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Paleoproterozoic mafic associations of the Irkut block from the Sharyzhalgai uplift are gabbro-dolerite dikes and small gabbronorite and monzodiorite massifs, which formed at 1.87-1.84 Ga and were coeval with granitoids and basite intrusions of the South Siberian magmatic belt (SSB). All the Paleoproterozoic mafic associations of the Irkut block are characterized by the presence of biotite and alkali feldspar, enrichment in K₂O, LILE, Th, and light REE, highly fractionated multielement spectra with sharp Nb and Ti depletion, and extremely low ε_Nd( T ) from -5.1 to -10.1. In these compositional features, they are similar to mafic complexes in the central and eastern parts of the SSB (the Baikal uplift and the western Aldan shield). Their geochemical and isotopic characteristics did not result from crustal contamination but point to derivation from the subcontinental lithospheric mantle (SCLM) enriched by reaction with felsic subduction-related and OIB-like mafic melts formed at a low degree of melting. The geochemically contrasting Paleoproterozoic gabbronorites in the Onot block of the Sharyzhalgai uplift are marked by depletion in K₂O, Ba, LILE, Th, and light REE, weak depletion in Nb, and higher ε_Nd( T ) from -0.3 to -1.4. The gabbronorites indicate not only an increase in the contribution of a depleted source to their genesis but also the heterogeneity of the subcontinental lithospheric mantle below the south margin of the Siberian Craton. The formation of enriched SCLM domains throughout the South Siberian belt was mainly the result of Archean subduction-related metasomatic processes. The wide distribution of Paleoproterozoic mafic complexes with subduction geochemical signatures and negative ε_Nd( T ) on most early Precambrian cratons is due to global change in the composition and an increase in the heterogeneity of the subcontinental lithospheric mantle toward the end of the Archean.

In this paper, we present a description of the characteristics of the Lotmvara-II sill, which is a representative of the Serpentinite Belt (SB) composed of a series of shallowly emplaced ultrabasic intrusive bodies. The Paleoproterozoic SB complexes were derived from a large-scale mantle plume of komatiitic melt. The sill consists predominantly of fine-grained (locally nearly micrograined) harzburgites with subordinate zones of dunites and orthopyroxenites, located in the central and marginal parts, respectively. It formed from an Al-undepleted komatiitic magma of extremely high Mg content and may represent a near-surface laccolithic “ridge.” In general, the sill is comparatively homogeneous and does not have distinct zoning in the distribution of Mg# values in rock compositions (Mg# = 84.2-88.9, average 86.7). Detailed studies show that olivine, chromian spinel, and ilmenite are the most strongly magnesian in the central part of the body. The maximum values of Mg# equal to 90.7-91.4 in the compositions of olivine at the center of the sill are interpreted as “centers of initial crystallization”. The low values of Mg# equal to 73.4-76.4 are attributed to manifestations of the recurrent generation of olivine. The values of Mg# of orthopyroxene in the sill are within the range 84.6 to 92.3. Orthopyroxene grains in a porphyritic texture are surrounded by a rim of calcic amphibole (autometasomatic in origin); they do not differ compositionally from normal grains. The Zn content of the chromian spinel generally decreases toward the marginal parts of the sill. There is an insignificant degree of magmatic differentiation in the sill with respect to the principal components, but incompatible elements (REE and HFSE) locally show increased levels of their relative enrichment, which is reflected in the nature of the mineral associations described. Thus, the sill has a cryptic zonal structure, which is consistent with its overall crystallization from the center to the edges. The data gathered suggest the presence and significant development of volatile components, halogens, CO₂, and especially magmatic H₂O, which are capable of strongly lowering the liquidus and reducing the density and viscosity of the high-magnesium melt, thereby improving its mobility during ascent from the mantle to the near-surface level of the crust. An increase in ƒ_O2 is observed during in situ subvolcanic crystallization of the sill, as noted earlier in the related complexes of the belt. The relatively small volume of the komatiitic magma in the sill crystallized fairly quickly, resulting in unusual mineral intergrowths. Thus, the Lotmvara-II sill is a novel member in the Serpentinite Belt-Tulppio Belt (SB-TB) in the Paleoproterozoic SB-TB megastructure of the Fennoscandian Shield.

