Abstract: Mountain summits in the Slovak part of the Western Carpathians bear evidence of human presence from the Late Bronze to the Late Iron Age. According to fire-induced changes in archaeological record and finds of weaponry, some of the extreme upland sites (EUS) were viewed as places of safety or refugia violently destroyed within a short period. We have focussed on three sites with summits at 1300–1550 m a. s. l. and found out that two of them were used in 650–400 calBC and 390–150 calBC, respectively. By the first systematic use of 14C dating and targeted 14C sampling, we have overcome the inherent chronological imprecision of their artefactual record and opened new vistas for interpretation of this type of sites. PubDate: Fri, 23 Jun 2023 00:00:00 GMT
Abstract: This work considers the impact of the internal alpha and beta dose rates in quartz grains obtained from sandy sediments on the results of luminescence dating. The internal dose rates reported here (ca. 0.01–0.21 Gy · ka−1) play a particularly important role, because of low (ca. 0.8–0.9 Gy · ka−1) or very low (ca. 0.4–0.6 Gy · ka−1) external dose rates. In these cases, the internal dose rates form a significant fraction of the total dose rates, often exceeding 10%. Ignoring this contribution would have made the considered luminescence ages artificially older. In our study, we measure both the internal alpha and beta contributions as the latter is usually neglected in the case of quartz. The dose rate measurements were performed using the innovative μDose system. PubDate: Sat, 10 Dec 2022 00:00:00 GMT
Abstract: In this work we investigate the quartz etching process using hydrofluoric acid for trapped charge dating (TCD) applications. It is done using material collected from an active sand mine in Bełchatów Nowy Świat, central Poland. Approximately 20 kg of material was collected and prepared using routine procedures that are applied in TCD laboratories. The material was sieved using 180–200 μm meshes, and the selected fraction was etched for various time intervals. Sieved samples were etched for durations from 0 min up to 180 min and measured with microscope image analysis (IA), laser diffraction (LD), and mass loss which were used to estimate the depths of etching. Our results show statistical data on how non-uniform the etching process is. We estimate this as a function of etching time from IA, LD and mass loss. In our investigation, mass loss measurements with the assumption of spherical grains correspond to the decrease of radius of ca. 0.151 ± 0.003 μm · min−1. In case of LD, a rough etch depth estimation corresponds to a range 0.06–0.18 μm · min−1 with median at 0.13 μm · min−1. Microscope IA gives a 0.03–0.09 μm · min−1 with a median at 0.05 μm · min−1. Moreover, quartz grains are fractured into smaller pieces while etching. It means that assumptions that are used in etch depth estimation from mass loss are not correct. They incorrect not only because grains are not spheres but also because the number of grains is not constant. Therefore, the etch depth estimated from mass loss might be overestimated. Using microscope IA we report etch depth ranges that might be used to roughly estimate the etch depth uncertainty. PubDate: Tue, 10 May 2022 00:00:00 GMT
Abstract: To better understand the factors controlling the quartz luminescence sensitivity in loess deposits, samples from two loess sections in southern Tajikistan are investigated. Both pattern and amplitude in the variations of quartz luminescence sensitivity of these two sections are similar, showing higher values in pedocomplex units and lower values in the loess units. Similar trends of variation are found between the quartz luminescence sensitivity and climate proxies, including frequency-dependent magnetic susceptibility, median grain size and IRSL/[post-IR] OSL ratio. Laboratory experiments involving thermal activation and repeated bleaching/irradiation cycles reveal much larger sensitivity enhancement for samples with initial lower sensitivity from loess units than those from pedocomplex units with higher sensitivity. The observed systematic contrast in quartz luminescence sensitivity between the loess and pedocomplex units are interpreted as resulting from the differentiation of the weathering products from the source area and subsequent sensitization during the sedimentary transfer prior to deposition. PubDate: Fri, 31 Dec 2021 00:00:00 GMT
