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This special issue is dedicated to discussing the possibility of the stage division of the Vendian system, specifically, a composite section of the Siberian platform is proposed as a stratigraphic standard. For the Ordovician system of the Siberian platform and Northeastern Russia, certain changes in stratigraphic charts are proposed, nomenclative issues and different variants of correlations of regional horizons with the GSS of Russia are considered. A geochemical analysis of Bajocian and Bathonian belemnite rostra of Arctic Siberia was carried out and for the first time a comprehensive C, O and Sr isotope characterization of the sections was obtained, making it possible to propose a comparison of the studied sections with the European standard and to develop paleogeographic models. Comprehensive studies of the Upper Jurassic and Lower Cretaceous series of the Anabar Bay deposits (Laptev Sea) led to an improved biostratigraphic division for this reference section and to the identification of the levels for interregional and global correlation. The magnetostratigraphic division of the Jurassic-Cretaceous boundary interval and its comparison with the Tethyan regions are discussed. Taking into account biostratigraphic data, the δ¹³C_org variation curve can also serve as a correlation tool. The clinoform structure of Upper Jurassic strata was revealed in the northwest of the Anabar-Khatanga depression, based on the interpretation of seismic profiles calibrated against studied sections. The formation of this complex allows us to consider this stage as the initiation of the Verkhoyan orogeny in this folded area. Analysis of variations in the thickness of sediments allows us to deduce that intense tectonic-sedimentary processes took place during the Late Jurassic epoch, along with subsidence of the bed of the sedimentary basin. Analysis of a specific assemblage of lacustrine fossils from the reference section of the upper part of the Lower Cretaceous series of Transbaikalia and of published data showed that this fossil assemblage was widespread in East Asia. Biofacies analysis made it possible to reconstruct the paleoenvironments of this time.

The way towards the stage subdivision of the Vendian starts with the assemblage of a complete composite geological section of this interval of the Earth’s history, a succession of geological bodies each reflecting a certain ecosystem state. A Vendian composite section of the Siberian Platform, which is a succession of regional to sub-global scale geological bodies reflecting particular states or unidirectional transformations determined by episodic expansion of relatively oxygen-rich environments onto the shelf and alternating with large-scale oceanic anoxia and euxinia events is proposed as a reference for constructing the stage subdivision of the Vendian. The redox instability had to be accompanied by changes in nutrient availability and could not but affect the course of macroevolution and macroecology. The geological record of the Vendian of the Siberian Platform is also marked by episodic increase in alkalinity of the World Ocean. At least five such alkalinity events could be provisionally identified in the composite section of the Vendian of the Siberian Platform. A hypothesis is proposed suggesting that the alkalinity events could control the appearance and disappearance in the geological record of a distinctive suite of sedimentary structures in carbonates, the discrete nature of early diagenetic cementation of aluminosilicoclastic sediments, and fossilization of soft-bodied organisms in the Vendian.

The chronozonal structure of the Mangazeya Superhorizon of Eastern Siberia, which includes the Listvyazhny and Baksan horizons and their chronozones, is considered. Their volumes and stratotypes are given and their place in the regional and global stratigraphic structure is shown, where Mangazeya occupies the middle parts of the Kuzmovsky regional complex and the Caradocian stage of the Upper Ordovician. Proper names for the Lower Dolbor Horizon (Amutkansky) and the Upper Dolbor Horizon (Cherlechinsky) are introduced for the first time.

In the Middle Ordovician sections of the Eriekhe River basin, which are of crucial importance to correlate the regional stratigraphic units of Northeast Russia and the General Stratigraphic Scale (by graptolites), we identified a diverse ostracod assemblage. The new data substantially supplement the Middle Ordovician paleontology of this region. The analysis of the stratigraphic distribution of these assemblages made it possible to verify the correlation of the Eriekhe Structural Facies Zone (SFZ) suites with regional stratigraphic units of the Northeast Russia and, based on homotypic ostracod assemblages, with the horizons of the Siberian Platform. The joint findings of ostracods and graptolites in the studied section allowed us to correlate the horizons of the Northeast Russia and the Siberian platform with the stages of the General Stratigraphic Scale.

The Middle Jurassic sedimentary strata of Siberia remain poorly studied chemostratigraphically. We contribute to the knowledge with pioneering C, O, and Sr isotopic data for carbonate material of belemnites from the Yuryung-Tumus Peninsula and the lower reaches of the Lena River, as a basis for comprehensive description of the north Siberian Bajocian and lower Bathonian. The obtained chemostratigraphic constraints, with new ⁸⁷Sr/⁸⁶Sr ratios and previous δ¹³C and δ¹⁸O estimates, also include data for the lower Bathonian in the Sokur section (Central Russia). Despite the limited amount of material, chemostratigraphy, along with the available biostratigraphic data, allows reliable correlation of the Boreal sections with the primary standard of Northwest Europe, which is impossible for these strata with any of the two methods alone. The δ¹³C, δ¹⁸О, and ⁸⁷Sr/⁸⁶Sr patterns correlate with the records of eustatic, climatic, tectonic, and paleogeographic events. The new δ¹⁸O data and the inferred paleotemperatures for the latest early Bajocian and the Bajocian/Bathonian boundary reveal two excursions of notable seawater warming near the Siberian Arctic coast, which were synchronous with episodes of global sealevel rise. It was presumably during the eustatic events that the N-S Komi Strait (first naming) opened twice in the territory of the Russian Plate. The strait connected the Boreal and Tethyan seas and thus changed the oceanic circulation patterns. Specifically, it opened a gateway for a warm current from the south to northern Siberia responsible for the high seawater temperatures recorded in the δ¹⁸О patterns of belemnites.

