The Adygean segment encompasses the transition zone between the Central and Western segments of the Greater Caucasus (GC). It is located within the western part of the Laba–Malka monoclinal zone (northern slope of the GC). North of this area, the Western Kuban and Eastern Kuban basins are situated. They are separated by the Adygean uplift and generally form the southern part of the Western Pre-Caucasus basins. We have carried out geological and structural studies of the lower part of the Alpine cover (Middle–Upper Jurassic) within the Adygean segment and interpreted seismic profiles of Mesozoic–Cenozoic strata in the Western Pre-Caucasian basins. It was revealed that tectonogravitational detachments are widespread within the Adygean segment on the northern slope of the GC and in the southern part of the Pre-Caucasus basins. They occurred as a result of slipping of sedimentary layers mainly in the north direction: down the slope of the GC orogen. Our tectonophysical studies have shown that the detachments took place in conditions of reverse and normal faulting due to vertical-oblique flattening and predominantly subhorizontal stretching. We have concluded that tectonogravitational detachments were formed by the interaction of two factors: vertical uplift of the GC orogen, caused by endogenic (tectonic) reasons, and gravitational slip of geomasses from the slopes of this mountain structure. Analysis of seismic sections crossing the Western Pre-Caucasian basins has shown the widespread development of clinoforms, which are paleodeltas of terrigenous material brought from the Scythian Plate and the East European Platform. The distribution of clinoforms in Cenozoic strata of the Pre-Caucasus basins allows us to suggest that southward-directed sedimentary flows existed from the Paleocene to the Late Pliocene. Based on this, we believe that the formation of the modern GC orogen and accompanying coarse molasse began no earlier than the end of the Pliocene, probably in the Eopleistocene. The formation of tectonogravitational detachments, which is one form of manifestation of the recent orogeny of the GC, led to the development of various structures: asymmetric folds, small thrusts, domino structures, faults, ramp folds, and thrust duplexes. Along the detachments there are ramp structures of local tension and compression, which form multisized cells of lateral rock-mass transport. Such cells facilitate activation of the migration, redistribution, and localization of hydrocarbons.

The article is devoted to the characteristics of the Juldybaevo floristic assemblage of the Republic of Bashkortostan, Russian Federation. This assemblage has an Early Permian (Kungurian) age and includes a number of representatives of Permian spore and gymnosperm plants, which are characteristic of the Early Permian stage of the florogenesis of the Western Angaraland. The information about the regional geology and stratigraphy of the Cis-Uralian Foredeep is given. A detailed description of the Juldybaevo floristic assemblage is given. This assemblage includes representatives of the equisetophytes, pteridosperms (lyginopteridophytes), ginkgophytes, vojnovskyopsids, and conifers. The main trends in the evolution of the Early Permian floras of the Western Angaraland are analyzed. The authors’ ideas about the paleogeographic and paleoclimatic conditions of the Juldybaevo flora are presented.

The first results of the U–Th–Pb isotope dating of detrital zircons (dZr, N = 130, n = 91) from the middle Danian sandstones (63.9–65.3 Ma) of the Cretaceous–Eocene Novorossiisk–Anapa flysch widely developed in the Sochi synclinorium (southern slope of the Western Caucasus) are presented. The maximum and minimum dZr age is 2973 ± 12 Ma and 318 ± 3 Ma, respectively; weighted average age of the four youngest dZr is 322 ± 7 Ma. There are no signs of erosion products of the Jurassic magmatites involved in the structure of the Greater Caucasus and Crimean Mountains into the sedimentary basin, where the Novorossiisk–Anapa flysch was formed. The results have revealed a high degree of similarity between the provenance signals of the Danian sandstones from the Novorossiisk–Anapa flysch, some Paleogene–Neogene and Early Quaternary (Early Pleistocene) sandstones of the Western Caucasus and Western Cis-Caucasia, red-colored Upper Permian and Lower Triassic sandstones of the Moscow syneclise, as well as Late Quaternary alluvium at lower reaches of the Don and Volga rivers draining vast expanses of the Russian Plate. These facts suggest: (1) the absence of eroded mountain structures of the Greater Caucasus and Crimea in the middle Danian; (2) the main volume of detrital material composing the Novorossiisk–Anapa flysch was formed due to the recycling of Permian–Triassic and younger sequences of the Russian Plate.

