Multiple-aliquot Regenerative-dose Research Articles

Characteristics of the quartz isothermal thermoluminescence (ITL) signal from the 375 °C peak and its potential for extending the age limit of quartz dating

The quartz isothermal thermoluminescence (ITL) signal measured at 330 °C (ITL330) has been proposed as a method to measure deep traps in quartz, i.e., 375 °C TL peak, therefore offering the potential to extend the dating limit of quartz. However, little is known about the applicability of this signal for dating. We therefore investigate the characteristics of the ITL330 signal, in terms of the origin of the signal, thermal stability, and bleachability. Since the trapping sensitivity changes induced by high temperature treatments undermine the application of the single aliquot regenerative dose (SAR) protocol, here we evaluate the reliability and applicability of the multiple aliquot methods, i.e., multiple aliquot additive dose (MAAD) and multiple aliquot regenerative dose (MAR) protocols, using samples from the Luochuan section on the Chinese Loess Plateau with the independent age control. Results indicate that the ITL330 signal is closely associated with the 375 °C peak of the glow curve, originating from a deep trap at about 1.8 eV with a thermal lifetime of ∼1010 years at 10 °C. The natural ITL330 dose response curve (DRC) indicates the signal has a theoretical dating range up to ∼800 Gy, equivalent to ∼230 ka. When the natural DRC is compared with the laboratory generated DRCs using MAR and MAAD protocols, they start to diverge in shape after ∼200 Gy, resulting in significant ITL330 age underestimation beyond ∼70 ka. However, application of the pulsed-irradiation (PI) method for the MAAD protocol reveals that the shape of the natural DRC can mostly be reproduced with the PI-MAAD protocol and thus it can provide reliable ages up to natural saturation at ∼230 ka. While further investigations are required to assess the impact of the repeated pulse irradiation and heating on the signal and determine the optimal pulsed irradiation conditions, it appears that this approach can be a promising step forward to provide a better simulation of the trapping conditions in nature.

A comparative study of sand- and silt-sized quartz fractions for MAR-VSL dating using loess-palaeosol deposits in southern Germany

Multiple-aliquot regenerative-dose violet stimulated luminescence (MAR-VSL) dating studies of the Chinese loess-palaeosol sequence in Luochuan using sand- and silt-sized quartz have previously produced inconsistent results; the VSL ages were in agreement with their independent ages up to ∼900 ka for sand-sized quartz, whereas the silt-sized VSL ages underestimated the independent chronology beyond ∼100 ka. Here we therefore evaluate the VSL dose response pattern of sand- (63–100 μm) and silt-sized (4–11 μm) quartz grains from the loess-palaeosol sequence in southern Germany in high resolution but with a limited age range up to ∼160 ka. All the samples studied benefit from good age control provided by reliable quartz optically stimulated luminescence (OSL) ages and fading corrected feldspar post-infrared infrared stimulated luminescence at 225 °C (pIRIR 225 ) ages, which can be used for assessing the validity of the estimated VSL ages. The comparison of the MAR standardised dose response curve (DRC) using regeneration doses up to ∼1000 Gy for both grain size fractions demonstrates that they are almost similar in shape with comparable characteristic saturation doses. The comparison of the natural and laboratory generated DRCs of each grain size reveals that they broadly overlap in the low dose range for both fractions, while in the high dose range the deviation between natural and laboratory DRCs is higher for the silt-sized quartz fraction. It is also shown that the magnitude of the characteristic saturation dose is dependent upon the size of the maximum given dose, especially for the silt-sized quartz. The constructed laboratory standardised DRCs to very high doses (up to ∼6000 Gy) showed continuous signal growth at high doses, particularly in the case of silt-sized quartz grains, thereby confirming our previous observation. The sand-sized quartz has a much less pronounced linear growth component and can therefore be considered more suitable for dating samples with equivalent doses falling on the high dose region of the DRC.

