Quaternary Geochronology最新文献

{"title":"New chronological constraints on the history of the Kalahari Group from the Upper Ugab Valley, Namibia","authors":"A. Kuzmenko , A. Torfstein , A. Hidy , Y. Geller , S. Vainer , A. Matmon","doi":"10.1016/j.quageo.2025.101677","DOIUrl":"10.1016/j.quageo.2025.101677","url":null,"abstract":"<div><div>The sedimentary fill of the Kalahari Basin, which extends across several countries in southern and central Africa, records landscape evolution processes and holds archeological evidence of early hominid occupation. Recent studies have demonstrated that the majority of the Kalahari Group sediments were deposited between the Pliocene and the recent present. However, due to limited access to natural outcrops in the flat Kalahari topography, the chronology of the sequence, mostly its earlier part, is not well constrained.</div><div>Here, we set out to study the geologic history of the Ugab drainage system, located in northern Namibia adjacent to the western margin of the Kalahari Basin. The evolution of the upper Ugab drainage system and the adjacent region of the Kalahari Basin were modulated by similar climatic and geologic conditions and processes. Furthermore, the continental water divide at the Ugab catchment headwaters is pushed eastward, further than any ephemeral river draining to the Atlantic Ocean. This geometry raises the possibility of a local drainage divide migration and implies that the upper part of the Ugab drainage system was part of the Kalahari Basin until captured westward to the Atlantic Ocean. Thus, the lower part of the sedimentary section exposed in the upper Ugab Valley may be a remnant of the eroded Kalahari Group. We report new chronological constraints on Kalahari Group units from the “Base Camp” outcrop in the upper Ugab Valley, using cosmogenic <sup>26</sup>Al and <sup>10</sup>Be dating in quartz and U-Th dating of carbonate cements and tufa. The study site is comprised of a ∼20 m thick cemented conglomerate sequence overlain by 20–25 m of carbonate and siliceous duricrusts. We developed a novel multi-stage numerical model for interpreting cosmogenic <sup>26</sup>Al and <sup>10</sup>Be data, following key stages of landscape evolution through a Monte Carlo simulation. This model reconstruction indicates that fluvial deposition of at least 70–100 m of sediments in the upper Ugab Valley had commenced most likely during the Miocene. Following sediment accumulation, surface stability was maintained for a mean most probable duration of 8.86 <sup>+6.82</sup>/<sub>-1.51</sub> Myr, and then followed by a short (<∼300 ka) erosional phase that removed a minimum of 32–53 m of the valley fill. Fine-grained sediments were then deposited during the Middle Pleistocene on top of the erosional surface and cemented by calcite and dolomite at a low gradient valley floor. The beginning of the final incision through the duricrust layer and the subsequent emergence of ground water springs are indicated by tufa deposits dated to 58.3 <sup>+22.2</sup>/<sub>-17.5</sub> ka. Quartzite samples from the re-exposed top of the conglomerate show simple cosmogenic exposure ages that range between 15.8 and 39.4 ka. Though the model suggests a gradual exposure, with at least two different incision rates over time, the overall exposure time i","PeriodicalId":54516,"journal":{"name":"Quaternary Geochronology","volume":"89 ","pages":"Article 101677"},"PeriodicalIF":1.7,"publicationDate":"2025-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143936184","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Assessing the potential of a modified post-isothermal IRSL (pIt-IR) protocol to circumvent the problems posed by anomalous fading in polymineral fine grains","authors":"Nina Ataee,&nbsp;Helen M. Roberts,&nbsp;Geoff A.T. Duller","doi":"10.1016/j.quageo.2025.101676","DOIUrl":"10.1016/j.quageo.2025.101676","url":null,"abstract":"<div><div>Attempts to find a ‘non-fading’ infrared stimulated luminescence (IRSL) signal have been ongoing in the past two decades, due to complications regarding measurement and application of anomalous fading as well as higher age uncertainty introduced by fading correction. In this research, the potential of the post-isothermal IRSL (pIt-IR) protocol to generate ages without the need for fading correction is investigated. Polymineral fine grain samples were collected from a sediment core from Lake Chew Bahir in Ethiopia which is supported by independent age control. The