The Ura Uplift section in the Patom Highlands area of Siberia is one of the most complete Neoproterozoic carbonate-siliciclastic succession with excellent chemostratigraphic records (d13C and 87Sr/86Sr). Present study reveals the first finds of Ediacaran macrofossils within thick siliciclastic/carbonate succession of the Chencha and Zherba formations with well-established negative d13C anomaly attributed to the Shuram Excursion in this section. The fossils are preserved in glauconitic and quartz sandstone horizons in shallow-marine tide-influenced nearshore environment and share many taphonomic and morphological features with the White Sea-and Nama-type biotas. On the one hand, stratigraphic position of some of fossils within the uppermost Shuram Excursion falls into the time interval-573-567 Ma and therefore is correlative to the Avalon-type fossil assemblage. On the other hand, the new fossil assemblage indicates to the earlier appearance of some Nama-type species, such as erniettomorphs, than it was thought. In addition, the new assemblage is characterised by low-diversity metazoan community dominated by microbial textures. It potentially supports the hypothesis that the Ediacaran shallow water fossil assemblages were significantly less species-rich than their deeper water counterparts. The discovery of the old -est macrofossils in South Siberia both opens a new window to understand their palaeoecology and taphonomy, and demonstrates that palaeontological potential of such a vast region has not entirely been realised. (c) 2023 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.

An Erratum to this paper has been published: https://doi.org/10.1134/S1028334X2306017X

— The paper considers the geologic structure of the region and the current problems and prospects for the development of its energy potential and environmental safety. We provide grounds for the necessity of integrated projects aimed at studying the deep structure of the Caspian region as a single object by its five coastal states: Azerbaijan, Iran, Kazakhstan, Russia, and Turkmenistan. The proposed Geokhazar project is aimed at obtaining the lacking parametric geological and geophysical information about the deep subsurface structure of the water area of a sedimentary basin in the unique intracontinental catchment of the Earth. The project provides for the development of a universal prospecting concept taking into account the emplacement and conservation of hydrocarbon fields under severe thermobaric conditions at great depths and the absence of regionally consistent drainage systems; the determination of the factors influencing the nature of long- and medium-frequency eustatic fluctuations in the Caspian Sea level; and the assessment of the energy (geothermal and hydrocarbon) resources of the deep subsurface in the Caspian, cis-Caucasian–Mangyshlak, and South Caspian oil and gas provinces.

Fossil material of Ediacaran macroscopic algae has been found in the Vendian reference section, in the upper part of the Dal’nyaya Taiga Group of the Ura uplift, in the southern part of the Siberian Platform. The macrofossils discovered in the upper part of the Dal’nyaya Taiga Group are morphologically similar to carbonaceous Miaohen biota from the Ediacaran of South China; however, they occupy a lower stratigraphic level. Hence, the finding of algae macrofossils both develops our understanding of the evolution of marine ecosystems in the Proterozoic and demonstrates that the paleontological potential of one of the most representative Upper Precambrian sections has not been fully plumbed.

In 2020–2021 the palaeopascichnid fossils were found in the Krasnaya Gorka Site (Shirokovsky Reservoir, Kosva River area, Perm Region), a type Vendian fossil locality (problematic discoidal casts and arumberiamorph structures) for the Central Urals discovered by Yu.R. Bekker in 1972. In the stratigraphical context, the fossil locality is associated with Chernyi Kamen Formation of the Upper Vendian Sylvitsa Group. The results of morphometric analysis of palaeopascichnid fossils made possible to distinguish three morphological types: Palaeopascichnus delicatus, Yelovichnus gracilis, and Palaeopascichnus linearis. Finding of a large number of palaeopascichnid fossils both develops the understanding of their palaeobiology and taphonomy, and also demonstrates that palaeontological potential of the type fossil locality and one of the most representative section of the Chernyi Kamen Formation has not entirely been realized.

The authors have proposed a scheme for the formation of the hydrocarbon capacity of the West Siberian oil and gas basin in a paleosubduction geodynamic setting and continue developing the idea concerning the abiogenic deep genesis of hydrocarbons due to the low-temperature serpentinization of mantle peridotites during spreading in the Ordovician back-arc basin, which occupied at that time within the area of the future West Siberian basin, and the high-temperature hydration of peridotites in the mantle wedges above the subduction zones during the Selurian and Devonian. Another source of abyssal hydrocarbons is the serpentinization of mantle peridotites fragments in water saturated basement. A major role is being established in the formation of hydrocarbon deposits in the sedimentary cover of Western Siberia in the vertical migration of deep hydrocarbon fluids through degassing pipes, including anomalous annular zones, through deep thrusts, which are active gas-oil supply channels and along a large zone of Neogene-Quaternary low-amplitude horizontal shifts in the basement thickness. Deep-seated faults that comprise triassic rift system of West Siberian play a major role in water removal from deep sources. The feeding with new portions of oil and gas in hydrocarbon fields of West Siberian basin continues in present time, which provides renewability of regional hydrocarbons. The total volume of methane generated in the serpentinization zones of mantle peridotites is formed from two sources — abiotic (reaction of hydrogen with carbon dioxide dissolved in seawater) and biotic (methanogens). The origin of hydrocarbons is considered in the context of a new polygenetic scheme of oil and gas formation in the process of «abiogenic-biogenic» synthesis.