Abstract: Optically stimulated luminescence (OSL) dating of fine-grained (4–11 μm) fluvial sediments is rarely attempted but is crucial for constraining the evolution of mud-dominated floodplains. This study investigated the applicability of OSL dating to fine-grained deposits in the Mekong River, Cambodia based on a very young (<600 yr) point-bar to riverbank succession and modern flood deposits. In succession, fine-grained quartz OSL provided the youngest ages, whereas age estimates by multi-grain sand-sized quartz OSL, and feldspar and polymineral infrared-stimulated luminescence are >200 years older than the fine-grained quartz OSL age estimates. Ages of fine-grained quartz OSL are concordant with the minimum ages obtained from the single-grain quartz OSL. These results are supported by the generally small residual doses (<0.1 Gy) measured in modern fine-grained flood-plain deposits. This indicates that fine-grained sediments in the Mekong River (Cambodia) are sufficiently bleached at deposition and can yield reliable quartz OSL ages for establishing the chronology of the floodplain. The sufficient bleaching of fine-grained quartz partly results from the long transport distance and may also occur in other large river systems. PubDate: Fri, 31 Dec 2021 00:00:00 GMT
Abstract: Carbonated rocks constitute one of the main lithologies of the southeastern Tibet area, China, a tectonically very active zone. However, due to the lack of suitable dating materials, it is difficult to carry out chronological studies of the local tectonic evolution in such carbonate areas. In the present study, electron spin resonance (ESR) method had been applied on the dating of carbonates heated during fault activity of the Lijiang-Xiaojinhe (LX) Fault, an important active fault located in the northwest of Yunnan Province. Clear displaced landforms show that the fault has undergone strong late-Quaternary activity. During the fault activity, the heat produced by friction lead to the melting of the frictional surface of the rocks, and the melting can attenuate or zero the ESR dating signal of carbonate. The aim of the present paper was to check the ability of carbonate use to chronologically identify fault activity using electron spin resonance (ESR) method. The results showed the last fault activity of the LX fault was dated by ESR about 2.0±0.2 ka ago, in agreement with historical and radiocarbon data. Hence ESR can be if necessary a practicable dating alternative method for the study of fault activity chronology in carbonate rock area. PubDate: Fri, 31 Dec 2021 00:00:00 GMT
Abstract: In this study, we explored the potential of a NaI(Tl) scintillator-based gamma spectrometer for the accurate determination of burial dose rates in natural geological samples using a full spectrum analysis (FSA) approach. In this method, an iterative reweighted least-square regression is used to fit calibration standard spectra (40K, and 238U and 232Th series in equilibrium) to the sample spectrum, after subtraction of an appropriate background. The resulting minimum detection limits for 40K, 238U, and 232Th are 4.8, 0.4 and 0.3 Bq·kg−1, respectively (for a 0.23 kg sample); this is one order of magnitude lower than those obtained with the three-window approach previously reported by us, and well below the concentrations found in most natural sediments. These improved values are also comparable to those from high-resolution HPGe gamma spectrometry. Almost all activity concentrations of 40K, 238U, and 232Th from 20 measured natural samples differ by ≤5% from the high resolution spectrometry values; the average ratio of dose rates derived from our NaI(Tl) spectrometer to those from HPGe spectrometry is 0.993 ± 0.004 (n=20). We conclude that our scintillation spectrometry system employing FSA is a useful alternative laboratory method for accurate and precise determination of burial dose rates at a significantly lower cost than high resolution gamma spectrometry. PubDate: Fri, 31 Dec 2021 00:00:00 GMT
Abstract: The Huxushan archaeological site in northern Hunan Province, China, was recently excavated, from which stone tools including handaxes were unearthed. The deposits of the site are chemically weathered, which makes it difficult to date the site using numerical dating techniques except for optically stimulated luminescence (OSL) method. Here, we used various luminescence procedures including single-aliquot regenerative-dose (SAR), sensitivity-corrected multiple-aliquot regenerative-dose (SMAR) and thermally transferred optically stimulated luminescence (TT-OSL) SAR procedures on fine-grained quartz, and two-step post-infrared infrared stimulated luminescence (pIRIR) and multi-elevated-temperature pIRIR (MET-pIRIR) procedures on fine polymineral fractions. The results show