Luminescence dating of the late Quaternary sediments in Hangzhou Bay,China

Coastal plain of Hangzhou Bay, to the south of the present Yangtze Estuary, is closely linked to the evolution of the Yangtze River delta. However, absolute age of Pre-Holocene sediments is limited, which hinders the understanding of this area's environmental evolution. In this study, using optically stimulated luminescence (OSL), single aliquots and single grains of quartz and K-feldspar were used to date the late Quaternary sediments in coastal plain on the southern Hangzhou Bay. The vertical difference in particle size composition render either silt- or sand-sized quartz for dating. Cross-checking of multiple OSL dating methods indicated that the upper ∼65 m recorded the Holocene part of the succession; sediment from a depth of 136.6 m was dated to ∼180 ka. It was found that the single-grain method was more reliable in comparison to single-aliquot age, the former minimized the effect of signal components. Single-grain quartz and K-feldspar luminescence yielded consistent ages at sample depth of 136.6 m (∼160–180 ka), while the latter gave robust age at depth of 115.5 m (∼150 ka). This chronology is in general in accordance with neighbouring cores and can constrain paleomagnetic dating results in those cores. Taking together, the study site has thickest Holocene deposits in comparison to the highland centered around Taihu Lake on the southern Yangtze delta. Moreover, the luminescence characteristics of quartz from different sample depths, behaved differently with respect to luminescence sensitivity, signal components and saturation level, perhaps reflecting varied provenance and weathering characteristics caused by climate change.     

Luminescence dating of Holocene sediment cores from a wave-dominated and mountainous river delta in central Vietnam

Sediments of river deltas provide valuable records of past coastal environments. Optically-stimulated luminescence (OSL) dating has become an alternative to radiocarbon dating for constraining the sediment chronology in large deltas that allow for sufficient sunlight bleaching of sediments during the fluvial transport. However, its applicability to smaller deltas with mountainous riverine systems has not been confirmed yet. To check this, we examine multiple signals from two Holocene sediment cores in the wave-dominated Thu Bon River delta in central Vietnam. Two cores were collected, respectively, 3.9 km and 1.2 km inland from the present shoreline and both show a >-25-m thick succession of coarsening-upward mud to sand deposits. Coarse grains (180–250 μm in diameter) of quartz and K-feldspar, and fine grains (4–11 μm in diameter) of quartz and polymineral were extracted from the upper and lower parts of the cores for multi-grain measurements of quartz OSL, and of feldspar infrared-stimulated luminescence (IRSL) at 50 °C (IR₅₀) and post-IR IRSL at 175 °C (pIRIR₁₇₅) to determine burial ages. In addition, facies analysis and radiocarbon dating were conducted. The landward core consists of transgressive to early regressive estuarine and prodelta facies, which is overlain by a sandy beach-shoreface facies. The seaward core consists of a relatively simple shallowing-upward succession from muddy prodelta facies to sandy beach-shoreface facies. All luminescence ages except for pIRIR₁₇₅ of fine grains are mostly consistent with the radiocarbon ages. Instead, pIRIR₁₇₅ ages of fine grains are significantly overestimated with variable offsets. OSL and IR₅₀ of fine grains provide reasonable age estimates, as these grains were likely well bleached during the transport even along a short and steep mountainous river. Consistent age estimates of all signals from sand indicate that sand was well-bleached in the beach and shoreface owing to the frequent sediment reworking by waves and currents. These results support the hypothesis that luminescence dating is applicable to Holocene wave-dominated deltas and reiterate that comparing different luminescence signals is an effective way to check reliability of the age estimates in environments where the sunlight bleaching is not ensured.     

