Dating Himalayan sediment using luminescence methods is challenging. The quartz in those deposit are generally dim (low luminescence sensitivity) and the presence of feldspar micro-inclusions within them render difficult to date them using optically stimulated luminescence. Thus the palaeoscientific investigations suffer heavily by the lack of well constrained chronological framework. Rather than struggling to date quartz, perhaps dating these micro-inclusions in quartz can be a better alternative in that context. This research is a further attempt to date using inclusions by focusing on the appropriate dose rate computation. Dose rate to the micro-inclusions was computed according to the types of mineral and size of micro-inclusions that were identified with the use of energy dispersive X-ray microanalysis, inductively coupled plasma mass spectroscopy and thin section petrography. For this study 10 lacustrine/riverine sediment samples were selected from the central to eastern stretch of Himalaya. These analyses suggested that the inclusions are predominantly of Na-feldspar with a size of ∼5 μm. Inclusions receive, on average, 3 % more dose rate than quartz and hence the equivalent dose from inclusions must be larger by 3 %, if well bleached. Poor bleaching may be inferred from the disproportionate difference between estimated equivalent dose from inclusions and quartz. The estimated depositional ages of inclusions within quartz, after incorporating the correct dose rate and appropriate age model for poorly bleached sediments, are comparable with their expected ages. Thus, this method of dating inclusions within quartz can be an alternative one to reliably date Himalayan Quaternary deposits using luminescence.
Bioapatite carbonate provides an alternative material for radiocarbon dating when collagen is degraded. However, its reliability is vulnerable to diagenetic alteration and environmental isotopic exchange. This study evaluates carbonate chemical pretreatment protocols through 14C and Fourier Transform infrared spectroscopy (FTIR) analysis of seven archaeological bones from three sites across diverse environments. Results reveal environment-dependent preservation: arid Lafuqueke specimens yield relatively accurate 14C ages, humid Naminan Cave bones exhibit significant age underestimation, while semiarid Gedachuan samples show intermediate age offset. Extended weak acid treatment (1M acetic acid, 36h) outperformed short HCl protocols (0.04M or 1M HCl, 0.5h) in removing diagenetic carbonates, with efficacy confirmed by FTIR carbonate peak attenuation. We demonstrate that environmental context dictates bioapatite preservation and show that optimized acetic acid pretreatment can enhance 14C dating reliability to some extent for collagen-deficient bones.
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.
The discovery of long-term accumulations of snow petrel stomach-oil deposits in Antarctica have provided an excellent opportunity to reconstruct changes in climate, ice-sheet thickness and sea ice. However, providing age constraints on the deposition of these biological accumulations can be challenging, particularly when they extend beyond the radiocarbon age limit (ca. 55 ka). Luminescence dating is successfully used here to provide accurate ages for rocks underlying and incorporated into snow petrel stomach-oil deposits in East Antarctica. The agreement between the different luminescence signals measured from K-feldspars, in addition to the independent age control (radiocarbon dating) gives confidence in the results. We show the potential for reconstructing ice-sheet histories from multiple burial events with prior exposure durations recorded in the luminescence depth profiles of the rocks. Our study extends beyond the traditional sedimentary contexts usually used for luminescence dating, and into biological accumulations, which has not previously been done. We show that rock luminescence dating can overcome some challenges of using radiocarbon dating for biological accumulations (e.g. young carbon contamination, marine reservoir uncertainty) and can potentially extend the dateable age range to at least Marine Isotope Stage 5 according to the saturation limit of the luminescence signal measured for these samples. This is key for using these stomach-oil deposits to quantify the contribution to sea-level rise provided by Antarctic Ice Sheet retreat, and changes in sea ice during the last warm interglacial period experienced on Earth.