Comparison of Equivalent Doses Obtained with Various post-IR IRSL Dating Protocols of K-Feldspar

Abstract Five dating protocols with post-infrared infrared (IR) stimulated luminescence signals (i.e. pIRIR) were performed on the K-feldspar of loess samples. Two of them were the single-aliquot regenerative-dose protocol (SAR) with two-step pIRIR stimulation, with the first IR stimulation at 50°C or 200°C and the second at 290°C (pIR50IR290, pIR200IR290). Two of them were the SAR protocols with five-step or six-step IR stimulation at multiple elevated temperatures to 250°C or 300°C (MET-pIRIR250, MET-pIRIR300). The final one was the multiple-aliquot regenerative-dose (MAR) protocol with the MET-pIRIR300 signal, together with a 500°C heat treatment administered before the test dose (‘MAR with heat’). The results show that when the equivalent dose (D e) of the sample was less than 500 Gy, all of the protocols gave consistent results; however, when D e exceeded 750 Gy, all of the SAR protocols underestimated De . The pIR50IR290 signal had the highest degree of underestimation, while the pIR200IR290, MET-pIRIR250 and MET-pIRIR300 signals had similar De values and similar degrees of underestimation. Possible reasons for the SAR D e underestimation are discussed. We suggest that only the ‘MAR with heat’ protocol is suitable for samples with D e exceeding 750 Gy.

Chronology of the Huxushan Paleolithic Site in South China: Inferred from Multiple Luminescence Dating Techniques

Abstract The Huxushan archaeological site in northern Hunan Province, China, was recently excavated, from which stone tools including handaxes were unearthed. The deposits of the site are chemically weathered, which makes it difficult to date the site using numerical dating techniques except for optically stimulated luminescence (OSL) method. Here, we used various luminescence procedures including single-aliquot regenerative-dose (SAR), sensitivity-corrected multiple-aliquot regenerative-dose (SMAR) and thermally transferred optically stimulated luminescence (TT-OSL) SAR procedures on fine-grained quartz, and two-step post-infrared infrared stimulated luminescence (pIRIR) and multi-elevated-temperature pIRIR (MET-pIRIR) procedures on fine polymineral fractions. The results show that the fine quartz grains have excellent luminescence properties and the quartz SAR-, SMAR- and TT-OSL ages for the samples agree with each other and in stratigraphical order except for one sample. The fine polymineral fractions exhibited relatively weak pIRIR and MET-pIRIR signals, resulting in difficulty in constructing the dose-response curve for MET-pIRIR signals and the stratigraphically inconsistent pIRIR(100, 275) ages. The seven samples yielded their quartz OSL ages ranging from about 62 ka to 133 ka. The two samples from the cultural layer was dated to 78 to 92 ka using different procedures on fine quartz. However, given the systematically older pIRIR ages obtained with the fine polymineral grains for the two samples, their quartz OSL ages are considered to represent the minimal ages of this layer, and their pIRIR(100, 275) ages of 118 and 110 ka represent the upper age limit, indicating that the site was occupied by hominins during Marine Isotope Stage 5.

Extending the age limit of quartz OSL dating of Chinese loess using a new multiple-aliquot regenerative-dose (MAR) protocol with carefully selected preheat conditions

Abstract Optically Stimulated Luminescence (OSL) dating on quartz is well established following the introduction of the Single-Aliquot Regenerative-dose (SAR) protocol. Despite its widespread use, it has a major drawback in frequently underestimating the age of samples with equivalent dose (De) larger than ~120 Gy. In this study, we investigate fine-grained quartz extracted from Chinese loess with fairly well known ages. For these samples, we determined that the Des obtained using the standard SAR protocol (i.e., with preheat and cut-heat temperatures of 260 °C and 220 °C respectively) significantly underestimated the expected burial doses larger than 100 Gy. The dependence of OSL intensity on preheating conditions was investigated using both natural and bleached aliquots. Both the natural and regenerative OSL intensities increase with the preheat temperature to a maximum at ~260 °C and decrease afterwards. However, the regenerated OSL intensity demonstrates a greater variability compared to the natural one. This difference in variability could not be corrected by the test dose OSL responses when a standard SAR protocol was used. A simple multiple-aliquot regenerative-dose (MAR) protocol with a carefully selected preheating condition can resolve the problem of inadequate sensitivity correction between the natural and subsequent regenerative cycles. The growth of the MAR dose-response curve (DRC) was in good agreement with the sensitivity-corrected natural OSL signals up to ~340 Gy, which extends the upper age limit of quartz OSL samples of Chinese loess back to at least 110 ka.

