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The paper considers data on the composition, age, and formation conditions of the Ulzutui and Kydzhimit sequences, which are ascribed to the Eravna Series of the Eravna Subzone of the Uda–Vitim Zone. The Eravna Series, at least 2400 m thick, is composed of tephroturbidites with a significant amount of lavas and tuffs of felsic and intermediate compositions, with which tectonic-gravitational mixtites are spatially and genetically related. The features of the structure and composition of the Eravna Series indicate the formation of sediments in an open deepening marine basin adjacent to the zone of active volcanism. Based on miospores, the time of formation of the Ulzutui Sequence was constrained, for the first time, to the Late Devonian–Early Carboniferous (late Famennian–early Tournaisian), the Kydzhimit Sequence is limited to the Early Carboniferous (Visean) age. At this time, the Kydzhimit volcanic zone was formed. The suprasubduction nature of the zone is evidenced by the following features of volcanic rocks: predominance of felsic varieties, affiliation of basalts to the tholeiitic series, and dacites and rhyodacites to the calc-alkaline series, the presence of high-K rock varieties corresponding to the K-Na alkalinity, very low MgO contents, low and moderate TiO2 contents, high Al2O3 and K2O, enrichment of the volcanogenic rocks in large-ion lithophilic elements relatively to high-field strength elements, Nb minimum, and negative εNd, their spatial association with monzonites (with suprasubduction signatures) and tephroturbidites, as well as metallogenic specialization (Cu and Zn) of the Eravna Series. We believe that the ore-bearing sequence for the pyrite–base metal Ulzutui and Ozernoe deposits is the Upper Devonian–Lower Carboniferous Eravna Series. [ABSTRACT FROM AUTHOR]

In the contemporary urban environment, a complex of natural and anthropogenic sedimentation processes takes place, as a result of which a significant amount of sediments of dust and dirt is formed. The aim of the study is development and testing of approaches to the dust and dirt sediments as an indicator of ecological and geochemical state of urban environment. The studies were carried out on the territories of large cities of Russia differing in lithogenic substrate and located in different natural-climatic and economic zones. During the study, the granulometric, chemical, and mineral composition of the contemporary surface deposited sediments in the areas of multistory residential buildings has been determined. Some patterns and trends in the formation of environmental and geochemical situation, and also the indicators of alteration in the geochemical conditions of cities have been discovered. [ABSTRACT FROM AUTHOR]

Detailed studies of processes of sediment-record formation are necessary for accurate sediment-derived paleo environmental reconstructions. In order to understand the deposition of sediments in meromictic Lake Shira (southern Siberia, Russia), we conducted a multi-year seasonal sediment trap study of sediment fluxes of chemical elements, organic and inorganic carbon, total nitrogen and photosynthetic pigments for a period from 2012 to 2017. In 2015 and 2016, a rare event of transition from meromixis (i.e. long-term hypolimnetic anoxia) to holomixis was observed, which was accompanied by the temporary disappearance of hydrogen sulfide from the water column in spring and a decrease in hydrogen sulfide in other seasons compared to the meromictic state. In general, we did not reveal any noticeable differences between the meromictic and holomictic states in the composition of sediments, except for okenone. The content of okenone, a specific carotenoid of purple sulfur bacteria, decreased in traps during the holomictic state and did not considerably increase two years after the meromixis restoration. Using a freeze-corer, we observed that the content of okenone in the uppermost 3-mm layer of sediments also decreased markedly from 2013 to 2017, as well as in traps. The sedimentation flux of molybdenum reflected the seasonality of hydrogen sulfide content in the water column, and it was maximal in winter, in contrast to all other sediment components. Other components reflected the seasonality of organic production and terrigenous inputs, with the maximum in late summer and autumn. An increase in the sedimentation rate of terrigenous elements in the autumn of 2012 was supposedly caused by the anomalous amount of precipitation in August 2012. Since detailed inter-annual observations of sedimentation processes are not often found in limnology, we hope that our results will be useful for reconstructing regional climate and, further, the understanding of sediment dynamics of stratified temperate water bodies. [ABSTRACT FROM AUTHOR]

Channel avulsions on river deltas are the primary means to distribute sediment and build land at the coastline. Many studies have detailed how avulsions generate delta lobes, whereby multiple lobes amalgamate to form a fan‐shaped deposit. These studies often assume a steady subsidence and uniform basin depth. In nature, however, lobe building is disrupted by variable subsidence, and progradation of lobes into basins with variable depth: conditions that are prevalent for tectonically active areas. Herein, we explore sediment dispersal and deposition patterns across scales using measurements of delta and basin morphology compiled from field surveys and remote sensing, collected over 150 years, from the Selenga Delta (Baikal Rift Zone), Russia. Tectonic subsidence events, associated with earthquakes on normal faults crossing the delta, displace portions of the topset several meters below mean lake level. This allogenic process increases regional river gradient and triggers lobe‐switching avulsions. The timescale for these episodes is shorter than the predicted autogenic lobe avulsion timescale. During quiescent periods between subsidence events, channel‐scale avulsions occur relatively frequently because of in‐channel sediment aggradation, dispersing sediment to regional lows of the delta. Avulsion settings for the Selenga Delta preserve discrete stratal packages that could contain predominately deep channels. Exploring the interplay between tectonic subsidence and sediment accumulation patterns will improve interpretations of stratigraphy from active margins and basin models. Plain Language Summary: River deltas distribute sediment and build land in coastal regions by abruptly shifting course through a process called channel avulsion. The fan‐shaped morphology of river deltas arises from multiple avulsion events that deposits sediment in a radial fashion over time. Our understanding of how deltas build such morphology assumes that size of the downstream basin, such as a lake or ocean, is constant over time. However, geological activities like earthquakes and basin subsidence alter the size and shape of the delta. We complied and analyzed 150 years of delta morphology data from the Selenga Delta (residing in a tectonically active area) in Russia to understand how earthquakes and subsidence impacts channel avulsions and delta landforms. We determined two distinct avulsion styles for the Selenga Delta: a regional‐scale avulsion that is driven by earthquakes, and a local‐scale avulsion that is caused by sediment deposition. The two distinct scales of avulsions blend over time to shape the delta system. In addition, the regional‐scale avulsion produce unique subsurface records that can be used to understand the history of a delta. Our work highlights the importance of understanding the variety in downstream basin processes that impact delta morphology. Key Points: Tectonic subsidence produces variable receiving basin depth, and drives lobe‐scale avulsions by modifying delta‐topset gradientChannel‐scale avulsions occur during periods of tectonic quiescence, and disperse sediment to nourish the deltaic shorelineHierarchical avulsion styles could lead to preservation of discrete stratal packages that contain predominately deep channels [ABSTRACT FROM AUTHOR]