Due to homonymy, a new name Cephalonega Fedonkin, nom. nov. was proposed for the genus of Vendian macroorganisms, Onega Fedonkin. The improved diagnosis of this genus and evidence that this genus belongs to Proarticulata, an extinct phylum of Metazoa, are given. A detailed characterization of the phylum and all Proarticulata classes is given for the first time.

The paper is devoted to the integrated analysis of the interdisciplinary problem of the genesis of hydrocarbon potential in suprasubduction provinces. A geodynamic model is proposed for the formation of petroleum pools on the shelves of the Meso-Cenozoic back-arc basins in the western Pacific Ocean. Original data on the tectonics and composition of the mantle peridotites of the Polar Ural ophiolite complexes are given for comparison. These data are used to consider the low-temperature lizardite–chrysotile and high-temperature antigorite types of peridotite serpentinization in the back-arc basins and in the mantle wedges above the subduction zones of the paleozoic Paleouralian ocean. It is established that these processes are responsible for the abiogenic synthesis of hydrogen and methane. Of great theoretical and applied importance are the conclusions concerning the high antiquity of serpentinization as a hydrogen source, the possible relationships of the origin of life and its early evolution with hydrogen emission in the benthal, the predominance of chemoautotrophic prokaryotes with hydrogen exchange among the primary producers of organic matter in anaerobic conditions, and the high probability of naphthidogenesis based on the prokaryotic communities in the Archean and Proterozoic. The origin of hydrocarbons in the framework of the considered model is regarded from a viewpoint of a polygenetic paradigm of oil and gas generation.

Рассмотрены представления о геологическом разрезе юго-западной части поднятия Менделеева, относящегося к Восточно-Арктическим поднятиям Северного Ледовитого океана. Представления сложились на основании анализа материалов, полученных при батиметрической съёмке, видеонаблюдении и опробовании дна с помощью технических средств научно-исследовательской подводной лодки. Выделена нижняя толща кварцитопесчаников и доломитов видимой мощностью 230 м, залегающая в низах видимого разреза между глубинами 1500-1270 м. Со стратиграфическим и угловым несогласием она перекрывается верхней толщей известняков и песчаников видимой мощностью 40 м. Нижняя толща прорывается субвулканическим комплексом вулканитов составом от базальтов до андезитов, а в низах склона к ней прислоняется туфовая толща видимой мощностью 50 м.

This communication considers the ideas about the geological structure of the southwestern Mendeleev Rise belonging to the East Arctic rises of the Arctic Ocean. These ideas have resulted from analyzing the data obtained from bathymetric surveys, visual observations, and bottom coring using the technical tools of a research submarine. We distinguished the lower sequence of quartzite sandstones and dolomites, which has a visible thickness of about 230 m and occurs in the lowermost visible section, at depths between 1500 and 1270 m. This sequence is superimposed with stratigraphic and angular unconformity by the upper sequence of limestones and sandstones having a visible thickness of 40 m. The lower sequence is pierced by subvolcanic rocks of basaltic to andesitic composition, and in the lowermost part of the slope, a tuffaceous sequence having a visible thickness of 50 m adjoins it.

New paleomagnetic and magnetostratigraphic data are presented for the stratotype of the Upper Riphean Lopata Formation (Teya River, Yenisei Ridge). The paleomagnetic pole calculated is significantly distinct from the Phanerozoic and Riphean poles of the Siberian Platform and is similar to the Late Vendian–Early Cambrian poles of the Madagascar Group. The stratigraphic range studied is characterized by an anomalously high frequency of geomagnetic inversions (15 zones of magnetic polarity), which is comparable with the inversion frequency of the Late Vendian sections of Baltica. These data, along with previous paleontological findings, indicate an age of the Lopata Formation of 555–540 Ma.

Rangea is the type genus of the Rangeomorpha, an extinct clade near the base of the evolutionary tree of large, complex organisms which prospered during the late Neoproterozoic. It represents an iconic Ediacaran taxon, but the relatively few specimens previously known significantly hindered an accurate reconstruction: Discovery of more than 100 specimens of Rangea in two gutter casts recovered from Farm Aar in southern Namibia significantly expands this data set, and the well preserved internal and external features on these specimens permit new interpretations of Rangea morphology and lifestyle. Internal structures of Rangea consist of a hexaradial axial bulb that passes into an axial stalk extending the length of the fossil. The axial bulb is typically filled with sediment, which becomes increasingly loosely packed and porous distally, with the end of the stalk typically preserved as an empty, cylindrical cone. This length of the axial structure forms the structural foundation for six vanes arranged radially around the axis, with each vane consisting of a bilaminar sheet composed of a repetitive pattern of elements exhibiting at least three orders of self-similar branching. Rangea was probably an epibenthic frond that rested upright on the sea bottom, and all known fossil specimens were transported prior to their final burial in storm deposits.