Northern West Siberia Research Articles

Sequence Stratigraphy of the Jurassic Strata and Occurrences of Potential Sandstone Reservoirs in the ST Gas Field, Northern West Siberia Basin

Jurassic strata in the ST gas field of the northern West Siberia Basin have been regarded as a potential exploration target with undiscovered hydrocarbon resources. However limited research has been performed on the sequence stratigraphy of the Jurassic strata, as well as its sandstone distribution controlled by variable sea level change and sediment input. In this paper, four third-order sequences (SQ1, SQ2, SQ3, and SQ4) and nine fourth-order sequences for the Jurassic strata are interpreted based on seismic facies analysis and the lithology stacking patterns of seven wells. SQ1 is characterized by the special Bazhenov Formation which is featured by regionally distributed deep marine shales. SQ2 (J1) is composed of a coarsening upward sequence, the base of which is an unconformable surface that can be recognizable in both seismic profiles and well logging data. SQ3 (J2-J8) is composed of a complete fining-upward and coarsening-upward sequence, showing a series of transgressive and regressive successions. A complete SQ4 has not been drilled through by all the seven wells, only showing a coarsening upward succession on its top (J9) which evolves into a fining upward succession at the base of SQ3. Combined with the seismic inversion result, which predicts sandstone distribution, a sequence evolution model was built for SQ3 showing a full unit of transgressive system tract and highstand system tract (TST-HST) which often occurs in shallow marine shelves. During sequence development, most reservoir sandstones are deposited in the shelf and tidal delta environment at the bottom of the TST and the top of HST, and mudstones are deposited as shelf mudstones, especially at maximum flooding surface. That is controlled by both accommodation and sediment input. Generally, under this sequence framework, the depositional architecture can be further analyzed with implications for source rock, reservoir sandstones, and sealing rock, which may guide future gas exploration and exploitation in this area.

What caused the unseasonal extreme dust storm in Uzbekistan during November 2021?

An unseasonal dust storm hit large parts of Central Asia on 4–5 November 2021, setting records for the column aerosol burden and fine particulate concentration in Tashkent, Uzbekistan. The dust event originated from an agropastoral region in southern Kazakhstan, where the soil erodibility was enhanced by a prolonged agricultural drought resulting from La Niña-related precipitation deficit and persistent high atmospheric evaporative demand. The dust outbreak was triggered by sustained postfrontal northerly winds during an extreme cold air outbreak. The cold air and dust outbreaks were preceded by a chain of processes consisting of recurrent synoptic-scale transient Rossby wave packets over the North Pacific and North Atlantic, upper-level wave breaking and blocking over Greenland, followed by high-latitude blocking over Northern Europe and West Siberia, and the equatorward shift of a tropopause polar vortex and cold pool into southern Kazakhstan. Our study suggests that the historic dust storm in Uzbekistan was a compound weather event driven by cold extreme, high winds, and drought precondition.

Thermal Conductivity Variations in Frozen Hydrate-Bearing Sand upon Heating and Dissociation of Pore Gas Hydrate

High-latitude permafrost, including hydrate-bearing frozen ground, changes its properties in response to natural climate change and to impacts from petroleum production. Of special interest is the behavior of thermal conductivity, one of the key parameters that control the thermal processes in permafrost containing gas hydrate accumulations. Thermal conductivity variations under pressure and temperature changes were studied in the laboratory through physical modeling using sand sampled from gas-bearing permafrost of the Yamal Peninsula (northern West Siberia, Russia). When gas pressure drops to below equilibrium at a constant negative temperature (about −6 °C), the thermal conductivity of the samples first becomes a few percent to 10% lower as a result of cracking and then increases as pore gas hydrate dissociates and converts to water and then to ice. The range of thermal conductivity variations has several controls: pore gas pressure, hydrate saturation, rate of hydrate dissociation, and amount of additionally formed pore ice. In general, hydrate dissociation can cause up to 20% thermal conductivity decrease in frozen hydrate-bearing sand. As the samples are heated to positive temperatures, their thermal conductivity decreases by a magnitude depending on residual contents of pore gas hydrate and ice: the decrease reaches ~30% at 20–40% hydrate saturation. The thermal conductivity decrease in hydrate-free saline frozen sand is proportional to the salinity and can become ~40% lower at a salinity of 0.14%. The behavior of thermal conductivity in frozen hydrate-bearing sediments under a pressure drop below the equilibrium and a temperature increase to above 0 °C is explained in a model of pore space changes based on the experimental results.