Accelerated glacier retreat and lake expansion on the Tibetan Plateau (TP) under global warming have profoundly impacted the Asian water tower and increased downstream geo-hazard risks. Maritime glaciers in the southeastern TP have undergone the most intensive recession on the plateau. Revealing the late Quaternary evolutionary history of proglacial lakes in this region can provide crucial records for assessing future trends of glacier dynamic and lake fluctuation, yet such records remain poorly documented. Here, we reconstructed the fluctuation history of Ranwu proglacial Lake in SE TP based on optically stimulated luminescence (OSL) and AMS C-14 dating of a high platform composed of thick lacustrine silts and a sequence of near-shore sandy profiles. Given the incomplete bleaching observed in K-feldspar pIRIR (post-IR IRSL) signals, a robust chronology was established by integrating results of single-grain quartz, Minimum Age Model (MAM) of SG K-f pIRIR(225), fine grain quartz, and C-14 ages. The results reveal a major lake highstand occurred from similar to 29 to 25 ka, reaching an elevation of >4390 m (+464 m above the modern lake and covering an area of similar to 324 km(2)). We deduce that a dam was formed to block water while a strong Indian Summer Monsoon precipitation contributed to the lake highstand. Subsequently, a low lake level occurred around 23 ka (+10 m), followed by a gradual rise to about +350 m from similar to 20 ka to 12 ka, possibly linked to the formation of a dammed lake associated with regional glacier advance during the LGM. Since 12 ka, no relevant sediments have been found from slopes near the modern lake, implying that the dam likely breached during deglaciation and a rapid drainage occurred. Our results provide new evidence to understand the evolution of Ranwu Lake and the complex interactions between glacier dynamics and lake level change.
Tephrochronology is an established technique for dating and correlating sedimentary sequences, but it can be challenging to deploy when tephra layers are mixed, i.e., when they contain tephra from different sources. Mixing of tephra deposits is likely a ubiquitous process in regions with high levels of volcanic activity and dynamic landscapes, but remains understudied: to our knowledge, no one has systematically analysed the frequency and degree of mixing in terrestrial sedimentary sequences, nor assessed the reliability of a mixed, visible tephra layer as a chronostratigraphic horizon. We addressed this knowledge gap by quantifying tephra mixing in sedimentary sections encompassing the Landnam tephra layer (LTL), a key chronostratigraphic horizon in Iceland. We logged nine stratigraphic profiles in three sites associated with the earliest settlement of Iceland and analysed the major element chemistry of 44 tephra layers (957 shards in total). We used a statistical technique (clustering) to identify distinct geochemical populations within each layer and made novel use of Shannon's diversity (entropy) index (H') to estimate the degree of mixing. Our analysis showed that 43% of the tephra layers were mixed to some degree and around a quarter exhibited marked geochemical heterogeneity. We attributed the mixing to human activities associated with Norse colonisation of Iceland, which created a mixture of unstable surfaces (where tephra could be remobilised) and stable surfaces (where tephra layer formation was possible). We propose a model for the formation of mixed tephra layers. Our work has implications for the dating of the earliest phases of human colonisation in Iceland and the use of tephrochronology in areas - both proximal and distal to tephra sources - where conditions promote surface instability.
Lacustrine sediments from the Qinghai-Tibet Plateau (QTP) provide critical archives for reconstructing past climate and environmental changes, however, robust chronological frameworks are essential for their accurate interpretation. Recent advances in luminescence dating have significantly improved the precision and reliability of age estimates, making it a key geochronological tool. In water-lain depositional settings, incomplete bleaching remains a major challenge for luminescence dating. Single-grain (SG) techniques provide a powerful approach to assess sediment bleaching history and, when combined with appropriate age models, enable the derivation of depositional ages that more faithfully reflect the true sedimentary chronologies. Nevertheless, their application to lake sediments remains exploratory, particularly with respect to signal selection and data processing. To assess the applicability of SG feldspar IRSL and pIRIR signals, particularly for dating young lacustrine sediments, this study presents detailed SG luminescence dating of a lacustrine sediment core from Kusai Lake (northern QTP) with independently constrained varve-based ages. The results demonstrate that (1) dim grains exhibit higher fading rate and dispersion; (2) the overestimation of pIRIR225 ages conflicts with dose recovery results, suggesting caution is warranted when interpreting dose recovery test; and (3) both fading-corrected IR50 ages and residual-corrected pIRIR225 ages match the independent varve-based chronologies. This study highlights the importance of preferentially selecting low-temperature signals and analyzing brighter grains in SG K-feldspar luminescence dating to improve the accuracy and reliability of chronological frameworks in young lacustrine environments.