Luminescence dating of cobbles from Pleistocene fluvial terrace deposits of the Ara River,Japan

Constraining the ages of fluvial terraces is essential to understanding fluvial responses to climate and sea-level changes and estimating uplift/incision. Luminescence dating of sand or silt grains from fluvial terrace deposits in Japan is difficult because sand layers are often absent from gravelly deposits, quartz grains are typically dominated by medium/slow components and/or contaminated by feldspars, and short transport distances and short residence times in riverbeds result in poor bleaching of luminescence signals. Luminescence dating of cobbles may overcome these difficulties, but few studies have applied this technique to fluvial terrace deposits. Here, we examine the utility of luminescence dating applied to three granodiorite cobbles from a late Pleistocene fluvial terrace deposit of the Ara River, Japan. We investigated variations of the infrared stimulated luminescence (IRSL) and post-IR IRSL signals with depth in each cobble. The IRSL and post-IR IRSL signals generally increase with depth, indicating that the cobbles were not completely bleached before deposition. Nonetheless, the IRSL ages of the cobble surfaces (19–17 ka) are consistent with the age of a tephra layer (16–15 ka) at the base of loess deposits overlying the terrace. In contrast, IRSL ages of sand-sized feldspar grains overestimate the depositional age because of incomplete bleaching, whereas silt-sized quartz grains greatly underestimate the depositional age, likely because of the thermal instability of the medium component. Our results demonstrate that luminescence dating of cobbles could provide a better understanding of fluvial systems in which luminescence dating of sand grains is difficult.     

Luminescence dating of the Huliu River terraces in the Nihewan Basin,North China

As one of the most important regions for early human occupation in East Asia, Nihewan Basin in North China is well-known for an abundance of archaeological sites with ages spanning the last 2 Ma. In recent 10 years, more than 27 new archaeological localities have been discovered from the Yuxian (sub-basin of Nihewan), and all of them are with no age control. The lack of reliable ages for these localities affects our understanding for the evolution of the stone-tool technology in the Nihewan Basin. As many localities were founded in the river terrace, the fluvial terrace sequence of the Huliu River (main river of the Yuxian) was investigated. Based on single-grain post-infrared infrared stimulated luminescence (pIRIR) procedure on potassium (K-) feldspar, our results reveal that the formation ages of three Huliu River terraces are 139.6–115.7, 19.7–5.5, and <0.9 ka, respectively. On the basis of these pIRIR ages, the formation of the fluvial terrace sequence may provide informative constraints on the human occupation in the Huliu River terrace in the Nihewan Basin, if a clear stratigraphic correlation is established between the archaeological sites and the dated terrace deposits.     

Luminescence dating of glaciolacustrine silt in overdeepened basin fills beyond the last interglacial

OSL and IRSL dating are applied to samples from a 152 m-long drill core to constrain the timing of three glaciolacustrine depositional periods within the infill of an overdeepened bedrock trough in the Lower Glatt valley, N Switzerland. The characterisation of the dose-response suggests that the polymineral IRSL₅₀ and pIRIR_180/225 signals are close to saturation, while quartz OSL ages are within the range of reliable dating. The demarcation of the upper quartz OSL dating limit, however, remains challenging. Dose-recovery tests performed with long storage periods were used to investigate the reliability of the high region of the dose-response curve. They suggest an upper limit for reliable dating of ∼400 Gy for these samples, which was considerably lower than the commonly used 2D₀ criterion. Lifetimes were calculated for the quartz OSL and the thermal stability of the signal is not considered as problematic for the determined ages. Allowing for a contribution from inherited dose due to partial bleaching, places the infill of the overdeepened valley within the penultimate glacial cycle (MIS6).     

Luminescence dating of volcanic eruptions in Datong,northern China

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

Unexpectedly old luminescence ages as an indicator of the origin of the upper Volga River valley sediments

