derived from two inferences, Frequentist and Bayesian, are compared for OSL data analysis. Controlled laboratory experiments were designed to investigate: (1) dose recovery behaviour and (2) dose variability. (1) Dose recovery tests were performed on single grains of quartz close to saturation. We test whether the Central Dose Model (CDM, Galbraith, 1999), which is the most commonly used model, is capable of converging towards the given dose. Furthermore, a set of new Bayesian age models developed by Combès and Philippe (2017) is applied to determine the dose recovery ratio. The results suggest that the CDM underestimates the given dose if no D0 criterion is applied. (2) Bayesian models and frequentist models (CDM and Average Dose Model: ADM, Guérin et al., 2017) are used in dose variability experiments to compare the estimated average dose. To mimic natural beta dose heterogeneity to single grains of quartz, log-normal dose distributions with different dispersions were created artificially. The results indicate an underestimation of the average dose by at least 10% for CDM, lognormal-median and Cauchy for dispersion values greater than 40%. Conversely, we show that the ADM, the Bayesian lognormal-average and Gaussian models converge towards the average of the distribution and display almost no underestimation, for a significant gain in accuracy.

Luminescence dating of pre-Eemian (pre-MIS 5e) fluvial terraces in Northern Bavaria (Germany) – Benefits and limitations of applying a pIRIR225-approach

Quartz optically stimulated luminescence (OSL) and post-IR IRSL dating of potassium-rich feldspar separates were applied to fluvial sediments which had been supposed to be of pre-Eemian (pre-MIS 5e) age. Our aim was to establish a reliable chronology for the upper three terrace levels from a sequence of five fluvial terraces in a region of Northern Bavaria (Germany) characterized by a complex Pleistocene fluvial history. The investigated quartz samples proved to be in dose saturation and the calculated OSL ages could only be interpreted as minimum age estimations. The performance of the used pIRIR225-approach was tested by a set of bleaching experiments, dose recovery tests (DRT) and measurements of sample specific laboratory fading rates. Despite applying a pIRIR225-protocol, the phenomenon of ‘anomalous fading’ remained a major problem for age calculation in this study. Although various fading correction methods were applied, only the model proposed by Huntley and Lamothe (2001) could successfully be used. Overall, the corrected pIRIR225-ages were in good agreement with age constraints derived from stratigraphical and sedimentological findings. For some feldspar samples, however, the determined ages were far beyond a realistic age range for a meaningful interpretation when considering the (morpho-)stratigraphical setting. Although the reasons for these significant age overestimations are not clear so far, they might either indicate methodological limitations of the post-IR IRSL approach or point to serious problems attributed to the luminescence properties of the used K-feldspar separates or to the specific regional environmental settings during sample deposition. Despite these problematic findings, the numerical results derived from the post-IR IRSL measurements could be used to establish a preliminary chronological framework for the various evolutionary stages identified for the research area.

Dose recovery performance in double IRSL/pIRIR SAR protocols

In an attempt to test feldspar dating techniques that would use both IR50 and pIRIR225 equivalent doses, we investigated the impact of various thermal treatments on the recovery of a laboratory dose. It is observed that the most reliable protocols for delivering acceptable recovery ratios may be sample dependant. Appropriate thermal treatments, including a potentially efficient pre-test dose thermal wash (PTD TW) could yield dose recovery ratios in a range of ±5% around unity for both IR50 and pIRIR225 signals. These experiments are strong indications that rigorous dose recovery tests should be carried out before the measurement of the equivalent dose of feldspar in double SAR protocols.

