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KDE plots of loess from the Kalaus and Chograi sites in the Manych depression, and the Budennovsk site at the northern Caucasus foothills.

KDE plots of loess from the Kalaus and Chograi sites in the Manych depression, and the Budennovsk site at the northern Caucasus foothills.

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Constraining the controls on the distribution of sediment at a continental scale is a critical step in understanding long-term landscape and climate evolution. In particular, understanding of the role of rivers in wider sediment routing and impacts on aeolian loess formation on a continental scale remains limited. Extensive Quaternary loess deposit...

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... ages peak at 620 Ma. Mesoproterozoic ages form a broad peak between 950 and 1150 Ma, while older Mesoand Palaeoproterozoic ages are present in great abundance, peaking at 1480 Ma, 1640 Ma and 1775 Ma. This pattern is clearly defined by the higher-n loess sample from the Kalaus section. Archean ages show a broad double-peak at 2700 and 2800 Ma (Fig. 7). Few zircons are older than 2800 Ma. The Budennovsk section (MIS 3-2) is located proximal to the Manych sites, but in contrast to these sites, which crop out along rivers flowing through the Manych depression, the more southern Budennovsk section is located higher up on the northern foothills of the Greater Caucasus (Fig. 7). The ...
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... at 2700 and 2800 Ma (Fig. 7). Few zircons are older than 2800 Ma. The Budennovsk section (MIS 3-2) is located proximal to the Manych sites, but in contrast to these sites, which crop out along rivers flowing through the Manych depression, the more southern Budennovsk section is located higher up on the northern foothills of the Greater Caucasus (Fig. 7). The Budennovsk loess sample also contains an abundant age fraction at 300 Ma. An age peak at 450 Ma is well defined and abundant too, while a less pronounced age fraction appears around 600 Ma. The Proterozoic and Archean ages are less frequent compared to the Palaeozoic age fractions (51% and 32%), in contrast to the Kalaus and ...
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... The Budennovsk loess sample also contains an abundant age fraction at 300 Ma. An age peak at 450 Ma is well defined and abundant too, while a less pronounced age fraction appears around 600 Ma. The Proterozoic and Archean ages are less frequent compared to the Palaeozoic age fractions (51% and 32%), in contrast to the Kalaus and Chograi samples (Fig. ...
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... sites Kalaus (MIS 3-2) and Chograi (MIS 4-3), located in the Manych depression, also fit into the South EEP province group, showing the characteristic abundant Palaeozoic peaks at 300 Ma and 450 Ma, a well-defined age fraction at 600-630 Ma, and abundant Archean ages, in addition to the characteristic abundance of Meso-and Palaeoproterozoic ages (Fig. 7). This allows us to outline the South EEP province as shown in Fig. 14. Due to their very similar zircon age distribution and the low-n analysis of the Chograi sample, these two Manych depression loess samples are combined to one Manych sample for further consideration (Table ...
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... volcanic rocks from the East Manych and southwestern zone of the Scythian Platform ( Tikhomirov et al., 2004). However, the sporadic occurrence of these rocks in the region is inconsistent with the number of corresponding ages in the loess samples and corresponding Early-Middle Triassic ages are also largely present in the Budennovsk loess sample (Fig. 7). Even though Lower Jurassic magmatism is reported from the Crimean Mountains, Eltigen loess does not contain zircons of this age, in contrast to the Manych and Budennovsk loess, which contain a few Lower Jurassic aged grains. This suggests that these Mesozoic ages might nevertheless derive from the Caucasus, where several thermal ...
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... ages peak at 620 Ma. Mesoproterozoic ages form a broad peak between 950 and 1150 Ma, while older Mesoand Palaeoproterozoic ages are present in great abundance, peaking at 1480 Ma, 1640 Ma and 1775 Ma. This pattern is clearly defined by the higher-n loess sample from the Kalaus section. Archean ages show a broad double-peak at 2700 and 2800 Ma (Fig. 7). Few zircons are older than 2800 Ma. The Budennovsk section (MIS 3-2) is located proximal to the Manych sites, but in contrast to these sites, which crop out along rivers flowing through the Manych depression, the more southern Budennovsk section is located higher up on the northern foothills of the Greater Caucasus (Fig. 7). The ...
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... at 2700 and 2800 Ma (Fig. 7). Few zircons are older than 2800 Ma. The Budennovsk section (MIS 3-2) is located proximal to the Manych sites, but in contrast to these sites, which crop out along rivers flowing through the Manych depression, the more southern Budennovsk section is located higher up on the northern foothills of the Greater Caucasus (Fig. 7). The Budennovsk loess sample also contains an abundant age fraction at 300 Ma. An age peak at 450 Ma is well defined and abundant too, while a less pronounced age fraction appears around 600 Ma. The Proterozoic and Archean ages are less frequent compared to the Palaeozoic age fractions (51% and 32%), in contrast to the Kalaus and ...