Verification of soil erosion models (WATEM/SEDEM for rainfall and tillage soil erosion and regional model of the State Hydrological Institute for snowmelt soil erosion) was carried out on the basis of estimates of soil erosion and deposition rates in an arable catchment of dry valley in the Vorobzha River basin located in the central part of the Srednerusskaya Upland in the forest-steppe zone. The rates of soil loss/gain for the entire period of agricultural use were obtained using the soil truncation method. The rate of sediment deposition in the dry valley bottom for the period after the 1986 was determined based on interpretation the Chernobyl-derived 137Cs depth distribution in the sediments. Comparison of the model calculations with field-based method estimates was generally in good agreement. Also, the erosion model calculation satisfactorily reflected the pattern of zones with different intensity of soil erosion. WATEM/SEDEM made it possible to take into account the movement of soil matter by tillage erosion. Some discrepancies between the modeling results and field data were mainly due to the insufficiently detailed input parameters, e.g., the data on crop rotations or local microrelief specifics. WATEM/SEDEM did not accurately estimate the rate and volume of sediment accumulation, especially for areas beyond cropland. [ABSTRACT FROM AUTHOR]

To understand the dynamics of sediment deposition and the potential influences of complex current systems in large lakes, Lake Imandra (Kola Peninsula) has been investigated. Seismic and echo‐sounder data of the central part of Bolshaya Imandra reveal the sediment architecture in unprecedented detail. In addition, the sediment core data indicate highly variable depositional processes since the Late Pleistocene. The complex morphology of the lacustrine basin favoured accumulation of sediment in depressions, where they were preserved from erosion. Three main stratigraphic units (SU I–III) were identified above the acoustic basement. The oldest SU III is best preserved along a tectonic trench and interpreted as glacial deposits partly eroded by the Scandinavian Ice Sheet during Marine Isotope Stage (MIS) 2. The overlying SU II deposits are regarded as a till related to MIS 2 glaciation. The youngest SU I represents glaciofluvial, glaciolacustrine and lacustrine sediment deposited after ice retreat. As the north–south‐trending main axis of Bolshaya Imandra runs parallel to the predominant wind direction, the basin is subject to strong wind‐induced surficial currents and compensatory subsurface currents. These currents occur in water depth of 0–15 and deeper than 30 m, respectively, and their velocity prevents sediment accumulation. [ABSTRACT FROM AUTHOR]

The paper presents an assessment of the rates of erosion and sedimentation in hollows of the Temeva Rechka small dry valley catchment, dominated by forest-steppe gray forest soils (Luvic Retic Greyzemic Phaeozems), over the past 55–60 years with the use of the radiocesium technique. This catchment is located in the Myosha River basin (Republic of Tatarstan, European Russia). The hollows have been grouped by the catchment's slope aspects, hollow length, hollow bottom gradient, and shape of the thalweg profile of the hollow bottoms; origin and age, as well as by the specifics of erosion/sedimentation processes. Short agrogenic hollows with a small catchment area on relatively steep western slopes of the Temeva Rechka small dry valley, probably formed after human deforestation, have been identified. The shape of their catchments contributes to the formation of surface runoff, sufficient for the erosion of a significant part of their bottoms at a rate of about 2–4 t/ha per year. Older, polygenetic, and relatively long hollows with a slightly sloping bottom and larger catchments serve as sediment transit zones between plowed areas and the Temeva Rechka small dry valley bottom. They are characterized by alternating areas of soil erosion and sediment accumulation. The average rate of soil erosion in these landforms is 0.8 t/ha per year. In some hollows, when several small tributaries (smaller hollows) flow into their lower parts, soil erosion loss increases to 3 t/ha per year. The average soil erosion loss is 6 t/ha per year on short slopes of the hollows; in their upper parts, it can reach 11 t/ha per year. There is a general decrease in the rates of soil erosion and accumulation of eroded material in recent decades due to changes in climate and land use. [ABSTRACT FROM AUTHOR]

Bryozoan fauna from several outcrops of sediments of the Kunda Stage (Darriwilian, Middle Ordovician) of Estonia and NW Russia contains 18 species which belong to the palaeostomate orders Cystoporata, Esthonioporata, Trepostomata, and Cryptostomata. The studied material comes mainly from the collection of the Department of Geology, Tallinn University of Technology, as well as was specimens I have collected. One genus with one species and one more species are new: Pakripora cavernosa gen. et sp. nov. and Dianulites pakriensis sp. nov. Four bryozoans are identified to genus level only. One cryptostome bryozoan shows unique morphology unknown in any similar genera. In general, the studied fauna shows close relations to other localities within the Baltic region, with some few relations to the Ordovician of China. The bryozoans developed massive and erect colonies, showing adaptation to the shallow to moderately deep environment with moderate water energy and relatively high level of sedimentation. [ABSTRACT FROM AUTHOR]

The study of the hydrocarbon potential of the Arctic is being considered in Russia as the most crucial direction of preparing a new raw material base of oil and gas, which will replace the extracted reserves in traditional areas of development during the second third of this century. The sharp fall in global hydrocarbon prices has led to a reduction in research and exploration costs, especially in hard-to-reach areas and hard-to-recover reserves as well as the need to determine the contribution to the country's fuel and energy balance from the hydrocarbons development of the Arctic zone, including the shelf, without which it is impossible to plan and develop new expensive projects. A fair assessment of oil and gas potential, based on a set of ideas about the processes of formation of sedimentary basins and oil and gas generation processes, contributed to obtaining new geophysical information on the results of seismic work executed in the Arctic zone of the Russian Federation between 2010 and 2020. A quantitative assessment of oil and gas resources was performed using geological analogies (for wellstudied geological and geophysical areas) and the volume-genetic method (for less studied basins). It showed significant differences from the most well-known assessments of the Arctic, both in terms of the total volume of hydrocarbons and their phase composition. It was concluded that there is ambiguity in assessing the potential of deepwater zones of the Arctic seas. Because of that, it is important to study coastal and shallow areas, especially oil content. [ABSTRACT FROM AUTHOR]

The article presents the results of a study on sediment deposition processes in the palaeolake shore zone, at the multilayered Serteya II archaeological site in Western Russia. In recent years, geomorphological, palaeopedological and palaeoecological research was undertaken in strict cooperation with archaeological fieldwork. The Serteya II site occupies a substantial area of a kame terrace and biogenic plain within a palaeolake basin. From an archaeological point of view, the site is represented by few Mesolithic artefacts, but mostly by remnants of hunter-gatherer-fisher communities attributed in the Russian scientific tradition to the Neolithic period and dated from 6300 BC to 2000 BC. Later, the area was used by people in the Bronze Age, Early Iron Age and Early Middle Ages. The integration of archaeological and multidisciplinary palaeoenvironmental research allowed the natural and human induced deposition of mineral-organic and minerogenic sediments to be reconstructed, as well as the development of structures in the lake shore zone. The changes from lacustrine to fluvial system were documented and the human impact is recorded mostly in the acceleration of slope processes. [ABSTRACT FROM AUTHOR]