that the fine quartz grains have excellent luminescence properties and the quartz SAR-, SMAR- and TT-OSL ages for the samples agree with each other and in stratigraphical order except for one sample. The fine polymineral fractions exhibited relatively weak pIRIR and MET-pIRIR signals, resulting in difficulty in constructing the dose-response curve for MET-pIRIR signals and the stratigraphically inconsistent pIRIR(100, 275) ages. The seven samples yielded their quartz OSL ages ranging from about 62 ka to 133 ka. The two samples from the cultural layer was dated to 78 to 92 ka using different procedures on fine quartz. However, given the systematically older pIRIR ages obtained with the fine polymineral grains for the two samples, their quartz OSL ages are considered to represent the minimal ages of this layer, and their pIRIR(100, 275) ages of 118 and 110 ka represent the upper age limit, indicating that the site was occupied by hominins during Marine Isotope Stage 5. PubDate: Fri, 31 Dec 2021 00:00:00 GMT
Abstract: We sheared simulated-quartz gouges using a low-velocity rotary shear apparatus and evaluated the relationship between electron spin resonance (ESR) intensity and displacement quantitatively considering problems of contaminants. ESR intensity of E1’ centre increased while OHC and peroxy centre kept constant with the increasing displacement up to 1.4 m. Microstructural analysis showed grain size reduction and fracture of starting gouges; hence, the fracture can affect the change in ESR intensity. ESR measurements were also conducted for starting gouges with variable amounts of contaminants, and it was confirmed that the effect of contaminants on the change in ESR intensity was negligible. Moreover, we estimated the temperature rise by the frictional heating on the surface and between particles, and it was shown that the effect of frictional heating on ESR intensity was also negligible in our experimental condition. Therefore, we could clarify the relationship between ESR intensity and fracturing with various displacements separately from contaminants and frictional heating. The results imply that the zero-setting of ESR signals cannot occur by the fracture with low frictional heating at the shallow depth. PubDate: Fri, 31 Dec 2021 00:00:00 GMT
Abstract: The loess sediments widely distributed in the Central Shandong Mountains are sensitive records of East Asian monsoon changes for situating in a key region connected to the Eurasian Plate and the Pacific Ocean. However, the detailed processes of palaeoclimatic changes are poorly understood for the lack of high-resolution chronology. In this study, the chronology of Heishan loess palaeosol sequence in the Central Shandong Mountains is investigated using quartz SAR OSL and K-feldspar post-IR infrared (IR) stimulated luminescence (post-IR IRSL) dating method. The quartz is sensitive, fast component dominated and saturate at ∼150 Gy (∼50 ka). The measured K-feldspar pIRIR290 De showed no dependency on the first IR stimulation temperature between 50°C and 260°C. The K-feldspar pIRIR290 ages are consistent with the stratigraphy up to ∼75 ka. In establishing the chronological sequence for the study section, quartz OSL ages <50 ka and the K-feldspar pIRIR290 ages >50 ka were selected. Derived sedimentation rates show two relatively rapid stages of ∼32.0 ± 5.5 cm/ka for the palaeosol (∼11–8 ka) and ∼54.8 ± 1.1 cm/ka for the loess (∼34–30 ka). An erosional hiatus of loess between ∼30 ka and ∼17 ka is identified. We conclude that the pIRIR290 of loess sediments is applicable for samples during ∼8–75 ka. PubDate: Fri, 31 Dec 2021 00:00:00 GMT
Abstract: Luminescence dating technology has been used for chronological constraints on lacustrine sediments due to the ubiquitous materials (e.g., quartz and feldspar) as dosimeters, and a relatively long dating range, compared with the commonly used radiocarbon dating method. However, quartz dating on the Tibetan Plateau may suffer from dim and unstable luminescence signals. In the current study, we investigate a lake-related outcrop from the shore of Cuoe Lake on the central Tibetan Plateau. Both coarse-grained quartz and K-feldspar fractions were extracted, and OSL and post-IR IRSL signals were measured from these fractions, respectively. Combining the stratigraphy analysis and dating results, this study shows that: (1) quartz appears to be unsuitable for dating because of very dim natural signals and even anomalous fading (average g-value: 4.30 ± 2.51 %/decade). The suitability of the applied pIRIR protocol measured at 150°C (pIRIR150) for K-feldspar samples was confirmed by a set of luminescence tests; (2) compared with the luminescence-based chronology, the 14C age of shells from the same sediment layer yielded older age by ∼7 ka, which is likely attributed to hard water reservoir effect in Cuoe Lake; (3) the lake level reached its peak and maintained high-stand during the early Holocene (∼9.4–7.1 ka). This study highlights the applicability of K-feldspar luminescence dating when the counterpart quartz OSL is insensitive and encounters anomalous fading. PubDate: Fri, 31 Dec 2021 00:00:00 GMT