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... The Budennovsk loess sample also contains an abundant age fraction at 300 Ma. An age peak at 450 Ma is well defined and abundant too, while a less pronounced age fraction appears around 600 Ma. The Proterozoic and Archean ages are less frequent compared to the Palaeozoic age fractions (51% and 32%), in contrast to the Kalaus and Chograi samples (Fig. ...
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... sites Kalaus (MIS 3-2) and Chograi (MIS 4-3), located in the Manych depression, also fit into the South EEP province group, showing the characteristic abundant Palaeozoic peaks at 300 Ma and 450 Ma, a well-defined age fraction at 600-630 Ma, and abundant Archean ages, in addition to the characteristic abundance of Meso-and Palaeoproterozoic ages (Fig. 7). This allows us to outline the South EEP province as shown in Fig. 14. Due to their very similar zircon age distribution and the low-n analysis of the Chograi sample, these two Manych depression loess samples are combined to one Manych sample for further consideration (Table ...
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... volcanic rocks from the East Manych and southwestern zone of the Scythian Platform ( Tikhomirov et al., 2004). However, the sporadic occurrence of these rocks in the region is inconsistent with the number of corresponding ages in the loess samples and corresponding Early-Middle Triassic ages are also largely present in the Budennovsk loess sample (Fig. 7). Even though Lower Jurassic magmatism is reported from the Crimean Mountains, Eltigen loess does not contain zircons of this age, in contrast to the Manych and Budennovsk loess, which contain a few Lower Jurassic aged grains. This suggests that these Mesozoic ages might nevertheless derive from the Caucasus, where several thermal ...

Citations

... Based on a comparison of the geochemical composition of loess sediments with that of sediments from potential source areas, the loess of the Chinese Loess Plateau is generally considered to originate mainly from the adjacent upwind deserts and Gobi desert in northwestern China with short transport distances (Yang et al., 2009;Chen and Li, 2011). Additionally, loess is also considered to be a mixing of dominant near source and minor distant source (e.g., Wu et al., 2021a;Költringer et al., 2022). ...
Article
Provenance studies are critical for the paleoclimatic reconstruction of loess. However, very little information is available about the provenance variations of the loess in the monsoon boundary zone, limiting our understanding of aeolian dust dynamics, the evolution of atmospheric circulation and driving mechanisms on the glacial-interglacial timescale. To this end, the integration of grain size end-member modeling, machine learning, sediment fingerprinting and wavelet transform analysis is performed for the Harbin loess in Northeast China to understand the long-term provenance variations, atmospheric circulation evolutions and forcing mechanisms. The results show the Harbin loess comprises three grain size end-members, EM1 (7.81 μm), EM2 (27.2 μm) and EM3 (54.41 μm), and they correspond to the background of atmospheric dust, the intensity of the southwesterly and of the East Asian Winter Monsoon (EAWM), respectively, indicating the three transport dynamics of dust delivered to this region. The quantitative source reconstruction indicates that the loess experienced the dramatic source variations, characterized by an abrupt termination of the dust contribution from the Hulun Buir Sandy Land at ∼ 250 ka, and by variations in the relative contribution of the dust sources (i.e., Songnen Sandy Land, Horqin Sandy Land, Onqin Daga Sandy Land, and to a lesser extent, Hulun Buir Sandy Land) during the glacial-interglacial cycles. The comparisons between the indicators, e.g., EM2, the deep-sea oxygen isotopes and the rate of dust accumulation in the North Pacific, combined with wavelet transform analysis indicating a dramatic shift of orbital cycles from the significant 100-kyr and 41-kyr cycles to a weakened 100-kyr cycle, suggest that the weakened EAWM induced by both reduced the Northern Hemisphere ice volume and summer solar radiation, accounted for a termination of the Hulun Buir Sandy Land as the loess source. However, the change in wind regimes due to the glacial-interglacial cycles, and climate change (e.g., enhanced aridification) are the dominant forcing for the variations in the relative contribution of the dust sources to the Harbin loess.