Late Quaternary OSL chronologies from the Qinghai Lake (NE Tibetan Plateau): Inter-comparison of quartz and K-feldspar ages to assess the pre-depositional bleaching

Abstract Signal resetting prior to deposition is an important factor for the accuracy of luminescence dating. In this study, resetting of the quartz optically stimulated luminescence (OSL) signal from samples collected from different depositional environments (alluvial, beach, and aeolian sediments) around the Qinghai Lake basin (northeastern Tibetan Plateau) was examined using its inter-comparison with post-IR infrared stimulated luminescence (IRSL) measured at 290 °C (pIRIR290) from K-feldspar. Dose recovery tests were carried out to test the success of the single aliquot regenerative-dose (SAR) protocol for quartz and feldspar. Additionally, stability tests (first IR temperature plateau and g-values) were performed for the pIRIR290. We observe that most of the K-feldspar pIRIR290 and quartz OSL ages are consistent with each other (within 10%), suggesting that the quartz OSL signal was well-bleached prior to the deposition. The ages of loess samples range between ∼13.1 and ∼1.5 ka, the alluvial sediments between ∼35 ka and ∼14 ka, and beach sediments between 60 and 50 ka, corresponding to early Marine Isotope Stage (MIS) 3. These quartz OSL chronologies suggest a lake highstand during very early MIS 3, a lowstand during late MIS 3 and MIS 2, and widespread loess accumulation through the Holocene in the Qinghai Lake basin.

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.

Variability in the thermal stability of OSL signal of single-grain quartz from the Nihewan Basin, North China

Abstract A large range of equivalent dose (De) values was observed by applying the single-aliquot regenerative-dose (SAR) procedure to the optically stimulated luminescence (OSL) signal of single grains of quartz extracted from sediments at the Yujiagou site in the Nihewan Basin, north China. Many quartz grains yielded De values close to zero, which results in severe age underestimation when compared with the results of potassium-rich feldspar grains measured using post-infrared infrared stimulated luminescence (pIRIR) procedure. Dose recovery tests suggest that the SAR protocol is suitable for De determination. However, a large grain-to-grain variation in thermal stability was identified based on single-grain pulse-annealing measurements. We found that most of the zero-dose or low-dose grains are associated with thermally unstable OSL signals, which explains the large dispersion of the quartz OSL De distribution. This is further confirmed by the short lifetime of the unstable OSL signals obtained using single-aliquot pulse-annealing test.

Quartz OSL and K-feldspar post-IR IRSL dating of loess in the Huangshui river valley, northeastern Tibetan plateau

Abstract The northeastern Tibetan Plateau (NETP) is located in the climatically sensitive semiarid zone between the regions controlled by the East Asian monsoon and the Westerlies and loess deposits there may preserve a record of regional paleoenvironmental change. Establishing a robust loess chronology is critical for interpreting and correlating environmental records. In this study, quartz optical stimulated luminescence (OSL) and K-feldspar post-IR infrared (IR) stimulated luminescence (pIR-IRSL) dating methods have been used to date the Ledu loess section in the Huangshui river valley, on the NETP. In terms of quartz OSL dating, the results from both the 63–90 μm and 38–63 μm quartz fractions are consistent within errors. The reliability of the 63–90 μm K-feldspar pIRIR dating was confirmed by internal check using preheat plateau, dose recovery, anomalous fading, and residual dose tests. The results suggest that the K-feldspar pIRIR signals at stimulation temperatures of 170 and 225 °C were well bleached before deposition of Ledu loess. Comparison between quartz OSL and K-feldspar pIRIR dating indicates that quartz ages older than 50 ka (∼150 Gy) may be underestimated. In establishing the chronological framework for the study section, we selected quartz OSL results for ages 50 ka. The results demonstrate that aeolian dust accumulated continuously between 67 and 25 ka, and there were two gaps in deposition, between 25 and 2 ka and from 80 to 67 ka.

