A detailed luminescence chronology of the Lower Volga loess-palaeosol sequence at Leninsk

We present a detailed luminescence chronology of the loess-palaeosol sequences in the Lower Volga region of Russia at the Leninsk site – an important palaeogeographic archive describing the climate and environmental conditions of regressive stages of the Caspian Sea. The chronology of these sediments has received very little attention compared to the under- and overlying marine deposits. The degree of bleaching was addressed by making use of the differential resetting rates of quartz and feldspar. Our results show that the quartz OSL and feldspar pIRIR_50,290 signals were sufficiently bleached before deposition and uncertainties in bleaching have a negligible impact on the reliability of the luminescence ages. The combined quartz OSL and K-feldspar pIRIR_50,290 chronology constrains the main stages of the Northern Caspian Lowland evolution during the Late Quaternary. During early MIS 5 (130–120 ka), the northern part of the Lower Volga was covered by a shallow brackish water estuary of the warm Late Khazarian Caspian Sea transgression. After ∼122 ka, the Volga incised the Northern Caspian Lowland surface following sea-level decrease and the start of subaerial conditions at Leninsk. Loess accumulation rate increased towards the end of MIS 5 and two palaeosols of presumably MIS 5с and MIS 5a age formed, exhibiting features evidencing a dry, cold climate, influenced by long seasonal flooding by the Volga River. Cryogenesis affecting the MIS 5a soil is a regional phenomenon and is dated to between ∼70 and 90 ka. The overlying thick Atelian loess unit formed during the cold periods of MIS 4 and MIS 3. Clear erosional features at the top of the Atelian loess are constrained by luminescence to ∼35 to ∼24 ka, allowing reconstruction of erosion of 150–200 cm of loess.     

Age comparison by luminescence using quartz and feldspar on core HPQK01 from the Pearl River delta in China

Reliable chronology is critical for reconstructing estuarine delta process. In this study, detailed chronological framework has been performed on a core HPQK01 (52 m in depth) from the central Pearl River delta (PRD) of China. Both quartz OSL and feldspar post-IR IRSL (pIRIR) methods for late Pleistocene sediments, as well as radiocarbon dating for Holocene sediments, were applied to date the core. Results show that quartz OSL ages range from 125 ± 18 ka to 58 ± 6 ka, and that all of them were minimum ages due to the OSL signal saturation. Feldspar pIR₂₀₀IR₂₉₀ protocol shows some overestimation in dose recovery test, with the recovered to the given ratio of 1.2, while a ratio of around 1 was obtained for feldspar pIR₅₀IR₂₅₀ signals. Robust ages have been obtained from feldspar fading corrected pIR₅₀IR₂₅₀ dating with ages ranging from 150 ± 17 ka to 98 ± 12 ka. AMS ¹⁴C results suggest that subtidal-intertidal zone was deposited during the middle Holocene from 8.21 ± 0.19 cal ka BP to 4.99 ± 0.25 cal ka BP. The sedimentology of core HPQK01 record two marine transgressive-regressive cycles. Based on the dating results, the lower fluvial sediment unit (T2) could be correlated to marine isotope stage (MIS) 6, and the lower marine unit (M2) was deposited during MIS 5. A sedimentary hiatus occurred with age range of from MIS 4 to MIS 2. Since middle Holocene, another marine stratum (M1) has been accumulated. Overall, our findings suggest that feldspar pIRIR dating method has the potential to establish the Quaternary chronostratigraphic framework of the PRD for samples with ages within 150 ka.     

Late Quaternary evolution of lower reaches of the Volga River (Raygorod section) based on luminescence dating