equivalent dose (D_e) values determined using the pIR₅₀IR₂₂₅ pIt-IR protocol are in agreement with the fading corrected pIRIR₂₂₅ D_e values for the upper ∼40 mcd of the core (∼200 Gy), below which the pIR₅₀IR₂₂₅ pIt-IR D_e values underestimate the fading corrected pIRIR₂₂₅ D_e values. This underestimation appears to be a consequence of the IR₅₀ signal approaching field saturation since pIt-IR D_e determination depends on both IR₅₀ and pIRIR₂₂₅ signals. Increasing the measurement temperature of the first IR signal in the pIRIR₂₂₅ pIt-IR protocol (from 50 to 150 °C, i.e. pIR₁₅₀IR₂₂₅ pIt-IR) appears to extend the upper limit of the pIt-IR protocol by producing D_e values that are consistent both with the fading corrected pIRIR₂₂₅ D_e values (within 1σ uncertainties), and also in agreement with the ages of two known-age tephra (within 2σ uncertainties) down to ∼90 mcd of the core (∼450 Gy, ∼180 ka). This demonstrates that the pIt-IR protocol is capable of producing D_e values and ages that do not require fading correction as long as the first IRSL signal in the pIRIR₂₂₅ pIt-IR protocol is not in field saturation. However, verification of the accuracy of the D_e values and ages generated using the pIt-IR protocol is provided by comparison of the fading corrected IR₅₀ and corrected pIRIR₂₂₅ D_e values/ages, which could otherwise be collected directly through more conventional pIRIR protocols that are shorter in duration than pIt-IR measurement sequences. This raises questions regarding the benefit of using a pIt-IR protocol rather than a pIRIR protocol for dating, the primary advantage of which remains circumvention of the problems posed by anomalous fading for sediments that are younger than the field saturation values of the first IR signal measured in a pIt-IR protocol.</div></div>","PeriodicalId":54516,"journal":{"name":"Quaternary Geochronology","volume":"88 ","pages":"Article 101676"},"PeriodicalIF":1.7,"publicationDate":"2025-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143921853","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Determining equivalent dose for optically stimulated luminescence (OSL) dating with physically meaningful dose response curves","authors":"George Kitis ,&nbsp;Georgios S. Polymeris ,&nbsp;Jun Peng","doi":"10.1016/j.quageo.2025.101671","DOIUrl":"10.1016/j.quageo.2025.101671","url":null,"abstract":"<div><div>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 <span><math><msub><mrow><mi>D</mi></mrow><mrow><mi>e</mi></mrow></msub></math></span> 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 <span><math><mi>W</mi></math></span> function. These simulations are subsequently extrapolated to experimental OSL dose–response curves obtained from dating experiments. The <span><math><msub><mrow><mi>D</mi></mrow><mrow><mi>e</mi></mrow></msub></math></span> was estimated by solving the new dose–response expressions and the error <span><math><msub><mrow><mi>σ</mi></mrow><mrow><msub><mrow><mi>D</mi></mrow><mrow><mi>e</mi></mrow></msub></mrow></msub></math></span>, 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 <span><math><msub><mrow><mi>D</mi></mrow><mrow><mi>e</mi></mrow></msub></math></span> 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 <span><math><msub><mrow><mi>D</mi></mrow><mrow><mi>e</mi></mrow></msub></math></span> 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 <span><math><msub><mrow><mi>D</mi></mrow><mrow><mi>e</mi></mrow></msub></math></span> saturation, through direct evaluation of the derivative of the DRC.</div></div>","PeriodicalId":54516,"journal":{"name":"Quaternary Geochronology","volume":"88 ","pages":"Article 101671"},"PeriodicalIF":1.7,"publicationDate":"2025-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143911735","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Testing micro-aliquot SGC and LnTn methods for age determination up to 780 ka using coarse K-feldspar grains from Nihewan Basin, northern China","authors":"Shengxia Xu ,&nbsp;Xue Rui ,&nbsp;Yujie Guo ,&nbsp;Bo Li","doi":"10.1016/j.quageo.2025.101673","DOIUrl":"10.1016/j.quageo.2025.101673","url":null,"abstract":"<div><div>The Nihewan Basin in northern China is a key region for the study of Paleolithic archaeology of East Asia, due to the discovery of Paleolithic sites with ages spanning the entire Pleistocene. However, many Paleolithic sites assigned to the Middle to Late Pleistocene are still not dated or poorly dated, which affects our understanding the stone tool technology