The White Sea being connected with the Arctic Ocean via the Barents Sea has an influence on its water temperature/salinity structures and biological processes and thus has an indirect impact on the Eurasian climate system. In this work, we have managed to find a correspondence between the climate fluctuation in the Holocene and changes in the geochemical and microfossil properties in the sediment core of the White Sea. For the first time, the element speciation in the sediment core covering about 10,000 cal yr BP period was investigated. The cooling periods (the early Holocene and the Subboreal stage) were characterized by a trend of increase in Si, Al, and Ti contents and Ti/Al ratios, which reflect lithogenous contribution, and decrease in geochemically labile forms of trace elements. A significant increase in the content of organic-bound trace elements and biogenic components (Сorg, BSi, and chlorin) was observed during periods of Holocene climatic optimums. The evident relationship between the metal speciation and indicators of the sedimentation paleoenvironment is observed at the stage of the active phase of early diagenesis after the slowing down of the biogeochemical processes. Down-core decrease in the Mn oxyhydroxide content exhibited a weakening of diagenesis processes at the ~130–150 cm depth. [ABSTRACT FROM AUTHOR]

In the Southern Trans-Urals, the Quaternary deposits dated back to the Early Pleistocene (2.58–0.77 Ma) are scarce, incomplete, and often severely eroded. Data scarcity is a major challenge for accurate geological correlation and for integration of regional data into continent-wide stratigraphic frameworks. We provide a review of stratotypes and type localities for regional stratigraphic subdivisions of the Eopleistocene (the units correlated with the Calabrian stage of the Western European stratigraphical timescale, 1.8–0.77 Ma) with particular focus on small mammals and their biochronological significance. Subdivisions of the Eopleistocene which have been officially accepted in Russia include three regional chronostratigraphic units (Horizons) starting from Uvel'ka to Chumlyak, and Sarykul. We show that the Calabrian deposits are characterized in the Southern Trans-Urals by sequential changes in the evolutionary level of micromammal assemblages that could be directly correlated with the mammal-based biochronological zones MQR of Russia (Vangengeim and Tesakov, 2008; Tesakov and Titov, 2013) within the interval from MQR 10 to MQR 8. Analysis of micromammal assemblages reveals incongruent positioning of the officially accepted Uvel'ka, Chumlyak, and Sarykul' Horizons in the regional stratigraphic chart. The revealed incongruences appear to be a result of the difficulty to delineate chronostratigraphic units using the highly eroded and reworked sediments of fluvial origin. The complete cycles of alternating fluvial-lacustrine sedimentation and subaerial exposure provide the most reliable sections to establish the chronostratigraphic units of the Calabrian stage of the Early Pleistocene in the Southern Trans-Urals. The position of Chumlyak and Sarykul' Horizons in the regional stratigraphic chart of the Southern Trans-Urals is proposed to be changed. The validity of the Uvel'ka Formation as a chronostratigraphic unit should be further verified, with a particular focus on faunal proxies (mollusks, ostracods, and small mammals). [ABSTRACT FROM AUTHOR]

The lithochemistry potential for comparison and correlation of terrigenous deposits and paleoreconstructions of facies sedimentation settings is studied on the example of the Komsomolsk section. The completed works and analysis of the first data on the contents of chemical components and values of lithochemical modules of the Upper Jurassic–Lower Cretaceous rocks making up the Komsomolsk section confirm the folded structure of this section previously identified by other methods. It is established that the layers of the southwestern and northeastern parts of the section are wings of a single syncline fold, while a "barren" sequence exposed in the northeasternmost part of the section lies at its base. The importance of combining different methods is noted. [ABSTRACT FROM AUTHOR]

The paper presents the results of studying the geological structure of the Ludlowian boundary sediments and data on lithology, bio- and chemostratigraphy, and large-scale biotic reconstruction at the boundary Ludlow-Pridoli. The results obtained make it possible to draw a conclusion about the stratigraphic incompleteness of the Ludlow section in the Subpolar Urals and the interruption in sedimentation at the end of the Ludlow. [ABSTRACT FROM AUTHOR]

The generative potential of kerogenous shale sequences in the Caucasus Maykopian series, the southern part of European Russia, is evaluated. The Khadum and Batalpashin sediments in the Eastern and Central Fore-Caucasus include three types of kerogen: I, II and III. The Khadum sediments are dominated by a more "noble" type II kerogen, mixed humic-sapropelic organic matter (OM). The Maykopian series may be attributed to the category of "rich" and "very rich" ("outstanding") oil source rocks. The maturity extent of the subject sediments within the region varies between the grades of protokatagenesis (maximum pyrolysis temperature (Tmax) = 390 °C) and MC4 (Tmax = 471 °C). Based on the pyrolytic studies, the Khadum and Batalpashin sediments are distinct from other pelitic rocks in rather high generative potential values. The average value of the total generative potential (S1 + S2) in the studied samples from the Khadum and Batalpashin Formations is 4.83 mg HC/g rock. The quantitative estimate of the hydrocarbon generative potential of the Khadum and Batalpashin sediments in this region was conducted for the first time. The total initial generative hydrocarbon potential of the sediments is 133.4 BT, being 92.7 BT for the Khadum Formation, and 40.7 BT for the Batalpashin Formation. [ABSTRACT FROM AUTHOR]

The physical-chemical stage of marginal filters in minor rivers of the White Sea catchment area by the example of the Umba River, flowing to Kandalaksha Gulf, has been explored. Application of the method of physical-chemical modeling on the basis of field data allowed establishing migration forms of a number of elements in the “river-sea” system and deposition of solid phases when mixing waters. The mixing of river and sea water is accompanied by the sedimentation of predominantly goethite, hydromuscovite, and hydroxylapatite. Sediments in mixing river and sea waters were found to be mainly composed by goethite, hydromuscovite, and hydroxylapatite. The research has added to the knowledge of the role of the abiotic part in the marginal filters of small rivers in the Arctic. [ABSTRACT FROM PUBLISHER]

We have obtained the first detailed δС record in Permian-Triassic boundary sediments in deepwater facies in Northeast Asia (Kolyma-Omolon region, Balygychan Basin). Our data show good convergence both with the Setorym River section (South Verkoyansk region), where the Permian-Triassic boundary has been determined approximately, and with a number of other sections of Permian-Triassic boundary sediments in the Boreal and Tethyan Superrealms, in particular, in the Buchanan Lake section in Arctic Canada, the Festningen section on Spitsbergen, the Wadi Shahha section on the Arabian Peninsula, and published sections in the Dolomites. [ABSTRACT FROM AUTHOR]

Early diagenesis of organic matter in bottom sediments of Lake Baikal is a focus of many geochemical studies, because it is one of the few sites of petroleum formation in a nonmarine environment. Although Baikal is a rift lake and considered one of the prospective fields for deep biosphere investigations, the transformation processes of organic matter by microbial communities from deep bottom sediments and likely entering of the microorganisms from deep sediments into the near-surface sediments were not previously studied in Lake Baikal. The natural microbial community from near-surface sediments of the cold methane seep Goloustnoe (Southern Baikal Basin) was incubated with methane and the diatomSynedra acusat 80°C and 49.5 atm to simulate catagenesis. The 11-month incubation yielded the enrichment culture of viable thermophilic microorganisms. Their presence in low-temperature sediment layers may be indicative of their migration through fault zones together with gas-bearing fluids. After culturing, molecular biological methods allowed for the detection of both widespread microorganisms and unique clones whose phylogenetic status is currently unknown. The sediment after the experiment showed the formation of polycyclic aromatic hydrocarbon, retene. Retene can be either a conifer or algal biomarker, thus, interpretation of paleoclimate data is tenuous. [ABSTRACT FROM AUTHOR]