The normally-closed Caspian Sea is known for large changes in relative sea-level (of ∼170 m) during the late Quaternary. These transgressive/regressive events influenced the topography, sedimentation and ecosystems of a large area, of up to 1 million km². The Volga River has played an important role in the water balance of the Caspian Quaternary basins but our understanding of the temporal evolution is poorly constrained. Recent studies on the evolution of the Lower Volga have focused mainly on the subaerial sequence of loess-palaeosol series corresponding to a long-duration Caspian low stand (the so-called “Atelian regression” from ∼90 to ∼25 ka). In this study we address, for the first time, the temporal evolution of the Volga River during the late Quaternary, as recorded in the many layers of alluvial sands at the Raygorod reference section. This 50 m high outcrop contains a complicated sequence of different types of interlayered alluvium (channel and floodplain facies), a loess-palaeosol sequence with a weakly developed palaeosol, and marine sediments of the Khvalynian transgression (Chocolate Clay facies). The new chronology, based on 35 samples, is derived using optically stimulated luminescence (OSL) analysis of sand-sized quartz, with support from post-infra-red infra-red stimulated luminescence (post-IR IRSL) from K-rich feldspar grains to date the older parts of the section. The new ages identify five stages of the topography development in the northern parts of the Lower Volga: (1) an MIS 5a flood-plain in deltaic/estuary environments (>90 ka) during a high-stand of the Caspian Sea (Hyrcanian transgression); (2) a transition from deltaic/estuary conditions to a river valley with normal alluvial sedimentation and sporadic stabilization reflected in palaeosol development (80–70 ka); (3) a palaeo-Volga channel migration at elevations of 4–8 m msl during 69–62 ka, evidence of a brief increase in Caspian Sea-level and blocking of the Volga flow; (4) a subaerial stage with high-speed accumulation of loess during MIS 4 to MIS 2, containing one weakly developed palaeosol (MIS 3c) and pedocomplex of three combined palaeosols of the beginning of MIS2 (30–24 ka); (5) a rapid Khvalynian transgression, starting at the Raygorod location at ∼18.3 ka, with relatively weak marine erosion of the top 40–60 cm of loess cover, presumably because of the rapid migration of the coastline in the flat Northern Caspian Lowland.     

Testing the accuracy of quartz OSL dating using a known-age Eemian site on the river Sula, northern Russia

Quartz optically stimulated luminescence (OSL) forms the basis for the chronology of Weichselian ice advances in Arctic Eurasia developed over the last few years. There is almost no age control on this chronology before 40 ka, except for some marine sediments correlated with marine isotope stage (MIS) 5e on the basis of their palaeofauna. Results from more southern latitudes have shown that dose estimates based on quartz OSL and the single aliquot regenerative (SAR) dose procedure may underestimate the age of MIS 5e deposits. Here we use the same method to date well-described marine sediments, thought to have been deposited during the very beginning of the Eemian interglacial at 130 ka, and exposed in two sections on the river Sula in northern Russia. Various quality-control checks are used to show that the OSL behaviour is satisfactory; the mean of 16 ages is 112±2 ka (σ=9 ka). This represents an underestimate of 14% compared to the expected age, a discrepancy similar to that reported elsewhere. In contrast to SAR, the single aliquot regeneration and added (SARA) dose procedure corrects for any change in sensitivity during the first OSL measurement. The SARA results are shown to be 10% older than those from SAR, confirming the geological age estimate and suggesting that SAR ages may underestimate older ages (larger doses), despite their good performance in the younger age range.     

The upper Pleistocene loess-palaeosol sequence at solonovka on the Cis-Altai plain,west Siberia – First luminescence dating results

Loess-palaeosol deposits of the Upper Pleistocene cover an extensive territory in the south of Western Siberia. Previously, most studies of loess-palaeosol sequences were carried out on river bank sections of the Ob river around Novosibirsk and upstream of this location (Ob Loess plateau); more recently, the focus of research has shifted towards the inner part of the Cis-Altai plain. Despite a good knowledge of the structure of regional loess-palaeosol sequences, there is a considerable lack of absolute dating beyond the radiocarbon limit. However, recent high resolution luminescence dating of a key Marine Isotope Stage 5 (MIS 5) stratotype at Lozhok has identified the presence of a long hiatus in the deposit. As a result, the published ages of the main units have been underestimated, because the existing chronology is largely based on palaeosol counting. This new observation argues for an urgent re-evaluation of the accepted chronostratigraphy of Western Siberian Late Quaternary. Here we present the first luminescence data for a loess-palaeosol sequence of the Cis-Altai plain, at the Solonovka key section, using both quartz optically stimulated luminescence and feldspar post-infrared infrared stimulated luminescence from 25 samples. The results show that the deposits were formed during the Late Pleistocene. The ∼1 m thick well-developed upper pedocomplex (PC1) has cryoturbation cracks filled with upper loess; this a characteristic regional benchmark for stratigraphic correlation. Two distinct hiatuses in sedimentation are found in the section: at the boundary of MIS 3/2, and after the formation of the MIS 5 Berdsk pedocomplex (PC3 and 2) until the beginning of the formation of MIS 3 deposits. The age of the thick PC3 palaeosol at the base of the section is determined as MIS 5, confirming evidence for the pronounced Kazantsevo (Eemian) interglacial in the loess-palaeosol record of Western Siberia. The results of our study emphasize the importance of understanding the palaeogeomorphological background to soil development, and the necessity of absolute chronology; we consider that the position of MIS 5 in the regional chronostratigraphic chart of South Western Siberia requires further study.     