Although the Upper Volga has been the focus of extensive research for several decades, its origin and evolution remain uncertain. According to the most popular model, the Upper Volga drainage network formed at the end of the last deglaciation (MIS 2); before that, the river basin was occupied by a large MIS2 proglacial lake. In this study we test this hypothesis by luminescence dating several fluvial terraces in the Upper Volga valley. Despite the expected late-MIS 2 age, our results show that quartz is in saturation, and the feldspar pIRIR₂₉₀ signal gives much older dates than expected (∼300–∼500 ka). We argue that, in most sections, feldspar was very likely to be well bleached prior to deposition. Thus, if the ages of sedimentary structures are overestimated, this could only result from sediment transport in darkness. It is widely accepted that the MIS 6 glaciation was the last to cover the Upper Volga basin, and so such conditions would be most easily attributed to a subglacial environment. But this explanation is confounded by the absence of till on top of most sections. The alternative explanation, that the ages accurately reflect last deposition, calls into question the well-established MIS 6 border on the Russian plain, and we conclude that further studies are required to resolve this inconsistency.     

Luminescence chronology of fossiliferous fluvial sediments along the middle Atbara River,Sudan

Fluvial sediments of the middle Atbara River Valley, eastern Sudan, contain abundant vertebrate fossils and stone tools. Previous work described two sedimentary units, the Butana Bridge Synthem (BBS) and the Khashm El Girba Synthem (KGS), with three divisions each (BBS1-3 and KGS1-3, from bottom to top, respectively). ²³⁰Th/U dating on bivalve shells suggested an age of ∼126 and ∼92 ka for the basal KGS2 and basal KGS3, respectively, and mammalian biochronology in combination with magnetostratigraphy suggested an age of late Early to early Middle Pleistocene for the underlying BBS. To establish a detailed chronology of this fluvial sedimentary sequence, we collected 17 luminescence samples from both sides of the Atbara River close to the Butana Bridge. Quartz OSL dating was applied to samples from the upper part of the profile (upper KGS2 and KGS3), but the signal reached saturation within the upper ∼10 m of the sequence. To select a suitable feldspar signal to date older samples beyond the limit of the quartz OSL, a comparison of the quartz OSL, feldspar post-IR IRSL at 225 and 290 °C, and pulsed IRSL signal at 50 °C was conducted for a sample from KGS3. The result showed that only the fading corrected pulsed IRSL yielded an age consistent with the quartz OSL, and the post-IR IRSL signals (both at 225 and 290 °C) overestimated the quartz age significantly. We therefore selected the pulsed IRSL signal to date the older deposits. The luminescence ages indicate that the entire BBS - KGS sequence was deposited between 224 ± 23 ka and <17 ± 1 ka, corresponding to marine isotope stages (MIS) 7–2, significantly revising previous conclusions.     

Single-grain quartz OSL dating of debris flow deposits from Men Tou Gou,south west Beijing,China

Debris flows in the mountainous regions south west of Beijing, China occur frequently and often result in considerable mass movements with disastrous consequences for human life, infrastructure and agriculture. Obtaining chronological information on such events is important for the prediction of the return frequency of these debris flows, risk assessment and climate change research. In this project, we use quartz single-grain optically stimulated luminescence (OSL) methods to determine the burial ages of five debris flow samples from the Zhai Tang region ∼60 km west of Beijing. OSL characteristics were found to be acceptable despite the low inherent brightness of quartz extracted from these samples. Single-grain thermal transfer was determined to be negligible and beta dose recovery experiments were satisfactory. The quartz single-grain dose distributions strongly indicate that the samples were poorly bleached prior to deposition; relative over-dispersions are larger than 60%. Minimum age modelling indicates that all five samples were deposited within the past few hundred years, indicating that catastrophic debris flows are occurring under the historically-recent land-use pattern.     

Luminescence dating reveals a rapid response to climate change of fluvial terrace formation along the Ani River,northeastern Japan,during the last glacial period

