Northern West Siberia Research Articles

Adaptive Approach in Maize Breeding for the Urals Region

Middle and Southern Urals’ maize growing area is characterised by a wide range of edaphoclimatic conditions and by a variety of factors which may limit growth and development of maize. The factors may vary from severe warmth shortage in the North of the region to sharp aridity in the South. Consequently, fast-ripening maize breeding is dictated by limited heat resources. Depending on the growing area and the purpose of the crops (silage or corn), hybrids adapted for the regions must be characterised within the limits of 110 and 170 according to FAO classification. The purpose of the research is to measure ultra-early maize hybrids’ adaptability within forest-meadow and forest steppe zones of the Middle and the South Urals on maize’s growth stability and ripening, crop productivity and grain moisture at harvest. During the period from 1999 to 2019 experimental hybrid combinations and FAO 100-120 type industrial hybrids were assessed. These hybrids were created with the use of a local maize variety of Northern Caucasia, West Siberia and foothill areas of the Republic of Altay as a source material. Local maize varieties of Northern Caucasia, West Siberia and foothill areas of the Republic of Altay were used as initial material to create these hybrids. As a result of these three research phases early blossom maize varieties’ competitive advantages were discovered. These varieties’ grain formation and grain filling last within a favourable temperature background and have their biological ripeness before diurnal temperature achieves biological minimum required for maize growth. This advantage ensures minimum grain moisture at harvest and maximum genetic potentiality’s productivity implementation thanks to grain filling of full value. This advantage also assures high starch content and highly digestible energy concentration in dry matter. It has been established that ultra-early hybrids’ cultivation is the main condition to obtain high energy fodder in northern areas of the Urals despite of minor gross productivity loss. Commercial maize hybrids F1 Koubanskii 101 SV and Koubanskii 102 MV pass development stages from sprouts to ear corn blossom within the limits of 44 to 58 days depending on the vegetation period conditions. These hybrids’ cultivation in forest-steppe areas is of importance to produce dried and canned corn. Forest-meadow cultivation is of importance to obtain high grain canned products and high energy silage

Conceptual Models of Gas Accumulation in the Shallow Permafrost of Northern West Siberia and Conditions for Explosive Gas Emissions

Gas accumulation and pressurized unfrozen rocks under lakes (sublake taliks) subject to freezing in shallow permafrost may lead to explosive gas emissions and the formation of craters. Gas inputs into taliks may have several sources: microbially-mediated recycling of organic matter, dissociation of intrapermafrost gas hydrates, and migration of subpermafrost and deep gases through permeable zones in a deformed crust. The cryogenic concentration of gas increases the pore pressure in the freezing gas-saturated talik. The gradual pressure buildup within the confined talik causes creep (ductile) deformation of the overlying permafrost and produces a mound on the surface. As the pore pressure in the freezing talik surpasses the permafrost strength, the gas-water-soil mixture of the talik erupts explosively and a crater forms where the mound was. The critical pressure in the confined gas-saturated talik (2–2.5 MPa for methane) corresponds to the onset of gas hydrate formation. The conditions of gas accumulation and excess pressure in freezing closed taliks in shallow permafrost, which may be responsible for explosive gas emissions and the formation of craters, are described by several models.

A Gas-Emission Crater in the Erkuta River Valley, Yamal Peninsula: Characteristics and Potential Formation Model