The composition of permafrost deposits holds information on the paleo-environment during and following deposition. Sampling natural exposures and drilling are two methods used to access permafrost archives. In this study, we combine both approaches at the western coast of the Buor Khaya Peninsula in the south-central Laptev Sea (Siberia) to study late Pleistocene permafrost; namely the Yedoma Ice Complex (IC), which is prominent across much of eastern Siberia. Two Yedoma IC exposures and one drill core were studied for cryolithological (i.e. ice and sediment features), geochemical, and geochronological parameters. Borehole temperatures were measured for three years to capture the current thermal state of permafrost. The studied sequences were composed of ice-oversaturated silts and fine-grained sands with considerable amounts of organic matter (0.2 to 24 wt%). Syngenetic ice wedges intersect the frozen deposits. The deposition of the Yedoma IC, as revealed by radiocarbon dates of sedimentary organic matter, took place between 54.1 and 30.1 kyr BP. Continued Yedoma IC deposition until about 14.7 kyr BP is shown by dates from organic matter preserved in ice-wedge ice. For the lowermost and oldest Yedoma IC part, infrared-stimulated luminescence dates on feldspar show deposition ages between 51.1 ± 4.9 and 44.2 ± 3.6 kyr BP. End-member modelling was applied to grain-size-distribution data to unmix sedimentation processes during Yedoma IC formation. Three to five statistical end-members were detected within Yedoma IC deposits of different ages, which we interpret as signals of alluvial, proluvial, and aeolian transport and redeposition as well as in-situ frost weathering in a polygonal tundra landscape. The study captures the internal variation of Yedoma IC characteristics and puts its local stratigraphy into regional scale. The cryolithological inventory of the Yedoma IC preserved on the Buor Khaya Peninsula is closely related to the results of other IC studies, for example, to the west on the Bykovsky Peninsula, where formation time (mainly during the late Pleistocene MIS 3 interstadial) and conditions were similar. Local freezing conditions on Buor Khaya, however, differed, and created solute-enriched (salty) and isotopically-light porewater pointing to deep active-layer and thaw-bulb freezing after deposition. Due to intense coastal erosion, the biogeochemical signature of the studied Yedoma IC represents the terrestrial end-member for, and is closely related to organic matter currently being deposited in the marine realm of the Laptev Sea shelf. [ABSTRACT FROM AUTHOR]

On the basis of a high-resolution chronostratigraphic framework of the Eastern Russian Platform, a comparison between Late Barremian–Aptian global and regional sea-level trends was performed. The detailed evaluation of the long-term (3rd order) Aptian sea-level cycle results in the recognition of sea-level and climate as controlling factors on depositional environments in the basin. The rising part of the Aptian sea-level cycle lasted from the Deshayesites tenuicostatusis Zone to the Deshayesites deshayesi Zone, and transgression is responsible for the local development of anoxia on the Eastern Russian Platform. The Lower Aptian bituminous shales and sheeted calcite concretions associated with the Eastern Russian Platform are interpreted as being a regional manifestation of Oceanic Anoxic Event OAE 1a. The Late Aptian “cold snap” that occurred during the Early Cretaceous greenhouse world coincided with a simultaneous global and regional sea-level lowstand, peak shallowing of the basin, and the almost complete absence of sediments due to subaerial exposure in the studied region. The global distribution of the lowstand gives clear evidence for sea-level fluctuations, and intrinsic climate control on sequences in the study area. [ABSTRACT FROM AUTHOR]

The upper Frasnian coral biostrome, well-exposed in the Russkiy Brod quarry, Central Devonian Field, Russia, has been studied in detail with respect to paleoecology and sedimentary environment. The biostrome, formed by auloporid tabulates and solitary and colonial rugose corals, originated in an offshore environment characterized by calmer periods with slow or halted sedimentation, and more energetic periods when sedimentation rate increased. The episodic, higher sediment influx and stronger hydrodynamic regime are not only well-expressed in the microfacies, but also in the variability of colony integration of the rugose corals observed even within single coralla. Distinct development of constrictions, rejuvenescences and deflection of growth directions in rugose corallites may also indicate unstable sedimentary conditions. The latter features, however, may have, in part, also resulted from syn vivo biotic interaction with the associated auloporids. Both the facies and paleontological observations suggest that the biostrome originated by the colonization of deposited bioclasts by pioneering auloporids, creating the framework for settlement of later generations of auloporids and rugose corals. Apart from abundant auloporids representing a single species and associated rugose corals, the other encrusters are not numerous and poorly diversified, represented by dominating foraminifers, followed by single species of productid brachiopods, stromatoporoids, microconchids and cornulitids. The coral-associated macrobenthos has similarly a low diversity, being represented by single species of spiriferid and rhynchonellid brachiopods, and gastropods. Being developed in an offshore carbonate sedimentary system devoid of any organic-rich deposits, and characterized by extremely low abundance and diversity of suspension-feeding organisms, the biostrome is considered to have originated in a low productivity, oligotrophic environment strictly dominated by heterozoan coral communities. Its development in a well-oxygenated, oligotrophic environment during the time when organic-rich, black Kellwasser facies developed elsewhere, additionally attests for multi-causal scenarios for the Frasnian–Famennian event, during which other factors were responsible in different paleogeographic and facies settings. [ABSTRACT FROM AUTHOR]

The first geochemical data of the Benevka section chert rocks belonging to the Taukha terrane of the Sikhote-Alin Late Jurassic-Early Cretaceous accretionary prism, Russia Far East are discussed in this work. In particular, the geochemical data obtained show that the content of Ce increases progressively from the low horizons of stratigraphic succession represented by bedded cherts to the upper horizons composed of clayey cherts, which gradually pass to siliceous mudstones at the uppermost part. Correspondingly, the value of the negative Ce anomaly (Ce/Ce*) decreases progressively up the Benevka section. The Ce anomaly value of bedded cherts ranges 0.34-0.69 (well-developed negative Ce anomalies), whereas those of upper horizons of bedded cherts and lower horizons of clayey cherts vary from 0.75 to 0.87 (slightly less, but also well-developed negative Ce anomalies). Slight negative Ce anomalies (0.91-0.94) were revealed in the upper horizons of clayey cherts and in siliceous mudstones. In addition, the NASC-normalized La/Ce ratio (i.e., La/Ce) has been calculated, the value of which also decreases progressively upward of the measured stratigraphic section from 2.87 to 1.02. The totality of all geochemical data indicates that the Benevka section chert rocks were formed in an oceanic depositional environment, but in different paleo-ocean locations. The lowermost horizons of bedded cherts were deposited to near spreading ridge-proximal depositional environment. The open-ocean and transition zone between open-ocean and near continental margin depositional environments are reconstructed for the upper horizons of bedded cherts and low horizons of clayey cherts. The upper horizons of clayey cherts and siliceous mudstones were accumulated at near continental margin depositional environment. [ABSTRACT FROM AUTHOR]