Holocene permafrost peatland evolution in drained lake basins on the Pur-Taz Interfluve, North-Western Siberia

The permafrost properties and cryostructure of Holocene peatlands and underlying the Pre-Holocene deposits within Pur-Taz interfluve in the Northern West Siberia were studied. The cryolithological description, particle size, botanical compositions based on plant macro-fossils, and radiocarbon age from 8500 ± 240 cal BC to 1810 ± 150 cal AD were defined. The polygonal peatlands were formed in lacustrine-bog basins. The “arboreal” horizon at the bottom of the peat, which is characteristic of Northern West Siberia, was identified. This “arboreal” horizon dates to the Boreal and Atlantic periods of the Holocene – 8500 ± 240 cal BC and 7390 ± 210 cal BC, which explains the occurrence of forest tundra in the area of typical modern tundra during the Holocene Climatic Optimum. The vegetation composition of peat-forming plants, the ash content, and the decomposition degree of organic matter were controlled by changing natural conditions and dynamics of peat accumulation during the Holocene: flooding and burial of woody vegetation, overgrowing and eutrophication of water bodies, the gradual accumulation of peat and syngenetic ice-wedge polygon formation, peat accumulation slowing caused by drainage of drained lake basin surface. Organic frost boils on the peatland surface indicate modern deepening of the permafrost Table and are related to an increase of the microorganism activity in the thawed, poorly decomposed peat. The peat accumulation rate was about 1 mm per year. A 2-m peat layer containing ground ice has accumulated over 2500 years.The purpose of the present work is study of the history of the vegetation on the northern limits of treeline. Examination of the peat, macrofossil, decomposition degree, and ash content history of a peat sections on the Pur-Taz Interfluve in North-Western Siberia, provides a long-term view of vegetation dynamics, peatland change, and climate history during the Holocene at the Arctic treeline.

Imaging Arctic Permafrost: Modeling for Choice of Geophysical Methods

Knowledge of permafrost structure, with accumulations of free natural gas and gas hydrates, is indispensable for coping with spontaneous gas emission and other problems related to exploration and production drilling in Arctic petroleum provinces. The existing geophysical methods have different potentialities for imaging the permafrost base and geometry, vertical fluid conduits (permeable zones), taliks, gas pockets, and gas hydrate accumulations in the continental Arctic areas. The synthesis of data on cryological and geological conditions was the basis for a geophysical–geological model of northern West Siberia to a depth of 400 m, which includes modern permafrost, lenses of relict permafrost with hypothetical gas hydrates, and a permeable zone that may be a path for the migration of gas–water fluids. The model was used to model synthetic seismic, electrical resistivity tomography (ERT), and transient electromagnetic (TEM) data, thus testing the advantages and drawbacks of the three methods. Electrical resistivity tomography has insufficient penetration to resolve all features and can run only in the summer season. Seismic surveys have limitations in mapping fluid conduits, though they can image a horizontally layered structure in any season. Shallow transient electromagnetic (sTEM) soundings can image any type of features included into the geological model and work all year round. Thus, the best strategy is to use TEM surveys as the main method, combined with seismic and ERT data. Each specific method is chosen proceeding from economic viability and feasibility in the specific physiographic conditions of mountain and river systems.