High resolution OSL and post-IR IRSL dating of the last interglacial–glacial cycle at the Sanbahuo loess site (northeastern China)

Northeastern China is located in the East Asian monsoon region; it is sensitive to both high and low latitude global climate systems. Loess deposits in the region have considerable potential as sensitive archives of past climate changes. However, research into loess deposition and climate change in this region is restricted by the lack of independent age control. In this study, coarse-grained quartz SAR OSL and K-feldspar post-IR infrared (IR) stimulated luminescence (post-IR IRSL; pIRIR₂₉₀) methods have been used to date the Sanbahuo loess site in northeastern China. The quartz OSL characteristics are satisfactory. The measured pIRIR₂₉₀ D_e's do not vary significantly with IR stimulation temperatures between 50 °C and 260 °C; a first IR stimulation temperature of 200 °C was adopted. Dose recovery tests were performed by adding different laboratory doses to both laboratory bleached (300 h SOL2) samples and natural samples; the results are satisfactory up to ∼800 Gy. Resulting quartz OSL and feldspar pIRIR₂₉₀ ages are in good agreement at least back to ∼44 ka; beyond this feldspar pIRIR₂₉₀ ages are older. The feldspar ages are consistent with the expected age of the S1 palaeosol (MIS 5). There appears to have been a period of fast loess deposition at ∼62 ka, perhaps indicative of winter monsoon intensification with a very cold and dry climate that lead to a serious desertification of dunefields in northeastern China.     

Problems associated with luminescence dating of Late Quaternary glacial sediments in the NW Scottish Highlands

Linking the timing of glacial episodes and behaviour to climatic shifts that are documented in ice and marine sedimentary archives is key to understanding ocean-land interactions. In the NW Scottish Highlands a large number of closely spaced (‘hummocky’) moraines formed at retreating glacier margins. Independent age control on one palaeo-glacier limit is consistent with the timing of Younger Dryas (YD) glaciation in the area, but adjacent glacier lobes have remained undated due to the lack of sites and material for ¹⁴C dating. Direct dating of ice-marginal moraines using optically stimulated luminescence (OSL) techniques has never been attempted before in Scotland, but if successful, they may be the most appropriate methods for constraining the age of sediment deposition in the absence of organic material. Coarse-grained quartz and K-feldspar minerals from supraglacial sheet flow deposits and glacilacustrine sediments within ice-marginal moraines were analysed using the single-aliquot regenerative-dose (SAR) protocol. Independent age control and clear geomorphological relationships indicate that all samples should yield YD or post-Last Glacial Maximum (LGM) ages. Quartz OSL shine down curves showed low luminescence sensitivity, significant medium-to-slow components, a weak fast component, and scattered SAR data; Linearly Modulated-OSL (LM-OSL) measurements confirmed that the fast component was weak or absent. In contrast, feldspar infrared stimulated luminescence (IRSL) was highly sensitive with excellent SAR data. However, SAR data from 3 mm diameter aliquots of feldspar (200 grains) give higher than expected equivalent doses (D_e) by an order of magnitude. SAR measurements of small clusters of feldspar grains (ranging from 1–8) considerably broaden the apparent D_e distribution, but even the lowest value is about 2–3 times the expected D_e. Two possibilities arise to explain the quartz and feldspar data: (1) that glacial sequences in the NW Highlands re-work inherited (older) glacial deposits and that some of the pre-Devensian existing glacial landforms have only been modified during Devensian glaciation; or (2) that the sedimentary processes operating in these ice-marginal environments are not conducive to adequate bleaching of quartz and feldspar grains. Our study implies that ice-proximal supraglacial sediments from this region in NW Scotland reflect older ages of deposition, but dating YD sediments has not been possible.     