Abstract: Wuhan area located middle Yangtze River Basin, is dominated by East Asian Monsoon. Widely developed Holocene flu-lacustrine sediments are ideal materials for the reconstruction of paleoclimate change and geo-environment evolution, for which the chronology is a key issue. In this study, 20 luminescence dating samples were collected from a flu-lacustrine sequence and the reliability of the quartz OSL dating to these samples were checked by using luminescence characteristics of dose recovery test and thermos transfer test. Our results indicate that different grain size fraction of 4∼11 μm, 38∼63 μm, and 90∼125 μm were well-bleached before burial. Dating results show that all these ages range from 0.8 ± 0.1 to 7. 9 ± 0.7 ka between 4.25 and 38.55 m, and most of them follow the stratigraphic sequence and other climatic recorder within the normal range of error. Disordered OSL ages may be caused by complicated transport-deposit processes. As a consequence, OSL dating method of SAR-SGC protocol could provide a significant chronology for Holocene flu-lacustrine sediment in large river depo-system. PubDate: Fri, 31 Dec 2021 00:00:00 GMT
Abstract: This study provides methodological aspects on the equivalent dose estimation for travertine samples, namely heated calcium carbonate, using the TL multiple-aliquot additive-dose approach. Large equivalent doses (EDs), within the range 750–1300 Gy, were calculated using the plateau method based on the NTL glow curve. Moreover, a component resolved TL glow-peak analysis was carried out, using the integrated intensity of the NTL glow peaks for the ED estimation after deconvolution based on the OTOR model. Three different TL peaks were used, termed P4, P5 and P6. The integrated intensity of TL glow peak P4 resulted in age overestimation (15–26%), compared to the age provided using the plateau method. This overestimation could be attributed to the fact that the temperature range of P4 does not coincide with the plateau region of each sample. Milder overestimation (8–14%) was noticed using the integrated intensity of TL glow peak P6, mostly due to the poor deconvolution resolution. Only the integrated intensity of TL glow peak P5 after deconvolution provides ED values compatible with those yielded using the plateau method, with good accuracy. The present study suggests not using the TL intensity (neither in terms of integrated intensity nor of peak height intensity) for ED estimation; instead it is highly recommended to use either the plateau method, or alternatively integrated intensity of TL peak P5 after deconvolution. Unfortunately, using the peak height of TL P5 is not recommended, due to overlapping with P6. PubDate: Fri, 31 Dec 2021 00:00:00 GMT
Abstract: The present study aimed at quantifying the relationship between TL and either CW-OSL or LM-OSL using commercially available magnesium oxide. The samples were bleached at two different temperatures, and a component-resolved analysis on the integrated signals was performed. According to the data of the present study, each one among the five observed LM-OSL component receives electrons from at least two different TL peaks. Two different fast OSL components were resolved in the LM-OSL curves, both accumulating electrons from all TL glow peaks with Tmax>150°C. Component C3 is very well correlated with the TL peaks at 102, 135 and 194°C, while components C4 and C5 are related to the TL glow peaks of 292°C, 353°C and 464°C. We note that for CW-OSL the resolution is good when two or more components differ in intensity by an order of magnitude. Blue stimulation depletes substantially the first two TL peaks but not the third peak. Substantial depletion of the high-temperature TL peaks is achieved only by using the LM-OSL configuration. The results of the present study suggest that the traps that contribute to TL and OSL are the same, despite using different recombination pathways. PubDate: Fri, 31 Dec 2021 00:00:00 GMT