Effect of structural features of sedimentary cover on gas composition of permafrost table in northern West Siberia

Here, we analyzed geochemical indices of gases from core samples of permafrost table and evaluated data acquired from electric survey at the field of the Nadym-Pursk petroleum-bearing region. The Nadym-Pursk region is located in the northern West Siberia that is presently the major object of raw hydrocarbon (HC) exploration. The geologic exploration practice has demonstrated that the seismic survey efficiency is notably influenced by heterogeneous rocks of permafrost table, especially within permafrost distribution zones. The exploration efficiency for oil and gas can be enhanced using data from surface geochemical surveys that rely on vertical HC migration from deposits. The adequate interpretation of both seismic and geochemical survey data requires insights on the structure of permafrost table and on processes occurring therein. This study aimed to explore if geologic structural features of the territory affect the composition of gases dispersed in the permafrost table and identify the role of non-geological factors. The gas compositional features of the permafrost table were associated with HC migration channels, frost mounds, and probable gas hydrates within the permafrost distribution zone. The distribution of deep (He and H2) and catagenic (light methane homologues) gases stems from tectonic activity. This conclusion was made from the isotopic assay of samples from several holes, from the correlation between methane and homologues, from the presence of migration channels as per electric survey data, and essentially from the presence of deep gases. The enhanced content of methane is due to its active migration from both diagenetic zone (biogenic methane) and Cenomanian gas pay zones, which along with the respective geotemperature regime of subpermafrost strata is a favorable factor for gas hydrate generation. The natural connections between data from frost mounds point to their distinct genesis: the compositional genesis of gases is influenced by deep degassing and gas accumulation from diagenetic zones.

Changes in Unfrozen Water Contents in Warming Permafrost Soils

Climate warming in the Arctic, accompanied by changes in permafrost soil properties (mechanical, thermal, filtration, geophysical), is due to increasing unfrozen pore water content. The liquid component in frozen soils is an issue of key importance for permafrost engineering that has been extensively studied since the beginning of the 20th century. We suggest a synthesis and new classification of various experimental and calculation methods for the determination of unfrozen water content. Special focus is placed on the method of applying measurements to the water potential, which reveals the impact of permafrost warming on unfrozen water content. This method was applied to natural soil samples collected from shallow permafrost from northern West Siberia affected by climate change, and confirms the revealed trends. The obtained results confirm that unfrozen water content is sensitive not only temperature but also particle size distribution, salinity, and the organic matter content of permafrost soils.

The Structure of Permafrost in Northern West Siberia: Geophysical Evidence

The permafrost of Arctic West Siberia stores extremely rich resources of hydrocarbon fuels that remain a key energy source and an important element of the global economy. A large amount of natural gas in permafrost is bound in gas hydrates which may become an alternative fuel of the future. Shallow subsurface in the permafrost area of northern West Siberia has been studied by transient electromagnetic (TEM) soundings to estimate the permafrost thickness and to detect faults as channels for fluids and heaving features as possible indicators of gas hydrate accumulations. The shallow transient electromagnetic (sTEM) surveys were conducted in discontinuous and continuous permafrost at two sites in northern West Siberia (the northeastern Yamal Peninsula and the southern Gydan Peninsula), with a focus on the vicinities of lakes and cryogenic landforms (frost mounds). The sTEM method resolves well the heterogeneous permafrost structure, with faults, numerous unfrozen zones (taliks), and frost mounds marked by resistivity and seismic anomalies. Some lakes are located above faults, and their origin may be related to deformation, whereas the frost mounds may mark deep-seated fluid dynamic processes. Local thickening of permafrost may be associated with the presence of gas hydrates. The detected features may trace gas migration pathways and reveal possible sites of gas emission.