Shedding light on the timing of the largest Late Quaternary transgression of the Caspian Sea

The Late Quaternary history of the Caspian Sea remains controversial. One of the major disagreements in this debate concerns the stratigraphic correlation of various deposits in the Caspian Basin. In this paper we identify and date, for the first time, the Enotaevka regression, lying between the two major phases of the largest Late Quaternary Caspian Sea transgression, the Khvalynian transgressive epoch, and provide a minimum estimate of sea level decrease during this regression. The River Volga is the major source of water to the Caspian; the Lower Volga region is unique in its record of palaeogeographic events, and this provides the opportunity to build a single stratigraphic and palaeogeographic history for the Pleistocene of Central Eurasia. Here we use luminescence to establish a new chronology for the largest Late Quaternary transgressive epoch of the Caspian Sea. The existing radiocarbon chronology does not allow the resolution of the two transgressive phases of this epoch (Early and Late Khvalynian). Based on clear palaeontological and geomorphological evidence, these must be very different in age, but shells associated with both transgressions gave very scattered ages of between 8 and 50 ka. This ambiguity has led to considerable discussion concerning the existence or otherwise of a deep Enotaevka regression phase between the two Khvalynian transgressions. Recently we have again identified these deposits at Kosika, on the right valley side of the Volga River. The new luminescence chronology described here, based on quartz OSL and K-feldspar pIRIR₂₉₀ ages, allows us to reconstruct the complicated history of Late Quaternary sedimentation in the southern part of the Lower Volga valley. The Kosika section reflects the following major stages: (1) the earlier Khazarian transgressive epoch; (2) a decrease in the sea level with the development of a freshwater lake/lagoon in the Volga valley; and (3) the Khvalynian transgressive-regressive epoch, including both the Early and Late Khvalynian transgressive periods, and the intercalated Enotaevka regression. Sea level during the early stage of the Khvalynian transgression reached Kosika at about 23–22 ka (approx. −1 to −2 m asl). This event is of the same age as the “grey clay” strata at the base of the Leninsk section marine unit (Kurbanov et al., 2021), also formed at the beginning of the Early Khvalynian transgression. Around 15–14 ka the Khvalynian basin moved to a regressive stage, and in the northern part of the Lower Volga the top part of the well-known ‘Chocolate Clay’ accumulated. In the southern part of the valley marine accumulation stopped at about 12–13 ka. This allows us to reconstruct a decrease in Early Khvalynian basin sea level between 15–14 ka and 13–12 ka ago, of about ∼15 m. At the Kosika section sediments derived from the Enotayevka regression are visible as a weakly developed palaeosol with evidence of surficial erosion, and these sediments are now dated to 13–12 ka. At 8.6 ± 0.5 ka, during the period of the Mangyshlak regression, aeolian deflation processes reworked sediments deposited by immediately preceding Late Khvalynian transgression.     

First high-resolution luminescence dating of loess in Western Siberia

The south of Western Siberia is an important part of the Eurasian loess belt, containing an extensive record of Quaternary landscape and climate evolution in up to 100 m thick loess deposits with as many as 10 pedocomplexes. However, this important Quaternary archive lacks a reliable absolute chronology, and this has prevented the linking of the widely accepted regional chronostratigraphic correlations with those of other parts of the Eurasian loess belt. Here we present the first results of detailed luminescence dating of the Late Pleistocene loess-palaeosol sequence at the Western Siberian stratotype section of Lozhok. According to the classical regional chronostratigraphic scheme, this sequence records the main stages of the environmental evolution of the region, including three palaeosols correlated with the warming stages of MIS 5e, MIS 5c and MIS 3. Our absolute chronology is based on 38 new luminescence ages (OSL, IR₅₀, pIRIR₂₉₀). Good agreement between the OSL and pIRIR₂₉₀ ages suggests sufficient bleaching before deposition. The resulting chronology reveals that, rather than being only Upper Pleistocene in age, the loess-palaeosol sequence at Lozhok actually formed in the Middle and Upper Pleistocene. The ages of individual horizons do not correspond to the previously accepted stratigraphic units and morphological features of pedocomplexes. Our Bayesian chronological model reveals remarkable variation in dust accumulation and preservation at the site. The new results unambiguously identify the presence of an erosional boundary with a hiatus lasting ∼90 ka. The upper pedocomplex, immediately below this discontinuity, formed in sediment deposited between 131 ± 9 ka and 122 ± 11 ka and clearly corresponds to MIS 5. The lower pedocomplex is found in sediment deposited between 240 ± 12 and 199 ± 9 ka, and correlates closely with MIS 7. These new findings demonstrate the urgent need for a wider programme to date the main stratotypes of loess-palaeosol sections in Western Siberia. Only then can the global implications of the regional climate record in this important continental-scale archive be correctly interpreted.     

