Gydan Peninsula Research Articles

Thickness and Structure of Permafrost in Oil and Gas Fields of the Yamal Peninsula: Evidence from Shallow Transient Electromagnetic (sTEM) Survey

The Yamal-Nenets Autonomous District, especially the Yamal Peninsula located in the permafrost zone, stores Russia’s largest oil and gas resources. However, development in the area is challenging because of its harsh climate and engineering–geological features. Drilling in oil and gas fields in permafrost faces problems that are fraught with serious accident risks: soil heaving leading to the collapse of wellheads and hole walls, deformation and breakage of casing strings, gas seeps or explosive emissions, etc. In this respect, knowledge of the permafrost’s structure is indispensable to ensure safe geological exploration and petroleum production in high-latitude regions. The extent and structure of permafrost in West Siberia, especially in its northern part (Yamal and Gydan Peninsulas), remain poorly studied. More insights into the permafrost’s structure have been obtained by a precise sTEM survey in the northern Yamal Peninsula. The sTEM soundings were performed in a large oil and gas field where permafrost is subject to natural and anthropogenic impacts, and its degradation, with freezing–thawing fluctuations and frost deformation, poses risks to exploration and development operations, as well as to production infrastructure. The results show that permafrost in the western part of the Yamal geocryological province is continuous laterally but encloses subriver and sublake unfrozen zones (taliks) and lenses of saline liquid material (cryopegs). The total thickness of perennially frozen rocks is 200 m. The rocks below 200 m have negative temperatures but are free from pore ice. Conductive features (<10 Ohm﮲m) traceable to the permafrost base may represent faults that act as pathways for water and gas fluids and, thus, can cause a geohazard in the oil and gas fields (explosion of frost mounds, gas blow during shallow drilling, etc.).

Chloritization of mixed siliciclastic-carbonate rocks: case study from Gydan Peninsula, Russia

Chloritization of mixed siliciclastic-carbonate rocks: case study from Gydan Peninsula, Russia

Geological structure of the Malyshevka Formation of the northeastern regions of Western Siberia according to the complex of geological and geophysical data

Data on the geological structure of the Malyshevka Formation in the northeastern regions of Western Siberia in the Gydan and western parts of the Yenisei–Khatanga oil and gas regions are presented. Based on the results of dissection of the Middle Jurassic deposits, three main types of section of the Malyshevka Formation were identified. Zoning of the suite by section type is proposed. Based on a comprehensive analysis of the wave pattern of the Jurassic section on a series of temporal seismic profiles, well geophysical data, and faunal determinations, a detailed correlation of Middle Jurassic sediments was performed. Based on the results of the work, a seismogeological model of the Malyshevka Formation of the northeastern regions of Western Siberia was built, which made it possible to resolve controversial issues regarding its volumes in the southern part of the Gydan Peninsula.

Behavioural lateralisation of swans in response to anthropogenic disturbance differs according to the locomotion type

The European population of Cygnus columbianus bewickii has a declining trend in number of individuals. Anthropogenic disturbance could be one of the reasons for this decline. Disturbance influences animal behaviour, including the manifestation of behavioural lateralisation. Therefore, investigating the impact of anthropogenic disturbance on behavioural lateralisation is essential for biodiversity conservation. Behavioural lateralisation manifests itself in a preference to use one of two paired organs (limbs or sensory organs) and a preference to avoid obstacles from a certain side. Earlier studies of behavioural lateralisation did not consider the locomotion type as an independent variable factor in the analysis, although it could affect the manifestation of behavioural lateralisation. We studied the influence of anthropogenic disturbance on behavioural lateralisation of swans, depending on the type of locomotion (swimming or flying). We have analysed 492 photos from aerial counts of two swan species (Cygnus columbianus bewickii, C. cygnus) in Yamal Peninsula and Gydan Peninsula. The photos were taken from a plane, while the birds were escaping from it as a source of anthropogenic disturbance. Pairs without and with chicks alone or in flocks were encountered swimming or flying. We found that swimming swans had a strong right-sided bias and right-eye bias for avoidance and observing the source of anthropogenic disturbance, and flying swans had a left bias. Swimming C. c. bewickii and C. cygnus exhibited similar behavioural lateralisation. These results were the same for following and leading birds. The presence of chicks did not change the direction of behavioural lateralisation but strengthened it for the following partners. The differences in behavioural lateralisation could be caused by the fact that swans in flight experience greater fear of a present aircraft than when they are on water. We conclude that the locomotion types influence behavioural lateralisation in response to anthropogenic disturbance. We recommend paying attention to accompanying factors when comparing the results of lateralisation studies. As the left side bias of flying birds in our study indicates that flying birds are more stressed than swimming ones, we recommend not forcing birds to fly during observations to reduce their stress.