evolution in the Nihewan Basin. The post-infrared infrared stimulated luminescence (pIRIR) signal from potassium-rich feldspar grains can be applied to date Middle to Late Pleistocene sediments, as this signal has significantly lower fading rate. In this study, to establish a robust chronological framework of the Nihewan Paleolithic sites more effectively, a micro-aliquot (MA) standardised growth curve (SGC) was constructed for pIRIR dating. The established MA SGC was tested for sediments up to 780 ka, and the obtained MA SGC D_e results were compared with those from single-aliquot (SA) measurement. Results from a number of tests suggest that the disagreement between MA and SA results is due to a small amount of anomalous fading in dimmer grains, which can be corrected by T_n threshold. By projecting the weighted mean L_n/T_n ratios (after T_n threshold correction) onto the MA SGC, the obtained pIRIR ages increase from top to bottom, and the sample from just above the B/M boundary (∼780 ka) yielded an age of <span><math><mrow><msubsup><mn>725</mn><mrow><mo>−</mo><mn>117</mn></mrow><mrow><mo>+</mo><mn>179</mn></mrow></msubsup></mrow></math></span> ka, which is consistent with the expected age. Our result suggested that the MA SGC method can reduce instrument time and has the potential to provide reliable age up to ∼700–800 ka in this region.</div></div>","PeriodicalId":54516,"journal":{"name":"Quaternary Geochronology","volume":"88 ","pages":"Article 101673"},"PeriodicalIF":1.7,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143928946","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Study the effect of irradiation, optical bleaching and heating on the thermal stability of OSL signals of quartz from dune sands in northern China","authors":"Zhijun Gong ,&nbsp;Hong Yan ,&nbsp;Ming Luo","doi":"10.1016/j.quageo.2025.101672","DOIUrl":"10.1016/j.quageo.2025.101672","url":null,"abstract":"<div><div>Variability in the thermal stability of quartz OSL signals has been observed for Late Quaternary sediments in different geographic setting in China. In this study, quartz grains were extracted from the Taklimakan Desert and the Hunshandake sandy land and the thermal stability of their quartz OSL signals were further investigated. Firstly, quartz aliquots of Taklimakan Desert were measured by using pulse annealing tests. It was found that the quartz from the Taklimakan Desert exhibited highly variable pulse annealing curves, showing the significant differences in the thermal stability of quartz OSL signals. Secondly, laboratory irradiation, optical bleaching and heating experiments were designed to test their effects on the thermal stability of quartz OSL signals. To compare the thermal stability among different quartz aliquots more efficiently, the thermal remnant ratio (TRR) was used as the proxy for the thermal stability, which was measured by using the ratios of the remnant OSL signals measured after cut-heat to 280 °C to those measured after cut-heat to 240 °C in the simplified pulse annealing tests. For the quartz samples from the Taklimakan Desert, it was found that the operated cycles of dosing and bleaching have relatively insignificant effects on the TRR values of quartz OSL. For the effect of heating on TRR value, it is dependent on samples. When the initial TRR value of quartz OSL is significantly less than 0.9, heating to high temperatures (e.g. ≥400 °C) has significant effect on the TRR value of quartz OSL. When the initial TRR value of quartz OSL is equal to or larger than 0.9, the effect of heating on the TRR value is not obvious. Such results suggest that different heating history of quartz plays an important role in the thermal stability of the quartz OSL signal. Thirdly, the TRR values of quartz OSL of Taklimakan Desert were compared with those of Hunshandake sandy land. For the Taklimakan Desert, it was found that only a part of the quartz grains exhibit TRR values equal to or larger than 0.9. In comparison, the TRR values for the majority of quartz grains from the Hunshandake sandy land are equal to or larger than 0.9. Such results demonstrate the different heating histories of quartz grains between the Taklimakan Desert and the Hunshandake sandy land, i.e. only a part of quartz grains from the Taklimakan Desert suffered from high temperature heating, while the majority of quartz grains from the Hunshandake sandy land suffered from high temperature heating during geological past. The different heating histories of quartz grains between the Taklimakan Desert and the Hunshandake sandy land are consistent with the different geological settings of the two regions. Our studies suggest that the proxy (i.e. TRR) of the thermal stability of quartz OSL has advantages over luminescence sensitivity for distinguishing the provenance of sediments with different heating histories.