Abstract: The Upper Kolyma district is the most important part of the Yana–Kolyma gold province, administratively located in Magadan Oblast, Russia. To date, historic production of the region is about 90Moz of gold, mostly from placers, but with about 5% contribution from lode deposits. Two major types of gold deposits are distinguished in the region: (1) Au-quartz veins related to regionally metamorphosed rocks; and (2) granitoid-related Au. Besides gold, tin deposits are also wide-spread and can be distinguished as: (1) Sn-quartz veins, (2) Sn-silicate-sulfide veins, and (3) Sn-polymetallic veins. Quartz-molybdenite (porphyry Mo) and Ag-polymetallic (Ag-quartz) veins are less abundant. Metamorphic zones and major regional faults are the most important factors of control for the Au-quartz veins. Granitoid intrusions are the most important ore-controlling factor for other deposit types. Field relationships between Au-quartz vein, granitoid-related Au mineralization and intrusions, as well as the 40Ar/39Ar dating reveal several pulses in formation of the Upper Kolyma gold deposits. The majority of granitoid-related Au deposits and occurrences in the region are related to the oldest (150Ma) metaluminous granitoid plutons of the subduction nature. 40Ar/39Ar dates for Au-quartz mineralization in the Upper Kolyma district correspond mostly to 139–125Ma, which is a period of less intense igneous and metamorphic activity in the area. We interpret these ages to indicate vein formation by metamorphic fluids, boiling from uplift and decompression, following Early Cretaceous collision-induced metamorphism. Most Sn-quartz, Sn-silicate-sulfide, Sn-polymetallic veins, as well as Ag-polymetallic and U-REE mineralization relates to the ca. 80Ma plutons, emplaced in an extensional setting. The 40Ar/39Ar data, obtained for Au-quartz vein mineralization, were used as a basis to develop a genetic model that assumes a time interval (from 1 to 15m.y.) between the ore-mobilizing processes and the timing of ore deposition. Such an interval can be interpreted by virtue of the regional uplift and irregular drop in pressure of fluid systems as the main factors of ore deposition. Iron- and As-bearing sulfides are typical for all hardrock deposits of the Upper Kolyma district, and they reflect the event and/or remobilization of gold. Pyrite is the main sulfide in greenschist metaturbidities and igneous rocks. Metamorphism of turbidites resulted in pyrite–pyrrhotite transformations with sulfur, arsenic, and metal mobilization. Arsenopyrite assemblages, usually dominating in the ores of all deposit types of the district, are products of geochemical evolution of the above-mentioned mobilized sulfur and arsenic. The Au-quartz vein deposits are characterized by pyrite–arsenopyrite assemblage, and arsenopyrite has almost a stoichiometric composition; the granitoid-related Au- and Sn-quartz veins are characterized by lollingite–arsenopyrite assemblage and As/S>1 in arsenopyrite; the Sn silicate-sulfide and Sn-polymetallic veins are characterized by pyrite–pyrrhotite–arsenopyrite assemblage and stoichiometric arsenopyrite; the Ag-polymetallic and quartz molybdenite veins are characterized by pyrite–arsenopyrite assemblage and As/S<1 in arsenopyrite. However, some deposits do not agree with the above-mentioned criteria, which can be explained either by overprinting of several mineralization types in an individual deposit or by metamorphism of its ores. The results demonstrate high importance of re-mobilization of metals due to the later hydrothermal and thermal events. [Copyright &y& Elsevier]

This study presents new data on transgressive-regressive and accommodation-sedimentation regimes in the eastern Russian Plate during the Middle Jurassic-Lower Cretaceous. The proposed generalized scheme illustrating the combined effects of three major factors (eustasy, tectonic “noise”, and depositional gradient) controlling the deposition of sequences with different stratal architecture allowed us to quantify the parameters of sedimentation (5S) and accommodation (5A) for second- and third-order cycles. A distinctive feature of the evolution of the Middle Jurassic-Lower Cretaceous sedimentary basin is the excess of accommodation space over sediment supply, which was not conducive to creation of clinoforms. The difference between stacking patterns in individual time intervals and the estimated values of 5A/5S may be indicative of the presence of unidentified stratigraphic breaks in the Bathonian and Late Tithonian-Berriasian, which were accompanied by erosion and reworking of sand strata. The stepwise regressive-transgressive deepening during the Oxfordian-Early Tithonian and transgressive-regressive shallowing during the Late Tithonian-Berriasian were probably caused by short-term manifestations of local tectonic “noise”, and depositional hiatuses accompanied by the erosion of missing elements in the structure of third-order cycles. The Lower Cretaceous succession exhibits no mismatch between transgressive-regressive and retrogradational-progradational cycling, which provides another supporting evidence for a quiet tectonoeustatic and sedimentation regime during the Early Cretaceous compared to that of Middle-Late Jurassic time. [ABSTRACT FROM AUTHOR]

The Kuranakh deposit, one of the largest lode gold deposits in Russia, is located within the Central Aldan Ore District on the southern flank of the Siberian craton. The host rocks are flat-lying Jurassic arkose and Lower Cambrian limestone and dolomite overlying a Precambrian metamorphic basement. The hydrothermal mineralizing event is associated with Mesozoic igneous activity. In the mine area, this igneous activity is manifested by three swarms of dikes with a few small plugs and sills of bostonite, microgabbro, and minette. Gold mineralization is spatially related to the dikes, which may be both pre-ore and post-ore in age. The Kuranakh deposit is interpreted as a low-sulfidation epithermal gold deposit with quartz–adularia alteration. Several sub-horizontal, blanket- or ribbon-like orebodies, up to 50m thick, occur mainly along the karstified contact between Cambrian calcareous footwall rocks and overlaying Jurassic clastic rocks within a narrow, but very long zone of about 25km. Originally, gold mineralization was associated with pyrite, arsenopyrite, sphalerite, and galena; however, total sulfides constituted only a few percent of the total rock mass. The deposit has been thoroughly oxidized and only traces of arsenopyrite and pyrite are rarely found. Gold occurs primarily as mineral grains, less than 5μm in size, usually contained within friable grains of porous goethite. Studies of fluid inclusions show a range of homogenization temperatures from 80°C to 220°C, but generally ranging from 110°C to 160°C. The center of the heat source may have been located in the southern end of the deposit, at its transition to the gold and uranium mineralization hosted in the Precambrian basement of the Siberian craton. [ABSTRACT FROM AUTHOR]

Highlights: [•] δ13Ccarb depletion of up to 17‰ is the result of post-depositional alteration. [•] Extensive fluid circulation caused secondary calcitization of carbonate beds. [•] Among least altered samples none have extremely low (less than −5‰) δ13Ccarb values. [•] Scarcity of least-altered Zaonega carbonates highlights the need for additional study. [Copyright &y& Elsevier]

This paper shows that the location of large petroleum and gas hydrate deposits is related to deep ore-controlling fault zones. The large mercury deposits within these zones testify to the high differentiation maturity of the deep and crustal fluids. The mercury mineralization in compound ore assemblages is considered as the main indicator of their maturity (stable duration of development). The petroleum occurrences in Cenozoic sedimentary basins reflect only some partial changes in the location of hydrocarbon deposits with regard to the neotectonics and dynamics of the permafrost rocks. [ABSTRACT FROM AUTHOR]