The purpose of this study is to establish the genesis and conditions of formation of different types of sediments in the permafrost area of Baydara Bay. Perennially and seasonally frozen and perennially and seasonally cryotic sediments have been identified on the basis of temperature measurements in core samples obtained during geotechnical drilling and thermal cone penetration tests along the profile crossing the bay. We suppose that permafrost was formed in this area in the course of epigenetic freezing during the Sartan regression. Seasonally frozen ground of the seafloor is subdivided into two types. The first type is characteristic of coastal shallows, where landfast ice contacts the seafloor. The second type is formed in the seaward part of the water area during the cold season, when the temperature of near-bottom seawater drops to values below the freezing point. Perennially cryotic (but unfrozen) ground is formed below the depth of the 0° isotherm traced during the warm season. Seasonally cryotic ground above this isotherm has above-zero temperatures in the warm season. In the winter season, under the impact of subzero temperatures of seafloor water, it is transformed into the cryotic or seasonally frozen state.

This study is devoted to substantiating the theoretical dependences of the porosity of the unconsolidated part of pressure ice ridges on the distance from the edges of the sail or keel. According to the crushing theory, particle sizes in crushed material follow a lognormal distribution. Ice blocks in unconsolidated parts of ice ridges can be considered as such crushed material. Information on the sizes of ice blocks and voids has been obtained from data on the penetration rate of thermal drilling of ice ridges and grounded ice ridges (stamukhi). It is argued that the average porosity of an ice ridge as calculated from thermal drilling data for a given depth is an estimate of the probability of finding a void at this depth. A statistical model of the depth-wise porosity distribution in the keel and sail of ice ridges as granular media is suggested. The average vertical size of voids decreases with distance from the edge of the keel or sail according to a logarithmic law, and the average vertical size of ice blocks remains approximately the same. The average porosity of the unconsolidated sail and keel changes according to a lognormal law with distance from their edge, and the porosity of the sail is approximately two times less than the porosity of the keel.

In recent decades, glaciers in Northern Siberia and the Far East have been influenced by climate change, especially small forms of glaciation. This process is also typical for the glaciers of the Koryak Highlands. To assess the dynamics of glaciation in this region, data from CORONA (1972), Sentinel-2 (2019) images, and the USSR Glacier Catalog (mid-1960s) were used. The USSR Glacier Catalog of the Koryak Highlands was compiled based on data from topographic maps and aerial photographs. The number of glaciers included in this catalog is almost 2.5 times higher than the number of glaciers identified on satellite images. For the studied region, the new electronic catalog Glaciers of Russia records 890 glaciers with a total area of 296.29 km². This region is abundant in rock glaciers, and apparently the USSR Glacier Catalog (and perhaps the new electronic inventory) mistook many rock glaciers for living glaciers at the time of its compilation. Therefore, the authors made a new estimate of glacier areas using CORONA images. The discrepancies between the areas of glaciers indicated in the Catalog and identified on satellite images were determined for groups of glaciers.

We performed geophysical studies to determine the structure of the frozen layer around and below the Uomullyakh-Kyuel Lagoon, the lagoon itself being a reference landform sculpted by thermokarst and thermal abrasion of the sea shoreline. The main purpose of the study was to determine talik depth under lagoon or the position of the subaquatic permafrost boundary. We performed electromagnetic and electrical studies with transient electromagnetic sounding and electrical resistivity tomography from lagoon ice during winter period and from water surface in summer. We matched borehole section data with temperature data from this same borehole and also with surface geophysical data. This comparison showed patterns of modern and relict taliks in the form of low electrical resistivity layers. We demonstrate that modern talik has developed to the depth of 30 m. At the same time, the relict talik is located between depths of 80-100 m, which correlates with data acquired by other researchers. We suggest that relict talik has a hydrological connection to the strata located under the seafloor; therefore it is seen clearly on geoelectric cross section. The lake that formed the relict talik had a size of at least 1450 by 900 m. Electrical resistivity tomography data acquired from the lagoon surface shows fragments of boundaries between frozen and unfrozen permafrost. Numerical modeling shows that electrical resistivity tomography quantitatively underestimates resistivity of the frozen permafrost by 5 to 10 times. In the subaerial-subaquatic transition zone, we track a gradual descent of the permafrost upper boundary and map a permafrost overhang, which sometimes appears beneath shallow water bodies. We suggest that gradual decrease of electrical resistivity in the direction from the seashore to the sea basin corresponds to the amount of salt transported into sediments and increase in their temperature.

Cryosophy can be considered as conceptual meta-views of cryology. Its main goals are the interdisciplinary integration of ideas about cold and creation of conceptual models ensuring the holistic perception of the cryosphere. To achieve these goals, the scientific understanding of the cryosphere as a system, which would rely on modern general theoretical approaches that have overcome logical empiricism on the way to holism with its epistemological principle “the whole is always more than just the sum of its parts”, is of major importance. One of the crucial factors that prevented the formation of a holistic scientific picture of the Earth’s cryosphere during the 20th century was that the cold shell of the planet, which consists of the glaciosphere, cryolithosphere, and atmosphere, was studied by different scientific disciplines. Only at present the scientific community has made the first steps in considering the cryosphere as an almost one hundred-kilometer sphere around the Earth, the near-surface and subsurface parts of which occupy significant territories of continents and oceans. Given similar understanding, the Earth’s cryosphere can be interpreted as a global geosystem, which penetrates significant areas of commonly accepted geospheres-atmosphere, lithosphere, and hydrosphere, as well as soil horizons and largely determines the matter and energy exchange between them. The examples presented in this paper indicate that the key to understanding the unity and diversity of the world of cold is the philosophical comprehension of the cryosphere as a complex system. Such an understanding should make it possible to overcome logical empiricism and reductionism on the way to holism.