Stone Tools of the Nomads of the Arctic Tundra from the Medieval Site of Khaltsyneisalya 1 on the Gydan Peninsula (use wear analysis)

The paper studies stone tools from the Khaltsyneisalya 1 site located on the eastern coast of the Ob Bay on the Gydan Peninsula. The ceramic material found at the site is attributed to the Tiuteisalinsky type of the Lower Ob culture, which was common among the nomads of the Arctic tundra in the Middle Ages. The resulting stone tools are represented by scrapers, knives and anvils. The presence of anvils in the materials of the site is a rather rare phenomenon, in contrast to the scrapers and knives that are consistently found on the sites of the Early Iron Age and the Middle Ages in the Arctic zone of Western Siberia. In order to establish their functional purpose, traceological analysis was carried out with experimental verification of the proposed functions. To establish the purpose of stone tools, experimental work was carried out to model wear marks, which made it possible to obtain important arguments for substantiating the function of the studied tools.

Formation of the Siberian Yamal gas emission crater via accumulation and explosive release of gas within permafrost

AbstractThe Arctic landscape has experienced many dramatic forms of change due to anthropogenic warming. Large crater‐like forms surrounded by fragmented blocks scattered outward to great distances with precursor mounds appeared in the continuous permafrost zone of the Yamal and Gydan peninsulas of Western Siberia. The morphologies of these craters, in addition to the abundant evidence of active and intense gas emissions across the region, indicate that they formed due the subsurface accumulation, pressurization, and explosive release of gasses trapped within the permafrost. Therefore, these craters were termed “gas emission craters” (GEC). However, some have suggested that in addition to gas accumulation, these features form in a manner similar to ice‐cored pingos and require pressurization due to the freezing of subsurface ice. This is despite the fact that not all GECs form in areas conducive to pingo‐like ice accumulation. Here, we test whether the pressurization and explosive release of methane gas alone can reproduce the observed morphology of the first‐discovered and most intensely studied GEC, Yamal crater. We use the available field and satellite data to constrain the initial dimension parameters of a model of the explosion process and consider several plausible configurations for the unknown interior cavity shape, the overlying permafrost cap thickness, and gas chamber volume. The explosion process is modeled in phases: gas migrates upward and accumulates in the subsurface until the gas pressure fractures the overlying cap, the expanding gas and cap blocks are initially accelerated outward together, and then the blocks are launched as projectiles. The sizes and locations of the ejected blocks found at Yamal crater are used to determine the initial gas pressures required to launch those projectiles to the observed locations. Finally, we estimate the amount of gas released in each of the multiple model runs testing different plausible internal cavity geometries. For the range of plausible block sizes and densities, and a subset of gas chamber volumes considered, we find that the gas pressure (0.6–2.6 MPa) required to launch the Yamal crater blocks to their observed distances was within the range of the sum of the ice/permafrost tensile strength and the lithostatic pressure (0.22–2.87 MPa). Thus, the observed blocks could have been launched by the energy required to fracture and displace the overlying permafrost cap. We show that the mechanism of formation of this GEC does not require pressure from the freezing of ice in the subsurface to crack and explode the overlying permafrost—gas pressure alone can produce these GECs. We expect that as our planet warms, the Siberian permafrost will continue to warm, weaken, and release gasses such as the greenhouse gas methane, and contribute to a permafrost carbon‐positive feedback cycle that would lead to the formation of even more explosive GECs.