The gas seeps in Kolyma lowland are associated with methane inclusions in permafrost. These inclusions are formed by methane squeezed by epigenetic freezing of methane saturated deposits. This is proved by the biological genesis of the methane, by the isotopic data and the lower radiocarbon age of the methane from the gas seep in comparison with the radiocarbon age of the host deposits. The experimental data and observations of methane distribution in permafrost indicate that the methane distribution in the stratum of frozen deposits is a result of methane migration during cryolithogenesis. The regularities of methane distribution in the deposits and formation of methane inclusions may change the idea of the character and volumes of emission of greenhouse gases into the atmosphere upon degradation of permafrost. [ABSTRACT FROM AUTHOR]

The article investigates the underwater landslide in the central part of the eastern slope of Sakhalin Island, in Russia and its possibility as tsunami sources. The researchers analyze the region showing closed depressions with round and slightly elongated forms in the northeasterly direction which are characteristic peculiarities of the morphology of the depression. They assess the pecularities of the sedimentary cover structure and the morphology of the depression which lead to the basis that the sedimentary formation is landslide. Moreover, the researchers take into the account the rate of sedimentation and deposition in the region against the age of the landslide and conclude that the landslide would certainly lead to a strong tsunami.

The article investigates the age of Neopleistocene sediments in the Tunka Rift Valley in southwestern Baikal Region, Russia using radiocarbon dating of large mammal fossils. It states that the method allowed age limits of key representatives of the large mammal fauna used for paleontological substantiation of Pleistocene reference sections of the Baikal region specified for southern East Siberia. It indicates that main bone-bearing sections of the Tunka rift are located in various areas including Slavin Yar, Shabartai, Elovka, Belyi Yar, Zaktui, and Bol'shoi Zangisan.

The article investigates the distribution of rare-earth elements in rocks and ores of the Kruchininskoe apatite-titanomagnetite deposit in 70 kilometer to the northeast of Chita in Transbaikalia, Russia. It states that the apatite-titanomagnetite deposit occurs in the Angashan gabbroid massif in the upper reaches of the Kruchina River. It cites ore-bearing gabbro-pyroxenitic and anorthositic as two complexes of basic rocks involved in the geological structure of the Angashan massif. It notes that rocks of the anorthositic series constitute the southern part of the gabbro-anorthosite massif

This study tests the paleomagnetic and proxy-data based Mid- to Upper Pleistocene sediment deposition history of Lake El'gygytgyn by applying different approaches of luminescence dating techniques on sediment cores taken from the centre of the 175m deep lake. For dating polymineral and quartz fine grains (4-11 µm grain size range) were extracted from nine different levels from the upper 28m of sediment cores 5011-1A and 5011-1B. According to the independent age model, the lowest sample from 27.8-27.9m below lake bottom level correlates to the Brunhes-Matuyama (B/M) reversal. Polymineral sub-samples were analysed by infra-red stimulated luminescence (IRSL) and post-IR IRSL measured at 290 °C (pIRIR290) using single aliquot regenerative dose (SAR) sequences. SAR protocols were further applied to measure the blue light optically stimulated luminescence (OSL) and thermally-transferred OSL (TT-OSL) of fine-grained quartz supplemented by a multiple aliquot approach. Neither low temperature IRSL measurements at 50 °C nor any OSL dating approach on quartz yielded reliable results. Deconvolution of their dose response curves revealed a pseudo-increase of the dose response curves and explains the observed underestimation. The pIRIR protocol applied to polymineral fine grains was the only luminescence technique able to provide dating results of acceptable accuracy up to ca. 700 ka when correlated to the existing proxydata and paleomagnetic based age record. We present the potential and limits of the different dating techniques and a correlation of pIRIR290 results with the proxy-data based age model. [ABSTRACT FROM AUTHOR]

Abstract: Results of modeling of the formation of the Vilyui sedimentary basin are presented. We combine backstripping reconstructions of sedimentation and thermal regime during the subsidence with a numerical simulation based on the deformable solid mechanics. Lithological data and stratigraphic sections were used to “strip” the sedimentary beds successively and calculate the depth of the stratigraphic units during the sedimentation. It is the first time that the evolution of sedimentation which is nonuniform over the basin area has been analyzed for the Vilyui basin. The rift origin of the basin is proven. We estimate the spatial distribution of the parameters of crustal and mantle-lithosphere extension as well as expansion due to dike intrusion. According to the reconstructions, the type of subsidence curves for the sedimentary rocks of the basin depends on the tectonic regime of sedimentation in individual basins. The backstripping analysis revealed two stages of extension (sediments 4–5 km thick) and a foreland stage (sediments >2 km thick). With the two-layered lithosphere model, we conclude that the subcrustal layer underwent predominant extension (by a factor of 1.2–2.0 vs. 1.1–1.4 in the crust). The goal of numerical experiments is to demonstrate that deep troughs can form in the continental crust under its finite extension. Unlike the oceanic rifting models, this modeling shows no complete destruction or rupture of the continental crust during the extension. The 2D numerical simulation shows the possibility of considerable basement subsidence near the central axis and explains why mafic dikes are concentrated on the basin periphery. [Copyright &y& Elsevier]

Abstract: Depositional ages for the middle part of the Neoproterozoic sedimentary succession exposed along Lake Baikal in the southern margin of the Siberian Platform have been constrained by the application of Sr isotope chemostratigraphy and Pb–Pb dating of carbonate rocks. The thick siliciclastic–carbonate Baikal Group is the type section of the regional Siberian succession. Although many of the Baikal Group carbonate rocks have undergone pervasive dolomitization by mixed meteoric-marine fluids, oolitic limestones in the 800-m-thick carbonate member of the Uluntui Formation preserve primary textures and high Sr contents (up to 3200ppm), suggesting that aragonite might have been the original precursor. The 87Sr/86Sr in the least altered high-Sr limestones (Mg/Ca<0.08 and δ 18O>−8‰ PDB) range within 0.70842–0.70876, values we interpret as representing the best proxy for coeval seawater. Stepwise dissolution using 0.5N HBr was applied to enrich samples in primary carbonate from the Uluntui Formation and nine data points from the five least altered, high-Sr limestones yielded a Pb–Pb isochron age of 560±30Ma with MSWD=0.6 and probability=0.8. This age matches that inferred from Sr isotope stratigraphy (580–550Ma) and further supports the inference that the Baikal paleobasin was connected to the contemporary oceans. Our Sr chemostratigraphy and Pb–Pb isochron age of the Uluntui limestones cast doubt on previously proposed correlations of the Baikal Group as late Mesoproterozoic to Cryogenian. Instead, the data indicate that the entire siliciclastic–carbonate succession of the Baikal Group was most likely deposited during the Ediacaran (or Vendian, of the Russian Stratigraphic Scale). [Copyright &y& Elsevier]