Abstract: The post-infrared (post-IR) pulsed blue light stimulated luminescence (PBLSL) signal has been employed to determine the equivalent dose (De) of feldspar contaminated quartz grains, but it sometimes suffers from the interference of feldspars. Since the green light stimulated luminescence (GLSL) signal of feldspars might be more reduced by a prior IR stimulation, we compared the characteristics of post-IR PBLSL and post-IR pulsed GLSL (post-IR PGLSL) signals of quartz and feldspars in this study to evaluate the feasibility of employing the green light for pulsed stimulation. We investigated the effect of the signal integration period, pulsed stimulation temperature, and prior IR stimulation temperature on the intensities of post-IR PBLSL and post-IR PGLSL of quartz and feldspars, and evaluated the potential feldspar interference on these two signals for the hypothetical and artificial quartz-feldspar mixture. The results demonstrate a lower feldspars contribution for the post-IR PGLSL signal. The feldspar interference only slightly increases with the increase of integration period for the post-IR PGLSL signal measured at low stimulation temperature, which permits a long integration period to be employed to enhance the signal to noise ratio. This study shows that the green light is a promising alternative for pulsed stimulation to suppress the feldspar contribution. PubDate: Fri, 31 Dec 2021 00:00:00 GMT
Abstract: We assessed the residual dose of K-feldspar grains from modern and Holocene beach–shoreface sands at Kujukuri, eastern Japan. Samples from the modern foreshore and shoreface (to 34 m depth) show residual doses <0.2 Gy for infrared-stimulated luminescence (IR)50 measured during post-IR infrared-stimulated luminescence (pIRIR)50/150, equivalent to potential burial age overestimation of only several decades for given dose rates. Residual doses of 1–3 Gy are retained by pIRIR50/150, equivalent to 400–1,300 years; pIRIR50/290 residual doses are up to 30 Gy, suggesting possible overestimation by >10,000 years. Residual doses of Holocene sands were also assessed by comparison with radiocarbon ages, revealing consistent results with modern sands. The pIRIR50/290 results show no pronounced correlation of residual dose with water depth, except for a few samples from <5 m depth with residual doses several tens of per cent lower than those of deeper sands, suggesting that most samples were not fully bleached and that sustained subaerial sunlight bleaching diminishes the difficult-to-bleach component. Compared to the uncertainties associated with other factors, such as the fading correction, the residual doses of IR50 and pIRIR50/150 are negligible for samples older than late and early Holocene, respectively. In contrast, the residual dose of pIRIR50/290 may lead to critical age overestimation of Late Pleistocene deposits if the residual dose is not properly corrected. PubDate: Fri, 31 Dec 2021 00:00:00 GMT
Abstract: In terms of fine-grain luminescence dating applications, the efficiency of α-radiation in producing luminescence is an important issue when determining environmental dose rates. Efficiency is usually assessed by measuring the ratio of luminescence intensities induced by known α and β laboratory doses. Consequently, most thermoluminescence (TL)/optically stimulated luminescence (OSL) readers besides the standard 90Sr/90Y β-source can also be equipped with a 241Am α-source. A crucial point is, however, the calibration of these sources. The calibration of β-sources is routinely performed using standard quartz samples previously irradiated by a known γ-dose, though, in the case of α-sources, the procedure is less standardised, partly because there are no calibration materials with a known α-efficiency value.In this study, we aimed to cross-calibrate the built-in α-source of a RISØ TL/OSL DA-20 luminescence reader by testing and comparing five procedures, applying different samples (quartz and polymineral), different protocols multiple aliquot regeneration (MAR) and single aliquot regeneration (SAR) and different calibration sources. Throughout the tests, the performance of the fine-grain RISØ calibration quartz was also assessed.Regardless of the applied procedure, the calculated α-dose rates with one exception gave similar results. On the one hand, the applied polymineral sample due to potential fading, fairly high residuals after bleaching and relatively low infrared stimulated luminescence (IRSL) sensitivity proved to be the least optimal choice for cross-calibration. On the other hand, the tested natural fine grain quartz gave almost identical results when using different types of bleaching and different calibration α-sources. The mean dose rate