Behavior of the electron trapping probability change in IRSL dating of K-feldspar: A dose recovery study

Abstract Dose recovery tests were performed on potassium feldspar using the single-aliquot regenerative-dose (SAR) multi-elevated-temperature post-IR IRSL (MET-pIRIR) dating protocol with a large number of samples from various backgrounds. The dose recovery ratios were always smaller than unity for the 50 °C IRSL signal, but the ratios increased with signals from elevated temperatures. For the pIRIR signal at 250 °C, the recovery ratios were within the range of 1.0 ± 0.1. Underestimations of the recovery ratios for low-temperature IRSL signals resulted from the increase of the electron trapping probability during the first preheat treatment. The electron trapping probability can be reset by solar bleaching. The modified SAR protocol with solar bleaching behind each cycle or the MAR protocol is recommended if the low-temperature IRSL signals are applied to obtain ages. Solar simulator with the xenon arc lamp is more efficient in reducing the electron trapping probability compared to the sunlight. Bleaching duration with the solar simulator should be chosen with caution.

Characterising the luminescence behaviour of ‘infinitely old’ quartz samples from Switzerland

Abstract Less than 20% of aliquots measured for a set of ‘infinitely old’ quartz samples (i.e. burial time >1 Ma) from the northern Alpine foreland of Switzerland were found to display a natural signal that was in saturation. The signals from small aliquots displayed a range of saturation levels of between ∼300 and 600 Gy and dose recovery tests were successful up to 350 Gy. A comparison of dose response curves and test-dose response for a single-aliquot regenerative-dose (SAR) and a sensitivity-corrected multiple-aliquot regenerative-dose (SC-MAR) protocols, showed similar growth and sensitivity. The addition of a large laboratory dose was able to bring the natural signals into saturation, and no evidence was found to suggest that the unsaturated signals were due to a problem with the SAR protocol. While laboratory isothermal decay measurements confirmed that the lifetime of the luminescence signal was insufficient beyond 1 Ma, a correction for the thermal loss of signal confirmed that natural signals should still be in saturation, and that thermal instability alone cannot explain the unsaturated signals. Fading tests recorded athermal loss of signal, and higher g-values displayed a significant correlation with lower levels of signal saturation. A combination of thermal and athermal loss of the signal is understood to be responsible for the unsaturated signals in these infinitely old samples. Extensive isothermal decay measurements revealed a surprisingly broad range of lifetimes for the quartz signals of over two orders of magnitude within the studied samples, and this was also observed in several batches of calibration quartz. While machine repeatability was shown to explain part of the observed variability, further work is encouraged on samples from other regions to establish the major source of the spread, and caution is recommended before making lifetime comparisons between studies and settings.

Thermoluminescence of electronic components from mobile phones for determination of accident doses

The dosimetric properties of resistor substrates extracted from the circuit board of mobile phones were studied in detail using Thermoluminescence for the purpose of dose reconstruction following a radiological accident or attack. Many studies have shown the usefulness of this material using Optically Stimulated Luminescence but TL studies are scarce. The typical glow curve of a set of irradiated resistors has a peak at about 170 °C. Unexposed resistors showed a strong zero dose signal in the higher temperature region, peaking between 300 and 350 °C, which also led to a minor zero dose being detected in the chosen integration window of 100–200 °C. Exposure to white light can significantly increase the zero dose, presumably due to phototransfer of charge carriers from deep traps into the dosimetric trap. The dose response of the TL signal was linear up to several Gy but an irreversible sensitivity change was observed in the first thermal readout. A correction factor was therefore deduced from a number of dose recovery tests. Similar to the OSL signal, the TL signal is not stable but fades with time since irradiation. Overall, a slightly smaller fading rate up to 60 days was observed for the TL signal, as compared to the OSL signal. A protocol is proposed for TL based on the measured properties and validated in irradiation trials.