Damage assessment for bearing capacity of frozen grounds due to temperatures change and permafrost thawing in the arctic zone of the Russian Federation by the middle of the 21st century

Changes in the bearing capacity of frozen soils under various scenarios of warming in the Arctic zone of the Russian Federation (AZRF) by 2050 are considered. Deformations and destruction of buildings and engineering structures in the Russian Arctic will develop gradually. Taking into account the climatic scenarios (RCP2.6, RCP4.5, RCP8.5), in aggregate, 1/3 of the AZRF territory will experience a decrease in bearing capacity by more than 15% by the middle of the century; the Arctic coast of the European North of Russia, Yamal and the Gydan Peninsula are in the danger zone.

Running overnight and struggling to find sea ice: long-distance movement by an Arctic fox (Vulpes lagopus) from Russia

Given the scale, speed, and complexity of recent changes in the Arctic, our understanding of their multiple implications for Arctic biota is still limited. We detail for the first time in the vast Russian Arctic the long-distance movement of an Arctic fox ( Vulpes lagopus (Linnaeus, 1758)) tracked with a GPS/iridium collar providing considerably high precision (several meters) and frequency of locations (every 4 h). Revealed diurnal activity patterns of the Arctic fox indicate that it ran greater distances in night hours and shortest in day hours during the most intense movement period. The movement records suggested several attempts to leave the land, as it seemed to encounter open water four times on different parts of Yamal peninsula. The Arctic fox crossed the Ob Bay towards the Gydan peninsula and satellite imagery of discontinuous ice during crossing suggested that it might have stayed on pieces of floating ice. Our observation may support evidence that a reduction in the duration and extent of sea ice could affect the ability of Arctic foxes to cover long distances and thus, in the long term, the connectivity between populations. Similar studies are needed aiming to understand movement ecology of the Arctic foxes in the changing Arctic.

Russian Arctic Vegetation Archive—A new database of plant community composition and environmental conditions

AbstractMotivationThe goal of the Russian Arctic Vegetation Archive (AVA‐RU) is to unite and harmonize data of plot‐based plant species and their abundance, vegetation structure and environmental variables from the Russian Arctic. This database can be used to assess the status of the Russian Arctic vegetation and as a baseline to document biodiversity changes in the future. The archive can be used for scientific studies as well as to inform nature protection and restoration efforts.Main types of variables containedThe archive contains 2873 open‐access geobotanical plots. The data include the full species. Most plots include information on the horizontal (cover per species and morphological group) and vertical (average height per morphological group) structure of vegetation, site and soil descriptions and data quality estimations. In addition to the open‐access data, the AVA‐RU website contains 1912 restricted‐access plots.Spatial location and grainThe plots of 1–100 m2 size were sampled in Arctic Russia and Scandinavia. Plots in Russia covered areas from the West to the East, including the European Russian Arctic (Kola Peninsula, Nenets Autonomous district), Western Siberia (Northern Urals, Yamal, Taza and Gydan peninsulas), Central Siberia (Taymyr peninsula, Bolshevik island), Eastern Siberia (Indigirka basin) and the Far East (Wrangel island). About 72% of the samples are georeferenced.Time period and grainThe data were collected once at each location between 1927 and 2022.Major taxa and level of measurementPlots include observations of >1770 vascular plant and cryptogam species and subspecies.Software formatCSV files (1 file with species list and abundance, 1 file with environmental variables and vegetation structure) are stored at the AVA‐RU website (https://avarus.space/), and are continuously updated with new datasets. The open‐access data are available on Dryad and all the datasets have a backup on the server of the University of Zurich. The data processing R script is available on Dryad.

Distribution and Morphometry of Thermocirques in the North of West Siberia, Russia

The Arctic zone of West Siberia (Yamal and Gydan peninsulas) is an area with continuous permafrost and tabular ground ice close to the surface, active thermodenudation, and related landforms: retrogressive thaw slumps (RTS); in Russian referred to as thermocirques (TC). The dimensions of most TCs have not been determined so far. We use Sentinel 2 imagery to measure each TC area ranging from 0.55 to 38 ha with a median of 2.5 ha. Around 95% of TCs have an area of less than 10 ha. The largest areas are gained due to the merging of several neighboring TCs. The ArcticDEM is used to determine TC edge elevation and slope angle. In general, the Median TC of the Yamal peninsula has an area of 1.8 ha, an elevation of the edge of 17.7 m, and a slope angle of 2.5°. The Median TC of the Gydan peninsula has an area of 2.6 ha, elevation of the edge of 29.4 m, and slope angle of 3°. TCs of the Gydan peninsula occupy higher positions and slightly steeper slopes compared to TCs of the Yamal peninsula. The ranges of the median and the largest TC areas are consistent with the reported RTS dimensions in North America.