... More recently the intercalated subaerial terrestrial deposits have also received attention and have been described as loess-palaeosol sequences Makeev et al., 2021;Költringer et al., 2020Költringer et al., , 2021. These aeolian deposits, made up of near-source reworked Volga alluvium, are widely distributed in the Northern Caspian lowland (Kurbanov et al., 2018a(Kurbanov et al., , 2018bKöltringer et al., 2022) and show signs of both pedogenic and cryogenic reworking (Yanina, 2012;Költringer et al., 2020Költringer et al., , 2021Lebedeva et al., 2018;Makeev et al., 2021;Rogov et al., 2020;Taratunina et al., 2021). As such, Lower Volga loess is also of great value for palaeoclimate reconstruction, in addition to the marine deposits in the Northern Caspian lowland (Kurbanov et al., 2018a(Kurbanov et al., , 2018bKöltringer et al., 2020Költringer et al., , 2021. ...
... Furthermore, the Lower Volga loess area is located in the middle of the continent-wide Eurasian loess belt. The provenance of the deposits has been investigated in detail, and their considerable importance as a palaeoclimate archive clearly demonstrated (Költringer et al., 2020(Költringer et al., , 2021(Költringer et al., , 2022. As a result, investigation of Lower Volga Loess has the potential to provide a better understanding of Eurasian climate and continental-scale landscape evolution during the Late Quaternary. ...
... That these phases enabled pedogenesis in an arid and cold climate is indicated by clear signs of cryogenic reworking. The loess is composed of glacial material that was fluvially transported long distances from proglacial outwash plains in the northern East European Plain and the Ural Mountains before deflation by dominant W-E and NW-SE winds from near-source Volga alluvium (Költringer et al., 2021(Költringer et al., , 2022. These studies provide an understanding of the prevailing Late Quaternary environmental conditions in the Northern Caspian lowland but a reliable chronostratigraphy is needed for correlation of Lower Volga loess-palaeosol sequences with regional and global climate events. ...
Article
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 pIRIR50,290 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 pIRIR50,290 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.
... Despite the long history of studies of the LPSs in the Cis-Caucasian region, the nature of the high thickness of deposits has not yet been explained in detail. The problem of the sources and sedimentation patterns of dust material have not been conclusively solved [9][10][11][12], and there are no reliable models of the spatial and temporal variability of the loess sedimentation rate. These problems arise mainly due to a lack of reliable data on the structure, age, and composition of loess deposits. ...
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The origin of the loess deposits of the Cis-Caucasus Region, which form an almost continuous cover on the plains from the Sea of Azov to the Peri-Caspian Depression, is one of the controversial issues of paleogeography of the southern part of European Russia. The remarkably high thickness (up to 140 m) and extended coastal outcrops in the west and in the east of the region studied is of special interest to geologists and geographers who consider the loess strata as a unique record of climate conditions of the Quaternary period. The data on the structure, texture, and geochronology of the Upper Pleistocene and Holocene loess deposits, obtained from the study of 25 borehole logs and outcrop sections, distributed through the territory of the Cis-Caucasus region were received. The average sedimentation rates and the average sand fraction content were estimated for the stratigraphic units correlated with the global climatostratigraphic units (marine isotope stages (MIS)). It has been established that the source of the loess (wind erosion areas), are the valleys and estuary alluvial plains of large rivers: the Terek, Kuma, Volga, Kuban, and Don. The Peri-Caspian Depression was the dominant source of mineral dust throughout Late Pleistocene and Holocene. Large massifs of weakly fixed sands and sandy loams of the western Caspian region in combination with a high level of climate aridity and strong east winds created the prerequisites for the transport of huge volumes of mineral dust westward as far as the Sea of Azov.
... A similar observation has been reported by Sainz de Murieta et al. (2021) but this discrepancy is currently not well-understood. Higher fading rates for these individual samples cannot be ruled out, but we consider this very unlikely, since Költringer et al. (2022) argue for a common source for all lower Volga basin sediments. Rather, we presume this phenomenon is most likely related to inaccuracy in the measurement of the internal component of feldspar dose using IRSL signals . ...
... Aeolian sediments (loess and loess-like) form the middle part of Raygorod section. Költringer et al. (2021Költringer et al. ( , 2022 argue that the source for loess sedimentation in this region is Volga River alluvium. The Volga River drains the central East European Plain, which is covered with middle and late Quaternary moraines sourced from Scandinavia and the Ural Mountains (Morton et al., 2003;Makshaev and Svitoch 2016;Tudryn et al., 2016). ...
Article
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.