The complex body-trace fossils of Vendian soft-bodied biota have been found for the first time in the Central Urals during the study of the Vilukha and Sinii Kamen members of the Chernyi Kamen Formation of the Upper Vendian Sylvitsa Group (Kos’va River area, Perm Krai of Russia). These sedimentary sequences were exposed along the valley of the Shirokovskii Reservoir. Among the fossils, the chuariomorpha-like species Beltanelliformis konovalovi, previously described from the Konovalovka Member of the Chernyi Kamen Formation, was identified. However, the morphological analysis of the new fossil material revealed a number of principal differences from representatives of the genus Beltanelliformis Menner, 1974. It was shown that the taxon B. konovalovi, most likely, does not belong to this genus and probably needs further revision, and, in turn, the fossil locality at the Shirokovskii Reservoir allows us to establish a new area with fossils of the Precambrian mobile organisms.

An Erratum to this paper has been published: https://doi.org/10.1134/S1028334X23070061

New data on the U–Pb age (SHRIMP-II) and trace element composition (SIMS) of zircons from granites of Bolshoi Tyuters Island (Outer Islands of the Gulf of Finland) are presented. The upper intersection of the discordia (1825 ± 11 Ma) is taken as the age of crystallization of granites cutting through secondary quartzites and thereby determines their youngest age. Subconcordant zircons located in the upper part of the discordia have growth oscillatory zoning and geochemical characteristics of zircons of magmatic origin. The age of the lower intersection of discordia and concordia is about 570 Ma. It is supported by the independent zircon generation represented by black CL domains and rims in magmatic zircons characterized by increased contents of non-formula elements (light REEs, Ca, P, Ti, Nb, etc.), up to anomalous values. The age of the lower intersection of discordia and concordia can be considered as related to the Timan (Ediacaran) or Finnmark (Early Caledonian) thermal activation of the Fennoscandian Shield discovered earlier based on zircons from Kola Group gneisses.

The methodological approaches of seismostratigraphic analysis are tested in paleogeographic reconstructions of the Eastern Paratethys separate basins, which were isolated from the World Ocean in various periods. The scales and consequences of the Early Oligocene Solenovian regression are assessed for the territory of the Eastern Paratethys. Based on the paleogeographic reconstructions and data on the changes in the geodynamic setting of the Black Sea–Caspian region, we reconstructed the depths of the Early Oligocene (Solenovian) basin of the Paratethys for its initial (transgressive), transitional, and final (regressive) stages. Our model takes into account the oscillations of the relative sea level, as well as the influence of later tectonic deformations on the structure of the Oligocene basin.

Macroscopic fossils as composite molds and casts of Ediacara-type soft-bodied organisms were found in the Dzhezhim Formation of the Timan Range for the first time. Among them, representatives of palaeopascichnids, arboreomorphs, chuariomorphids, microbial colonies, and trace fossils were identified. This finding of such a large number of various Ediacaran fossils on the Timan Range not only develops our understanding of their paleogeographic range but also clarifies the age limits of the deposition of the Dzhezhim Formation, the stratigraphic position of which in the Upper Precambrian section was controversial.

The Rb–Sr age of glauconite and the U–Pb LA-ICP-MS age of detrital zircons from sandstones of the Riphean Okos Formation and the Vendian Ust-Pinega Formation were determined in the Keltmen-1 parametric borehole, drilled in the Vychegda trough of the Mezen syneclise in the northern part of European Russia. The model Rb–Sr age of glauconite (870–820 Ma) and the U–Pb age of the youngest detrital zircon (1005 ± 14 Ma) limit the time of accumulation of the Okos Formation to the first half of the Late Riphean, which is in good agreement with the biostratigraphic data available. The U–Pb age of the youngest detrital zircon from the lower part of the Ust-Pinega Formation suggests that accumulation of Late Vendian sandstones into the Mezen Basin began about 575 Ma. Thus, the duration of the stratigraphic hiatus between the Riphean and Vendian is estimated to be about 250–300 Ma. In the Late Riphean and Late Vendian, the Mezen basin was filled with terrigenous material of Archean–Late Proterozoic age (from 3.25 to 1.02 Ga), the sources of which were rocks of the Baltic Shield. In the lower part of the Ust-Pinega Formation, a population of detrital zircon of Vendian age (730–575 Ma) was discovered, a possible source of which could have been rocks of the Proto-Ural–Timan Orogen.