An accurate chronology of marine terraces older than marine isotope stage (MIS) 5e in Japan remains elusive because of the limited number of available tephra markers. The aim of this work was to refine the chronology of MIS 7 and older marine terraces in southern Hokkaido using fading-corrected K-feldspar luminescence dating and to assess regional uplift rates through comparison with sea-level curves. We applied multiple forms of infrared-stimulated luminescence (IRSL) dating to K-feldspar extracted from eight outcrops (surfaces OIV to OI), including uncorrected post-IR IRSL (pIRIR225), fading-corrected pIRIR225, and post-isothermal IRSL (pIt-IRSL), using single-aliquot regenerative-dose protocols throughout. Fading-corrected pIRIR225 ages from MIS 5e terraces closely matched the known chronology defined by the Toya tephra (109 +/- 3 ka). In contrast, uncorrected pIRIR225 and pIt-IRSL ages were systematically younger than the MIS 5e reference age, indicating that only fading-corrected pIRIR225 ages yielded reliable estimates. Terraces previously correlated with MIS 7 and MIS 9 were further refined to substages MIS 7e and MIS 9a-e based on luminescence ages. A comparison between global sea-level reconstructions and terrace elevations, assuming steady uplift, revealed a consistent spatial difference in relative uplift between the Toyokoro Hills and the Shiranuka Hills. Our results demonstrate that fading-corrected K-feldspar luminescence dating provides robust chronological constraints for marine terraces and offers new insights into the tectonic evolution of southern Hokkaido during the Middle to Late Pleistocene.
The Singa calvaria, found on the western bank of the Blue Nile in Sudan in 1924, shows a combination of modern and archaic features of Homo sapiens. A previous study applying U-Th dating of calcrete precipitates surrounding the calvaria and associated mammal teeth inferred a minimum age of 133 +/- 2 ka. However, detailed age constraints on the Singa calvaria are still lacking. The Abu Hugar site, located just 35 km to the south of Singa, produced vertebrate fossils and stone artifacts previously thought to be contemporaneous with the calvaria. Here, we applied optically stimulated luminescence (OSL) dating on the fluvial sediments and radiocarbon dating on soils and shells from Singa and Abu Hugar. Small aliquots for quartz and single grains for K-feldspar were used in luminescence dating to address possible partial bleaching issue. Using a Bayesian age-depth model and assuming continuous deposition, we estimated a considerably younger burial age of 39 +/- 4 ka for the Singa calvaria. Though we cannot rule out an older age, our new age estimate suggests that the Singa hominin might significantly postdate the origin of anatomically modern humans and the dispersal of Homo sapiens out of Africa. In contrast, the fluvial sediments from Abu Hugar have much older OSL ages of similar to 120-210 ka for the exposed profile, with the oldest fossiliferous level possibly as old as similar to 315 ka. Our dating results challenge the previously assumed contemporaneity of the Singa calvaria and the faunal and lithic records of Abu Hugar, and reflect a complex Pleistocene depositional history of the Blue Nile.
The Velika Vrbica loess-palaeosol sequence, situated on the south-western bank of the Danube River in north-eastern Serbia, represents one of the key Quaternary records in the lower Danube basin, covering the MIS 5-MIS 1 period. Previous investigations of the upper 500 cm established a high-resolution chronology and revealed unexpected patterns of dust accumulation during interstadial phases. In this study, we extend the analysis to the full similar to 12 m thickness of the sequence, spanning from Marine Isotope Stage (MIS) 5 to the Holocene, with emphasis on refining the geochronological framework and testing the performance of different luminescence signals. A comprehensive set of quartz optically stimulated luminescence (OSL) and K-feldspar post-infrared infrared stimulated luminescence (pIRIR(290)) ages, complemented by linear modulated OSL (LM-OSL) analyses, provides a robust chronology. Bayesian age-depth modelling constrains the timing of key stratigraphic units, including the S1 palaeosol (MIS 5), the overlying L1 loess (MIS 4-2) with its interstadial palaeosol (L1SS1), and the Holocene soil (S0). Quartz and K-feldspar ages display systematic differences: younger deposits show feldspar overestimation consistent with incomplete bleaching, whereas older horizons (MIS 5-4) yield excellent agreement between the two signals. LM-OSL results confirm that the fast component dominates most of the profile, supporting the reliability of equivalent dose determinations across multiple stratigraphic units. The resulting chronology demonstrates that the Velika Vrbica site preserves a continuous record of loess accumulation and pedogenesis over the last similar to 130 ka. These findings not only refine the temporal framework for south-eastern European loess but also provide an important evaluation of the applicability and limitations of quartz and K-feldspar luminescence signals in establishing long-term chronologies.
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.
