Aeolian systems, including deserts/dunefields and downwind loess regions across the mid-latitudes of the Northern Hemisphere, are important components of global terrestrial ecosystems. These aeolian systems respond sensitively to large-scale atmospheric circulation patterns via aeolian activity and dust emissions. However, it remains unclear whether earth surface processes and their dynamics were identical across these regions in northwestern China during the late Quaternary. Using end-member analysis (EMA) of a typical loess-aeolian sand sequence, this study reconstructs a detailed history of aeolian activity from the western part of the desert-loess transitional belt since 20 ka. The results indicate that grain size component EM2 (peak at-126 mu m) is a dependable proxy of regional aeolian activity, as it is primarily transported via saltation from proximal sources. Aeolian intensity gradually decreased after the Last Glacial Maximum, reached a minimum during 9.0-5.0 ka, and then intensified. This pattern is consistent with regional syntheses of aeolian archives from comparable settings. However, it differs substantially from the aeolian history of the upwind Tengger Desert hinterland, which recorded the weakest aeolian activity during-7.0-3.5 cal ka BP. This suggests the spatio-temporal heterogeneity of the environmental evolution of the aeolian-loess sedimentary system of northwestern China. Quantitative analyses indicate that aeolian processes across the northwestern margin of the loess-desert transitional belt were primarily modulated by the Indian Summer Monsoon throughout both the past 20 ka and the Holocene. This assessment distinguishes the region from the upwind desert areas, where the evolution of various atmospheric circulations and their interactions played a more important role. Our findings provide spatiotemporal evidence of the divergent environmental evolution between the desert-loess transitional belt and the upwind desert region in northwestern China. Especially, they highlight different trajectories of aeolian activity under global warming, indicating the need for region-specific strategies to combat future aeolian desertification.

The SAR-SGC protocol combines the single aliquot regenerative (SAR) and standardised growth curve (SGC) protocols with the advantage of saving measurement time. This protocol has been applied to diverse sediment types. However, the minimum number of SAR and SGC aliquots required to obtain the accurate equivalent dose (D-e) remains unclear. We here systematically investigate how the number of aliquots for SAR and additional L-n/T-n measurements influences the stability and consistency of D-e derived from the SAR-SGC protocol, in comparison with the full SAR method. Both measured and simulated datasets from the lower Yellow River plain were used. Statistical simulation (Random Sampling Without Replacement Method) results show that D-e values could be accurately estimated within acceptable uncertainty (<10%) using 4-10 SAR aliquots and additional 4-12 L-n/T-n aliquots per sample, which reduces machine time by at least 60% compared to the full SAR method. The SAR-SGC method is also applicable for constructing SGCs for sedimentary sequences with D-e < 50 Gy. For such a sequence, 3 samples can be selected, with 6 SAR aliquots measured per sample to establish the SGC. Compared to the full SAR method for each individual sample, this approach maintains D-e accuracy while saving machine time by more than 80%. It enables high-resolution sampling for a sedimentary sequence, which enables further refining the chronology using Bayesian age modelling.

In this study, a GdTbDyErPr rare-earth high-entropy alloy (RE HEA) was successfully synthesized and its magnetic properties and magnetocaloric effect (MCE) were systematically investigated. The results indicate that the as-cast GdTbDyErPr RE HEA exhibits a single-phase hexagonal close-packed (HCP) structure with lattice parameters of a = 3.609 Å and c = 5.734 Å. Based on large parameter Ω, high mixing entropy (ΔSmix), and small parameters δ and εi, it can be inferred that the GdTbDyErPr alloy forms a disordered solid solution. The GdTbDyErPr RE HEA undergoes a first-order magnetic transition near about 143 K. The parameters |∆ |, RC, and RCP are determined to be 6.8 J∙kg‒1K‒1, 352 J∙kg‒1 and 462 J∙kg‒1 for GdTbDyErPr RE HEA under 0 T to 5 T. The facile synthesizability and remarkable MCE of the GdTbDyErPr RE HEA position it as a promising candidate for magnetic cooling technology