Methane is a powerful greenhouse gas, and the abrupt degassing events that recently have formed large craters on the Russian Arctic Yamal and Gydan Peninsulas have caused major concern. Here we present field data on cover sediments and evolution of a gas-emission crater discovered in the Erkuta–Yakha River valley in the southern Yamal Peninsula in June 2017. The crater is located south of other similar craters discovered over the past decade in northern West Siberia. Data were collected during a field trip to the Erkuta crater in December 2017 which included field observations and sampling of permafrost soil and ground ice from the rim of the crater. All soil and ice samples were measured for contents of methane and its homologs (ethane and propane) and carbon dioxide. The contents of carbon dioxide in some samples are notably higher than methane. The strongly negative δ13С of methane from ground ice samples (−72‰) is typical of biogenic hydrocarbons. The ratio of methane to the total amount of its homologs indicate a component of gases that have migrated from a deeper, thermogenic source. Based on obtained results, a potential formation model for Erkuta gas-emission crater is proposed, which considers the combined effect of deep-seated (deep gas migration) and shallow (oxbow lake evolution and closed talik freezing) causes. This model includes several stages from geological prerequisites to the lake formation.

Analysis of Water–Gas System Equilibria in Jurassic–Cretaceous Reservoirs (by the Example of the Yamal-Kara Depression)

Abstract —The paper presents results of the pioneering study of equilibria in the water–gas system by the example of Jurassic–Cretaceous deposits of the Yamal–Kara depression located within northern West Siberia and its Arctic regions. Numerical modeling of physicochemical equilibria and evasion–invasion processes in the water–gas system allowed determination of the degree of groundwater saturation with gases and the nature of diffusive redistribution of gases in the media that form at the hydrocarbon deposit–groundwater contact. According to the degree of water saturation with gases (Kg), aquifers with poorly (<0.2) to ultimately (0.8–1.0) gas-saturated waters have been established. The revealed increase in the degree of groundwater saturation with gases in sinking producing reservoirs reflects its dependence on their total gas saturation. All waters with a total gas saturation of more than 1.8 L/L become ultimately saturated with gases (Kg = 1.0), thus theoretically predetermining the formation of hydrocarbon accumulations. Major gas condensate deposits are confined to the zone of gas-saturated waters with Kg from 0.8 to 1.0, while oil accumulations, to waters with lower gas saturation. Based on the established nature of water–gas, we can argue that oil and gas accumulations in Jurassic–Cretaceous reservoirs act as a conservative element of the lithosphere, i.e., its geologic and geochemical “relics”. The surrounding subsurface waters, as a more active constituent of the system, have largely anticipated its geochemical development, which is manifested in the differentiation of the fugacity ratios of individual gases in groundwater and hydrocarbon accumulations. The composition of the latter is therefore subjected to slow directional changes while the equilibrium is established, to usher in the qualitatively new state of the geochemical water–gas system.

Morphological development, distribution and ecology of the arctic oribatid mite Hermannia scabra (Acari: Oribatida: Hermanniidae) and synonymy of Hermannia gigantea.

The topotypes (adult and juvenile instars) of the arctic oribatid mite Hermannia scabra (L. Koch, 1879) (Oribatida, Hermanniidae) from Vaygach Island (easternmost arctic Europe) were investigated and compared with those of Hermannia gigantea Sitnikova, 1975 collected from southwest Taymyr Peninsula, northern Middle Siberia, resulting in the following new taxonomic proposal: Hermannia scabra (L. Koch, 1879) (= Hermannia gigantea Sitnikova, 1975, syn. nov.). The morphology of its all instars is described and illustrated in detail on the base of specimens collected from the northern West Siberia (Shokalsky Island). The main morphological traits are summarized. Two northern species of Hermannia with granulate notogaster, namely H. scabra and H. nodosa Michael, 1988, were regularly mixed up in the literature. Their differential diagnosis is provided after elaboration of spacious materials. The morphological differences of juvenile instars of five species of Hermannia (H. gibba (C.L. Koch, 1839), H. jesti Travé, 1977, H. nodosa, H. reticulata Thörell, 1871, and H. scabra) are given. The biotopic preferences of arctic members of Hermannia are briefly observed.