</div></div>","PeriodicalId":54516,"journal":{"name":"Quaternary Geochronology","volume":"88 ","pages":"Article 101672"},"PeriodicalIF":1.7,"publicationDate":"2025-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143895516","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An evaluation of two cryptotephra quantification methods applied on lacustrine sediments with distant Laacher See tephra fallout","authors":"V. Meier ,&nbsp;T. Hrstka ,&nbsp;J. Ohser ,&nbsp;J. Siquans ,&nbsp;B. Brandstätter ,&nbsp;G. Kletetschka ,&nbsp;D. Vondrák","doi":"10.1016/j.quageo.2025.101670","DOIUrl":"10.1016/j.quageo.2025.101670","url":null,"abstract":"<div><div>Detailed quantification of volcanic glass is crucial for improving the resolution of paleoenvironmental reconstructions and facilitating more accurate comparisons between distant sedimentary cryptotephra records. Here we present and evaluate two methods for the quantification of cryptotephra, shown on lake sediments from a site with distant Laacher See tephra fallout. Our methods initiate with delineating the extent and distribution of the cryptotephra layer within the sediments, accomplished through the integration of X-ray fluorescence (XRF) and computed tomography (medical- and μ-CT). The first quantification method involves the well-established process of shard extraction through stepwise density separation, followed by improved and statistically evaluated quantification introducing a new standardized marker. While the method itself is used widely for many years among cryptotephra researchers, we demonstrate how the new marker improves its precision for cryptotephra quantification, providing a robust, straightforward laboratory-based technique. Additionally, we introduce an innovative, software-based method that combines an SEM-based automated mineralogy analysis on thin sections with customized image analysis, which allows to study the area fraction of the glass phase, its depth-dependent variation, particle concentration with a focus on clustering behavior, depth-dependent particle count, total particle count, and particle size distribution within the glass phase. The significance of both methods lies in the efficiency and precision of cryptotephra quantification, enabling a deeper understanding of shard concentration and distribution. This study emphasizes the methodological innovations, offering improved tools for cryptotephra quantification, without focusing on detailed application-based analyses.</div></div>","PeriodicalId":54516,"journal":{"name":"Quaternary Geochronology","volume":"88 ","pages":"Article 101670"},"PeriodicalIF":1.7,"publicationDate":"2025-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143868298","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dating earthworks with luminescence: Insights from the medieval ringfort of Den Burg, Texel (the Netherlands)","authors":"Roy van Beek ,&nbsp;Elizabeth L. Chamberlain ,&nbsp;Kirsten de Nooijer ,&nbsp;Sander Gerritsen ,&nbsp;Michiel Bartels ,&nbsp;Jakob Wallinga","doi":"10.1016/j.quageo.2025.101669","DOIUrl":"10.1016/j.quageo.2025.101669","url":null,"abstract":"<div><div>Ancient human-made earthworks such as mounds, middens, levees, raised or terraced fields, enclosures and forts are omnipresent in many areas across the globe. They may offer rich and important information on past societies. However, harvesting such data is significantly hampered by the general lack of robust earthwork chronologies. Dating earthworks is notoriously difficult due to a variety of factors, including a scarcity of closely datable archaeological finds, the frequent absence of suitable and relevant material for radiocarbon dating, and lacking or ambiguous historical sources. Luminescence dating may provide a solution for these problems because it enables direct dating of sediment, a ubiquitous and relevant material in earthwork construction. In this paper we focus on ringforts: circular or semi-circular defensive structures surrounded by earthen banks and ditches, which originated in the first millennium CE and appear to reflect major transformations in