A robust chronological framework for loess deposits in arid central Asia (ACA) is critical to paleoenvironmental reconstruction in this region. Some research used different dating methods to cross-validate the age determinations. However, age discrepancies between radiocarbon (C-14) and luminescence dating for the same section have been increasingly revealed, which have cast doubt on the reliability of these two methods in ACA. Specifically, during the late Holocene, comparative analyses of these two methods in this region remains less investigated. In this study, we dated the BST loess section at the northern piedmont of Kunlun Mountains in ACA, using the post-infrared infrared stimulated luminescence (pIRIR) signal of both medium-grained (38-63 mu m) and coarse-grained (63-100 mu m) K-feldspar mineral. The reliability of the dating procedures and results was verified through standard internal checks and evaluation criteria. The results show that the luminescence ages of the medium and coarse grains are basically consistent, and both are in excellent agreement with the published C-14 ages of charcoals. In addition, the stable carbon isotope of organic matter (delta C-13(org)) of BST loess section was measured to infer the moisture variations. Our study suggests that (1) Loess of the BST section deposited since the late Holocene (similar to 3.6 ka), with the dust accumulation rate (DAR) substantially higher than that of loess elsewhere; (2) Humidity of this region gradually increased since similar to 2 ka as reflected by delta C-13(org); (3) Luminescence dating methods are highly valuable for providing age control for late Holocene loess in ACA.

Non-linear dose-response curves are common in many thermoluminescence (TL) and optically stimulated luminescence (OSL) dosimetric applications, especially in TL and OSL dating. In most cases, these calibration curves are characterized by saturating exponential expressions; consequently, the accuracy of equivalent dose D-e is highly dependent on the specific position along the saturating exponential curve. In the present work, accuracy is estimated through numerical simulations using novel analytical dose-response expressions based on the Lambert W function. These simulations are subsequently extrapolated to experimental OSL dose-response curves obtained from dating experiments. The D-e was estimated by solving the new dose-response expressions and the error sigma(De), arising from the uncertainty of the natural signal, was evaluated through analytical expressions derived using error propagation theory. Finally, an analytical expression was derived for the derivative of the dose-response function, and the accuracy of D-e correlated with the derivative at the point corresponding to the unknown dose. The newly derived analytical expressions, based on physical models, enable the determination of D-e in both linear and non-linear regions of the dose response curves (DRC). This model offers a significant advantage over other existing empirical expressions, whose results lack theoretical justification. The present study offers a general and objective method to identify samples potentially affected by D-e saturation, through direct evaluation of the derivative of the DRC.

Extensive paleosols have intermittently developed across the East Asian Summer Monsoon (EASM) region over the past 20kyrs but climate forcing mechanisms remain uncertain. In this paper, we compile 593 absolute ages of 87 aeolian sand-paleosol profiles from the Hulun Buir (HB), Otindag (OD) and Qinghai Lake (QH) dune field of central China to more accurately understand paleosol development across this region. In addition, paleoclimatic records from Hulun Lake, Dali Lake and Qinghai Lake from within the dune field are quantitatively analyzed to understand the main drivers of paleosol development. Results show that effective moisture was the pacemaker of paleosol development in the OD dune field with peak deveiopment of paleosols in the mid-Holocene (8-3.5 ka). The HB dune field also extensively developed paleosols during the mid-Holocene optimum (9-4 ka), corresponding to strong effective moisture and high lake-level in the Hulun Lake record. Paleosols were widely developed in the QH dune field during the middle to Late Holocene (6-1 ka), which was not correlated with the precipitation and temperature records of the Qinghai Lake alone, but was in phase with the effective moisture records (i.e., high lake-level and Thaumarchaeol content). These results confirm that effective moisture is the main forcing mechanism of paleosol development at the edge of the EASM region. This explains the delay of the mid-Holocene optimum compared to the early Holocene insolation peak, because the increased evaporation caused by the increase in insolation and temperature in the early Holocene may have been sufficient to reduce the effective moisture, resulting in increased regional aeolian activity and dust availability. We also suggest that the correlation between magnetic susceptibility and precipitation in the dune fields in northern China is not a simple linear relationship, but a potential proxy for regional effective moisture. This study is important for understanding the mechanism of paleosol development and related climate dynamic feedbacks in arid and semiarid regions, as well as for combating land desertification.

