The Neoproterozoic Katav Formation, which is a part of the Ural stratotype section, was considered to be remagnetized in the Late Paleozoic for many years. If the primary magnetization of the rocks is proven, the magnetostratigraphic record found in the Katav Formation may become a good paleomagnetic benchmark in the Neoproterozoic history of the Earth and serve as a source of information about deep processes in the Earth and their evolution. In this work, the arguments in favor of the primacy of the high-temperature characteristic component of magnetization of the Neoproterozoic Katav Formation rocks, previously put forward by V.E. Pavlov and I. Galle, were verified and confirmed on more extensive and detailed material. New paleomagnetic data have been obtained for two sections of the Katav Formation in the Southern Urals near the town of Yuryuzan and the village of Galiakberovo, as well as the overlying Inzer Formation near the village of Galiakberovo. A detailed magnetostratigraphic section of the Katav Formation for the Yuryuzan section is presented. The analysis of the upper part of the section shows 39 polarity intervals within the 74.6 m thick strata. The new data confirmed the existence of a trend of displacement of paleomagnetic directions from bottom to top along the studied sections of the Katav Formation, directed towards the paleomagnetic direction of the overlying Inzer Formation. The total value of the displacement in the Katav Formation is consistent in sections located at a distance from each other, located in areas with slightly different geological history. A significant difference in the direction of the characteristic component of magnetization in the Katav Formation from the corresponding directions in the Inzer Formation was confirmed. Generalization of new and previously obtained data gives grounds to consider the primary characteristic component of magnetization of the Katav Formation deposits, previously considered to be remagnetized. The frequency estimates of the geomagnetic reversals revealed by the new data in the upper part of the Yuryuzan section using the results of our previously performed cyclostratigraphic analysis are 11–12 reversals per million years. Thus, the existence of another interval of geomagnetic field hyperactivity in the Neoproterozoic is confirmed.

In order to obtain new paleomagnetic data on Vendian rocks in the Southern Urals, we studied the high-temperature magnetization component in sandstones of the Uryuk Formation, the carrier of which is hematite. The distinguished hematite vector in the collection of samples differs from the previously obtained intermediate-, intermediate-high-temperature magnetization component of magnetite, which is part of the same rocks. The average directions of the hematite component of magnetization of the Uryuk Formation were compared with the average directions of the overlying Basu Formation. The metachrony of the magnetite component and the synchrony of the hematite component are suggested.

Reconnaissance sampling and study of carbonate rock samples from the outcrop of the Upper Riphean section of the Katav Formation near the basin of the Bolshoy and Maly Kazamash rivers. An average paleomagnetic direction was obtained for the section, which differs in declination from the previously published average paleomagnetic directions of the Katav Formation in the Southern Urals. In addition, a large number of magnetic field inversions were recorded in this section. The paper discusses the prospects for further study of the section, the necessity of which is determined by the issues of regional geology and the study of the magnetic field of the Late Precambrian. Проведен рекогносцировочный отбор и изучение образцов карбонатных горных пород из разреза катавской свиты верхнего рифея в бассейне рек Большой и Малый Казамаш. Для разреза получено среднее палеомагнитное направление, отличающееся по склонению от опубликованных ранее средних палеомагнитных направлений катавской свиты на Южном Урале. Кроме того, в разрезе зафиксировано большое количество инверсий магнитного поля. В статье обсуждается перспективность дальнейшего исследования разреза, необходимость которого обусловлена вопросами региональной геологии и изучением магнитного поля Земли в позднем докембрии.