Fluvial terraces along the middle reaches of many Japanese rivers were formed during the last glacial period as a result of changes in sediment discharge related to cooler temperatures and/or reduced water discharge because of lower precipitation. The influence of climate change on these fluvial terraces is not yet fully understood because most previous studies lacked detailed reconstructions of the chronology of terrace development. This study provides a detailed luminescence chronology of fluvial terrace deposits along the Ani River, northeastern Honshu, Japan, and compares that chronology to paleoclimatic records. Eight samples for luminescence dating were obtained from an outcrop of terrace deposits (∼10 m thick) in the Ani River valley. The fading-corrected infrared stimulated luminescence (IRSL) ages are consistent with the fading-corrected post-IR IRSL ages for some samples, which suggests that fading corrections were effective despite the higher fading rates of the IRSL signal. However, for the other samples, the post-IR IRSL ages are significantly older than the fading-corrected IRSL ages due to incomplete bleaching. The pulsed IRSL signals are close to field saturation for older samples, which might have resulted in a greater variation of the ages. Fading-corrected IRSL ages demonstrate periods of rapid aggradation during 105–90 ka and 75–60 ka. Comparison of terrace development with paleoclimatic records indicates that the two periods of fluvial deposition correspond to decreases in precipitation caused by weakened East Asian summer monsoon precipitation and possibly decreases in temperature. The results of this study show that the Ani River responded rapidly to climate change on a time scale of a few tens of thousands of years during the last glacial period.     

Luminescence characteristics of Scandinavian quartz,their connection to bedrock provenance and influence on dating results

The success of optically stimulated luminescence (OSL) dating relies to a large extent on suitable characteristics of the analysed mineral, in this case quartz. Previous OSL dating of Quaternary sediments in Scandinavia has shown that quartz characteristics vary widely across the region, resulting in dating studies with varied success. The aim of this study is to provide an overview of quartz luminescence characteristics in Sweden and Norway, evaluate their effect on dating results and discuss the underlying causes of their variability.A qualitative assessment of luminescence signal characteristics of quartz from Late Quaternary sediment deposits, from a range of geological and geographical settings, has been made by re-analysing data from samples previously dated at the Lund Luminescence Laboratory, Sweden. This allowed a general characterisation of signals and a study of the relationship of these properties to dating result ‘quality’. To quantify the results, selected samples were further analysed with single-grain measurements and with small aliquots.The results show that the average luminescence signal from quartz is fairly dim but dominated by a fast signal component and changes little during measurement. Dose determination precision is ∼4% for 8-mm aliquots and ∼6% for 2-mm aliquots. However, the luminescence signal characteristics have a spatial variation across Sweden and Norway, which appears to correlate with large-scale bedrock units. In areas of sedimentary bedrock outside the Scandinavian mountains and within the Blekinge-Bornholm province, the quartz is brighter and has a stronger fast signal component, while in the Caledonian orogenic belt, the signal is very weak and lacks a fast component. These differences lead to a range in precision of doses, from ∼2% to >40% (for doses in the order of 5–400 Gy), and in the number of rejected aliquots (0–100%) depending on location, but also implies that quartz luminescence can be used as a provenance indicator in part of Sweden and Norway.     

Luminescence dating without sand lenses: An application of OSL to coarse-grained alluvial fan deposits of the Lost River Range,Idaho, USA

Optically stimulated luminescence (OSL) dating is increasingly used to estimate the age of fluvial deposits. A significant limitation, however, has been that conventional techniques of sampling and dose rate estimation are suitable only for thick (>60 cm) layers consisting of sand size or finer grains. Application of OSL dating to deposits lacking such layers remains a significant challenge. Alluvial fans along the western front of the Lost River Range in east-central Idaho, USA are one example. Deposits are typically pebble to cobble sheetflood gravels with a sandy matrix but thin to absent sand lenses. As a result, the majority of samples for this project were collected by excavating matrix material from gravelly deposits under light-safe tarps or at night. To examine the contributions of different grain-size fractions to calculated dose-rates, multiple grain-size fractions were analyzed using ICP–MS, high resolution gamma spectrometry and XRF. Dose rates from bulk sediment samples were 0.4–40% (mean of 18%) lower than dose-rate estimates from the sand-size fractions alone, illustrating the importance of representative sampling for dose rate determination. We attribute the difference to the low dose-rate contribution from radio-nuclide poor carbonate pebbles and cobbles that occur disproportionately in clast sizes larger than sand. Where possible, dose rates were based on bulk sediment samples since they integrate the dose-rate contribution from all grain sizes. Equivalent dose distributions showed little evidence for partial bleaching. However, many samples had significant kurtosis and/or overdispersion, possibly due to grain-size related microdosimetry effects, accumulation of pedogenic carbonate or post-depositional sediment mixing. Our OSL age estimates range from 4 to 120 ka, preserve stratigraphic and geomorphic order, and show good agreement with independent ages from tephra correlation and U-series dating of pedogenic carbonate. Furthermore, multiple samples from the same deposit produced ages in good agreement. This study demonstrates that with modified sampling methods and careful consideration of the dose rate, OSL dating can be successfully applied to coarse-grained deposits of climatic and tectonic significance that may be difficult to date by other methods.     