Krotovinas, the infilled burrows created by small mammals through bioturbation, represent a distinct pedogenic process and provide valuable records of soil and landscape history. Traditionally, macro- and micromorphological features are analyzed to investigate the origin of burrow fills, and ages are often estimated using 14C dating. However, in some environments, morphological features can be misleading and material for 14C dating is insufficient. This study explores the potential of luminescence techniques to address these issues. We studied a Chernozem profile with typical krotovinas, forming from fluvial sediment in northeast China. Three krotovinas of different depths and colors (two black and one yellow) were sampled, along with their respective supposedly undisturbed counterparts from the surrounding soil. We conducted single-grain (SG) luminescence dating of the K-feldspar fraction and multigrain (MG) luminescence dating of both quartz and K-feldspar fractions. Significant differences in luminescence ages between samples inside and outside the krotovinas at both MG and SG levels suggest the presence of vertical bioturbation. Comparisons of SG distributions among samples indicate that the yellow krotovina at ca.70 cm was the result of upward transportation from a lower layer and was formed after the end of the Last Glacial Maximum. The two black krotovinas at ca. 80 and 160 cm are genetically linked, and probably formed in a single, rapid, simultaneous filling event occurring no earlier than 2.7 ka. This study highlights the unique role of luminescence dating in elucidating formation processes of krotovinas and the soils in which they are found.

As the largest semi-fixed dune field in China, the Horqin Sandy Land (HSL) provides a valuable opportunity to study the surface processes and paleoenvironmental evolution of drylands in the monsoon region. However, limited data and a single qualitative approach hinder our understanding of the sediment erosion and transport process of the HSL. The ability to trace and quantify sediment provenance of the HSL is increasingly needed to properly understand the source-to-sink processes, and to accurately interpret aeolian-fluvial interactions in terms of a comprehensive database and multidisciplinary approach perspective. This study integrates previously existing grain-size, heavy mineral, element geochemistry, Sr-Nd-Hf isotopic, and zircon-geochronological databases with new petrographic, TIMA automation heavy mineral data and statistical analysis. Together, the high degree of recycling of HSL severely limits the provenance identification of element fingerprints, although these elements are largely inherited from the parent rocks and are not affected by chemical weathering. The heavy minerals, Sr-Nd-Hf isotopes, and zircon U-Pb age composition together reveal that the HSL sediments are a binary mixture of the Palaeozoic-Mesozoic igneous rocks in the Great Xing'an Range (GXR) and the Precambrian metamorphic rocks in the Yanshan Mountains. The isotopic end-element mixing models, multidimensional scaling (MDS) diagrams and inverse Monte Carlo models of detrital zircon ages indicate that GXR and Yanshan Mountains account for similar to 60 % and similar to 40 % of the source contributions, respectively. Under the strong influence of the northwest to west winds controlled by the Mongolia-Siberian High, detrital material from the GXR is consistently transported to the interior of the dune field and intensively reworked. The Laoha River and the Yangxumu River originating from the Yanshan Mountains provide stable detrital sources for the HSL. In addition, the transverse flow of the Xilamulun River and the West Liao River has provided sufficient space and sediment for the dunes, which is conducive to the full mixing of materials inside the dune field. The sediment in the southeast of HSL shows an obvious Yanshan Mountains source dominance and a grain-size dependence. The coarse fractions (>63 mu m) mainly modified from the river channel sand and alluvial plain of the Yangxumu River (similar to 75.8 %), while the fine fractions (<63 mu m) have a strong affinity with the loess deposit of Yanshan Mountains (similar to 52.4 %). The fluvial-lacustrine deposits during the last glacial maximum served as a temporary transit station, providing a direct dust source for the modern dunes in the HSL region. Aeolian-fluvial interaction controls the geomorphology and landscape evolution of the HSL in the monsoon region; however, it is challenging to derive insights into the landscape evolution from studying surface samples.

Abstract Mollisols are highly fertile soils and function as significant carbon reservoirs. However, determining their ages and formation processes is challenging due to extensive pedoturbation, which undermines conventional dating methods. Here, we employed luminescence, a light‐sensitive property of minerals widely used in geological dating, to investigate and quantify soil mixing. We analyzed over 2,400 luminescence ages of individual K‐feldspar grains from a Mollisol profile in Northeast China, and for the first time, we were able to determine the intensity of pedoturbation in the Mollisol profile over the past 50,000 years. The results showed that the current pedoturbation can penetrate to a depth of approximately 80 cm, with the intensity decreasing with depth. By identifying a significant intensification in historical pedoturbation, we inferred that the paleoenvironment might be suitable for the formation of Mollisols 16,400 years before present.