early historical societies. We present the results of a detailed luminescence study of a ringfort underlying the modern town centre of Den Burg, on the Wadden Isle of Texel in the Netherlands. We dated samples from different sedimentary contexts (bank and ditch infills) using both quartz optically stimulated luminescence (OSL) and feldspar single-grain post-infrared infrared stimulated luminescence (pIRIR). We analyze the results in the context of age interpretations based on other proxy data (radiocarbon dates, archaeological finds, historical evidence). This yields a new, robust dating chronology that changes the biography of the ringfort. The initial construction dates between 730 and 840 CE, making Den Burg the oldest known ringfort in the Low Countries. We reflect on the best practices for luminescence dating of earthworks and on archaeological implications for other ringforts in the Netherlands and beyond.</div></div>","PeriodicalId":54516,"journal":{"name":"Quaternary Geochronology","volume":"88 ","pages":"Article 101669"},"PeriodicalIF":1.7,"publicationDate":"2025-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143842661","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"High-precision radiocarbon dating and carbon reservoir effect of a maar lake in South China","authors":"Yao Gu ,&nbsp;Huayu Lu ,&nbsp;Hongyan Zhang ,&nbsp;Pengyu Lin ,&nbsp;Xiaoyi Dong ,&nbsp;Yao Wang ,&nbsp;Shuangwen Yi ,&nbsp;Fuzhi Lu ,&nbsp;Fan Yang","doi":"10.1016/j.quageo.2025.101668","DOIUrl":"10.1016/j.quageo.2025.101668","url":null,"abstract":"<div><div>High-resolution maar lake records with robust age control provide an ideal foundation for investigating paleoclimate change. However, in tropical-subtropical South China, the carbon reservoir effect of lake sediments is poorly understood, resulting in a lack of high precision records, hindering the comprehensive understanding of regional climate change and its forcing mechanism. In this study, based on a newly drilled core from the Tianyang (TY) maar lake located in South China, we conducted detailed radiocarbon dating of various materials to assess the reservoir effect and establish a reliable high-resolution chronology of the maar lake. Comparing radiocarbon ages of different grainsize and different fractions, the ages of bulk samples were closest to those of plant remains or charcoals which we consider as the reliable dating materials. Pairs of bulk samples and plant remain or charcoal ages indicate a limited but variable reservoir effect in TY maar lake. The reservoir effect is negligible from the surface to 623 cm (0–30.95 ka) and then gradually increased from negligible to approximately 700 years between the depth of 623–747 cm (30.95–37.15 ka). We hypothesize that the reservoir effect in the deeper part of the lake results from a combination of longer mean residence time due to lower sedimentation rates and increased groundwater level, which is linked to higher sea levels during the marine isotope stage 3 (MIS3). After reservoir correction, Bayesian age-depth modelling was performed based on 53 reliable radiocarbon ages, achieving a high-resolution chronology of TY maar lake covering the past ∼37 ka period with a mean age model uncertainty of 357 years, providing a reliable dating framework for paleoclimate reconstruction.</div></div>","PeriodicalId":54516,"journal":{"name":"Quaternary Geochronology","volume":"88 ","pages":"Article 101668"},"PeriodicalIF":1.7,"publicationDate":"2025-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143769296","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Developing a new approach to the luminescence dating of sediments from glacial contexts","authors":"M.D. Bateman ,&nbsp;E. Davies ,&nbsp;D.J.A. Evans ,&nbsp;D.H. Roberts ,&nbsp;E.R. Connell ,&nbsp;E.J. Rhodes","doi":"10.1016/j.quageo.2025.101659","DOIUrl":"10.1016/j.quageo.2025.101659","url":null,"abstract":"<div><div>Whether glacial sediments were exposed to light (bleached) prior to burial is uncertain but critical for luminescence dating. In such contexts, quartz can have unstable and weak signals, feldspar have less bleachable and fading signals and both require statistical modelling to extract the true burial age data. This paper presents a new approach using feldspars measured at multiple elevated temperatures (MET) and screened to select grains with plateau equivalent dose values which should be the well-bleached and unfaded grains upon which to base a true burial age. The