Testing the upper limit of luminescence dating based on standardised growth curves for MET-pIRIR signals of K-feldspar grains from northern China

The standardised growth curve (SGC) method has been applied to potassium-rich feldspar (K-feldspar) from samples at the Nihewan Basin, northern China. It was observed that the shapes of SGCs obtained from multiple-aliquot regenerative-dose (MAR) and single-aliquot regenerative-dose (SAR) procedures are different at high doses (>900 Gy) for the multiple-elevated-temperature post-IR IRSL (MET-pIRIR) signals observed at high temperatures (e.g., 290 °C) This difference can be attributed to the presence of residual signals in the MAR SGCs due to solar bleaching involved in the MAR procedure. Similar shapes of the SAR and MAR SGCs were obtained after correcting for the residual signals. Comparing the De estimates for both methods suggests that the SAR SGCs yield more reliable results. We tested the SAR SGCs for sediments from the Dadaopo section in the Nihewan Basin, including materials from the Brunhes/Matuyama (B/M) boundary (~780 ka). By interpolating the central re-normalised Ln/Tn ratios onto the corresponding SAR SGCs, the 290 °C MET-pIRIR signals yielded ages in stratigraphic order, and the sample from the B/M boundary yielded an age estimate broadly consistent with the expected age. Our results suggest that the MET-pIRIR SAR SGC method has the potential to date samples up to ~700–800 ka in this region.

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.

Luminescence dating of volcanic eruptions in Datong, northern China

In this study, fine-grain quartz was used for luminescence dating for lava baked samples from different sites in Datong. Optical stimulated luminescence (OSL), thermal transferred OSL (TT-OSL)/recuperated OSL (Re-OSL) and thermoluminescence (TL) dating protocols were applied. For these samples, the OSL signals saturate at about 300–400 Gy, which limits their age to less than 100 ka based on their ambient dose rates. The TT-OSL/Re-OSL method has poor dose recovery. TL dating gives reliable results, and multiple-aliquot regenerative-dose TL method with sensitivity change correction based on the 325 °C TL peak of a test dose can be applied for samples up to 400 ka. The results indicate that the ages of the volcanoes in Datong are from 380 ka to 84 ka. The volcanic activity started earlier in the southeast area than those in the northwest part, which is consist with the literature data.

Maximum age limitation in luminescence dating of Chinese loess using the multiple-aliquot MET-pIRIR signals from K-feldspar

Numerical dating of loess is important for Quaternary studies. Recent progress in post-infrared infrared-stimulated luminescence (pIRIR) signals from potassium-rich feldspar has allowed successful dating of Chinese loess beyond the conventional dating limit based on quartz optically stimulated luminescence (OSL) signals. In this study we tested the multiple-aliquot regenerative-dose (MAR) pre-dose multiple-elevated-temperature post-IR IRSL (pMET-pIRIR) procedure on samples from the palaeosol S5 (∼480 ka) and S8 (∼780 ka) layers from the Luochuan and Jingbian sections, respectively. The results show that (1) compared to sensitivity-corrected signal (Lx/Tx), a higher saturation dose is observed for the sensitivity-uncorrected MET-pIRIR signals (Lx), suggesting that MAR is advantageous for dating old samples; (2) negligible fading component can be achieved using the pMET-pIRIR procedure; (3) for the sample from the top of palaeosol S5, De values (1360 + 226/-167 Gy) broadly consistent with expected De (1550 ± 72 Gy) can be obtained using the sensitivity-uncorrected 300 °C MET-pIRIR signal. Our study suggests that a De value of about 1800 Gy may be the maximum dating limit of Chinese loess using the MAR pMET-pIRIR procedure.