The paper presents the results of U-Pb isotope dating of zircons extracted from rocks of the southern part of the Baltic Shield (Early Riphean conglomerates and Paleoproterozoic secondary quartzites) and makes a comparison of these results with the ages of crystalline complexes of the East European Platform (EEP). The paper presents the study results on composition of quartzites from the Bol. Tyuters and Gogland islands. There has been discussion about tectonic and paleogeographical features in the period prior to the beginning of Riphean sedimentation in the northeastern part of the EEP. It is concluded that the conglomerates are composed of erosional products of mainly Paleoproterozoic and less frequently Archean crystalline complexes. At the same time, the rocks at the base of the generalized section of Riphean deposits (Gogland group), did not contain any zircons with ages referring to 200 million years prior to the inferred time (1640–1660 Ma) of the beginning of the conglomerate sequence formation. The rocks that compose the Gogland group and their underlying Paleoproterozoic basement rocks have significant differences. We associate these differences with the existence of pre-Riphean sheet-like deposits, comprising rocks of essentially quartz composition, in the southern Baltic Shield, in the upper levels of the peneplenized Paleoproterozoic basement structure. The deposits relics are only found on the Bol. Tyuters Island; in all other places, these deposits were completely eroded or underwent significant structural and material transformations. The absence of detrital zircon grains with ages ranging from 1.87 to 1.65 Ga in the clastic rocks of the Riphean basal horizons implies no noticeable Pre-Riphean and Early Riphean orogenic movements in the northeastern part of the EEP. Tectono-magmatic reactivation in this region occurred only in the middle of the Early Riphean.

The paper presents the first results of U-Pb LA-ICP-MS isotope dating (GIN RAS) of accessory zircon from magmatites of the Kastel Mountain and detrital zircons from the sandy matrix of conglomerates of the lower subformation of the Demerdzhi formation (vicinity of the Southern Demerdzhi Mountain). The three age estimates – (±1σ) – 147±1, 156±1 and 167±1 Ma, – obtained for granitoids of the Kastel intrusive, are consistent with the concept of its longterm and multi-stage magmatic evolution. The age of 167±1 Ma coincides with the final stages of the episode of bimodal magmatism widespread throughout the Mountainous Crimea from the Cape Fiolent to the Karadag. The intrusion of the first portions of basic magma near this time boundary had initiated the Kastel intrusion formation. The fractionation of basic magma during the second stage about 156±1 Ma gave rise to the formation of silicic melts from which the plagiogranites, comprising most of Kastel intrusive, were crystallized. About 147±1 Ma, the residual portions of silicic melts as small aplite veins intervened in the main volume of the intrusive and the adjacent host rocks.A comparison was made of the currently known ages of magmatites and detrital zircons from sandy rocks of some of the Triassic-Jurassic sedimentary strata of the Mountainous Crimes in order to clarify the source areas of the materials constituting the stratified rocks. It was shown that the magmatites of Kastel Mountain were a local source for the Demerdzhi formation.

The first results of U–Th–Pb isotope dating of detrital zircons (dZr) from the Chenka sandstones of the Cimmerides of the Mountainous Crimea are presented. Carboniferous–Triassic dZr dominate among dZr from Chenka sandstones. Analysis of previously obtained sets of dZr ages from the different-age and lithology formations of Cimmerides of the Mountainous Crimea has revealed the certain regularities in the change in time of the provenance signal and, accordingly, of the sources, the erosion products of which compose the studied formations. A comparison of the obtained of U–Pb ages of dZr from Chenka sandstones with similar data for sandstones from the Upper Triassic–Jurassic formations has shown that the provenance signals of the Chenka sandstones and Upper Triassic–Lower Jurassic flysсh strata are different, but the provenance signals of the Chenka sandstones and Middle–Upper Jurassic coarse clastic strata are similar. Detrital zircons from the Chenka sandstones are characterized by the parameters of the distribution of Th/U values intermediate between those from sandstones of flysch strata and from sandstones of coarse-grained strata. In general, the obtained isotope-geochronological and geochemical data and some features of the internal structure of dZr from the Chenka sandstones can be used as a strong argument in favor of interpretation of Chenka sandstones as an independent stratigraphic unit with an age not older than the Middle Jurassic. The similarity of the characteristics of dZr from sandstones of the Chenka sandstones with those of Middle–Upper Jurassic coarse clastic sequences casts doubt on the correlations of the Chenka sandstones with a number of lithologically similar units of the southwestern regions of the Mountainous Crimea, specified as Early Jurassic in age based on faunal finds.

Macrofossils of the Vendian soft-bodied organisms were found for the first time in the Vizinga and Ust’-Palega formations of the Upper Precambrian in Chetlasskii Kamen Hill (Middle Timan, Arkhangelsk oblast). Representatives of palaeopascichnids, aspidellamorphs, and possible frondomorphs, trace fossils, and microbially induced arumberiamorph structures were identified among molds and three-dimensional casts of fossils. Previously we revealed Vendian macrofossils in the Upper Precambrian in Dzhezhim-Parma Hill (South Timan, Komi Republic). The discovery of one more locality of various Ediacaran fossils in the middle part of the Timan Ridge significantly expands their paleogeography and also clarifies the time frame of deposition of the Vizinga and Ust’-Palega formations, the position of which in the Upper Precambrian section of Central Timan was debatable.