Aeolian sediments accumulated along the desert-loess transition zone of the Tengger Desert include heterogeneous textures and complex component structures in their grain-size distributions (GSD). However, the sources of these aeolian sediments have not been resolved due to the lack of large reference GSD sample datasets from adjacent regions that contain various types of sediments; such datasets could be used for fingerprinting based on grain-size properties. This lack of knowledge hinders our understanding of the mechanism of aeolian dust releases in these regions and the effects of forcing of atmospheric circulations on the transportation and accumulation of sediments in this region. In this study, we employed a multi-scale grain-size analysis method, i.e., a combination of the single-sample unmixing (SSU) and the parametric end-member modelling (PEMM) techniques, to resolve the component structures of sediments that had accumulated along the desert-loess transition zone of the Tengger Desert. We have also analyzed the component structures of GSDs of various types of sediments, including mobile and fixed sand dunes, lake sediments, and loess sediments from surrounding regions. Our results demonstrate that the patterns observed in coarser fractions of sediments (i.e., sediments with a mode grain size of >100 μm) from the transition zone match well with the patterns of component structures of several types of sediments from the interior of the Tengger Desert, and the patterns seen in the finer fractions (i.e., fine, medium, and coarse silts with a modal size of <63 μm) were broadly consistent with those of loess sediments from the Qilian Mountains. The deflation/erosion of loess from the Qilian Mountains by wind was the most important mechanism underlying the production of these finer grain-size fractions. The East Asia winter monsoon (EAWM) played a key role in transportation of the aeolian dust from these source regions to the desert-loess transition zone of the desert.

Parametric decomposition techniques including single-sample unmixing and parametric end-member modelling are routine mathematical methods used for interpreting grain-size distributions. In this study, transformed probability density functions for the Lognormal, Weibull, Skew Normal, and Skewed Generalized Normal distributions are derived and efficient open-source numerical programs applying these functions are presented. These new functions contain two free shape parameters characterizing the peak position and magnitude of a unimodal distribution, and they can be more easily initialized and constrained compared to their original counterparts, as the two shape parameters can be estimated directly from the grain-size distribution or its derivatives and can only vary within very narrow intervals. This enables the decomposition to converge to both reproducible/stable and structurally/genetically reasonable solutions. The transformed functions are applied to grain-size distributions of aeolian sediments collected from around the Tengger Desert, using both the single-sample unmixing and parametric end-member modelling methods, and the results of different functions are compared. The implications of the results for parametric decomposition of sediment grain-size distributions using unimodal mathematical distributions are discussed.

One of the biggest challenges in optically stimulated luminescence (OSL) dating is to deal with sediments that are affected by post-depositional mixing. Equivalent dose (De) distributions of such samples are commonly analysed using the finite mixture model (FMM), which can statistically identify dose components of grains derived from sedimentary layers with different ages. The FMM has been increasingly applied in OSL dating of sediments from key geological and archaeological sites that are critical for understanding the evolution of Quaternary environment and human history. The burial age of the dated layer is commonly determined by dividing the De value of the target dose component estimated using the FMM by the total dose rate of the bulk sample. However, a systematic investigation of the reliability of this method for different post-depositional mixing situations has not been conducted. This study aims to investigate the reliability of the burial ages so obtained, using simulated mixed single-grain De distributions. We assess the performances of two different protocols-a user-specified or an automatically estimated between-grain dispersion value, & sigma;b. A number of factors influencing the reliability of the determined burial age are investigated, including the inherent dispersion in different dose populations, the proportion of grains associated with the target layer, the sample size used, the difference in dose rates and burial ages between the mixing components, and the time when mixing occurred. Published single-grain samples affected by post-depositional mixing are synthesized and their FMM results are assessed. Our results show that the reliability of FMM is controlled by the analytical and the intrinsic errors and depends critically on the proportion of grains for the target layer. The simulation and synthesized results caution against using an arbitrarily specified & sigma;b as input for the FMM. The intrinsic accuracy of the burial age is controlled by multiple factors for both synchronously and asynchronously mixed samples. The FMM ages derived from sediment samples affected by serious post-depositional mixing should be constrained by independent chronological information.