A combined luminescence and radiocarbon dating study of the Ili loess, Central Asia

Similar to the loess in the Chinese Loess Plateau (CLP), the loess deposits in the Ili basin of Central Asia arid area play an important role in understanding the climate and environmental changes. However, in contrast to the intensively investigated loess deposits in the CLP, the Ili loess is still insufficiently known and poorly understood. The geochronology study of the Ili loess remains controversial. In order to examine the potential of optically stimulated luminescence (OSL) dating for the Ili loess, we carry out a combined luminescence and radiocarbon dating study on a 6.9 m loess section in the south margin of the Ili basin. Polymineral fine grains were investigated by post infrared (IR) OSL using a Multiple-Aliquot Regenerative-dose (MAR) protocol. Radiocarbon dating of organic carbon were carried in a 3 Megavolt (MV) multi-element Accelerator Mass Spectrometry (AMS). The results indicate that the OSL ages are in agreement with the observed stratigraphy in the field, which is well correlated with that of the CLP, but the AMS 14C ages are much younger than the OSL and assumed stratigraphical ages. Thus, the OSL dating technique may provide an absolute chronology in this loess section. Further methodological approaches and more samples analysis will lead to the improvement of this chronology for high-resolution paleoclimatic interpretation.

The estimation of basic experimental parameters in the fine-grained quartz multiple-aliquot regenerative-dose OSL dating of Chinese loess

The sensitivity-corrected multiple-aliquot regenerative-dose (MAR) protocol provides a reliable approach for fine-grained quartz optically stimulated luminescence (OSL) dating. For reliable estimation of the equivalent dose (De), we investigated certain basic experimental parameters in the fine-grained quartz MAR OSL dating of Chinese loess. (1) For suitable bleaching of the natural OSL signal of the regenerative-dose aliquots, the effect of bleaching duration using sunlight, SOL2 and blue LEDs on De was studied, and it is found that the appropriate method is a short-duration SOL2 (e.g. 5 min) or blue LEDs (e.g. 60 s) bleaching. (2) To select the appropriate test dose, the relationship between the test dose and De was investigated based on three samples having De values of approximately 11, 31 and 137 Gy respectively. It is suggested that the test dose for sensitivity correction may be limited to less than approximately 10–20 Gy. (3) Three commonly used fitting modes for quartz OSL growth curve were compared at three regenerative-dose scales. The results indicate that the mode of two saturating exponential functions plus a constant is appropriate and universal. (4) The comparison of De values derived using OSL approach with those obtained using the recuperated OSL (ReOSL) protocol shows that the reliable De estimation in the fine-grained quartz MAR OSL dating of Chinese loess may be limited to less than approximately 300 Gy. (5) The comparison of growth curves for 18 samples from the Weinan, Xifeng and Jingyuan sites shows that it is feasible to construct a standardized growth curve (SGC) for fine-grained quartz OSL signal in the Chinese Loess Plateau (CLP).

Closely-spaced recuperated OSL dating of the last interglacial paleosol in the southeastern margin of the Chinese Loess Plateau