A detailed post-IR IRSL chronology for the last interglacial soil at the Jingbian loess site (northern China)

The chronology of dust deposition and climate during the last interglacial is poorly known on the Chinese Loess Plateau. Here, 51 samples were taken from the ∼5 m S1 palaeosol (MIS5) at the desert marginal Jingbian site to develop what is currently the most detailed S1 chronology on the Plateau using instrumental dating techniques. We use the post-IR IRSL signal from sand-sized grains of K-rich feldspar. Signal resetting in the agricultural layer shows that it is possible to almost completely zero this signal in nature. First IR stimulation plateau measurements show that there is no clear dependence of D_e on first IR stimulation temperature between 50 and 260 °C suggesting negligible signal fading. Resultant ages are consistent with a last interglacial age (∼130 to ∼75 ka) and are also consistent within errors with continuous linear sedimentation rates. The average mass accumulation rate for S1 is ∼150 g m⁻² a⁻¹, considerably higher than at many other sites but within the overall range of Loess Plateau estimates. The remarkably stable sediment accumulation at the site contrasts with a more complex record of environmental and monsoonal change recorded in grain-size and magnetic susceptibility.     

Luminescence dating of Middle Pleistocene (MIS 7) marine shoreline deposits along the eastern coast of Tunisia: A comparison of K-feldspar and Na-feldspar IRSL ages

In the present study, we applied the IRSL_50°C dating method to both K- and Na-feldspar coarse grains from interglacial coastal deposits in north-eastern Tunisia. We used the yellow IRSL_50°C signal of Na-feldspars and the blue IRSL_50°C signal of K-feldspars. The key-sites for this study are at El Hajeb (Sahel area) and Dar Oufa (Cap Bon Peninsula). These deposits belong to the “Douira Unit” which has previously been assigned to marine isotope stage (MIS) 7 on the basis of amino acid ratios and chronostratigraphic evidence.In order to assess the reliability of the IRSL_50°C ages of the “Douira Unit”, we extended the IRSL dating technique to K- and Na-feldspars from two MIS 5 samples, with independent age control, collected within shallow-marine sands in the Sahel area and on the Jerba island (southern Tunisia).Two protocols of age correction for the observed fading in K- and Na-feldspars have been applied: (1) the Huntley and Lamothe (2001) fading correction and (2) the dose rate correction developed by Lamothe et al. (2003). The fading corrected IRSL ages of the “Douira Unit” and both MIS 5 control samples, measured on K- and Na-feldspars, are in good agreement with their expected ages.     

Methane and the Microbiological Processes of Its Transformations in the Water of the Upper Volga Reservoirs

Specific features of CH₄ distribution and the extent of its transformations in the water of reservoirs in the Upper Volga basin are considered. Methanogenesis was detected in water at some stations. The quantitative characteristics of CH₄ and methane oxidation are shown to correlate with the environmental conditions of the reservoir.     

Sedimentary evolution of a foreland basin from the northeastern Qilian Mountains based on the integration of geomorphological and luminescence dating of alluvial conglomerates and fluvial terrace sediments

Sedimentary deposits in the foreland basin of the northeastern Qilian Mountains are crucial documents recording tectonic activity and climate changes on the Tibetan Plateau. In this study, luminescence dating was used to date alluvial conglomerates and fluvial terrace sediments collected from the Beida River in the Jiuquan Basin, a foreland basin in the Hexi Corridor, northeastern Qilian Mountains. Detailed sedimentology and luminescence ages reveal that alluvial conglomerates accumulated from before 620 ka to 12 ka and that sediment accumulation rates increased at ∼330 ka and ∼35 ka, coinciding with the dates of two tectonic events (∼350 and ∼50 ka) and followed by climate cooling (from marine isotope stage (MIS) 9 to MIS 8 and from MIS 3 to MIS 2). This reveals that variations in the sediment accumulation rates are controlled by the coupling of tectonic uplift and climate cooling. The highest terrace (T7) that developed on the alluvial conglomerate base formed at ∼ 12 ka. The incision rate in the early Holocene was ∼2.1 mm/yr and increased to ∼14.6 mm/yr during the middle and late Holocene. The variations in the river incision rate provide geomorphic evidence for Holocene climate patterns in arid and semiarid areas. Luminescence dating offers a credible temporal framework for the deposits and reveals climate and tectonic effects on the evolution of the foreland basin, northeastern Qilian Mountains.     