Lake Pernatoe is located on Paramushir Island, Kuril Arc, in the area of sand dunes. The 7-m-thick sediments of this lake pertain to the Holocene and contain palustrine, marine, and lacustrine facies. The rock magnetic properties of the sediments are analyzed for tracking the changes in sedimentation conditions. Marine facies are noted with low content of magnetic minerals; their magnetization is dominated by the paramagnetic component; pseudo-single-domain particles of magnetic material and iron sulfides (pyrite) are present. Pyrite frequently occurs in diatoms in the form of chains, spherules, and crystals. The lacustrine facies show high values of the magnetic parameters; they contain multidomain particles, mostly titanomagnetite and magnetite. Sands and sandy silts have the maximum values of magnetic parameters and reflect the stages of aeolian activity, corresponding to climatic cooling and marine regressions. On the basis of magnetic properties, four stages of active aeolian sedimentation are identified in the Holocene. [ABSTRACT FROM AUTHOR]

Lake El'gygytgyn/NE Russia holds a continuous 3.58 Ma sediment record, which is regarded as the most longlasting climate archive of the terrestrial Arctic. Based on multi-proxy geochemical, mineralogical, and granulometric analyses of surface sediment, inlet stream and bedrock samples, supplemented by statistical methods, major processes influencing the modern sedimentation in the lake were investigated. Grain-size parameters and chemical elements linked to the input of feldspars from acidic bedrock indicate a windinduced two-cell current system as major driver of sediment transport and accumulation processes in Lake El'gygytgyn. The distribution of mafic rock related elements in the sediment on the lake floor can be traced back to the input of weathering products of basaltic rocks in the catchment. Obvious similarities in the spatial variability of manganese and heavy metals indicate sorption or co-precipitation of these elements with Fe and Mn hydroxides and oxides. But the similar distribution of organic matter and clay contents might also point to a fixation to organic components and clay minerals. An enrichment of mercury in the inlet streams might be indicative of neotectonic activity around the lake. The results of this study add to the fundamental knowledge of the modern lake processes of Lake El'gygytgyn and its lakecatchment interactions, and thus, yield crucial insights for the interpretation of paleo-data from this unique archive. [ABSTRACT FROM AUTHOR]

The data on the paleotsunami manifestations on some islands of the Lesser Kuril Ridge are presented. The sedimentation features during the different-intensity tsunamis are analyzed and the timing of the most significant events and their recurrence in the middle-late Holocene were determined. [ABSTRACT FROM AUTHOR]

The Lena River Delta, which is the largest delta in the Arctic, extends over an area of 32 000 km² and likely holds more than half of the entire soil organic carbon mass stored in the seven major deltas in the northern permafrost regions. The geomorphic units of the Lena River Delta which were formed by true deltaic sedimentation processes are a Holocene river terrace and the active floodplains. Their mean soil organic carbon stocks for the upper 1m of soils were estimated at 29 kgm-2 ± 10 kgm-2 and at 14 kgm-2 ± 7 kgm-2, respectively. For the depth of 1m, the total soil organic carbon pool of the Holocene river terrace was estimated at 121 Tg± 43 Tg, and the soil organic carbon pool of the active floodplains was estimated at 120 Tg± 66 Tg. The mass of soil organic carbon stored within the observed seasonally thawed active layer was estimated at about 127 Tg assuming an average maximum active layer depth of 50 cm. The soil organic carbon mass which is stored in the perennially frozen ground below 50 cm soil depth, which is excluded from intense biogeochemical exchange with the atmosphere, was estimated at 113 Tg. The mean nitrogen (N) stocks for the upper 1m of soils were estimated at 1.2 kgm-2 ± 0.4 kgm-2 for the Holocene river terrace and at 0.9 kgm-2 ± 0.4 kgm-2 for the active floodplain levels, respectively. For the depth of 1m, the total N pool of the river terrace was estimated at 4.8 Tg± 1.5 Tg, and the total N pool of the floodplains was estimated at 7.7 Tg± 3.6 Tg. Considering the projections for deepening of the seasonally thawed active layer up to 120 cm in the Lena River Delta region within the 21st century, these large carbon and nitrogen stocks could become increasingly available for decomposition and mineralization processes. [ABSTRACT FROM AUTHOR]

Abstract: Lake Baikal is the deepest and oldest lake on Earth. Extraordinary features of the lake are manganese and iron‐enriched layers and crusts occurring at different depths within the sediment. They can be broadly subdivided into an upper accumulation at the O2/Mn(II) redox boundary and one or more layers buried within the reducing part of the sediment. The processes leading to their formation and peculiar distribution within the sediment have remained subject of debate, in particular whether the burial of vast amounts of Mn and Fe-oxides results from a steady-state process or if it is the consequence of singular events, such as changes in sedimentation rate, bottom water oxygen concentrations, or the mass accumulation rate (MAR) of organic carbon (Corg), Mn or Fe. We retrieved short cores from the South basin, the North Basin, and Academician Ridge, determined sedimentation rates, contents of Corg, Mn and Fe, and estimated pore‐water fluxes from concentration profiles of O2, NO3 −, Mn(II), Fe(II), SO4 2− and CH4. A consistent picture emerged from the data showing that the upper Fe/Mn layer formed at the lower end of the oxygen penetration depth as a dynamic pattern, moving upward with the growing sediment. Thereby, reductive dissolution of Mn(IV) occurred at the lower margin. Upward diffusing Mn(II) was oxidized with O2 forming the upper boundary of the Fe/Mn accumulation. The buried Fe/Mn layers were immobilized within the sediment and underwent slow reductive dissolution mainly driven by the anaerobic oxidation of CH4. The process leading to the detachment of the ‘active’ Fe/Mn layer from the top redox interface is not unambiguously clear. However, we suggest a cyclic pattern where the burial of a Fe/Mn layer is accompanied by the generation of a new enrichment at the O2/Mn(II) redox boundary, which is subsequently nourished by the slowly dissolving old layer. [Copyright &y& Elsevier]

Problematic arumberia-type structures are widespread in Upper Proterozoic sedimentary rocks deposited in depositional environments subject to periodic desiccation and fluctuating salinity. Here we report two new occurrences of arumberia-type structures in the Krutikha Member of the Upper Vendian Chernyi Kamen Formation on the western slope of the Central Urals (Us'va River) and the Zigan Formation of the Asha Group in the South Urals (new road Sterlitamak-Beloretsk). The results of the study of these structures significantly expand paleontological characteristics of the Upper Vendian non-marine rocks and allow us to re-examine the paleontological importance of the hastily forgotten group of arumberia-type organisms. We distinguished six varieties of arumberia-type structures that for the sake of convenience were given formal Latin names in binominal nomenclature although they are not biological species. Two species- Arumberia banski and A. vindhyanensis-were erected by previous researchers, whereas the A. beckeri, A. ollii, A. usvaensis, and A. multykensis varieties are recognized for the first time. Despite similarity to erosional structures on the bottom of turbidite beds, erosion does not explain the genesis of the entire spectrum of arumberia-type structures including those preserved on ripple marks, with evidence of soft-body deformation, or with ribbon and filamentous fabric replaced by clay minerals. The diversity of arumberia could be only a manifestation of living systems. The species of Arumberia are distinguished by their different biostratinomy, the distance between the main structural units, the preservation of the main structural units, and the presence of additional structures between the main structural units. Most likely, the diversity of arumberia reflects not only taphonomic, but also ontogenetic and phenotypic variation. The level of morphological complexity and biostratinomic features of arumberia apparently exceed the organization of microbial mats and represent a non-actualistic type of microbial communities. The occurrence in extremely shallow-water depositional setting suggests that arumberia had evolved an adaption to periodic desiccation and that arumberia-type organisms, along with microbial mats, had been an important factor of sediment biostabilization in the Late Vendian non-marine environments. [ABSTRACT FROM AUTHOR]