determined for the source was 0.080 ± 0.004 Gy/s.The cross-calibration by using the RISØ fine grain quartz yielded somewhat higher but at the apparent uncertainty of luminescence dating still not significantly different dose rate for the source under calibration. Tests showed that the calibration quartz saturates at a relatively low α-dose, and the shape of α- and β-dose-response curves also depart from each other quite early, suggesting that cross-calibration with this material seems to be reliable only at low doses. For the first time, the a-value of the fine-grain calibration quartz was also determined using the freshly calibrated α-source, and the measurement yielded a 0.054 ± 0.003 value. We propose that after further validation of this result, the RISØ calibration quartz can ease the dose rate assessment of uncalibrated α-sources in the future. PubDate: Tue, 29 Jun 2021 00:00:00 GMT
Abstract: Olivine has so far attracted limited attention as a potential luminescence dosimeter. In particular, there is a dearth of information concerning the luminescence properties of geochemically characterised, pure olivine samples. Six well-characterised olivine samples from four intraplate settings are investigated in this study, including emission wavelengths and intensities, growth of signal with absorbed dose, signal stability and recovery of a given dose with a single aliquot regeneration (SAR) protocol. All tested olivines share a low-temperature (90–100°C) UV/blue thermoluminescence (TL) peak, and five of six samples also produce a low-temperature red/yellow emission. Higher temperature TL peaks, which would be thermally stable over geological timescales and could be used for dating, are rarely observed at low doses (c. 46 Gy), but detectable though dim at significantly higher doses (c. 460 Gy). Photostimulated luminescence (PSL) emissions are very dim, but reliably detected emissions are stimulated by blue, yellow and infrared (IR) light. PSL yielded generally successful dose recovery results; however, all tested signals are prone to significant anomalous fading and complex thermal transfer between unbleachable and bleachable traps. These characteristics must be addressed if olivine is to be used as a natural dosimeter for luminescence dating. Given the variety of luminescence responses, it appears that olivine samples in future dating work may need to be individually characterised prior to measurement. PubDate: Tue, 29 Jun 2021 00:00:00 GMT
Abstract: The Gliwice Luminescence Laboratory (GLL) is a part of the Institute of Physics – Centre for Science and Education at the Silesian University of Technology, which has gradually evolved since the 1980s. To date, nearly 3500 samples have been dated using luminescence from materials such as ceramics, bricks, and sediments from archaeological and geological sites. Currently, the laboratory is equipped with four luminescence readers and three gamma spectrometers, allowing luminescence dating of approximately 300 samples annually for the needs of research projects. This article focuses on the laboratory procedures used in GLL to obtain luminescence ages. Recent improvements of the GLL's facilities and new equipment, as well as the performance spanning the Laboratory's 30 years of activity, are discussed in terms of obtained results and the involvement in national and international projects. PubDate: Sat, 17 Apr 2021 00:00:00 GMT
Abstract: Establishing a chronology of events is a critical step in reconstructing the palaeoclimate and it is important for all types of environmental records, including speleothems. Here, we analysed a unique series of flowstones deposited between 3.2 Ma (marine isotope stage (MIS) Km3) and 0.08 Ma (MIS 5). The studied flowstones are located in a classic karstic environment, the Račiška Pečina Cave in south-western Slovenia. Further, a detailed chronology of events was constructed based on oxygen isotope stratigraphy (OIS), combined with magnetostratigraphy and U-series dating. Two curves were selected as reference records where the LR04 record was used as the global curve and a Mediterranean record was used as the regional curve. The Račiška Pečina profile was divided into two segments separated by a principal disconformity. The lower segment correlated better with the regional Mediterranean curve, while the upper segment was with the global LR04 curve. These findings suggest that the main factors controlling environmental conditions in the cave area changed between 3.2 and 0.8 million years ago. PubDate: Wed, 14 Apr 2021 00:00:00 GMT
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