Luminescence properties of common salt (NaCl) available in Nigeria for use as accident dosimeter in radiological emergency situation

In the event of a radiological accident or attack, it is important to assess and quantify radiation dose to the population. This could be done using materials in the vicinity that are sensitive to ionizing radiation. Common salt (NaCl) is known to be a sensitive thermoluminescence (TL) phosphor. Luminescence properties of common salt (NaCl) used in Nigeria were investigated using an automated luminescence reader Risø TL/OSL-DA-15, with attention focused more on the Optically Stimulated Luminescence (OSL). Strong radiation-induced TL and OSL signals were observed. The TL peaks occurred at about 100 °C, 240 °C and 280 °C. The dose response of both the TL and OSL signals showed a linear relationship. From the OSL pulse anneal curve with TL curve, a preheat temperature of 190 °C for 10 s was found adequate for the OSL measurements. There was no significant difference in the OSL decay for stimulation temperatures of 100 and 120 °C. Fading experiment over a storage period of 14 days showed about 13 and 3% decrease in the OSL signal of sample 1 and sample 2, respectively. The ratios of measured to given dose for dose recovery test were within ±19% of unity. Within the limit of error the samples could be used as a complementary emergency dosimeter in radiological accident situation.

Dose recovery and residual dose of quartz ESR signals using modern sediments: Implications for single aliquot ESR dating

Electron spin resonance (ESR) dating is a promising method for dating sedimentary quartz beyond a million years. Here we investigate the use of modern quartz samples with well bleached optically stimulated luminescence (OSL) signals to study the bleachability of the ESR signals, and to further check the applicability of the ESR single aliquot regenerative dose (SAR) protocol. The residual doses from five samples using both the Al- and Ti-centres were in general found to be large and, especially for the Al-centre, with a large variability. Although it is known that the Ti-centre is fully bleachable in nature, a subtraction of the residual dose using a modern analogue should be considered. Dose recovery tests were performed by using the single aliquot regenerative and added dose (SARA) method, and the dose recovery ratio (measured-to-added dose ratio) was obtained from the slope of the added vs. measured dose plot. The dose recovery ratio from the Ti-centre was satisfactory for all five samples indicating the validity of the proposed ESR SAR protocol. However, only one sample yielded a SARA plot for the Al-centre. This could be explained by the decrease in sensitivity caused by the annealing step in the SAR protocol and/or to the erroneous subtraction of the intensity of the peroxy centre, which overlaps with the Al-centre.

Thermoluminescence investigations on tobacco dust as an emergency dosimeter

Silicates extracted from tobacco dust in cigarettes were investigated for their suitability as an emergency dosimeter in accidental situation using thermoluminescence technique. A typical glow curve (at a heating rate of 2 °C s−1) of irradiated dust silicates in the transmission window between 300 and 500 nm has two prominent peaks at about 83 °C and 137 °C and a weak one at about 181 °C which were all distinguishable from the natural thermoluminescence. The TL spectrum of highly irradiated dust samples showed the existence of three dominant emissions at 1.66 eV (745 nm), 2.2 eV (560 nm) and 2.81 eV (440 nm), which are similar to those reported for feldspar. Repeated irradiation and TL measurement did not affect the sensitivity of the 137 °C peak, if the glow curve is terminated at 300 °C. A linear dose response of the TL signal was observed for doses between 0.1 and 10 Gy. A preheat temperature of 110 °C was found to be optimal for the emptying of the low temperature peak which is not stable. The TL signal is not stable but fades with time since irradiation. Furthermore it can be bleached by daylight but the dust seemed to be sufficiently light shielded in intact cigarettes. Based on the experimental dosimetric properties, a measurement protocol for the detection of absorbed radiation dose was developed. The result of a dose recovery test showed a reasonable agreement between fading corrected dose and given dose.

The luminescence dating chronology of a deep core from Bosten Lake (NWChina) in arid central Asia reveals lake evolution over the last 220 ka