Formation of the Yamal Crater in Northern West Siberia: Evidence from Geochemistry

In the framework of this work, studies on the Yamal crater formed as a result of a cryogenic eruption of a water-gas fluid were carried out. The structure and variations of the composition of the geochemical field along the section of the upper horizons of permafrost are considered on the basis of field work, including the drilling of boreholes near the crater. The obtained regularities of the distribution of chemical elements, and gases between the mineral component of the soil and meltwater, suggest that permafrost at the site of the funnel are the remains of a sub-lake paleo-talik, from which mineralized water and gases were expulsed into the yet unfrozen reservoir that previously existed at this place. The component composition of gases suggests that they are products of biochemical processes similar to those that occur in modern peatlands. The δ13C value for methane extracted from the sediments of the near-contact zone of the Yamal crater was found to be −76‰. The predominance of high molecular weight normal alkanes in frozen bitumen indicates that the original organic substrate which was buried contained remains of higher vegetation. The Yamal funnel was formed by the sediment’s “explosion” while the water-gas fluid was released. The volume of the ejected sediment amounted to about 220 thousand m3.

Influence of snow cover on soil temperatures: Meso- and micro-scale topographic effects (a case study from the northern West Siberia discontinuous permafrost zone)

Snow cover distribution has a profound impact on ground temperature, on thickness of the active layer, and on permafrost. The purpose of this study was to evaluate the effects of snow cover on soil thermal regimes in West Siberia and to characterize the meso- and micro-scale spatial variation of winter ground surface temperature (GST). Maximum snow cover thickness (>80 cm) and duration (~8 months) were recorded for the lower elevation areas and in the forest site (using a vertical array of iButtons). Shallow snow cover and a late snow formation characterized open raised areas with shallow permafrost. Our results indicate that 20 cm snow cover thickness is the minimum for generating a significant insulating effect. Date of snow cover formation with thickness >20 cm had the strongest influence on soil temperature regimes. We found a significant negative correlation between winter GST and elevation. This relationship is indirectly controlled by snow cover redistribution. We additionally have shown that elevation, n-factor and winter GST are the variables most significantly affecting thaw depth in permafrost-affected soils. This research dictates the need for taking into account snowfall, and its redistribution due to the variability of local factors, in predicting the effects of climate change on soil temperatures and active layer depth. According to long-term meteorological data for West Siberia, a temporal trend in snowfall is not observed. Nevertheless, considerable interannual fluctuations in snow cover thickness can lead to interannual variations in the soil thermal regimes.

Varying climate response across the tundra, forest-tundra and boreal forest biomes in northern West Siberia

Satellite studies using the normalized difference vegetation index (NDVI) have revealed changes in northern Eurasian vegetation productivity in recent decades, including greening in tundra and browning in the boreal forests. However, apparent NDVI changes and relationships to climate depend on the temporal and spatial sampling and the biome and forest-land cover type studied. Here we perform a consistent analysis of NDVI and climate across four bioclimatic zones (tundra, forest-tundra, northern and middle taiga) in northern West Siberia (NWS), further stratified into eight forest-land cover types. We utilize NDVI data from the Moderate Resolution Imaging Spectroradiometer and climate reanalysis data from 2000 to 2016, a period including the record warm anomaly in 2016 (+2 °C–5 °C June–July surface air temperature (SAT) across NWS). Statistically significant (α = 0.05) correlations were found for two bivariate relationships at the biome level: between NDVImax and June–July surface air temperature (SAT)(r ∼ +0.79), and between middle taiga NDVImax and July precipitation (r ∼ +0.48). No significant statistical relationships were found for the northern taiga and forest-tundra biomes. However, within these biomes we found that deciduous needle-leaf (larch) NDVImax is significantly correlated with July temperature (r ∼ +0.48). Qualitatively, spatial composites of NDVI and climate variables were effective for revealing insights and patterns of these relationships at the sub-regional scale. The spatial heterogeneity of NDVI patterns indicates divergent reactions of specific types of vegetation, as well as local effects that are clearly important on the background of a regional climate response.