... It is worth noting however, that while heavy mineral assemblage data has been used to support a BIIS (or FIS) origin for loess in Britain, no such evidence has been presented for the Rhine model. This model was proposed to emphasise the contribution that major rivers likely play in long distance silt transport, an idea which is supported by provenance data in many loess regions globally (Újvári et al., 2012;Nie et al., 2015;Fenn et al., 2022;Költringer et al., 2022). In the Rhine model the loess in southern Britain would be classified as 'perimontane' by Pye (1995) and would fall into the MR classification under the Taiyuan system (Li et al., 2020). ...
Article
Loess was first identified in England as early as the mid-19th century, although these deposits were later mapped as ‘brickearth’ or ‘head-brickearth’ by the British Geological Survey. Much of this material was subsequently recognised and named as loess again by soil scientists, most notably by J.A. Catt. The early reports of loess were mostly located in southeast England, however, more recently loessic deposits have also been reported from the north of England, possibly in Scotland, and as far west as western Ireland. Catt also appreciated that these deposits are the western limits of a broad cover of loess stretching across Eurasia. Here, contrasting models for the possible origin, transport pathways and reworking of these deposits are presented. While some of these British deposits are primary in situ loess, a range of processes has likely affected many of them, including periglaciation, Holocene climatic, and human impacts. Luminescence dating has confirmed British loess to be primarily of late Pleistocene age, however, examples of older loess are also reviewed. Deposits in southeast England are the thickest and best expressed today, and these have yielded significant insight into both the mechanism of the hydroconsolidation (collapse) of loess and landscape evolution in northwest Europe during the Last Glacial Period. The thin and regional nature of British and Irish loess may make it an excellent material for studying loess formation, with advantages over the thicker deposits of typical loess of central Europe, where the impact of smaller scale landscape processes may be less obvious.
... Несмотря на многолетнюю историю изучения ЛПС Предкавказья, до сих пор нет исчерпывающего объяснения природы необычайно высокой мощности отложений. До конца не решены вопросы об источниках поступления и механизмах накопления пылеватого материала [9][10][11][12], нет надёжных моделей пространственной и временной изменчивости скоростей накопления лёссов. В основном указанные проблемы связаны с недостатком достоверных данных о строении, возрасте и составе ЛПС. ...
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Происхождение лёссовых отложений Предкавказья, образующих практически сплошной покров на равнинах от Азовского моря до Прикаспийской низменности, остаётся одним из дискуссионных вопросов палеогеографии юга Европейской России. Феноменально высокая мощность лёссовопалеопочвенных серий (ЛПС) на востоке региона (до 140 м) и протяжённые береговые обнажения на западе вызывают особый интерес геологов и географов, рассматривающих эти толщи как своеобразную летопись природных условий четвертичного периода. В статье анализируются данные по строению, механическому составу и возрасту ЛПС верхнего плейстоцена и голоцена, полученные на основе изучения 25 скважин и разрезов, распределённых по территории Предкавказья. Рассчитаны средние темпы осадконакопления и средние содержания песчаной фракции для стратиграфических единиц, соотносимых с глобальными климатостратиграфическими подразделениями – морскими изотопными стадиями (МИС). Установлено, что источниками (областями дефляции) минеральной пыли, которая и формирует лёссовый покров, являются долины и приустьевые аллювиальные равнины крупных рек – Терека, Кумы, Волги, Кубани и Дона. Доминирующим на протяжении всего позднего плейстоцена и голоцена источником является Прикаспийская низменность. Крупные массивы слабозакреплённых песков и супесей западного Прикаспия в сочетании с высокой засушливостью климата и сильными восточными ветрами создали предпосылки для переноса огромных масс минеральной пыли на запад вплоть до Азовского моря.
... One of the most common methods in identifying sources of dust and pollutants is source-sink proxy comparison, which includes the analysis of rare earth elements (Tian et al. 2018), mineralogy (MalAmiri et al. 2022), elemental ratios , Nd-Sr isotopes (Jewell et al. 2021), U-Pb age spectrum (Költringer et al. 2022), quartz oxygen isotope (MalAmiri et al. 2022), etc. In such studies, the isotope composition of particular matter (PM) is examined and then these elements are categorized based on source apportionment methods such as factor analysis, chemical mass balance, positive matrix factorization and principal component analysis and finally the contribution of dust and pollutants from PM is determined (Thunis et al. 2019). ...
