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—The previous paleomagnetic studies of the Upper Vendian Zigan Formation sediments on the western slope of Southern Ural revealed uncommonly numerous magnetic polarity zones (Bazhenov et al., 2016). The dating of magmatic zircons from the tuff interlayer constrained the age of this formation to 547.6 ± 3.8 Ma. The rate of reversals estimated from most general considerations is about 20–30 per Myr which is approximately two to three times higher than the highest reversal frequency in Phanerozoic. In this work, a more accurate estimate of the rate of reversals is obtained from cyclostratigraphic study of the lower red-rock part (74 m) of the Zigan Formation in its continuous section along the Sterlitamak–Magnitogorsk road—the longest one among those previously studied by the paleomagnetic method. The correlation of the detailed cyclostratigraphic studies with the magnetostratigraphic column allowed a more reliable estimation of the reversal rate. The studied section in which we identified 20 reversals was accumulated during 1.6 Myr, i.e., the reversal frequency in this interval was 12–13 per Myr. Our quantitative assessment shows that the previous studies overestimated the geomagnetic reversal frequency by a factor of two. However, even the reversal rate estimated in this study can be regarded anomalously high, and the previous conclusions about the existence of a period with anomalously frequent reversals in terminal Ediacaran 547.6 ± 3.8 Myr ago can be considered validated.

U–Th–Pb (SHRIMP II) isotopic dating of accessory zircons from Vendian (Ediacaran) ash tuffs of the Basa formation section (Asha Group, Southern Ural) was performed for the first time. The concordant age obtained (573.0 ± 2.3 Ma) can be interpreted as the upper age limit of the onset of the Timan Orogeny in the structure of the Southern Urals. Fossil remains of Kuckaraukia multituberculata and several paleopascichnids, belonging to the genera Palaeopascichnus and Orbisiana, were previously found in the rocks of the Upper Basa Subformation, and the first occurrence of Arumberia banksi was established. The age obtained indicates a more ancient age of this Vendian assemblage compared to the previously accepted one.

—The analysis of paleomagnetic data from Late Neoproterozoic complexes of Siberia and Australia is carried out. We show that the existing paleomagnetic datasets are in a disagreement with the concept of the axial-dipole configuration of the Late Neoproterozoic geomagnetic field: proposed non-actualistic models of the field do not reasonably explain the distribution of the paleomagnetic poles. We carried out analysis of paleomagnetic and virtual geomagnetic poles distribution based on simple geometric calculations. The analysis suggests that the configuration of the Late Neoproterozoic geomagnetic field was determined by the coexistence of a weak, long-lived source that was stably fixed in space, with a main dipole source that experienced sporadic multidirectional jumps within a certain preferred region of the Earth. Predominantly equatorial orientation of the main dipole source is substantiated by paleoclimate proxies. We propose a descriptive non-actualistic model of the Late Neoproterozoic geomagnetic field—the Devious Equatorial Dipole hypothesis, which brings paleomagnetic and paleoclimate data into accordance.

—Paleo- and rock magnetic, sedimentological, and isotope geochemical study is carried out for the carbonate member of Late Neoproterozoic Nichatka Formation (Siberian Platform, western slope of the Aldan Shield) enclosed within glacial deposits corresponding to the hypothetical event of “Snowball Earth” global glaciation. Based on the sedimentological, rock magnetic, and geochemical indications it is established that sediments composing this member have varve-type seasonal stratification and, according to our estimates, have been accumulated for at most 13 thousand years. Obtaining the detailed paleomagnetic data for the Precambrian varves allowed us to reveal a linear trend in the distribution of the virtual geomagnetic poles and to link it with the peculiarity of secular variation of the geomagnetic field during the time span of the Nichatka Formation. The paleomagnetic record in the periglacial sediments of the Nichatka Formation testifies to their deposition close to the equator which might be considered as supporting the Snowball Earth hypothesis. However, the absence of annual temperature fluctuations within the equatorial belt makes the formation of seasonal deposits at low latitudes barely possible and completely excludes such a possibility in the conditions close to total glaciation. The contradiction between paleoclimatic and paleomagnetic data is not explained in the context of the actualistic model of the geomagnetic field. The peculiarities of the paleomagnetic record in the Nichatka Formation, similar to the record of the field during the reversal, suggest that the geomagnetic field in the Neoproterozoic could be determined by substantial contribution of the low-latitude non-axial-dipole component. This peculiarity of the Neoproterozoic geomagnetic field can explain the entire set of the worldwide paleomagnetic data implying low latitude glaciations in the Neoproterozoic.