Jurassic paleogeography and sedimentation in the northern West Siberia and South Kara Sea, Russian Arctic and Subarctic

Abstract The study is focused on the depositional history of Jurassic oil- and gas-bearing sedimentary rocks, which currently occur at 3–6 km depth below the surface in the northern West Siberian Basin, the South Kara Basin and the western Yenisei-Khatanga Basin. Using data from deep wells, such as paleontological data and bedding geometries, lithology of rocks derived from cores and well log data, sediment thicknesses, results of detailed correlation of sedimentary cyclic units, and regional multichannel seismic reflection profiles, the authors produced 13 litho-paleogeographic maps of the studied region accompanied by W-E cross-sections. The maps present paleogeographic environments that existed during the deposition of each of 12 regional stratigraphic stages, namely: Lower Jurassic Zimniy (Hettangian – lowermost Upper Pliensbachian), Levinskiy (middle Upper Pliensbachian), Sharapov (uppermost Pliensbachian), Kiterbyut (lowermost Toarcian), Lower-Middle Jurassic Nadoyakh (uppermost Lower Toarcian – lowermost Aalenian), Middle Jurassic Laida (uppermost Lower Aalenian – lowermost Upper Aalenian), Vym (uppermost Aalenian – lowermost Bajocian), Leont'evskiy (uppermost Lower Bajocian – lowermost Upper Bajocian), Malyshev (uppermost Bajocian – lowermost Upper Bathonian), Middle-Upper Jurassic Vasyugan (uppermost Bathonian – lowermost Oxfordian), Upper Jurassic Georgiev (uppermost Oxfordian – lowermost Tithonian) and Bazhenov (uppermost Lower Tithonian – earliest Berriasian). The maps show the extent of exposed land, continental (alluvial plains), transitional (nearshore and coastal flood plains) and marine (water depth The presented results provide a more reliable framework for the re-evaluation of existing Jurassic hydrocarbon plays and identification of new plays in the West Siberian province.

Spatial structure and temporal variability of a surface urban heat island in cold continental climate

Warm urban climate anomalies are a challenging problem for city’s economy and ecology. This problem is even more pressing in boreal environment with its sensitive ecosystems and considerable anthropogenic urban heat flux. The boreal regions of Eurasia witness both rapid urbanization and accelerated regional warming in the twenty-first century. Still, local climate of boreal cities is only fragmentary studied. There were no studies addressing spatial and temporal variability of urban temperature anomalies in Eurasian cities with cold continental climate. There were many indirect reports indicating large temperature anomalies and longer growing season in boreal cities. This study considered a land surface temperature (LST) anomaly, frequently referred to as a surface urban heat island (SUHI), in a typical young mid-size boreal city of Nefteyugansk. This city exemplifies urban planning and energy use patterns of a pleiad of cities in this oil and gas region of northern West Siberia. The study is based on LST products from the MODerate resolution Imaging Spectro-radiometer (MODIS) onboard of the Terra and Aqua satellite platforms. The MODIS data for 14 years (2001–2015) were processed to reveal geographical extent and diurnal variations of the SUHI in summer (June, July, August) and winter (December, January, February) seasons. The study found that the mean annual SUHI has higher LST than the surrounding natural background by + 2.4 K. Considering the meridional temperature gradient in this region, such a strong SUHI makes the urban climate similar to climate found 600 km south of the city. The diurnal mean summer (+ 2.1 K) and winter (+ 2.4 K) SUHI intensities are rather similar in Nefteyugansk. The daytime (+ 2.1 K) and nighttime (+ 2.5 K) SUHI intensities are also similar in wintertime. In summertime, however, the daytime SUHI intensity (+ 3.3 K) is significantly larger than that in nighttime (+ 1.0 K). There is also larger interannual variability of the SUHI in the summer season, especially in nighttime. The SUHI statistics in Nefteyugansk discerns this cold continental city from previously studied cities in the temperate climate zone. Heating of apartment and industrial buildings maintains a large anthropogenic heat flux in the city (estimated to be on average of 15–20 W m−2) and therefore supports the persistent winter SUHI. Weak turbulent mixing in the stably stratified lower atmosphere traps the heat in the urbanized area. This study found that the SUHI footprint in Nefteyugansk is considerably (two to three times) larger than the area of the city proper itself.