Dating of lower terrace sediments from the Middle Rhine area, Germany

Modern and known-age Pleistocene fluvial sediments were investigated by optical dating of quartz to test the suitability of the approach for dating deposits from the deeply incised Middle Rhine Valley. Samples from modern flood sediments revealed skewed distributions indicating different residual levels of equivalent dose (D_e) within the different aliquots. Nevertheless, a substantial number of aliquots from the modern deposits reflect D_e values close to zero. For the Pleistocene samples, optical ages are in general consistent with age control given by the presence of the Laacher See Tephra and radiocarbon dating. However, some samples overestimate the known age by a few thousand years when using the arithmetic mean. This is apparently explained by including aliquots in the determination of mean D_e where the optical signal was incompletely bleached at deposition. The most difficult issue in this context is identifying a suitable approach that can distinguish between the variability of D_e due to partial bleaching and microdosimetry. However, even when considering these limitations it appears that optical dating will by a quite suitable method to date Pleistocene sediments from such a complex fluvial environment, especially when focusing on a precision scale beyond a few thousand years.     

Application of single-grain OSL dating to ice-proximal deposits,glacial Lake Benson,west-central Minnesota,USA

Glacial Lake Benson formed in west-central Minnesota as the Des Moines lobe of the Laurentide ice sheet retreated north of a small moraine in the Minnesota River lowland. Although previous research has constrained the timing of glacial Lake Agassiz immediately to the north, little age control is available for the formation of glacial Lake Benson and ice-marginal positions to the south. In order to constrain the age of glacial Lake Benson and test the application of single-grain optically stimulated luminescence (OSL) dating to ice-marginal deposits, seven OSL samples were collected from a variety of depositional settings. These included deltaic deposits linked to specific lake levels, pro-glacial fluvial, ice-contact and supra-glacial deposits. Single-grain OSL results indicate evidence for incomplete resetting (partial bleaching) of the luminescence signal, as expected for glacial environments, and therefore ages were calculated using a minimum age model. OSL results constrain the timing of ice-margin retreat and lake formation to 14.4–14.8 ka. Analysis of single-grain equivalent dose distributions indicates that deposits created by glacial-dominated processes typically had higher over-dispersion (>50%) and greater positive skew (>0.9) than deposits originating from fluvial processes. These results suggest that water-lain deposits should be targeted for OSL sampling over those created by glacial processes when dating ice-proximal settings.     

Luminescence dating of cyclone-induced washover fans at Point Lefroy (NW Australia)