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    Dust storms are one of the natural phenomena that occur in different countries, especially in arid and semiarid regions. This study aimed to identify pathways and dust sources affecting the Yazd city. Therefore, in the present study, a multidisciplinary approach based on the air parcel trajectories, geographical information and observational data was used to identify the origin of dust storms. In this regard, based on the available data, the analysis has been done in the 7-year period of 2012–2019. The Hybrid Single-Particle Lagrangian Integrated Trajectory model was used to model the backward trajectory of the air parcel on days associated with dust storms. The Cross-Referencing Backward Trajectory (CRBT) method was used to identify dust source contribution. To combine the results of different methods, including numerical modeling, satellite and meteorological data, the method of measurement of alternatives and ranking according to compromise solution (MARCOS) has been used. The CRBT results showed that Dasht-e Kavir has a significant contribution in dust storms in Yazd city. Also, effects of the air parcel height were investigated and the results showed that most of them passing through the Dasht-e Kavir had a height less than 500 m, and as a result, a significant amount of dust has been transported from this source to Yazd city. The MARCOS results showed that Dasht-e Kavir had the highest impact on dust storms in Yazd city.
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    The role of Quaternary ice sheet fluctuations in driving meltwater pulses and ocean circulation perturbations is widely acknowledged. What is less clear is the role of these processes in driving changes in past atmospheric dust activity, and possible wider links between dust and climate. Terrestrial windblown dust (loess) deposits along the northern fringe of the European loess belt potentially record past atmospheric dust emission from regions close to the former Eurasian Ice Sheet (EIS) and provide a means to evaluate the role of ice sheet fluctuations in the past dust cycle. Numerical loess chronologies across this region generally agree on greatly enhanced dust deposition rates during MIS 2, when the EIS reached its maximum extent. Yet, uncertainties over the sources of this material prevent understanding of the precise causes of this greatly enhanced atmospheric dustiness, and any potential link to ice sheet fluctuations and climate. In southeast England, loess accumulation dominantly occurred in two phases centered on 25e23.5 ka and 20e19 ka, matching the timing of coalescence of the Fennoscandian and British-Irish ice sheets and specifically advances and retreats of nearby ice lobes in the western North Sea. As such, these deposits provide an ideal test of the role of ice sheet fluctuations in atmospheric dust dynamics. Here we undertake such a test through a detailed provenance study of loess in southeast England and potential dust source sediments across the North Sea region. We group extensive new and published data sets of detrital zircon UePb ages from basement rocks and Cenozoic sediments in the North Sea area, which not only provide new insight into both loess source, but also the nature of sediment transport over NW Europe into the North Sea basin more widely. Multi-proxy evidence allows us to unambiguously identify ice sheet derived sediments in the exposed North Sea basin as the dominant source of loess in southeast England, while fluvial sediments delivered by rivers draining Continental Europe possibly contributed additional source material to the first loess accumulation phase. We propose that sudden retreats of the North Sea Lobe released substantial amounts of sediment rich meltwater into the southern North Sea and Channel basins, driving accelerated dust emission, loess deposition and provenance variability in NW Europe during MIS 2. Moreover, we propose that this model of dust activity driven by proglacial sediment availability may be applicable for EIS marginal regions more widely, even where resultant loess cover is rarely preserved due to extensive erosion and reworking along the ice marginal spillway. This implies the role of ice sheets in controlling wider dust emission may be underestimated. In addition to driving changes in ocean circulation through meltwater pulses, ice sheet dynamics in the Quaternary may have also driven substantial and abrupt changes in atmospheric dust activity. This mechanism may in part explain the coupling between dust and climate events widely seen in Quaternary dust sediment records and suggests a possible major role of high latitude dust emission in MIS 2 dustiness across Europe and beyond.
    Article
    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.
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    The problem of the source of mineral dust, which makes up the loess-paleosol sequence of Ciscaucasia, remains relevant. One of the main approaches to solving the problem is the spatial analysis of the structure and composition of the loess. Based on the core analysis of three boreholes, a sublatitudinal cross-section of the loess-paleosol sequence of the Upper Pleistocene and Holocene was constructed. A gradual decrease in the thickness of loess-paleosol sequence and grain size from east to west was found out. The total thickness of the Upper Pleistocene and Holocene deposits in the OT-20 section (eastern part) is 22.6 m, SB-1 (central part) – 9.7 m, YS-1 (western part) – 5.3 m. The average content of the sand fraction decreases in the same direction: OT-20 – 17.1%, SB-1 – 6.1%, YS-1 – 1.9%. The results indicate that the main direction of the aeolian transport during the Late Pleistocene and Holocene was from east to west. Sand deserts of the Caspian lowland are probably the main source of the material. Secondary sources of mineral dust are local sandy massifs spread on the terraces of large rivers like Don and Kuban. Compositional variations of loess in depth show that the intensity of eolian processes was higher during cold periods and lower during warm ones. The loess sequences in the east of Ciscaucasia have higher temporal resolution and more responsive paleoclimatic indicators than the western ones.