MET plateau approach was tested on an aeolian site in Canada and two former UK glacial sites. When applied to the Canadian aeolian samples, it showed that the method successfully accepted mostly well-bleached grains whilst excluding grains with fading or that had poor luminescence characteristics. When applied to a well dated glacial sequence it yielded ages in good agreement with existing independent chronologies. A previously undated glacial site yielded stratigraphically consistent ages but these are thought likely to be slight age over-estimates due to extremely limited bleaching at deposition. In summary, the MET plateau approach improved avoidance of partially bleached grains, avoided corrections for residuals and/or fading and reduced the need for statistical models to interpret equivalent dose distributions. However, some glacial sediments may have had so limited bleaching that these may still not be easy to luminescence date. The MET plateau approach if adopted could allow re-evaluation of existing glacial chronologies and extend luminescence dating to more glacial sediments.</div></div>","PeriodicalId":54516,"journal":{"name":"Quaternary Geochronology","volume":"87 ","pages":"Article 101659"},"PeriodicalIF":1.7,"publicationDate":"2025-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143684273","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Radiocarbon age anomalies in post-impact lake sediments of the Hapcheon impact crater, Korea and their implication for crater evolution","authors":"Jaesoo Lim ,&nbsp;Sangheon Yi ,&nbsp;Sujeong Park ,&nbsp;Arum Jung ,&nbsp;Youngeun Kim ,&nbsp;Sung Won Kim","doi":"10.1016/j.quageo.2024.101649","DOIUrl":"10.1016/j.quageo.2024.101649","url":null,"abstract":"<div><div>Impact craters caused by meteorite collisions are phenomena that dramatically alter the Earth's surface and disturb the natural carbon cycle in subsequent sedimentary environments. To determine the impact date and impact-driven old carbon effects on radiocarbon cycles recorded in post-impact lake sediments, we performed radiocarbon (¹⁴C) dating of various organic fractions (humic acids, humins, charcoal, and organic plant fragments of various sizes) in post-impact lake sediments of the Hapcheon impact crater, Korea. Charcoal and plant fragments larger than 500 μm in the post-impact lake sediments of core 20CR09 constituted the oldest fraction (&gt;45,000 cal BP), indicating pre-impact ages. Compared to micro-organic fragments (10–100 μm) consisting of terrestrial plant tissues, pollen, and limited freshwater algae with a narrow age range of 39,300–42,300 cal BP, the 100–500-μm plant fragments showed a slightly older age range of 41,670–43,910 cal BP throughout the 33-m-long lake sediment core. This suggests significant influence of well-mixed syn-impact organic fragments transported from slope deposits consisting of impact breccias and fallback deposits. Humin ages in the lake sediment of core 20CR05 were similar to those of the micro-plant fragments in core 20CR09, indicating that the humin fraction is mainly allochthonous. Humic acids at a depth of ca. 71 m, corresponding to the lowermost post-impact lake sediments (Stage 1), were dated to ∼21,000 cal BP, showing strong influence of post-impact humic acids ages. Whereas those from mid-depth lake sediments (Stage 2) were dated to 35,000–43,000 cal BP. This age reversal indicates increased input of syn-impact allochthonous humic acids, supported by positive correlation with terrestrial mineral input. This study demonstrated significant syn-impact radiocarbon effects and resultant age reversals in post-impact early lake sediments. The syn-impact age may be estimated by comparing ages of different-sized plant fragments (e.g., 10–100, 100–500, and &gt;500 μm), humin, and humic acids. These findings suggest that climatic and environmental interpretations of these post-impact early lake sediments should be conducted only after testing various organic materials, if radiocarbon dating is applied. Lastly, compared to surrounding areas following natural climate changes, post-impact early lake environments in impact craters must be considered as anomalies with different ecosystems due to hydrothermal activity.</div></div>","PeriodicalId":54516,"journal":{"name":"Quaternary Geochronology","volume":"86 ","pages":"Article 101649"},"PeriodicalIF":1.7,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143167775","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}