The possibility of precisely evaluating the equivalent beta dose in stimulated luminescence dating depends on the ability to fit the constructed dose response calibration curve with appropriate analytical expressions. There are a number of such expressions which successfully fit the dose response calibration curves. In the present study we use the recently developed analytical Pagonis-Kitis-Chen equation (PKC equation) to describe the dose response curves from a set of single-grain experimental data for a sedimentary sample from the Haua Fteah Cave in Libya. The PKC equation describes in analytical form the rate of filling of the electron traps during the irradiation stage in the one trap one recombination center model (OTOR). A detailed comparison was carried out between the PKC equation and two very successful equations existing in literature. The comparison criteria were the values of: (a) the reduced chi squared, (b) figure of merit, (c) Equivalent dose and (d) the possible physical meaning of the coefficients used as the free fitting parameters during the fitting procedure. The results show that the PKC equation is at least equally successful as the other two equations in fitting the experimental data.

In this study, the degree of bleaching of multi-grain coarse quartz optically stimulated luminescence (OSL) signal of near-surface aeolian samples collected around the Tengger Desert is assessed. The single-aliquot regenerative dose (SAR) protocol and the standardized growth curve (SGC) method are applied to measure the equivalent dose (D e ) of these samples. The bleaching degree of the samples is assessed by investigating 1) the relationship between L n /T n and SAR D e and 2) the SGC D e distribution. Various degrees of heterogeneously-bleached multi-grain dose distributions synthetized with a numerical simulation method is further used to validate the bleaching performance of the samples. It demonstrates that the investigated samples are characterized by tight D e distributions and the maximum D e estimate is smaller than 1.1 Gy. The numerical simulation method which uses as input a large proportion of fully-bleached grains and a small baseline dose is able to reproduce multi-grain D e distributions similar to the measured ones. We conclude that OSL signals of multi-grain coarse quartz extracted from most of the investigated aeolian samples are fully bleached before deposition.

Parametric curve-fitting techniques are routinely adopted to derive the components of individual grain-size distributions of sediment samples. However, due to the lack of methodologies and calculation platforms to efficiently generate reproducible unmixing solutions, and appropriate statistical techniques to analyze and visualize unmixing results characterized by complex and variable structures, the technique has seldom been extended to the systematic analysis of massive grain-size distributions in sedimentological and paleoenvironmental research. In this study, we use numerical techniques to develop a novel strategy enabling the efficient and flexible unmixing of single-sample grain-size distributions. The method was applied to a large set of grain-size distributions of late Quaternary aeolian sediments from the desert-loess transition zone around the Tengger Desert in North China. The potential structures of the pooled unmixed subpopulations were derived using a finite mixture model, taking variances into account, together with a pattern recognition (clustering) method. Five unimodal endmembers were identified by the finite mixture model and four prevalent structural patterns were recognized by the clustering method. The significances of the endmembers and structural patterns are discussed in detail. We demonstrate that the single-sample unmixing method can be used to complement the widely applied end-member modelling to reveal potential provenances of large datasets of grain-size distributions, and that the component structures of grain-size distributions may contain valuable information that can be used to constrain the associated paleoenvironmental conditions.

Loess contributes considerably to understanding the interactions between dust cycles and climate change. However, systematic and regional‐scale reconstructions of variations in the dust mass accumulation rate (MAR) using Central Asian loess are lacking. Based on the high‐resolution luminescence dating of 10 loess sections, we present a stacked suborbital‐scale (multi‐millennial‐scale herein) dust MAR record over the past 30 ka in the eastern Yili Basin, Central Asia, which shows obvious advantages at representing basin‐scale dust accumulation changes when compared with that based on individual sites. The stacked results in the eastern Yili Basin indicate that the MAR level remained high during the Last Glacial Maximum, followed by a dramatically decreasing trend throughout the last deglaciation, and exhibited a slight decrease during the early Holocene and early middle Holocene, followed by a clear increasing trend toward the late Holocene. We propose that changes in the Siberian High intensity dominantly modulated the aforementioned MAR variations. These results effectively link dust accumulation to the Siberian High, imply a possibly weakened dust activity in the Yili Basin at a long‐term scale under future global warming scenarios, and also provide a significant reference for dust accumulation reconstruction in other basins in Central Asia.