Reliable age dating of coastal sedimentary landforms is crucial for inferring storm frequencies and magnitudes from geological archives. However, in highly energetic coastal settings, radiocarbon dating is often biased by reworking and/or poorly constrained marine reservoir effects. Due to this, most cyclone-driven sediment archives from the semiarid coast of NW Australia – a region frequently affected by tropical cyclones but with a historical record limited to ∼150 a, and therefore strongly in need of long-term data inferred from geological evidence – are affected by chronological inaccuracies. Optically stimulated luminescence dating (OSL) may overcome these shortcomings by dating the transport of sediment directly. In turn it may be related to other challenges when applied to cyclone deposits from semiarid environments. The cyclone-induced washover fans at Point Lefroy, NW Australia, are composed of a heterogeneous mixture of coral fragments, shell hash and siliciclastic sand. This makes them particularly prone to high dose scatter resulting from a combination of partial bleaching, sediment mixing and dose-rate heterogeneity. The washover fans are further characterised by a discontinuous nature of cyclone deposition, as indicated by erosional features and macroscopic brunification horizons. By using a combination of quartz single grain dating, autoradiography, alpha counting and gamma spectrometry, sediment mixing and dose rate heterogeneity are identified as the main sources of dose scatter. The resulting chronology allows us to discriminate at least four well constrained phases of washover fan activity at ∼180, ∼360, ∼870, and ∼1300 a ago. Older but less well constrained activity phases occurred ∼1950, ∼2300, and ∼2830 a ago. While these phases of increased cyclone activity correlate with depositional units separated by potential palaeosols, OSL ages, quasi-continuous portable OSL reader measurements and gamma spectrometry measured with increased sampling resolution point to deposition of distinct washover units within a very short period of time. However, unambiguous discrimination between deposition of individual units by single events and deposition by several cyclones within periods of only a few decades is currently not possible.     

Chronostratigraphy of a sediment record from the Hajar mountain range in north Oman: Implications for optical dating of insufficiently bleached sediments

In this study we report on optical stimulated luminescence (OSL) ages of quartz extracted from a sedimentary record in the N-Oman mountain range. Equivalent dose (D_E) distributions derived from single aliquot measurements (SAR) of small aliquots (ca. 200 grains) were investigated to test whether the skewness and broadness of the dose distribution can be used as criteria for the identification of insufficient bleaching. Furthermore, the methods proposed by Lepper and McKeever [2002 An objective methodology for dose distribution analysis. Radiation Protection Dosimetry 101 (1–4), 349-352]. Singhvi [Juyal, N., Chamyal, L.S., Bhandari, S., Bushan, R., Singhvi, A.K., in press. Continental record of the southwest monsoon during the last 130 ka: evidence from the southern margin of the Thar Desert, India. Quaternary Science Review] and Fuchs and Lang [2001 Fuchs, M., Lang, A., 2001. OSL dating of coarse-grain fluvial quartz using single-aliquot protocols on sediments from NE Peloponnese, Greece. Quaternary Science Review 20, 783–787.] to derive D_E's from insufficiently bleached sediments were compared. At first, the investigations were carried out on artificially bleached, irradiated and mixed quartz material from the Oman study area to simulate insufficiently bleached sediments. Then, the various statistical methods for identifying insufficient bleaching and D_E derivation were applied to the natural samples from the study area, where 18 samples were measured. For the identification of insufficient bleaching the preferential parameter is the broadness of a distribution. For D_E calculation, both the Singhvi method and the Fuchs and Lang method produce similar results, which are consistent with the stratigraphic order. A drawback of both methods is their sensitivity to low outliers. The Lepper and McKeever method was not applied to the natural samples, due to limitations in its application to a small number of aliquots and due to the ambiguous identification of the rising limb of the dose distributions.     

Optical dating of aeolian and fluvial sediments in north Tian Shan range,China: Luminescence characteristics and methodological aspects

Loess and fluvial sand are important materials for dating river terraces and alluvial fans. This study focuses on the methodological aspects of dating loess and fluvial deposits from the northern flank of the Tian Shan range, China, using sand-sized quartz and potassium (K) feldspar. Luminescence characteristics of quartz and K-feldspar were studied for searching suitable dating procedures. Our results indicate that 1) most quartz aliquots were contaminated by feldspar, and were dated using a post-infrared optically stimulated luminescence (post-IR OSL) procedure. A Fast ratio acceptance threshold of 15 can be applied to select these aliquots with post-IR OSL signals dominated by quartz OSL; 2) the multi-elevated-temperature post-IR IR stimulated luminescence (MET-pIRIR) procedures are applicable for K-feldspar. A test dose of ∼30% of the natural dose is appropriate for dating of older (>10 ka) samples. An Age (T, t) plateau test can be used to evaluate the dating results; 3) for the loess samples, both quartz and K-feldspar were well bleached and are suitable for dating. Dating using K-feldspar is preferred for its higher efficiency; 4) for the fluvial sand samples, only the quartz grains were fully bleached. Single-aliquot dating of quartz gives reliable ages.     