New data on the distribution of Red-breasted goose and Lesser white-fronted goose in the south of the Gydan Peninsula

New data on the distribution of Red-breasted goose and Lesser white-fronted goose in the south of the Gydan Peninsula

FIRST DATA ON THE DYTISCIDAE (COLEOPTERA) FROM THE COASTAL TUNDRA OF YUGORSKY PENINSULA, POLAR RUSSIA

In July 2018, diving beetles were collected in the most typical water bodies and other habitats in the vicinity of Amderma, Kara Sea coast, northern Yugorsky Peninsula. The fauna comprises 15 dytiscid species from 7 genera. The most diverse genera were Agabus and Hydroporus. The record of Dytiscus lapponicus was the northernmost for this species, while the reports of Hydroporus cf. fuscipennis and Agabus pallens were the northernmost for the Palaearctic parts of their distribution ranges. Original photographs illustrate peculiar specimens of Dytiscus lapponicus with dark head, pronotum and scutellum. Most of the species show vast Holarctic Arcto-Boreal or Arcto-Boreal-Montane distributions. The species composition of the Dytiscidae is quite similar to those of the northernmost mainland regions of the European Northeast (Pakhancheskaya Bay, Kara Tundra and Pamal), as well as the Vaigatch and Dolgyi islands, being less similar to those of the south tundra regions (Kanin Peninsula, Bolvanskaya Bay and Antipayuta village, Gydan Peninsula). Among the study habitats, the most diverse beetle assemblage inhabited thermokarst lakes (up to 14 species, the maximum density noted was 1150 ind./100 trap-days). On the contrary, on salt marshes, only 2–3 beetle species were recorded and the total abundance was significantly lower (1.8–3.6 ind./100 trap-days).

Mapping retrogressive thaw slumps using deep neural networks

Retrogressive thaw slumps (RTS) are thermokarst features in ice-rich hillslope permafrost terrain, and their occurrence in the warming Arctic is increasingly frequent and has caused dynamic changes to the landscape. RTS can significantly impact permafrost stability and generate substantial carbon emissions. Understanding the spatial and temporal distribution of RTS is a critical step to understanding and modelling greenhouse gas emissions from permafrost thaw. Mapping RTS using conventional Earth observation approaches is challenging due to the highly dynamic nature and often small scale of RTS in the Arctic. In this study, we trained deep neural network models to map RTS across several landscapes in Siberia and Canada. Convolutional neural networks were trained with 965 RTS features, where 509 were from the Yamal and Gydan peninsulas in Siberia, and 456 from six other pan-Arctic regions including Canada and Northeastern Siberia. We further tested the impact of negative data on the model performance. We used 4-m Maxar commercial imagery as the base map, 10-m NDVI derived from Sentinel-2 and 2-m elevation data from the ArcticDEM as model inputs and applied image augmentation techniques to enhance training. The best-performing model reached a validation Intersection over Union (IoU) score of 0.74 and a test IoU score of 0.71. Compared to past efforts to map RTS features, this represents one of the best-performing models and generalises well for mapping RTS in different permafrost regions, representing a critical step towards pan-Arctic deployment. The predicted RTS matched very well with the ground truth labels visually. We also tested how model performance varied across different regional contexts. The result shows an overall positive impact on the model performance when data from different regions were incorporated into the training. We propose this method as an effective, accurate and computationally undemanding approach for RTS mapping.