Equilibrium modeling of water-gas systems in Jurassic–Cretaceous reservoirs of the Arctic petroleum province, northern West Siberia

To reveal the equilibrium state of oil and gas and water in a petroliferous basin with a high content of saline water, calculations of water-gas equilibrium were carried out, using a new simulation method, for the Arctic territories of the West Siberian oil and gas bearing province. The water-bearing layers in this area vary widely in gas saturation and have gas saturation coefficients (Cs) from 0.2 to 1.0. The gas saturation coefficient increases with depth and total gas saturation of the formation water. All the water layers with gas saturation bigger than 1.8 L/L have the critical gas saturation coefficient value of 1.0, which creates favorable conditions for the accumulation of hydrocarbons; and unsaturated formation water can dissolve gas in the existent pool. The gas saturation coefficient of formation water is related to the type of fluid in the reservoir. Condensate gas fields have gas saturation coefficients from 0.8 to 1.0, while oil reservoirs have lower gas saturation coefficient. Complex gas-water exchange patterns indicate that gas in the Jurassic–Cretaceous reservoirs of the study area is complex in origin.

Isotopic composition of heterogeneous ice wedges in peatlands of the Pur‐Taz interfluve (northern West Siberia)

AbstractHeterogeneous ice wedges were studied within the peatland of the drained lake on the Pur‐Taz interfluve (67°20′14.8″, 078°55′47.1″, Northwest Siberia). The elements of the ice‐wedge structure were identified: young ice wedge, shoulders, selvages, closed‐cavity ices, and ice lenses in a peatland. Different genetic types of ice (ice vein, congelation ice, and segregated ice) were revealed by analyzing the elements of the ice‐wedge structure under polarized light and analyzing their chemical compositions. Genetic types of the ice indicate the different mechanisms of ice‐wedge formation. The ice vein forms due to fast bilateral freezing of primarily meltwater in a thermal contraction crack. The congelation ice forms due to the slow freezing of free water that has accumulated into a thermokarst cavity. The segregated ice forms due to pore water migration to the freezing zone. The elements of the ice‐wedge structure have variable stable isotope values (δ18O from −13.5‰ to −21.9‰ and δD from −87.7‰ to −154.6‰). The high range of deuterium excess values (13.8‰ to 32‰) indicates fractionation at condensation. The mean winter paleotemperature calculated using Vasil’chuk’s equations for the ice‐wedge pats formed by the ice veins varied in the range of −18 to −22°C, which is not very different from current values and is consistent with the isotopic data of ice wedges from nearby regions of Northwest Siberia. The paleotemperature average error can equal 4.5°C if we ignore the data on the ice petrographic analysis. The error depends on where and how the ice wedges are sampled, because of varying genetic types within the ground ice. This could lead to different palaeoclimatological interpretations.

Yugra State University Biological Collection (Khanty-Mansiysk, Russia): general and digitisation overview.

BackgroundThe history of biological collections and digitisation initiatives in northern West Siberia is relatively new due to recent development of the region. The Center for Biodiversity Data Mobilization was established to promote the initiative, led by the Yugra State University. This organisation itself has a relatively young collection of biological specimens, which was, until recently, in a disintegrated state and only partly mobilised. The Yugra State University Biological Collection (YSU BC) currently includes three subdivisions differring by history and taxonomic groups, but also by details of management and storage conditions: the Fungarium, the Bryological collection and the Herbarium collection of YSU.The paper describes the general structure of the Yugra State University Biological Collection, its history, storage conditions, management practices, geographical, temporal and taxonomical coverage. The paper is underlined by three datasets of the collections databases published in GBIF, which are described in detail. The databases are managed in Specify 6 and 7 software and accessed through Specify Web Portal and through GBIF.New informationThe Yugra State University Biological Collection made an active reorganisation of physical storage conditions and data management recently, providing the model for other collections in the region. This paper describes the history, general structure, management practices and data management of all three parts of this collection for the first time.Although one part of the collection (Fungarium YSU) was mobilised earlier, last year, we mobilised data of the Bryological and Vascular plants (Herbarium) collections. The three datasets of the corresponding collections in GBIF were increased by about 6000 georeferenced records during the last year.