Luminescence dating of sediments from a Palaeolithic site associated with a solution feature on the North Downs of Kent,UK

Optically stimulated luminescence (OSL) dating has been applied to determine the burial age of sediment horizons within a sequence containing Lower Palaeolithic artefacts on an upland site associated with a solution feature (doline) at West Cliffe, located on the North Downs in Kent, UK. The study makes use of a novel extension of the single aliquot OSL measurement procedure to investigate the nature of significant overdispersion in equivalent dose values with very small aliquots of quartz inclusions, enabling single grain resolution to be approached with ∼90 μm diameter quartz extracted from the relatively fine-grained brickearth. A detailed examination of the uniformity of the distribution of radionuclide sources in the sampled volumes was also performed and this included the application of a spatially-resolved technique for beta dose rate measurement. The OSL ages, obtained for the burial of brickearth positioned stratigraphically below and above a clay and flint clast layer containing the artefacts and debitage, place the deposition of the artefacts to between ca 140 and 80 ka ago. This is significantly later than indicated by the artefact typology (>300 ka) and contrary to the expectation of in situ burial indicated by earlier research in this region. If displacement occurred on other upland sites this finding has important implications for establishing the timing of hominin use of the upland areas which, beyond broad attribution to Lower or Middle Palaeolithic origin, is uncertain and similar doubts apply to the interpretation of the environments that prevailed.     

Late Quaternary terrace formation from knickpoint propagation in the headwaters of the Yellow River,NE Tibetan Plateau

Upstream knickpoint propagation is an essential mechanism for channel erosion, carrying changes in base level, tectonics and climate across the landscape. Generally, the terraces on cross-sections at steady-state conditions have been widely reported. However, many landscapes in the field appear to be in a transient state. Here, we explore the mechanism of knickpoint initiation and fluvial evolution in a transient setting in the northeastern Tibetan Plateau. Analysis of channel profiles and terrace correlation indicates that the Yellow River is adjusted to match the increase in differentiated fault activity and climate change in a regional setting of continuous uplift. Consequently, a series of terraces were formed, and the number of terrace steps increased downstream, in the headwaters of the Yellow River. All terraces were dated using the optically stimulated luminescence method. The top terrace, distributed continuously in the whole basin with a gradient, was deposited during a cold period and abandoned at the climatic transition from cold to warm state, at approximately 14.6–9.5 ka. After that, one terrace formed at around 4.2 ka in the upper reach. In correlation with the continuous topographic gradient surface of this terrace, three terrace steps were formed in the down reach during the period from 9.5 ka to 4.2 ka. This phenomenon might indicate multiple phases of continuous headward migration of fluvial knickpoint waves and terrace formation during the downcutting. It was caused by fault activity and tectonic uplift of the gorge at the outlet of the basin, under influence of the gradual integration of the Yellow River from downstream. This phenomenon shows that the fluvial incision in a transient state along the high relief margin of the orogenic plateau can be caused by fault activity, in addition to widespread surface uplift, climatically driven lake spillover and the establishment of external drainage.     

Age of glacial and periglacial landforms in northern Hokkaido, Japan, using OSL dating of fine grain quartz

The timing of glacial advances, periglacial phenomena, and the ages of two marker tephras in northern Hokkaido were estimated by OSL dating. It appears that the glacier of Yamunai 2 stage on Rishiri Island expanded between 24 and 15 ka. In northern Hokkaido, OSL ages indicate ice wedge formation during the period 24–18 ka. These results indicate that both the glacial advance and the development of ice wedges were synchronous phenomena relating to the Last Glacial Maximum.