Preservation of soft-bodied organisms as casts is common in the Ediacaran fossil record and extremely rare in Cambrian rocks. Among the factors, limiting fossilization of soft tissues, there is bioturbation-sediment disturbance by burrowing organisms. It is the emergence of burrowing metazoans and associated sediment bioturbation that is thought to be one of the major causes for the disappearance of Ediacaran soft-bodied organisms from the fossil record around ~540 Ma. Here, we study an assemblage of fossils preserved as casts in the Fortunian carbonates of the Olenek Uplift (northeastern Siberian Platform) in association with a typical Fortunian ichnoassemblage. The overall morphology and preservation of the fossils reveal that they comprise microbially induced sedimentary structures and soft-bodied holdfasts. The latter are vaguely reminiscent of some Ediacaran holdfasts, though it is unlikely that they include their phylogenetic descendants. Three-dimensional preservation of the studied fossils was caused by authigenic crystallization of calcite and its further early-diagenetic dolomitization. Our study confirms the critical importance of specific environmental conditions ensuring preservation of soft-bodied organisms as three-dimensional molds and casts. This unique interplay of environmental factors became rare in the Cambrian Period, which was caused by intensification and expansion of bioturbation in marine basins.

Dataset on the Middle Devonian volcanic-carbonate-terrigenous sediments of Salair and the Kuznetsk trough, submerged northward under the Mesozoic-Cenozoic West Siberian geosyneclise (WSG) cover, have been presented. Mainly deep water sediments composed of thin- and fine-grained clastic material (with predominance of tephroids) and thin-, fine-clastic biodetrital limestones with slope slide breccia, as well as turbidites and peculiar “conglomerate-like” limestones (paleoseismites) were found. Sedimentary and geodynamic environments have been reconstructed for the Middle Devonian strata. Predominantly andesitic composition of pyroclastic ashes with fewer values of felsic and basic volcanic components have been determined. The structures related to the continental margin environments of the Siberian continent, the continental slope and its basement have been found. According to sedimentary and geochemical data, the paleogeodynamic environment within the studied region was relatively stable and generally corresponded to the island arc conditions. The paleoclimate of the source area changed from semi-humid in the late Emsian-early Eifelian (Malaya Salairka age) to aridic in the middle Givetian (Kerlegesh age). Basin sediments formed in the deep water oxic environments with good water aeration, excepting euxinic environments found in the lowermost part of studied succession.

A continuous history of annual air temperatures in the Russian Altai for the past 2000 years has been reconstructed for the first time by integrating climate archives stored in the bottom sediments of four lakes in Gorny Altai (Teletskoye, Kucherla, Lower Multa, and Middle Multa). The integrated chronology comprises all known climate events of the two millennia time span: Roman warm epoch (~200 to 500 AD), Dark Age cold epoch (~500 to 750 AD), medieval warming (~750 to 1300 AD), and Little Ice Age (~1300 to 1850 AD). The events distinguished in the integrated climate reconstruction agree perfectly in number and time with the events reconstructed from other climate proxies for the Altai and adjacent areas of West Siberia, Tyva, and West Mongolia. Therefore, the temperature patterns represent a common course of the 2000-year climate evolution over a large part of Central Asia. Similar synchronicity is observed with the available quantitative climate reconstructions for the Northern Hemisphere and its different regions. It means that the climate change in Central Asia over the past two millennia has followed the general global scenario.

The goal of this study was to improve the high-resolution biostratigraphy of the Upper Jurassic and Lower Cretaceous in the type section on the Nordvik Peninsula, Anabar Bay, Laptev Sea. The results were used to identify a succession of 13 foraminiferal biostratigraphic units, 9 dinocyst units, and 8 palynofloral biostratigraphic units in the rank of zones and local zones. Based on new data, the stratigraphic continuity of this section is proved for the Lower and Middle Volgian, where a major stratigraphic hiatus was previously assumed. The established zones have variable correlation potential. Different versions of the subdivision of the section based on ammonites are discussed and the proposed scale is justified. A reference level based on calcispheres/calcareous dinocysts is defined providing global correlations and calibration of beds near Jurassic-Cretaceous boundary in the Tethyan and Arctic regions. The magnetostratigraphic subdivision of the studied section and its comparison with the Tethyan regions are discussed. Together with biostratigraphic data, the proposed δ¹³C_org curve in the Upper Jurassic and lower part of the Valanginian can be a tool for detailed correlations in different regions of the Northern Hemisphere. The cyclicity of carbon isotope composition in the Upper Volgian and Boreal Berriasian and isotope events in the Volgian and Lower Valanginian are determined within the Arctic region. The distribution of geochemical parameters (C_org, δ¹³C_org and hydrogen index) is determined in studied section, geochemical stratification of the section and variations in major oxide compositions are demonstrated. A sharp change in geochemical parameters is identified at the base of the Paksa Formation (Upper Volgian). The distribution interval of the “subsurface chlorophyll maximum” is determined. The study shows that high concentrations of isotopically light organic carbon in the first diasterene geochemical subhorizon were caused by high phytoplankton productivity and were deposited under reducing conditions favorable for preservation of organic matter. The analysis of major oxide compositions of the studied rocks revealed that variations in the chemical composition of the studied rocks reflect changes in their mineralogy and petrography.