Anthropogenic carbonates such as lime mortars and plasters have been receiving growing attention as they are an invaluable source of information for archaeologists, conservators, and restorers of cultural heritage. Taking into account the production process, the age of mortars reflects the age of the building. Two physical dating methods currently enable us to date mortars: radiocarbon (14C) dating and optically stimulated luminescence (OSL), however both are not yet considered routine, due to a number of limitations.In this study we present the Electron Spin Resonance (ESR) analysis of historical lime mortars, as a first part of the ongoing project focused on establishing ESR as a method of dating anthropogenic carbonates in a form of lime binders. Since carbonate crystals are formed during the mortar production, this moment can be regarded as the zero point for the accumulation of trapped charges, and their concentration in a measured sample should reflect the age of the mortar.We investigated ESR signals in natural and laboratory-irradiated lime binders from several different archaeological sites, with ages ranging from about 2800 to 500 years old. The samples have been previously dated by radiocarbon method, which means they had undergone extensive characterisation and preparation, ensuring the selection of binder, which reflects the true age of the mortar. Since the samples were originally collected for radiocarbon dating no data on the annual doses was available, hence the goal of this work is a qualitative analysis of the signals found in a variety of mortars, assessing their potential suitability for dating. Despite the relatively young age of the investigated samples for ESR dating, measurable signals were detected in natural materials. With the aid of ESR simulations, signals commonly found in carbonates, such as CO2- isotropic and orthorhombic, CO3- orthorhombic, NO32- and NO22-, SO2- isotropic, SO3- axial and isotropic, surface defect caused by crushing, organic radical, as well as a signal caused by pyrolysis of organic matter, were identified in the laboratory irradiated samples. As there are almost no examples of ESR dating of Holocene carbonates, lime binders present an exciting opportunity to push forward the boundaries of ESR dating, which has great implications for Quaternary geology, and historical archaeology.
The study of estuarine sedimentary archives provides valuable insights into their geomorphological evolution over the past two centuries, enhancing our understanding of estuarine responses to climate change. Establishing a reliable and precise geochronological framework is therefore essential for monitoring these changes. This study evaluates the performance of quartz Single-Aliquot Regenerative (SAR) OSL and AMS 14C dating in four estuaries along the western coast of France. The results are compared with cartographic data, serving as an independent age control. Of the 14 OSL dated samples, 10 yield depositional ages consistent with cartographic data, whereas the remaining 4 appear to overestimate ages by 20-100 years. In contrast, AMS 14C dating reveals numerous stratigraphic inversions, with at least 12 out of the 16 measured samples overestimating the depositional age in some cases by up to 5000 years, in total disagreement with cartographic data. The discrepancy between the OSL and radiocarbon ages reflects the constant reworking of allochthonous material, to which is added the further uncertainty associated with the local reservoir age. These factors fundamentally limit the reliability of 14C dating regardless of the material analyzed. By contrast, the OSL signal displays remarkable resilience, with any age overestimation linked to partial bleaching remaining minor (on the order of decades) compared with the errors affecting 14C ages. This underscores the capacity of OSL dating to resolve short-term environmental changes and positions it as the most reliable tool for constructing high-resolution chronologies of the last centuries in macrotidal estuarine settings.
Understanding the temporal relationship between carbon pools in marine sediments is essential for reliable paleoenvironmental reconstructions, yet 14C-age discrepancies between organic and carbonate fractions remain poorly constrained. Here, we present the first assessment of the 14C-age offset between organic carbon (OC) and planktonic foraminifera from co-occurring stratigraphic layers of the Cabo Frio upwelling system (CFUS, off southeastern Brazil) over the past 5.8 kyr. Conventional 14C ages of the OC are, on average, 643 +/- 186 yr older than those of co-occurring foraminifera, likely reflecting long-term storage and winnowing of organic matter (OM) on the mid-shelf driven by local upwelling-related hydrodynamic processes. Higher OC apparent initial 14C-ages (AIROC) coincide with periods of intensified upwelling and stronger bottom currents, which prolong OC residence time before burial, and greater delivery of pre-aged terrestrial OM. Conversely, reduced AIROC corresponds to weaker hydrodynamic conditions and higher sedimentation rates that promote more rapid OC deposition. The new carbonate-based chronology developed for the investigated core revises the timing of Holocene paleoceanographic changes previously inferred from OC-based age models. Intensified South Atlantic Central Water (SACW) upwelling in the mid-shelf now aligns with the mid-Holocene sea-level highstand, while the development of stronger stratification and reduced SACW penetration occurs entirely within the late Holocene. The establishment of modern upwelling conditions shifted to younger ages, improving consistency with wider-scale climate phenomena and regional NE-wind variability. These results refine the temporal and mechanistic interpretation of Holocene variability in the CFUS and underscore the importance of multi-fraction 14C dating in dynamic coastal upwelling systems.