EXOGENOUS DRIVERS Of SURfACE URBAN HEAT ISLANDS IN NORTHERN wEST SIBERIA

Urban temperature anomalies, frequently referred to as the urban heat islands (UHIs), are of the most distinct and influential climatic factors with significant impact on urban life and environment. However, UHIs in high latitudes are still studied only fragmentary. There is a knowledge gap related to the urban temperature distinction with respect to local temperature anomalies of natural surface types. This study extends upon our recent high latitude regional-scale climatic survey in 28 cities in the Northern West Siberia (NWS) region. Based on MODIS land surface temperature (LST) products covering 15 years between 2001 and 2015, it was revealed that all 28 cities have significant surface urban heat islands (SUHIs). The strong statistical dependence (r = 0.73) on endogenous factors such as city size and the population was found. It was suggested that exogenous factors such as the background LC types could be significant as well. This study presents the analysis of the exogenous factors shaping the apparent SUHI intensities. The major contribution to the SUHI was revealed for water, sparse vegetation, grassland, and shrubland. There are no clear dependence between the partial SUHI intensity and the area fraction occupied by the given LC type. The mechanisms and pathways of the SUHI maintenance cannot be inferred solely from the remote sensing data. Further understanding requires numerical experiments with turbulence-resolving models.

Seasonal and Spatial Characteristics of Urban Heat Islands (UHIs) in Northern West Siberian Cities

Anthropogenic heat and modified landscapes raise air and surface temperatures in urbanized areas around the globe. This phenomenon is widely known as an urban heat island (UHI). Previous UHI studies, and specifically those based on remote sensing data, have not included cities north of 60°N. A few in situ studies have indicated that even relatively small cities in high latitudes may exhibit significantly amplified UHIs. The UHI characteristics and factors controlling its intensity in high latitudes remain largely unknown. This study attempts to close this knowledge gap for 28 cities in northern West Siberia (NWS). NWS cities are convenient for urban intercomparison studies as they have relatively similar cold continental climates, and flat, rather homogeneous landscapes. We investigated the UHI in NWS cities using the moderate-resolution imaging spectroradiometer (MODIS) MOD 11A2 land surface temperature (LST) product in 8-day composites. The analysis reveals that all 28 NWS cities exhibit a persistent UHI in summer and winter. The LST analysis found differences in summer and winter regarding the UHI effect, and supports the hypothesis of seasonal differences in the causes of UHI formation. Correlation analysis found the strongest relationships between the UHI and population (log P). Regression models using log P alone could explain 65–67% of the variability of UHIs in the region. Additional explanatory power—at least in summer—is provided by the surrounding background temperatures, which themselves are strongly correlated with latitude. The performed regression analysis thus confirms the important role of the surrounding temperature in explaining spatial–temporal variation of UHI intensity. These findings suggest a climatological basis for these phenomena and, given the importance of climatic warming, an aspect that deserves future study.

Hydrocarbon composition and structural parameters of resins and asphaltenes of naphthenic oils of northern West Siberia