Dynamics of Low-Lying Sandy Coast of the Gydan Peninsula, Kara Sea, Russia, Based on Multi-Temporal Remote Sensing Data

The retreat rates of Arctic coasts have increased in recent decades at many sites, and an essential part of coasts considered accumulative before have turned erosional due to global climate changes and construction in the coastal zone. In this paper, we study a 7 km long coastal section of the western Gydan Peninsula in a new construction area. Based on the interpretation of multi-temporal satellite imagery, we assessed coastal dynamics in distinct periods from 1972 to 2020. We analyzed the geological structure of the coast as well as changes in hydrometeorological parameters with time, and considering the human impact, we proposed the main drivers of spatial and temporal variations of coastal dynamics. The studied low-lying sandy accumulative marine terrace was more or less stable in the period before construction (1972–2014). However, with the area’s development, the coast dynamics changed drastically: in 2014–2017, three-quarters of the studied area experienced retreat, and the average retreat rate amounted to 5.8 m/yr, up to 28.5 m/yr near the construction sites. We relate this coastal erosion intensification to human impact combined with the growth of hydrometeorological forcing. Although coastal erosion slowed down after 2017, the retreat trend remained. In the coming years, with Arctic climate warming, erosion of the studied coast will continue.

Пространственное распределение естественного и антропогенного эолового рельефа на севере Западной Сибири

The authors show the differentiation of the modern aeolian landforms spatial distribution (natural and anthropogenic origin) for the northern part of the West Siberian Plain (an area of about 800 thousand km2) based on the analytical processing of Sentinel-2 satellite images (resolution 10 m/px). A deciphering technique was developed; it includes the use of unsupervised ISODATA classification algorithms, visual editing, verification of results based on high-resolution satellite images, and standard spatial analysis procedures. In total, 404,675 aeolian relief objects with a total area of 2228,18 km2 were identified. The average area of natural forms was 0,44 ha (the largest share in the Yamal district of the Yamalo-Nenets Autonomous Okrug – 1,02 %), the average area of anthropogenic forms – 2,84 ha (the largest share in the Purovsky district of the same region – 0,19 %). It was revealed that in the territories of oil and gas production, the maximum area of both natural and anthropogenic aeolian forms corresponds to the boundaries of the Urengoy field (19,14 and 34,58 km2, respectively). It was established that in the Yamal Peninsula, the modern aeolian relief is confined mainly to marine and hydroglacial deposits, while in that of Gydan Peninsula, a connection can be traced with glacial or marine ones that have experienced direct mechanical action of cover ice. It was revealed that the mentioned relief is often formed in areas with increased drainage, facing towards the direction of the prevailing winds in the spring-autumn period (terraces and the watershed of the Pur and Nadym rivers). The results of the study can be used at monitoring the reclamation of disturbed areas and the natural dynamics of vegetation as an indicator of global climate change in the north of Western Siberia.

Fatty Acid Content of Four Salmonid Fish Consumed by Indigenous Peoples from the Yamal-Nenets Autonomous Okrug (Northwestern Siberia, Russia).

Simple SummaryFish is an important source of nutritious fatty acids, which are necessary for the prevention of cardiovascular and neurological diseases. Many fish species are a major component of the human diet, especially for indigenous peoples from Siberia, Russia, but information about their fatty acid profiles is scarce. We studied the fatty acid content of four salmonid fish (Arctic cisco, least cisco, muksun, and Arctic charr) inhabiting water bodies of the Gydan Peninsula, Kara Sea basin. We found a high content of essential polyunsaturated fatty acids in local salmonid fishes. Arctic charr was the fish species with the highest concentration of fatty acids in the flesh. The results of our multivariate analysis may be useful for anglers, stakeholders, and local consumers.We assayed fatty acids in the flesh of Arctic cisco Coregonus autumnalis (adult and juvenile), least cisco Coregonus sardinella, muksun Coregonus muksun, and Arctic charr Salvelinus alpinus inhabiting water bodies of the Gydan Peninsula, Siberia, Russia. The highest concentrations of total and polyunsaturated fatty acids (PUFAs) were found in Arctic charr (27.8 and 9.5 mg g−1) and adult Arctic cisco (20.2 and 7.6 mg g−1), while the lowest concentrations occurred in juvenile Arctic cisco (7.5 and 3.6 mg g−1). Multivariate analyses divided all studied fish into five distinct groups with the highest similarity between least cisco and muksun and the highest dissimilarity between juvenile Arctic cisco and Arctic charr. Coregonid fish from the study area had a higher content of docosahexaenoic and eicosapentaenoic acids than their conspecifics from subarctic and temperate habitats. The flesh of the studied fish is a source of a healthy diet for humans. Taking into account that all the studied fish are components of the traditional diet of indigenous peoples in northwestern Siberia, our data may be useful not only for local consumers and anglers but also for stakeholders focused on food policy and food security in the area.