The objective of this study is to construct a numerically dated chronology of the last interglacial paleosol (S 1) in Chinese loess using luminescence dating. The recuperated optically stimulated luminescence (ReOSL) dating approach was applied to 18 closely-spaced (20 cm intervals) samples, with 15 of these collected from the S 1 unit at the Weinan site, which is located at the southeastern margin of the Chinese Loess Plateau (CLP). By using the multiple-aliquot regenerative-dose (MAR) approach, 18 fine-grained quartz ReOSL equivalent dose ( D E ) values, spanning about 249–466 Gy, were obtained. The validity of ReOSL MAR protocol was checked by dose recovery measurements and recycling ratio tests. By comparison of the dose-response curves of all the samples, we found that it is feasible to construct a standardized growth curve (SGC) for the ReOSL signal at the Weinan site. Considering the effects of pedogenesis of the S 1 unit during formation, the dose rate during the last interglacial was corrected, which should be beneficial for constructing a more reliable chronology. Finally, a detailed chronology of the S 1 unit was established. The results show that S 1 was deposited between approximately 76–127 ka, which confirms the early suggestion that the S 1 unit in Chinese loess corresponds to the whole marine oxygen-isotope stage (MIS) 5. The detailed ReOSL chronology of S 1 indicates the consistency of the substrata of S 1 with MIS 5a-e, but cannot determine whether they are exactly coeval. According to the present ReOSL age results, it is suggested that dust deposition is continuous at timescales larger than 14.1 ± 11.8 ky during the last interglacial and there is no hiatus longer than 4.4 ± 13.0 ky at the L 2/S 1 transition. Further work, e.g. minimizing the errors on ages and reducing the luminescence sampling intervals, is needed to understand the more detailed dust deposition conditions during the last interglacial in Chinese loess.

Investigating age underestimation in the high dose region of optically stimulated luminescence using fine grain quartz

The age range of the single-aliquot regenerative-dose (SAR) protocol applied to quartz optically stimulated luminescence (OSL) has become the subject of debate as age underestimations for samples of Eemian age (ca. 125 ka) and older are increasingly reported. In order to investigate the origin of the age underestimation, the behaviour of fine grain quartz samples taken from two sites was compared. Sediment from both sites originates in the Alps, with those from Azzano Decimo, northeastern Italy, already displaying a significant age underestimation before reaching the Eemian, while ages for samples from Niederweningen, northern Switzerland, agree with expected ages well beyond the Eemian. Estimated dose (D e) values for both sets of samples are up to around 400 Gy, and all meet the usual performance criteria for testing the reliability of the SAR protocol. D e values determined using a sensitivity-corrected multiple aliquot regenerative-dose (MAR) protocol were within 10% of those determined using a SAR protocol for both sites, and so could not overcome the significant underestimation seen at Azzano Decimo. Lifetime calculations confirmed the stability of the signal well beyond the age range required at both sites, for both the initial integral as well as that used for an early background subtraction. The relative percentage contribution of the fast and medium OSL components to the initial integral remained constant in both the natural signal and similar sized laboratory generated doses. The quartz OSL from both sites displayed similar characteristics under all analyses and no indication was found for the possible origin of the age underestimation seen at Azzano Decimo. In the comparisons made between the dose–response of both laboratory and naturally generated signals in these samples, no evidence was found to suggest that the presence of the high dose linear region is restricted to the laboratory. The reliability of quartz OSL ages derived from this part of the curve however, remain in question, and require the support of independent age control until a performance criterion can be found with which to test it.

Comparison of quartz OSL protocols using Lateglacial and Holocene dune sands from Brandenburg, Germany

We present the results obtained using various different protocols in the quartz optically stimulated luminescence dating of a Late Glacial and Holocene aeolian dune sequence near Eberswalde, north of Berlin, Germany. The Allerød `Finow’ palaeosol and the Laacher See tephra layer serve as chronostratigraphic markers, and further independent age control is provided by eight 14 C ages. The application of the single-aliquot regenerative-dose protocol (using blue light stimulation) and the multiple-aliquot regenerative-dose and additive-dose protocols (using broad-band blue and green light stimulation) are discussed. A comparison of radionuclide analyses using high-resolution gamma-spectrometry and neutron activation analysis is also presented. It is concluded that the two dosimetry methods give indistinguishable results, although the gamma spectrometry data are more precise. In contrast, the single-aliquot regenerative-dose protocol is between 2 and 10 times more precise than the multiple-aliquot protocols, and systematic differences in performance are also observed. The uncertainties in the dosimetry calculations are the largest contributor to the overall age uncertainties. The accuracy of the resulting ages is considered very satisfactory when tested against the independent age controls, over the entire age range from the present to 15 ka.