Abstract The Alpha-Mendeleev Rise is located in the Amerasia Basin. The work is based on a synthesis of interpretation of regional 2D MCS seismic profiles and data from rock sampling using special underwater vehicles on the slopes of seamounts. The Rise is represented by alternation of highs (horsts) and half-grabens. At the base of the horst cover, bright reflectors are distinguished, which are interpreted as volcanics. Half-graben sections are wedge-shaped and are similar in geometry to seaward-dipping reflectors (SDRs) of continental passive volcanic margins. Rock sampling has shown that the horsts are composed of sedimentary rocks of Paleozoic age, penetrated by intrusions. Aptian-Albian sections with volcanics (basalts, trachybasalts, trachyandesites) were identified on the horsts. U/Pb dating of igneous rocks showed that typical age of rocks is 110-114 Ma. Magmatic Cretaceous rocks contain zircons with ages ranging from pre-Barremian Mesozoic to Precambrian. The presence of these ancient zircons indicates that the Alpha-Mendeleev Rise is composed of continental crust. A model of the crustal structure of the Alpha-Mendeleev Rise is proposed. The upper and lower crust is approximately 20-30% saturated with intrusions of basic composition. At the base of the crust, a high-velocity layer up to 5 km thick is distinguished.

U-Th-Pb isotope dating of grains of detrital zircon from quartzites of the Suvanyak metamorphic complex, which forms the Suvanyak tectonic unit that forms the western part of the Uraltau uplift, located in the east of the West Ural megazone in the Southern Urals. The results of isotope dating of grains of detrital zircon from quartzites of the southern part of the Suvanyak metamorphic complex (samples G18-1 and R14-396) show that numerous populations of Late Neoproterozoic–Early Cambrian detrital zircon grains suggest a Peri-Gondwanan origin of the primary sources of detrital material for the protolith of the studied rocks. The structure of the Suvanyak tectonic unit involves metamorphic formations of different ages – Early Paleozoic in the south and Late Precambrian in the north, which are now formally united into a single Suvanyak metamorphic complex. Their differentiation requires additional research. For the Late Paleozoic southeastern margin of the Baltica (at that time already involved in the structure of the composite continent Arct-Laurussia), according to the results of isotope-geochronological study of detrital zircon from the sedimentary and metasedimentary sequences of the Southern Urals, a number of the following tectonic structures were identified. Near the southeastern edge of the margin, there was a Late Neoproterozoic–Early Cambrian oceanic basin, within which a volcanic arc or arcs were active during 650–520 Ma. The structure of the southeastern edge of the margin included the Peri-Gondwanan terrane or terranes (? Cadomian type), as well as thick Riphean-Early Paleozoic sedimentary sequences, autochthonous to the Baltica.

The Puchezh–Katunki crater is located in the central part of the East European Platform in the area of the Gorky Reservoir, has a diameter of 80 km, and is morphologically expressed by the central uplift of the basement (Vorotilov knoll) and the ring depression surrounding it, on the periphery of which there is a ring terrace. The crater is filled with various coptogenic (explosive (?)) formations: breccias of various types and bodies of suevites and tagamites. The results of studying the U‒Th‒Pb isotope system of detrital zircon grains from variegated explosive Puchezh breccias in the northwestern part of the ring terrace (three samples) are presented. The weighted average of the three youngest U‒Pb dates of detrital zircons from all studied samples is 258 ± 7 Ma, which corresponds to the Late Permian. We take this date as the lower age limit of the Puchezh breccias. The age sets of detrital zircon grains from the studied samples and from (1) crystalline rocks of the Vorotilov knoll and suevites of the ring depression and (2) Upper Permian–Lower Triassic sandstones of the Zhukov Ravine reference section (Moscow Syneclise) were compared. The absence of zircon grains, whose U‒Th‒Pb isotope system is similar to the parameters of those from the rocks of the Vorotilov knoll and suevites among the detrital zircons from the Puchezh breccia indicates the local nature of the Puchezh–Katunki explosion, the impact-thermal impact of which did not affect the detrital zircons in rocks of the marginal part of the ring terrace of the crater. A high degree of similarity of the age sets of detrital zircon grains from the lens of redeposited sandstones of the Puchezh breccias and Upper Permian rocks of the Zhukov Ravine section indicates that the Puchezh breccias were formed mainly due to the reworking of the Upper Permian–Lower Triassic sequences underlying the explosive formations. We consider the Uralian paleo-orogenic belt as the main provenance area for the deposits of the central regions of the East European Platform in the stratigraphic interval close to the Permian–Triassic boundary. The deposits were formed as a result of a high degree of mixing and averaging of clastic material of sedimentary flows containing the Uralian and Asha provenance signals.