Dipole pattern of summer ozone pollution in the east of China and its connection with climate variability

Abstract. Surface O3 pollution has become one of the most severe air pollution problems in China, which makes it of practical importance to understand O3 variability. A south–north dipole pattern of summer-mean O3 concentration in the east of China (DP-O3), which was centered in North China (NC) and the Pearl River Delta (PRD), has been identified from the simulation of a global 3-D chemical transport model for the period 1980–2019. Large-scale anticyclonic (cyclonic) and cyclonic (anticyclonic) anomalies over NC and the PRD resulted in a sharp contrast of meteorological conditions between the above two regions. The enhanced (restrained) photochemistry in NC and restrained (enhanced) O3 production in the PRD contributed to the DP-O3. Decreased sea ice anomalies near Franz Josef Land and associated warm sea surface in May enhanced the Rossby wave source over northern Europe and West Siberia, which eventually induced an anomalous Eurasia-like pattern to influence the formation of the DP-O3. The thermodynamic signals of the southern Indian Ocean dipole were stored in the subsurface and influenced the spatial pattern of O3 pollution in the east of China mainly through the Hadley circulation. The physical mechanisms behind the modulation of the atmospheric circulations and related DP-O3 by these two climate anomalies at different latitudes were evidently verified by large-scale ensemble simulations of the Earth system model.

Major-Ion Chemistry and Quality of Water in Rivers of Northern West Siberia

This study reports a synthesis of years-long hydrogeochemical monitoring in northern West Siberia, performed by the Russian Meteorological Service (Rosgidromet) and several academic institutions. Natural factors and intensive human economic activity lead to the disruption of the ecosystems of the northern territories of Western Siberia. The aim of this study is to estimate the background water chemistry parameters in the rivers of northern West Siberia in the beginning of the 21st century. The mean values hydrochemical and geochemical indicators were determined with STATISTICA software, which can be used as background values in assessing the actual and allowable anthropogenic impact on water bodies. We revealed four water chemistry provinces: western Ob Gulf and Ob estuary catchments (I); eastern Ob Gulf and Taz Gulf catchments, except for the Taz River and its tributaries (II); Taz River catchments (III); Yenisei River catchments, right bank (IV). The major-ion chemistry of the sampled river waters records a combination of geological, geomorphological, and hydrological conditions in the four provinces. The features typical of the northern West Siberian Plain are especially prominent in province II, which has the lowest average total of major ions (Σmi), the highest chemical oxygen demand (potassium dichromate COD), and the highest contents of Fe and phosphates. The Σmi value is the highest in province IV. The river waters from four provinces share similarity in quite high organic contents (both potassium dichromate and permanganate COD), as well as high NH4+ and Fe. The long-term average Σmi of the waters is predicted not to change much in the coming one or two decades, though it may decrease slightly in the winter season but increase in the fall and spring time.

Formation of Gas-Emission Craters in Northern West Siberia: Shallow Controls

Gas-emission craters discovered in northern West Siberia may arise under a specific combination of shallow and deep-seated permafrost conditions. A formation model for such craters is suggested based on cryological and geological data from the Yamal Peninsula, where shallow permafrost encloses thick ground ice and lenses of intra- and subpermafrost saline cold water (cryopegs). Additionally, the permafrost in the area is highly saturated with gas and stores large accumulations of hydrocarbons that release gas-water fluids rising to the surface through faulted and fractured crusts. Gas emission craters in the Arctic can form in the presence of gas-filled cavities in ground ice caused by climate warming, rich sources of gas that can migrate and accumulate under pressure in the cavities, intrapermafrost gas-water fluids that circulate more rapidly in degrading permafrost, or weak permafrost caps over gas pools.