The challenges in luminescence dating of faulting materials often arise from uncertainties in the extent of signal resetting caused by frictional heating and pressing along the fault. In this study, laboratory friction experiments were performed to simulate the influence of seismic slip rates on rock luminescence signals. High-speed friction generated rapid heating of the frictional interface, with temperatures reaching 500-800 degrees C. This process effectively reset the infrared-stimulated luminescence (IRSL) signal within the upper similar to 1.5 mm of gabbro surfaces, and fully reset the signal up to similar to 6 mm inward from surface edges. However, depth information was partly lost because mechanical cutting caused local detachment of thin rock slices. To overcome this limitation, we measured luminescence signals using the Ris & oslash; luminescence imager, which provides non-destructive and high-resolution IRSL and Infrared Photoluminescence (IRPL) measurements on granite samples. The lack of preheating may preserve some unstable charges and slightly underestimate the resetting ratios. Even so, the patterns are robust. High-speed friction eliminated similar to 99 % of IRSL intensities and reset 78 +/- 1 % of the IRPL955 signals. Low-speed friction reset 83 +/- 1 % of the IRSL signals and had only 29 +/- 1 % of IRPL955 signals. These results confirm that the Ris & oslash; luminescence imager is highly effective in detecting friction-induced signal resetting. The non-destructive imaging approach preserves depth information and offers higher spatial resolution than measurements on cut rock slices. IRSL and IRPL955 signals can potentially constrain the timing of high-velocity seismic slip. Their contrasting responses to different slip conditions may also reflect deformation processes associated with stick-slip and creep, providing additional insight into earthquake behavior.
Volcaniclastic ash deposits (tuffs) within the Turkana Basin in Kenya act as temporal markers to constrain the extensive fossil-rich sediments of the Koobi Fora Formation. By using geochemical fingerprinting and precise geochronology this study improves the temporal and spatial resolution of the Koobi Fora, Lower Koobi Fora and Karari Blue tuffs within the Koobi Fora Tuff Complex. Utilising a Bayesian approach to single-grain anorthoclase ages this study presents ages of 1.49257 +/- 0.00186 (2 sigma) Ma for the Karari Blue Tuff, 1.49430 +/- 0.00142 (2 sigma) Ma for the Koobi Fora Tuff and 1.51561 +/- 0.00090 (2 sigma) Ma for the Lower Koobi Fora Tuff. These results provide highly precise (<0.1 % uncertainties) anchoring ages for the stratigraphy of the Okote Member, implying an older age for the base of the Koobi Fora Tuff Complex (>1.51561 +/- 0.00090 Ma). The implications of the similar to 30 ka revision of the Lower Koobi Fora Tuff indicates older dates for significant hominin fossil sites in the Ileret (Area 1A) and Koobi Fora (Area 103) regions. The ages of the three tuffs provide the highest precision ages of the Koobi Fora Tuff Complex thus far and have important implications in the Koobi Fora Formation and correlates across the Turkana Basin.
Detailed chronological assessment has been performed on a strongly compressed submorainic organic layer found from a river valley in the Lemmenjoki area, Northern Finland, by using 14C and 518O analyses. Clear effect of reworked carbon from above has been observed within the basal part of the layer. The radiocarbon data combined with existing chronological information suggest that the layer was deposited during the Marine Isotope Stage 3 (MIS3), supporting the previously published interpretation. Particularly, most of the dates are indistinguishable from the 14C background level, indicating their association with the early phase of MIS3 time period. Oxygen isotopic data resembles the data from the last 400 years within the eastern Fennoscandia, suggesting similar growth conditions during the period compared to modern era.