The combination of permafrost history and dynamics, lake level changes and the tectonical framework is considered to play a crucial role for sediment delivery to El'gygytgyn Crater Lake, NE Russian Arctic. The purpose of this study is to propose a depositional framework based on analyses of the core strata from the lake margin and historical reconstructions from various studies at the site. A sedimentological program has been conducted using frozen core samples from the 141.5m long El'gygytgyn 5011-3 permafrost well. The drill site is located in sedimentary permafrost west of the lake that partly fills the El'gygytgyn Crater. The total core sequence is interpreted as strata building up a progradational alluvial fan delta. Four macroscopically distinct sedimentary units are identified. Unit 1 (141.5-117.0 m) is comprised of ice-cemented, matrix-supported sandy gravel and intercalated sandy layers. Sandy layers represent sediments which rained out as particles in the deeper part of the water column under highly energetic conditions. Unit 2 (117.0- 24.25 m) is dominated by ice-cemented, matrix-supported sandy gravel with individual gravel layers. Most of the Unit 2 diamicton is understood to result from alluvial wash and subsequent gravitational sliding of coarse-grained (sandy gravel) material on the basin slope. Unit 3 (24.25-8.5 m) has icecemented, matrix-supported sandy gravel that is interrupted by sand beds. These sandy beds are associated with flooding events and represent near-shore sandy shoals. Unit 4 (8.5- 0.0 m) is ice-cemented, matrix-supported sandy gravel with varying ice content, mostly higher than below. It consists of slope material and creek fill deposits. The uppermost metre is the active layer (i.e. the top layer of soil with seasonal freeze and thaw) into which modern soil organic matter has been incorporated. The nature of the progradational sediment transport taking place from the western and northern crater margins may be related to the complementary occurrence of frequent turbiditic layers in the central lake basin, as is known from the lake sediment record. Slope processes such as gravitational sliding and sheet flooding occur especially during spring melt and promote mass wasting into the basin. Tectonics are inferred to have initiated the fan accumulation in the first place and possibly the off-centre displacement of the crater lake. [ABSTRACT FROM AUTHOR]

Abstract: Remains of a male woolly mammoth (Mammuthus primigenius Blumenbach, 1799), radiocarbon dated to cal. 18,370 14C BP, were discovered in perennially frozen deposits in northern West Siberia (Gydan Peninsula, 72°10′ N, 79°35′ E). Microfossil and macrofossil samples from the inner part of the mammoth intestinal content, samples of the coat and skull taken from the mammoth carcass and samples of frozen deposits enclosing the carcass were studied for the purpose of reconstructing the mammoth’s diet, season of death, and its living environments. Pollen, biomorphs and plant macrofossils indicate that grasses and sedges were the main food items, supplemented with small amounts of dwarf birch and larch twigs and a variety of herbs and mosses. The plant remains found in the intestines indicate that the animal died in the middle of summer. The mammoth lived in a cold tundra-like environment with sedge-grass and dwarf shrub communities and scattered larch stands. [Copyright &y& Elsevier]

Abstract: In 1964 and 1999, respectively in the northern Sea of Azov Region in the Kagal’nik sand pit, two almost complete skeletons of Mammuthus trogontherii were found. The finds were dated to the early Middle Pleistocene freshwater deposits. Their individual ages were defined as 40 and 47 years. The proportion differences in size and some morphological characteristics suggest that they were probably of different gender. The elephants’ features coincide with those of representatives of the species from Süssenborn and Tiraspol, which were typical for the early stage of the Tiraspol faunal complex (=Cromerian) in Eastern Europe. [Copyright &y& Elsevier]

Abstract: A volcanosedimentary complex of Middle–Late Devonian deposits in northwestern Rudny Altai is described. Analysis of sedimentologic processes, the kind of manifestation and specific composition of volcanism, and petrographic and chemical compositions of sedimentary rocks permitted reconstruction of paleogeographic and geodynamic settings, which confirmed the hypothesis of the island-arc nature of the Rudny Altai zone in the Middle–Late Devonian. Also, an alternative variant of its rift nature is considered. The rift buildings are referred to as local isolated complexes confined to positive paleovolcanic structures rising above the bottom in the fore-arc basin. The denudated part of the rift system is formed mainly by slope facies. Clastics of rift buildings, together with fragments of silicite and felsic-volcanics layers, compose widespread olistostrome breccias. We have established the humid type of lithogenesis, which, together with minor sea level fluctuations, favors karst processes and the formation of red-colored and bauxite-like rocks. The coeval volcanics composing lava flows and tuff layers are mainly rhyolites and are often of ultrafelsic composition. [Copyright &y& Elsevier]

The Ordovician stratified rocks previously referred to Riphean or Vendian are widespread in the northern part of the Baikal-Vitim fold area. They include volcanosedimentary rocks which accumulated in continental riftlike troughs after Vendian-Cambrian platform regime and were accompanied by subvolcanic bodies. The coarse-clastic facies, frequently olistostromes with olistoplaques, are abundant in the marginal parts of the troughs. The sandy-silty-clay rocks dominate in the centre. The volcanic rocks represent the contrast rhyolite-basaltic series and compose paleovolcanoes of the central type, locally, complicated by calderas. Tuffaceous material is nearly almost present in synchronous sedimentary rocks. In the Ordovician, the northern part of the Baikal-Vitim fold area was an uplift of island arc type complicated by the riftlike troughs. It occupied the central part of the Baikal-Vitim arc. The location of the troughs was subjected to its structural plan. They were formed successively after the Riphean-Vendian Baikal-Muya volcano-plutonic belt. The uplift existed within a shallow basin occupying nearly the entire Siberian Platform and Baikal-Vitim fold area. The data obtained confirm that marine sedimentary basin with islands sometimes existed within the Baikal-Vitim fold area and was a part of the basin occupying the adjacent part of the Siberian Platform. The effect of pulsating plume in the northern part of the Baikal-Vitim fold area periodically, including Ordovician, led to the origination of the uplift and to renewal of tectonic and volcano-plutonic activity. [ABSTRACT FROM AUTHOR]

The first finding of prints of the Vendian Beltanelloides sorichevae Sokolov 1965 in the lower part of the Barakun Formation confirms the Vendian age of the Far Taiga Group, Patom Complex. This finding also raises a problem concerning the lower propagation limit of Beltanelloides sorichevae. [ABSTRACT FROM AUTHOR]