U–Pb dating, Hf-isotope, and trace-element studies on two detrital zircon samples from sandstone interlayers in the Upper Jurassic conglomerates of the Southern coast of the Mountainous Crimea provide new information on the primary crystalline complexes from which those conglomerates were sourced. The U–Pb age spectra of studied zircons suggest that they were most likely sourced from the (meta)sedimentary complexes of the Eastern and Western Pontides blocks and the Dobrogea platform. In particular, a close similarity of the Precambrian age spectra with the detrital zircons from Late Neoproterozoic–Late Paleozoic (meta)sedimentary complexes of the Dobrogea block provides strong supporting evidence for the affinity between the Pre-Mesozoic basement of the Crimea and the Dobrogea platform. The zircons in the first sample were recycled through Dobrogea sedimentary complexes and originated from terranes with Amazonia affinities, while zircons in the second sample were recycled through the Taurides and originated from terranes related to northeastern Africa and Arabia. The strong similarity of the Precambrian parts of the age spectra of the Dobrogea complexes and the sample K15-007 suggests a resemblance of the Crimea’s Pre-Mesozoic foundation and the Dobrogea platform. Initial analytical data are provided in Electronic Supplementary Materials A (ESM A). Descriptions of measurement parameters, methodologies, and constants used to process primary analytical data and some processing results are reported in ESM B (Figs. B1–B8). Schemes of locations within Balkans–Anatolia–Black Sea–Caucasus region the crystalline complexes with Jurassic, Triassic, Permian–Carboniferous, as well as Late Neoproterozoic–Cambrian and Ordovician–Devonian ages are in ESM C (Figs. C1, C3–C5).

The results of U–Pb-isotopic dating of detrital zircons from sandstones of the Proterozoic Pogor’uy Formation, occurring to the north and south of the East Angara block of Yenisei Ridge, are presented. The sandstones of the northern part of the East Angara block are dominated by Archean and Paleoproterozoic populations of detrital zircons, while the samples from the southern part of the East Angara block have been revealed up to 25% of Mesoproterozoic age grains. The detrital zircon ages allow limiting the maximum sedimentary age of the Pogor’uy Fm. and the entire interval of its formation to 1.2–0.9 Ga. The paleogeographic features of the Pogor’uy Fm. deposition in the context of the existing opinions on the location of Siberia within the Rodinia supercontinent were examined.

U/Pb-isotope dating of detrital zircons from conglomerates of the reference section of the Demerdzhi Formation on the western slope of Mount Southern Demerdzhi was carried out. A cluster of the five youngest, reliably dated zircons with an average age of 154.1 ± 0.73 Ma was revealed, which indicates that the formation of conglomerates overlying the studied layer began to form not earlier than in the Late Kimmeridgian. The dating obtained forces us to reconsider the age of the Demerdzhi Formation, which was previously specified as Oxfordian–Early Kimmeridgian. New data on the age of thecoarse-grained sedimentary rocks of the Crimean Mountains advance concepts about Late Jurassic Cimmerian tectonic activity on the northern Tethys margin.

The main results are presented on U/Pb-isotope dating of 100 detrital zircons and, selectively, on the Lu/Hf-isotope system of 43 grains from sandstones of the Lopatinskii formation (the lower stratigraphic level of the Chingasan group). Ages from 896 ± 51 to 2925 ± 38 Ma were obtained with a pronounced maximum of ~1890 Ma in the curve of probability density, along with eHf estimates from +8.4 to–15.1, which allow one to throw doubt upon the molasse nature of the Lopatinskii formation.

New data were obtained on δ13Сcarb and δ18O variations in the sequence of deposits of the Dal’nyaya Taiga series at the western and eastern flanks of the Ura anticline. The summary δ13С curve was plotted in view of the correlation of sequence–stratigraphic data of the basin analysis. A series of positive anomalies was found within the succession. Alternatives for global chemostratigraphic correlation of the Dal’nyaya Taiga series of the Ura uplift were considered.

As a result of a microfacies analysis of the section of Middle-Upper Tithonian Limestones of the Demerdzhi Plateau (Mountainous Crimea), 12 microfacies types of rocks were distinguished. It has been established that these microfacies types formed in the facies zones of an inner carbonate platform: the littoral, restricted and open marine and sand shoals of the margins of a carbonate platform. The sequence of the microfacies types in the vertical section corresponds to a transgressive trend with minor sea-level fluctuations of the second order. In addition, the communities of microencrusters, which played an active role in sediment stabilization and formation of small bioherms, have been studied. These communities are considered to be evidence of the shallowness of the paleobasin