ЭКОЛОГИЧЕСКИЙ ФОН ИННОВАЦИЙ РАННЕГО НЕОЛИТА СЕВЕРА ЗАПАДНОЙ СИБИРИ

In the mid-7th — early 6th millennium BC at the Mesolithic–Neolithic transition, a number of innovations appeared in the lifeways of people in the West Siberian taiga, including the first appearance of pottery (the defining criterion for the onset of the Neolithic), the intensification of the subsistence economy with an increasing role of aquatic resources, and the transition to a less mobile lifestyle. These innovations were reflected in the construction of long-term open and few fortified settlements, including circular layouts and the construction of ritual mounds (kholmy). These improvements attest to significant changes in subsistence economy as well as worldviews of the hunter-fisher-gatherers of the taiga zone of West Siberia. The emergence of these innovations chronologically coincides with the most prominent global climatic cooling event of the Holocene, which took place around 6.2 thousand years cal BC (the so-called 8.2 ka BP event) and had a substantial impact on the ancient societies of Europe and Southwest Asia. To reconstruct the paleoclimate of northern West Siberia, the most informative source to date are peatbogs, which contain, as a rule, complete sedimentation sequences of all Holocene periods, allowing a greater degree of reliability in using scientific methods in paleogeographical reconstructions. This article reviews current evidence on features and age of the peat formation process and additional information on the Early Holocene paleoclimatic developments in northern West Siberia. The preliminary data indicate that favourable climatic conditions led to balanced and probably abundant environmental resources in the early Atlantic period. At the same time, the sparsely populated territory might have seen the arrival of new population groups into the region, which might have introduced or triggered a number of socio-economic innovations such as the construction of fortified settlements with complex layouts and the tradition of clay pottery manufacture.

The penultimate interglaciation of northern Russia

This paper presents new field and laboratory data combined with previously published materials on interglacial sediments underlying two upper tills of northern European Russia and West Siberia. The emphasis is on the structure and chronometric data of marine strata with shells of boreal molluscs of Cyrtodaria genus indicative of the Atlantic marine invasion into these sedimentary basins during the late Middle Pleistocene. Another line of evidence for this time span is inferred from inter-till terrestrial sequences in the European Northeast with forest pollen spectra suggesting a climate much warmer than today. The decisive correlation signal is provided by optically stimulated luminescence and electron-spin resonance dates, indicating MIS 7 time, and by the geological position of two interglacial formations between the first, second and third from the surface glacial complexes. The collected evidence disagrees with the model of the unique boreal transgression and confirms that saline Atlantic water at least twice invaded northern Russia during the last 250 kyears. The sedimentary formations of the penultimate interglaciation can serve as a new intra-regional stratigraphic marker for the northern Pleistocene.

Radiometric normalization of Landsat thermal imagery for detection of tundra land cover changes: experience from West Siberia

ABSTRACT The potentiality and specificity of using multitemporal stacks of thermal infrared (TIR) satellite scenes for modelling changes in tundra land cover and predicting geohazards in areas under development are studied using the example of two areas in northern West Siberia. The study aims at developing and testing a method for relative radiometric normalization of Land Remote-Sensing Satellite (Landsat) TIR images applied to estimate changes in land surface temperature (LST) in the tundra with regard to the high-latitude climate conditions. The suggested normalization method (RNUC) differs from other similar approaches in the use of unsupervised classification to determine pseudo-invariant features where master and slave images are spectrally identical. The error in LST contrasts is minimized iteratively by choosing the optimal number of land-cover classes and linear regression coefficients by cross-validation. The normalization procedure ensures error reduction by a factor of two to four, which is evidence of its high performance. The results of processing and analysis of 19 pairs of Landsat thermal images at the sites of the Marre-Sale and Urengoy oil and gas-condensate fields using the RNUC method showed that the relative error of LST contrast normalization could be in the range of approximately 3% to 10%. Based on the time series of normalized values of LST and the normalized difference vegetation index (NDVI) of sites with pyrogenic damage in the area of the Urengoy oil and gas-condensate field, it is shown that the process of stabilization of the tundra cover is characterized by a negative correlation of these parameters and lasts 25 to 28 years. A positive correlation between LST and NDVI characterizes a different type of landscape transformation; in particular, it may be an increase in the thickness of secondary vegetation cover or a change in the hydrological conditions.