The lacustrine deposits of lakes in arid central Asia (ACA) potentially record palaeoclimatic changes on orbital and suborbital time scales, but such changes are still poorly understood due to the lack of reliable chronologies. Bosten Lake, the largest freshwater inland lake in China, is located in the southern Tianshan Mountains in centralACA. A 51.6‐m‐deep lacustrine succession was retrieved from the lake and 30 samples from the succession were used for luminescence dating to establish a chronology based on multi‐grain quartzOSLand K‐feldspar post‐IR IRSL(pIRIR290) dating. QuartzOSLages were only used for samples from the upper part of the core. The K‐feldspar luminescence characteristics (dose recovery test, anomalous fading test, firstIRstimulation temperature plateau test) are satisfactory and from the relationship amongst the quartzOSL,IR50andpIRIR290doses we infer that the feldspar signals are likely to be well bleached at deposition. Bacon age‐depth modelling was used to derive a chronology spanning the lastc. 220 ka. The chronology, lithology and grain‐size proxy record indicate that Bosten Lake formed at leastc. 220 ka ago and that lake levels fluctuated frequently thereafter. A stable deep lake occurred atc. 220, 210–180,c. 165, 70–60, 40–30 and 20–5 ka, while shallow levels occurred atc. 215, 180–165, 100–70, 60–40 and 30–20 ka. Bosten Lake levels decreased by at least ~29 m and possibly the lake even dried up betweenc. 160 andc. 100 ka. We suggest that the water‐level fluctuations in the lakes of ACA may not respond directly to climatic changes and may be affected by a number of complex factors.

Luminescence dating of glaciolacustrine silt in overdeepened basin fills beyond the last interglacial

Abstract {OSL} and {IRSL} dating are applied to samples from a 152 m-long drill core to constrain the timing of three glaciolacustrine depositional periods within the infill of an overdeepened bedrock trough in the Lower Glatt valley, N Switzerland. The characterisation of the dose-response suggests that the polymineral {IRSL50} and pIRIR180/225 signals are close to saturation, while quartz {OSL} ages are within the range of reliable dating. The demarcation of the upper quartz {OSL} dating limit, however, remains challenging. Dose-recovery tests performed with long storage periods were used to investigate the reliability of the high region of the dose-response curve. They suggest an upper limit for reliable dating of ~400 Gy for these samples, which was considerably lower than the commonly used 2D0 criterion. Lifetimes were calculated for the quartz {OSL} and the thermal stability of the signal is not considered as problematic for the determined ages. Allowing for a contribution from inherited dose due to partial bleaching, places the infill of the overdeepened valley within the penultimate glacial cycle (MIS6).

Evaluating isothermal thermoluminescence and thermally transferred optically stimulated luminescence for dating of Pleistocene sediments in Amazonia

Abstract The paleogeography of Amazonia lowlands during the Pleistocene remains hampered by the lack of reliable absolute ages to constrain sediment deposition in the hundred thousand to few million years timescales. Optically stimulated luminescence (OSL) dating applied to quartz has provided important chronological control for late Quaternary sediments, but the method is limited to the last ∼150 ka. In order to extend the age range of luminescence dating, new signals from quartz have been investigated. This study tested the application of isothermal thermoluminescence (ITL) and thermally transferred optically stimulated luminescence (TT-OSL) signals of quartz for dating of fluvial terraces from eastern Amazonia. ITL and TT-OSL signals measured in a modern fluvial sediment sample have shown small residual doses (4 and 16 Gy), suggesting adequate bleached sediments for the target dose range (>150 Gy). This sample responded well to dose recovery test, which showed that the ITL and TT-OSL signals grow to higher doses compared to the doses estimated by the conventional OSL signal. The ITL signal saturated for doses significantly lower than doses reported in the literature. Most dating samples were beyond the ITL saturation doses and only TT-OSL signals were suitable to estimate equivalent doses. Burial ages ranging from 107 to 340 ka were estimated for the fluvial terraces in the lower Xingu River. The main ages uncertainties are related to dose rate changes through time. Despite the uncertainties, these ages should indicate a higher channel base level during the Middle Pleistocene followed by channel incision, possibly due to episodes of increased precipitation in the Xingu watershed.

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.