A high-resolution tephrostratigraphic framework focusing on cryptotephra provides a key isochron and the accurate ages of past explosive eruptions in remote regions. The Japanese archipelago has many Quaternary volcanoes, and the tephrochronology using visible tephras of this region has been extensively studied. Research on Lake Suigetsu and other repositories have provided the tephrostratigraphic framework. A detailed cryptotephra study in central Japan can provide correlation to Lake Suigetsu records and strengthens the tephrostratigraphic framework in and around central Japan, but has not been extensively conducted. In this study, we focused on wetland deposits formed in the mountainous regions in central Japan and conducted coring excavation, cryptotephra analysis, fingerprinting, and radiocarbon dating to establish a high-resolution tephrostratigraphic framework. We excavated the Aizu region with late Pleistocene records from the YNH-P1 core and Holocene records from the YNH-P2 core and the Sekita Mountain region with late Pleistocene records from the NNM-P1 core and Holocene records from the CYI-P1 core. Towada-Chuseri, Asama-YKU, Aira-Tn, and Daisen-Kurayoshi tephras were identified in multiple cores, which played an essential role in refining tephrostratigraphy. Tateyama-E tephra, which erupted from the Norikura volcanic chain, was identified for the first time in the Aizu region (YNH-P1 core); it provided important chronological constraints for the north Kanto tephrostratigraphy. Moreover, Myoko-Otagirigawa and Myoko-Akakura tephras from Myoko volcano were accurately dated as 4.4-4.2 and 5.9-5.7 cal ka, respectively, based on tephrostratigraphy and radiocarbon dating. Results showed a more detailed tephrostratigraphic framework in central Japan than those reported in previous studies.
Glacigenic sediments are challenging to date with luminescence dating technique, particularly with regard to resetting of the luminescence signal before sediment deposition. In this study, six samples from four different ice-marginal positions in northern Germany were investigated to test different luminescence dating methods that account for heterogeneous bleaching of meltwater deposits. Multigrain measurements exhibited agreement between fading corrected infrared stimulated luminescence (IR) and fading corrected post-infrared IR measured at 225 degrees C (pIRIR(225)) ages, suggesting the studied samples were likely well bleached, as these signals bleach at different rates. Single-grain measurements showed a high proportion of saturated grains (up to similar to 33 %) in these samples. The single-grain results were therefore assessed using conventional single-grain analyses and the LnTn method. Accurate estimation of the overdispersion (OD) of a well-bleached grain population (sigma(b)) is essential for applying statistical age models. Because no suitable well-bleached analogue sample with comparable burial doses was available, sigma(b) was estimated by combining intrinsic OD (from dose recovery tests) and extrinsic OD in quadrature. Both D-e and L-n/T-n OD values exceeded the derived sigma(b) values, confirming that all studied samples are poorly bleached and that the Minimum Age Model (MAM) is required. MAM ages derived from conventional single-grain and LnTn approaches are generally consistent; however, standard MAM ages tend to be slightly younger than LnTn MAM ages, likely due to truncation of the D-e distribution through the exclusion of saturated grains. These finding demonstrate that (1) consistent IR50 and pIRIR(225) ages cannot be considered a reliable indicator of well-bleached samples, and (2) sigma(b) and overdispersion values should be determined and interpreted carefully, especially for old samples with a large number of saturated grains. We recommend applying the LnTn method at the single-grain level when dating partially-bleached samples with grains close to saturation, to obtain more reliable luminescence ages.
Potassium-rich feldspar (K-feldspar) is widely used in luminescence dating due to its high saturation dose, allowing the determination of ages for older sediments. Previous studies have shown that the 'sensitivity' of the post-infrared infrared stimulated luminescence (pIRIR) signal can retain a 'memory' of the pre-dose received but can be reset by sunlight bleaching. Building on the development of multi-aliquot and single-aliquot pre-dose multi-elevated-temperature post-IR IRSL (pMET-pIRIR) procedures, we investigate the performance of the singlealiquot regenerative-dose (SAR) pMET-pIRIR procedure for K-feldspar at the single-grain level. Solar bleaching experiments demonstrate that the sensitivity of the IRSL and MET-pIRIR signals can be effectively reset by a 3 h solar simulator bleaching step applied after each regenerative cycle. Integrating the SAR pMET-pIRIR procedure with the standardised growth curve (SGC)-based LnTn method successfully overcomes sensitivity carry-over, mitigates anomalous fading, extends the dating range and improves measurement efficiency for K-feldspar luminescence dating. Equivalent doses (De) can be determined using the sensitivity-corrected signal (Lx/Tx), regenerative signal (Lx) and test dose signal (Tx), providing flexibility across different dose ranges and improving dating reliability through cross-validation. Application to three sediment samples from China, including samples with independent known ages, confirms the method's ability to obtain accurate De values up to -1600 Gy (-440 ka), with the potential to date samples approaching -1 Ma using the Lx and Tx signals. The single-grain SAR pMET-pIRIR method offers a promising approach for dating older sediments and investigating heterogeneous luminescence behaviours among grains or post-depositionally disturbed deposits.