OSL and radiocarbon dating of a core from the Bohai Sea in China and implication for Late Quaternary transgression pattern

The Bohai Sea is a semi-enclosed continental shelf sea in northern China. Three transgression layers have been identified from the Late Quaternary strata in the western Bohai Sea and the coastal regions, which provide critical information on Late Quaternary sea-level fluctuations and landscape development. The three transgression layers were previously assigned to Marine Isotope Stage (MIS) 1 (transgression 1, T1), MIS 3 (T2) and MIS 5 (T3), respectively, mainly based on ¹⁴C dating. However, this chronological framework aroused an enigma that the regional sea level in MIS 3 was even higher than that of MIS 5, conflicting with the context of global sea-level pattern. In order to clarify this issue, here quartz optically stimulated luminescence (OSL) dating (four samples) was used to constrain the T2 chronology of borehole TJC-1 from the western Bohai Sea. Radiocarbon samples (eight) of peaty sediments were also measured for reference and comparison. All the four OSL samples showed saturation ages of >80 ka, suggesting that the T2 layer should have formed at least in MIS 5, instead of in MIS 3. Radiocarbon ages in T2 should have been severely underestimated, with a saturation age range of 22–30 cal ka BP, similar to all the previous published radiocarbon ages. The renewed OSL chronological framework for Late Quaternary transgressions in the western Bohai Sea is in better compliance with the history of global sea-level change.     

10Be dating of boulders on moraines from the last glacial period in the Nyainqentanglha mountains,Tibet

Chronologies of glacial advances during the last glacial period in the Nyainqentanglha mountain range may provide constraints on the past climate in a transition zone of the Asian monsoon.We present 15 new10Be exposure ages from two moraines in the Payuwang valley,on the north slope of the range.The inner moraine has exposure ages ranging from 18.0±1.7 to 30.6±2.8 ka(n=10),with a mean age of 23.8±4.0 ka,corresponding to the global Last Glacial Maximum(LGM).The outer moraine yields exposure ages ranging from 18.0±1.6 to 39.9±3.7 ka(n=5).Evidence for weathering leads us to view the oldest age as a minimum age,placing moraine formation during MIS3.Chronologies from the last glacial period from south slope of the Nyainqentanglha support this interpretation.Thus,there appears to have been a local LGM(LLGM)during MIS3 and a more limited glacial advance during the global LGM.Glacial advances during MIS3 in the Nyainqentanglha may correlate with millennial-scale climate change(Heinrich events).     

Luminescence dating of marine sediments from the Sea of Japan using quartz OSL and polymineral pIRIR signals of fine grains

Luminescence dating has long been used for chronological constraints on marine sediments due to the ubiquitous dating materials (quartz and feldspar grains) and its applicability over a relatively long time range. However, one of the main difficulties in luminescence dating on marine sediments is partial bleaching, which causes age overestimations. Especially, partial bleaching is typically difficult to be detected in the fine grain fraction (FG) of marine sediments. The recently developed feldspar post-IR IRSL (pIRIR) protocol can detect non-fading signals and thus avoid feldspar signal instability. In the current study, fine grains were extracted from a gravity core in the northern Sea of Japan, and the aim is to test the feasibility of using different luminescence signals with various bleaching rates to explore the bleaching conditions of fine grain fraction in marine sediments. The results suggest that the quartz OSL signal and polymineral pIRIR signals at stimulation temperatures of 150 °C and 225 °C (pIRIR₁₅₀ and pIRIR₂₂₅) of FG were well bleached prior to deposition. The OSL ages were used to establish a chronology for this sedimentary core and the resulting age-depth relationship is self-consistent and comparable with radiocarbon dates. We conclude that different luminescence signals with various bleaching rates can be used to test the bleaching conditions of fine grain fraction in marine sediments; and the luminescence dating can be applied to marine sediments with great potential.     