Chronostratigraphic records in the drylands of north China provide basic archives to reveal the dynamic connections between climate changes and the behaviour of aeolian systems. However, the interpretation of aeolian chronostratigraphy is not straightforward and may be associated with significant uncertainty due to a number of external and localised forces. Taking into account this complexity of aeolian systems, excluding preservation and sampling bias from palaeoclimatic signals requires that the interpretation of chronostratigraphic records be based on as many dates from as many sites as possible. Optically stimulated luminescence (OSL) dating provides a direct way to date aeolian sediments. However, the determination of equivalent dose (D-e) using the commonly applied single-aliquot regenerative dose (SAR) protocol is relatively time-consuming for samples with burial doses exceeding 50 or 100 Gy. In this study, the global standardised growth curve (gSGC) method is applied to multi-grain aliquots of coarse quartz from various sites covering a wide region of the south margin of the Tengger Desert in north China to rapidly determine D-e for a large number of aliquots and samples. The large between-aliquot variability in the shape of the dose response curve (DRC) is significantly reduced using a least-squares normalisation procedure. The results of a leave-one-out cross-validation (LOOCV) protocol demonstrates that D-e values determined using the gSGC and SAR methods are very consistent with each other up to at least 200 Gy and 400 Gy, for the 90-150 mu m and 63-90 mu m fractions, respectively. It suggests that the gSGC protocol can be used as an efficient procedure for D-e determination of a large number of aeolian samples from multiple sites. This in turn provides a better constraint for the interpretation of Late Quaternary aeolian chronostratigraphic records in drylands of north China.

Natural quartz minerals that contain impurities, complex defect structures, and multiple trap levels within their crystals have been widely used for optically stimulated luminescence (OSL) dosimetry. Accurate application of the single-aliquot regenerative-dose (SAR) protocol requires an equivalence between the sensitivity-corrected natural and regenerative growth curves. In this work, the sensitivity-corrected natural and regenerative growth curves of quartz OSL are modelled using a comprehensive kinetic model based on the band theory of solids. We demonstrate that the trapping behaviour of the deep electron trap exerts a critical influence on the inconsistency of the sensitivity-corrected natural and regenerative growth curves at high irradiation doses. A delay in saturation of the deep electron trap at high irradiation doses leads to a substantial increase in electron competition in the recombination centres during the irradiation of the test dose and a decrease in electron competition in the centres during the subsequent stimulation of the test dose OSL. As a consequence, the test dose OSL responses as functions of irradiation doses are inconsistent (incompatible) between natural and regenerative aliquots, and the sensitivity-corrected regenerative growth curve tends to be higher than the natural one in the high-dose region. There may be substantial deep electron traps within the crystal of natural quartz that cause their delayed saturation at high irradiation doses.

The application of a regeneration procedure for optically stimulated luminescence (OSL) dating requires that the dose-response curve (DRC) of a natural sample is the same as that of a laboratory-generated one. However, the build-up of the laboratory-generated DRCs of quartz has been widely reported in the literature, i.e., the laboratory-generated DRCs are significantly higher than the natural counterparts in the high dose region (above 150 or 200 Gy). This results in severe underestimation of equivalent dose (D e ) for quartz OSL in the high dose region during the application of a single-aliquot regenerative-dose (SAR) protocol. However, the potential mechanism governing the build-up of the laboratory-generated DRC is still unclear. In this study, we performed a comprehensive investigation of the natural and laboratory-generated OSL signals and DRCs using a kinetic model for quartz. We compared the differences in charge concentrations between natural and laboratory-irradiated aliquots following irradiation and monitored the competition for holes and electrons during preheat and stimulation, for the natural, regenerative, and test dose cycles. In the course of the modelling, we could see the build-up of laboratory-generated DRCs, the underestimation of D e , and a double exponential saturation characteristic of the DRCs. We demonstrated a discrepancy in competition for electrons in the deep electron trap and recombination centres during stimulation between the natural, regenerative, and test dose cycles. The simulation results are directly relevant to quartz OSL D e determination using the SAR protocol and reveal the mechanisms responsible for the experimentally observed different behaviours between natural and laboratory-generated DRCs.