The composition of saturated and aromatic hydrocarbons and the structural-group characteristics of resins and asphaltenes in four oils of northern West Siberia have been studied. As follows from the distribution of hydrocarbons, the Cenomanian oils (pools in the beds PK and K2c) of the Russkoe, Barsukovskoe, and Pangodinskoe fields are naphthenic and the Pangodinskoe oil sample from the Lower Cretaceous pool (bed BN9) is methanoic. The hydrocarbon composition pattern of the saturated fraction and the characteristics of the heterocyclic components of these oils point to their formation from dispersed organic matter of mixed genesis in the oil window. Hence, the oil source rocks are localized at depths much greater than the present-day level of the oil pools. Secondary (cryptohypergene) alterations (oxidation and biodegradation) in the shallow-depth oils determined their current predominantly naphthenic composition and considerably hamper reconstruction of the types of initial dispersed organic matter. We assume that the mixed genetic type of the studied oils is not only due to their heterogeneous source but also due to the reorganization of primary oil pools at the Cenozoic stage of tectogenesis. The Cenomanian Russkoe and Pangodinskoe naphthenic oils are saturated with adamantoids, which can be selectively accumulated during biodegradation.

Texture and structure of the Late Holocene ground ice in the Northern West Siberia

The Late Holocene ground ices are occurred due to freeze cracking, slope, thermocast, thermoerosion pro‑ cesses. New formation ice within may intervene to the Pleistocene, lower Holocene ground ice and perma‑ frost and can really complicate their structure. Relationship between seasonal and perennial new formation of ice with massive ice and permafrost was studied in cross section of the North Western Siberia. The features of texture and structure of ice formed in the thawing cavities, some cracks were determined. The differences in structure of the late Holocene ground ices and ground ices of the early Holocene and late Pleistocene were defined. The differences in ground ice texture and structure depend to the cavity configuration of the freezing and cracks and freezing temperature conditions. The quantitative parameters of the crystal structure can be used to identify closed‑cavity ice and crack ice in the composition of massive ice and determine mechanisms and conditions of formation before the Holocene ice wedges.

Spatial heterogeneity of greening and browning between and within bioclimatic zones in northern West Siberia

Studies of the normalized difference vegetation index (NDVI) have found broad changes in vegetation productivity in high northern latitudes in the past decades, including increases in NDVI (‘greening’) in tundra regions and decreases (‘browning’) in forest regions. The causes of these changes are not well understood but have been attributed to a variety of factors. We use Moderate Resolution Imaging Spectrometer (MODIS) satellite data for 2000–2014 and focus on northern West Siberia—a hot spot of extensive landcover change due to rapid resource development, geomorphic change, climate change and reindeer grazing. The region is relatively little-studied in terms of vegetation productivity patterns and trends. This study examines changes between and within bioclimatic sub-zones and reveals differences between forest and treeless areas and differences in productivity even down to the tree species level. Our results show that only 18% of the total northern West Siberia area had statistically significant changes in productivity, with 8.4% increasing (greening) and 9.6% decreasing (browning). We find spatial heterogeneity in the trends, and contrasting trends both between and within bioclimatic zones. A key finding is the identification of contrasting trends for different species within the same bioclimatic zone. Browning is most prominent in areas of denser tree coverage, and particularly in evergreen coniferous forest with dark (Picea abie, Picea obovata) or light (Pinus sylvestris) evergreen and evergreen-majority mixed forests. In contrast, low density deciduous needle-leaf forest dominated by larch (Larix sibirica), shows a significant increase in productivity, even while neighboring different species show productivity decrease. These results underscore the complexity of the patterns of variability and trends in vegetation productivity, and suggest the need for spatially and thematically detailed studies to better understand the response of different northern forest types and species to climate and environmental change.

Paleobathymetry of the Late Jurassic-Neocomian basin in northern West Siberia and the impact of natural processes

Paleobathymetrical reconstructions were performed for the Volgian-Neocomian basin in northern West Siberia. The proposed technique takes into account a number of factors, such as the rates of basin subsidence and sedimentation, sediment lithification and types of lithology, sea level changes, and isostasy. The role of each factor controlling the depth of the paleobasin is considered. The study reveals several stages of formation of the Neocomian clinoform complex of West Siberia, with different regimes of basin subsidence, sedimentation, and isostatic compensation.