Devensian glacial events in Buchan (NE Scotland): A progress report on new OSL dates and their implications

Optically stimulated luminescence (OSL) dating of a series of glaciofluvial/glaciodeltaic sediments in central Buchan and Aberdeen has recently been undertaken. The aims of this project are to test the chronological model proposed by the most recent regional review and the suggestion that parts of Buchan may have remained ice-free during the last glacial maximum (late marine isotope stage (MIS) 3 and MIS 2 29–15 ka). The preliminary results indicate that during the Devensian (ca. 116–12 ka), extensive areas of Buchan may have been glaciated earlier than previously believed (possibly during MIS 4, 72–60 ka), but parts of the region show no depositional evidence of later glaciation. Some waterlain sediments from the Ugie Valley have yielded OSL ages indicating deposition during MIS 5d to MIS 5a (116–72 ka). We discuss whether the absence of overlying glaciogenic sediments at these locations raises questions about the reliability of the OSL ages or about existing models of the Devensian glaciation of Buchan.     

Preservation of the last aggradation phase in climate-driven terraces: Evidence from Late Quaternary reach-specific fluvial dynamics of the Allier River (France)

There is limited knowledge about the preservation of aggradation phases in Quaternary fluvial records. Previous numerical modelling of erosion and deposition in Late Quaternary Allier River (France) generated the prediction that this river has reach-specific fluvial dynamics related to climate-driven tributary sediment-flux dynamics. To test this prediction, new optically stimulated luminescence (OSL) samples were collected of the Late Quaternary Fx terrace at five locations along a stretch of 60 km. OSL dates of both quartz and feldspar sand grains indicate that all relatively basalt-poor sediments display significantly different ages for each reach (ranging from 36.3 ± 2.0 to 21.1 ± 2.3 ka). The more basalt-rich terrace body consistently yields ages in the range 21.1 ± 1.7 to 16.1 ± 1.5 ka, suggesting contemporaneous aggradation along the whole studied Allier reach during this interval. Our own new OSL date of a Tartaret eruption around 16.8 ± 2.5 ka also fits this time window, suggesting a direct link with volcanic activity. However, there are many more dated volcanic events that coincide with the older basalt-poor units, making it less likely that a direct link between terrace-sediment basalt content and volcanic activity exists. The timings of the dated depositional events in MIS 3 and 2 all match with simulated climate drivers and published landscape erosion rates. Counterintuitively, the volcanic Chaîne des Puys area supplied more sediment during the cold and dry Last Glacial Maximum. Basalt content in the Allier terrace sediments reflects climate-related sediment-flux dynamics upstream. The scarcity of older basalt-poor sediment bodies from MIS 4 and 3 in the Fx terrace suggests that less sediment was supplied and/or the intermittent erosional phases in the Allier were very effective at removing them. We hypothesize that this observation of predominant preservation of the last aggradation phase could be a common phenomenon in most climate-driven terraces. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd     

The Assessment of the Diffuse Pollution from Agricultural Territories in the Upper Volga Basin and the Development of Measures to Reduce It: Case Study of the Yakhroma River

Water Resources - The possible input of nutrients-pollutants into water bodies in the Upper Volga basin from agricultural lands is evaluated for the case of the Yakhroma R. with a basin area of...     

Constraining the age of Quaternary megafloods in the Altai Mountains (Russia) using luminescence

Some of the largest catastrophic outbursts of periglacial lakes known in the geological history of the Earth have been identified in the Altai Mountains. Traces of these events are recorded in the form of large terraces, predominantly composed of gravel material with numerous horizons of large boulders and blocks. Determining the age of these large-scale events is difficult due to the lack of suitable material (e.g. organics, well-bleached sand) and the specific genesis of these sediments. The results of cosmogenic radionuclide dating suggest a post-LGM age both for the source of the flood water and for different elements of the catafluvial terraces in the Chuya and Katun river valleys. Nevertheless, the age(s) of catastrophic breakthrough remains controversial. On the basis of a few IRSL ages, and geological and other evidence, some view the event as occurring around MIS 5. In this study, we investigate loess-like loams overlying the catafluvial sediments on the surface of the highest level terrace, ∼200 m above present river level. A total of 24 samples for luminescence dating were obtained, for which the OSL, IR₅₀, and pIRIR_50,290 signals were measured to control the degree of signal zeroing and the dating reliability. The age of the loess in all three pits was from 0.5 ka at the top to 23 ka at the base of the loess strata. From a sand layer in the top of the catafluvial deposits, two ages of ∼85–90 ka were obtained from feldspar pIRIR_50,290. These results provide a minimum pre-LGM age for the geomorphological surface of a major catafluvial terrace in the Altai Mountains.