A multiproxy record of sedimentation, pedogenesis, and environmental history in the north of West Siberia during the late Pleistocene based on the Belaya Gora section

AbstractRecent revision of the Pleistocene glaciation boundaries in northern Eurasia has encouraged the search for nonglacial geological records of the environmental history of northern West Siberia. We studied an alluvial paleosol-sedimentary sequence of the high terrace of the Vakh River (middle Ob basin) to extract the indicators of environmental change since Marine Oxygen Isotope Stage (MIS) 6. Two levels of the buried paleosols are attributed to MIS 5 and MIS 3, as evidenced by U/Th and radiocarbon dates. Palynological and pedogenetic characteristics of the lower pedocomplex recorded the climate fluctuations during MIS 5, from thePicea-Larixtaiga environment during MIS 5e to the establishment of the tundra-steppe environment due to the cooling of MIS 5d or MIS 5b and partial recovery of boreal forests withPiceaandPinusin MIS 5c or MIS 5a. The upper paleosol level shows signs of cryogenic hydromorphic pedogenesis corresponding to the tundra landscape, with permafrost during MIS 3. Boulders incorporated in a laminated alluvial deposit between the paleosols are dropstones brought from the Enisei valley by ice rafting during the cold MIS 4. An abundance of eolian morphostructures on quartz grains from the sediments that overly the upper paleosol suggests a cold, dry, and windy environment during the MIS 2 cryochron.

Fungal literature records database of the Northern West Siberia (Russia).

BackgroundMycological research in the Northern part of West Siberia has now become sufficient for review and digitisation as over 460 scientific works have been completed mainly since the beginning of the 20th century. The history of research in the region started from isolated studies at the beginning of the 20th century, but regular and systematic research started from the 1970s. Over the following decades, several dozens of researchers have worked in the area, but the reported occurrences were scattered amongst a broad variety of publications, mainly hardly available. The great need in digitisation and accumulation of fungal records reported in published literature in a standardised regional database has now become evident. The «Fungal records database of the Northern West Siberia» (FuNWS) was initiated in 2016 according to contemporary biodiversity data standards (Darwin Core), to be compatible and accessible by the broad research community. The database has been supplemented ever since by the collective effort of specialists working in the area. According to the database summary report, there are 3358 fungal and fungus-like species revealed in the Northern West Siberia at present. The richest in species number classes are Agaricomycetes (60%) and Lecanoromycetes (33%) with a total of 25 classes represented. The FuNWS database was uploaded to Global Biodiversity Information Facility (GBIF) (Ygra State University Biological Collection publisher) on 11 November 2017 (earlier titled «Fungal Records Database of Yugra, FReDY») to provide open access to the data and its reusability (Filippova et al. 2020).New informationThis publication summarises the results of the digitisation of literature-based occurrence records of fungi and fungus-like organisms initiated in the Northern part of West Siberia for the first time in the history of mycological research. The bibliography of regional mycological publications was created to include about 460 published works (Suppl. material 2). In total, about 140 literature sources were digitised and about 22000 occurrence records were integrated into the FuNWS database (Filippova et al. 2020).

The freshwater reservoir effect in northern West Siberia: 14C and stable isotope data for fish from the late medieval town of Mangazeya

Abstract The freshwater reservoir effect (FRE) was estimated for the northern part of West Siberia for the first time, based on securely dated samples from the late medieval town of Mangazeya existed mainly in AD 1601–1650. Twelve specimens of six species of freshwater fish were selected for 14C dating, and C and N stable isotopes analysis. The FRE varies from ca. 310 to ca. 1970 14C years, and there is no consistency in terms of relationship to feeding habits or trophic level of fish; the FRE fluctuations for Mangazeya, as well as for other regions in northern Eurasia, are noteworthy. This information should be taken into account when 14C dating of bones of humans and domestic animals, who consume significant amount of freshwater fish, is conducted. This also applies to 14C dating of food crusts on the surface of pottery.