New materials on the stratigraphy and structural features of the Bathonian-Neocomian sections of the Anabar-Lena basin are presented. In the territory adjacent to the Taimyr mountain-folded system, a clinoform-like structure of the Upper Jurassic strata has been revealed, which are characterized by high thickness compared to adjacent sections in the east of this region. The lectostratotype of the Chernokhrebetnaya Formation (uppermost Lower Oxfordian-lowermost Volgian) is proposed. The most complete and continuous stratigraphic section is compiled, its litho- and chronostratigraphic correlations are given comparing to the sections of adjacent territories characterized in detail by fossil assamblages. The evidences for a new lithostratigraphic division of the territory are provided, facies zoning of sediments is clarified, a thickness chart of the Upper Bathonian-Boreal Berriasian strata of the Khatanga-Olenek interfluve is proposed.

The age of the Turga Formation in the Middendorf’s outcrop is determined as latest Barremian-earliest Aptian based on fauna and microfossil assemblages. The composition of the fauna and palynomorph assemblages allows correlations between the Turga Formation and the Yixian Formation and lower part of the Jiufotang Formation of Northeast China. Results of the petrographic and geochemical analysis as well as microfossil studies showed that sediments accumulated in a shallow lake with low-energy hydrodynamics, sometimes under low-oxygen conditions. Climate features (warm temperate climate transitional to subtropical) and type of vegetation (coniferous forests with admixture of hardwoods) are reconstructed taking into consideration the composition of spore-pollen assemblages.

Based on the results of a comprehensive experiment conducted in September 2020, the spatial distribution of the following trace gases over the seas of the Russian Arctic are analyzed: carbon monoxide (CO), ozone (O₃), nitrogen oxide and dioxide (NO and NO₂), and sulfur dioxide (SO₂). It is shown that the gas concentrations in the surface air layer over the seas (at a height of 200 m) vary in the range 18-36 ppb for O₃, 60-130 ppb for CO, 0.005-0.12 ppb for NO, 0.10-1.00 ppb for NO₂, and 0.06-0.80 ppb for SO₂. Over most seas, the distribution of the gases across the water area is heterogeneous, which most likely reflects differences in their uptake by the ocean and peculiarities of transport from the continent.

Atmospheric waves are of increased interest in connection with exchange processes occurring in the atmospheric boundary layer. Experimental results of sounding mesoscale Kelvin-Helmholtz waves by turbulent lidars in a stably stratified boundary layer of the atmosphere are presented. This paper presents the data of measurements by BSE-4 lidar (532 nm), which has been working over forest-steppe for a long time. Atmospheric waves in most cases were observed in the evening and at night in the range of heights from the land to 600 m, when the Richardson number in the surface air layer did not exceed a critical value of +1/4. Fourier analysis of the time series of the structural characteristic of the refractive index Cn² showed that the spectrum of the wave process in the atmospheric boundary layer consists of a set of monochromatic waves with different oscillation frequencies. During the observations, the period of the waves varied from 1 to 11 min, and their amplitude changed from 20 to 300 m. It is found that monochromatic waves exist from half an hour to two hours. The disappearance of some monochromatic waves is compensated by the appearance of new ones. The process of generating small-scale turbulence runs throughout the life cycle of a Kelvin-Helmholtz wave. The results indicate that the turbulent lidar ensures remote detection and observation of atmospheric waves.