Trends in normalized difference vegetation index (NDVI) associated with urban development in northern West Siberia

Abstract. Exploration and exploitation of oil and gas reserves of northern West Siberia has promoted rapid industrialization and urban development in the region. This development leaves significant footprints on the sensitive northern environment, which is already stressed by the global warming. This study reports the region-wide changes in the vegetation cover as well as the corresponding changes in and around 28 selected urbanized areas. The study utilizes the normalized difference vegetation index (NDVI) from high-resolution (250 m) MODIS data acquired for summer months (June through August) over 15 years (2000–2014). The results reveal the increase of NDVI (or “greening”) over the northern (tundra and tundra-forest) part of the region. Simultaneously, the southern, forested part shows the widespread decrease of NDVI (or “browning”). These region-wide patterns are, however, highly fragmented. The statistically significant NDVI trends occupy only a small fraction of the region. Urbanization destroys the vegetation cover within the developed areas and at about 5–10 km distance around them. The studied urbanized areas have the NDVI values by 15 to 45 % lower than the corresponding areas at 20–40 km distance. The largest NDVI reduction is typical for the newly developed areas, whereas the older areas show recovery of the vegetation cover. The study reveals a robust indication of the accelerated greening near the older urban areas. Many Siberian cities become greener even against the wider browning trends at their background. Literature discussion suggests that the observed urban greening could be associated not only with special tending of the within-city green areas but also with the urban heat islands and succession of more productive shrub and tree species growing on warmer sandy soils.

Simulating the formation of river runoff and snow cover in the northern West Siberia

The potentialities of a technique for simulating runoff hydrographs of northern rivers, developed earlier, are examined as applied to permafrost areas with high percentage of wetlands represented by the river basins of Taz, Pur, and Nadym in West Siberian Plain. The technique is based on the land surface model SWAP in combination with input data based on global data sets of land surface parameters and meteorological forcing data derived from observations from meteorological stations within or near the river basins. The ability of model SWAP to reproduce the many-year dynamics of basin-averaged snow depth and mean snow water equivalent in the Taz R. basin was also examined.

Polygamy among indigenous people of northern West Siberia in ethnographic and early census materials

This article may be the first comprehensive work on polygamous families among the Yamal indigenous nomadic people. Based on the analyses of ethnographic descriptions, early census materials, Polar census (1926–27) and Yamal (Nenets) okrug census (1932–33) it focuses on how polygamous families were registered in censuses; their composition, ethnicity and economy and most important: why did polygamy exist in a society with a demographic shortage of women?I argue that region's remoteness, Russian state politics and slow advances of the Russian Orthodox Church into the region helps explain the late existence of polygamous families. According to our data, there were up to 6,5 % polygamous families of reindeer herders in Yamal even in the early-mid 1930s.I argue that polygamy in the Yamal area was not primarily an ethnic or religious issue. It connected to the household's main occupation - reindeer herding, a nomadic way of life and was a distinct marker of wealth before the social changes started in early 1930s.Analyses of the fourteen polygamous families show that they were significantly larger than the average 5,5 members in the Yamal nomadic households; men were married to two women one of which was notably older, likely the widow of older late brother. I also advocate the opinion that polygamy in the north could be considered as a system of social security for women in general and widows in particular. Only genuine appreciation and general acceptance of the tradition, which let some men have more than one wife while depriving others of any hope of having their own family and children, could make this phenomenon last for centuries.

Formation history of large anticlinal trap structures for unique gas pools in northern West Siberia (by the example of the Medvezh’e field)

We consider the formation history of high-amplitude anticlinal trap structures for unique Cenomanian gas pools using the example of the Medvezh’e field. Analysis shows that the Turonian-Cenozoic was the most crucial stage of formation of the world’s largest gas-bearing province in northern West Siberia. This stage was marked by (1) the formation of large anticlinal traps—petroleum-promising objects; (2) the highest intensity of gas formation, which caused the filling of these traps; and (3) the formation of the Kuznetsov seal, which shields the giant Cenomanian gas pools.