A detailed post‐IR IRSL dating study of the Niuyangzigou loess site in northeastern China

In this study, we report standard quartz SAR OSL and post‐IR infrared (IR) stimulated luminescence (post‐IR IRSL; pIRIR290) measurements made on sand‐sized quartz and K‐feldspar extracts from the loess‐palaeosol sequence at Niuyangzigou in northeastern China. The quartz OSL characteristics are satisfactory. Extensive pIRIR50,290 dose recovery tests were performed by adding doses on top of the natural dose. We found that dose recovery ratios improve significantly when the test dose ranges between ~15 and ~80% of the total dose, and good dose recovery (within ±5% of unity) can be obtained up to ∼800 Gy. Otherwise, the dose recovery ratio deviates from unity. The De values also depend on the test dose size and so we conclude that the effect of test dose size should be routinely considered in pIRIR dating. First IR stimulation plateau pIRIR290 results are compared with multiple elevated temperature ‐pIRIR (MET‐pIRIR) data. It appears that the low temperature MET‐pIRIR data are strongly affected by poor dose recovery, but this is not the case for the pIRIR290 results. Natural signal measurements at the highest (first IR) stimulation temperature on a sample expected to be in field saturation suggest that ~10% signal loss occurs in pIRIR signals. Long‐term laboratory bleaching experiments (>80 days) show that a constant (or very difficult to bleach) residual pIRIR290 signal is reached after ~300 h, corresponding to a dose of 6.2±0.7 Gy. Quartz OSL and feldspar pIRIR50,290 ages are in good agreement at least back to c. 70 ka. Beyond this the quartz ages begin to underestimate but the feldspar ages are in agreement with the expected Last Interglacial age palaeosol.

High-resolution OSL dating of a coastal sediment sequence from the South Yellow Sea

The coastal sediments of the South Yellow Sea (SYS) provide a record of regional land– sea interactions. This study investigated the applicability of optical dating, using coarse-grained quartz, to provide a chronology of these sediments. A 150-m-long drilling core (YZ07) was retrieved from the southwest coast of the SYS on the northern flank of the Yangtze River delta. Overall, 28 samples extracted from the upper 50 m of core YZ07 were investigated. Preheat plateau and dose recovery tests were conducted. The optically stimulated luminescence (OSL) signals were typical of quartz and they were dominated by fast components. The spread in measured equivalent doses (D<sub>e</sub>s) for each sample was generally consistent with the OSL signals being fully reset before deposition. The OSL ages generally increased with depth and indicated a 24-ka sedimentary record for the upper 50 m of the core. The age–depth relationship revealed two distinct sedimentary periods: (1) very slow sedimentation or even a depositional hiatus from the last glacial maximum (LGM) to the early Holocene (~24 to 8 ka); (2) very fast sedimentation at a rate of ~6 m/ka during the middle to late Holocene (since ~8 ka). It is speculated that sedimentation within the study area since the LGM might have been related to sea level change, delta initiation, and incised-valley fill processes.

Sandy beach ridges from Xingkai Lake (NE Asia): Timing and response to palaeoclimate

Abstract Lake beach ridges and their sediments have been investigated as palaeoenvironmental records. Robust chronology is crucial to utilize this archive for palaeoenvironmental reconstruction and interpretation. This study investigates the optically stimulated luminescence (OSL) dating of quartz in two beach ridges of aeolian origin from Xingkai Lake (NE Asia). The applicability of the selected measurement procedure is validated by a set of internal tests on luminescence characteristics such as preheat plateau test and dose recovery test, and the reliability of the resulting 24 OSL ages are also confirmed by agreement with four 14C ages as well as two K-feldspar luminescence dates. The constructed chronologies are thought to be robust in the stratigraphic and geomorphologic context. The two aeolian beach ridges (B1 and B2) are dated to ∼32–15 ka and ∼1.2–0.5 ka, respectively, which are interpreted as two distinct periods of lake lowstand that could have caused beach exposure and provided a more extended sand source for foredune formation around Xingkai Lake. These two lowstands could be correlated to the dry/cold regional climate including the time span from late MIS3 to late glacial and the most recent one at the late Holocene.