Upper Cretaceous and Cenozoic Stratigraphy of the Gydan Peninsula

Abstract —The post-Cenomanian sedimentary sequence of the East Messo-Yakha oil and gas field in the southern Gydan Peninsula comprises twelve lithological units (beds) correlated to Upper Cretaceous, Paleogene, and Quaternary regional stratigraphic stages and formations. The facies of the sedimentary units are constrained from lithology and microfossils. The stratigraphic division is based on bio-stratigraphy (fauna and spore-pollen assemblages), paleomagnetism, and geochronology (quartz and feldspar grains dated by optically stimulated luminescence). The deposition record is interrupted by six large stratigraphic unconformities. The obtained data provide new insights into the Late Cretaceous, Paleogene, and Quaternary paleogeography of the area.

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.

Determining factors of the unconsolidated rocks of Cenomanian reservoir on the Bolshekhetskaya depression

The relevance of the article is associated with the importance of the object of the research. Dozens of unique and giant oil and gas fields, such as Urengoyskoye, Medvezhye, Yamburgskoye, Vyngapurovskoye, Messoyakhskoye, Nakhodkinskoye, Russkoye, have been identified within the Cenomanian complex. The main feature of Cenomanian rocks is their slow rock cementation. This leads to significant difficulties in core sampling and the following studies of it; that is the direct and most informative source of data on the composition and properties of rocks that create a geological section.The identification of the factors, which determine the slow rock cementation of reservoir rocks, allows establishing a certain order in sampling and laboratory core studies. Consequently, reliable data on the reservoir and estimation of hydrocarbon reserves both of discovered and exploited fields and newly discovered fields that are being developed on the territory of the Gydan peninsula and the Bolshekhetskaya depression will be obtained. This study is also important for the exploration and development of hydrocarbon resources of the continental shelf in the waters of the Arctic seas of Russia as one of the most promising areas.As a result of the analysis, it was found that the formation of rocks of the PK1-3 Cenomanian age of the Bolshekhetskaya depression happened under conditions of normal compaction of terrigenous sedimentary rocks that are located in the West Siberian basin. Slow rock cementation of reservoir rocks is associated with relatively low thermobaric conditions of their occurrence, as well as the low content of clay and absence of carbonate cements. Their lithological and petrophysical characteristics are close to the analogous Cenomanian deposits of the northern fields of Western Siberia and can be applied to other unconsolidated rocks studied areas.

Karyotype and COI gene sequence of Chironomusheteropilicornis Wülker, 1996 (Diptera, Chironomidae) from the Gydan Peninsula, Russia.

The karyotype features and gene COI sequence of Chironomusheteropilicornis Wülker, 1996 from the Gydan Peninsula are presented for the first time. Nine banding sequences were determined, eight of them hpiA2, hpiB1, hpiC1, hpiC2, hpiD1, hpiE1, hpiF3 and hpiG1 were previously known from European, Georgian (South Caucasus) and Siberian populations. One new banding sequence for Ch.heteropilicornis, hpiB2, was found. The hpiA2 banding sequence was found in all individuals, and this is its second finding after the Georgian population (Karmokov 2019). The hpiF3 banding sequence was found only in the homozygous state. Additional B-chromosomes are absent. The genetic distances (K2P) between Ch.heteropilicornis COI gene sequence from Gydan Peninsula and Norway are 1.1­–1.3%, and Georgia – 1.8%, much lower than the commonly accepted threshold of 3% for species of genus Chironomus Meigen, 1803. The phylogenetic tree for COI gene sequences estimated by Bayesian inference showed geographically determined clusters of Norway and Gydan and a separate lineage of the Georgian population of Ch.heteropilicornis. The analysis of karyotype and COI gene sequences shows that the population of Ch.heteropilicornis from the Gydan Peninsula has an intermediate position within the Ch.pilicornis group between Georgian, Yakutian and Norwegian populations. The position of Ch.pilicornis Fabricius, 1787 from Canada and Greenland on the phylogenetic tree is discussed.