We present a detailed magnetostratigraphic and cyclostratigraphic profile through the Riphean (Tonian) Katav Formation in the southern Urals. The study confirms the primary nature of the magnetization these rocks. The cyclostratigraphic study identified several orbital periods including the 405 ka long eccentricity. This allows us to quantify the reversal frequency in the Katav and our estimates range 7-12 reversals per million years. Based on our study, we identify an interval of magnetic field reversal hyperactivity in the Neoproterozoic interval. Age estimates for the Katav are contentious and range somewhere between 800 Ma and 900 Ma based on carbonate Pb-Pb ages and stable isotope correlations. The paleomagnetic poles obtained in this study of the Katav (and overlying Inzer) Formation do not fit anywhere on the Baltica apparent polar wander path between 1100 Ma and 900 Ma. Furthermore, they lie 90 degrees away from the 900 Ma segment of the path. We tentatively estimate their age to be closer to 800 Ma and perhaps confirm a previously hypothesized pulse of rapid true polar wander between 825 Ma and 790 Ma.(c) 2023 China University of Geosciences (Beijing) and Peking University. Production and hosting Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).

Detailed petrographic, electron-microscopic, and paleomagnetic studies were conducted on flatbedded synsedimentary carbonate breccias from three blocks of rocks (one block from Minyar, two blocks from Katav-Ivanovsk) to verify the ideas about the time of formation of the high-temperature component (HTC) of natural remanent magnetization (Jn) of limestones from the Upper Riphean Katav Formation, Southern Urals. Petrographic and electron-microscopic observations revealed that the composition of pebbles corresponds to that of the host matrix rocks, thus enabling the use of an intraformational conglomerate test. In all the studied blocks, the distribution of paleomagnetic directions for pebbles is generally chaotic, with the concentration parameter not exceeding 3. These test results meet the Graham criterion. The pebbles’ average Jn have a larger confidence oval and differ significantly from the matrix’s directions with a much smaller confidence oval. The Hodges-Ajne test was applied to the blocks from Katav-Ivanovsk. The Rayleigh test was used for the block from Minyar. The results obtained at this stage indicate that the HTC of magnetization of the Katav limestones may have a primary origin. If this is confirmed, the Katav Formation would be a good paleomagnetic record of the Earth’s Neoproterozoic history and provide valuable insights into the geomagnetic field behavior in the Late Precambrian.

In the western wing of the Bashkir megantiklinorium (Southern Urals), the Ediacaran is represented by sediments of the Asha Series, where the Basu and Zigan Formations having similar lithological composition are difficult to distinguish in incomplete and disconnected sections. In this paper, we present an example of the use of paleomagnetic data to solve this stratigraphic problem. New paleomagnetic data obtained in recent years made it possible to distinguish lithologically similar deposits of the Basu and Zigan Formations. The characteristic paleomagnetic directions for the Basu and Zigan deposits differ strongly, and therefore this difference can be used to determine the stratigraphic position of the rocks. Based on these data, a 20-m thick fragment of the Asha Series section located on the eastern side of the Avdyrdak anticline along the Ufa - Inzer - Beloretsk road was studied, wherefrom 50 samples were collected. Previous studies could not give an unequivocal answer to the question of which formation this section belongs to. We have obtained the data confidently indicating that the rocks in the studied outcrop are a part of Basu Formation.

Analysis of secondary magnetization components (Late Paleozoic remagnetization) makes it possible to trace the formation of the Southern Urals folded system. The paper presents new data on the Late Paleozoic remagnetization of rocks in the Southern Urals. The results of the paleomagnetic study of rocks in various structural zones of the Southern Urals, obtained since 2009, were revised and supplemented again to identify the remagnetization component. Combined analysis of the newly obtained results and previously published data on Late Paleozoic remagnetization shows that in the western segment of the western slope of the South Urals the intermediate-temperature magnetization component (ITC) was acquired prior to or at the initial stages of deformation. In contrast, the ITC observed in the eastern segment arose after folding. In the western part of the Magnitogorsk zone in Devonian-age rocks, the average for all sites is post-folding. Deformations here occurred long before the final stage of the development of the Urals, most likely in late Devonian — early Carboniferous. In the Magnitogorsk-Bogdanovsky graben, in the early Carboniferous rocks, ITC has arisen during the process of deformation or shortly before it and at its initial stages. The Late Paleozoic remagnetisation identified in the paleomagnetic records is regional in nature and probably reflects a collisional event of the final stage of the evolution of the Ural Paleocean. Collision processes which occurred in the Southern Urals from the Late Devonian until the Late Permian time had undoubtedly left their trace in the western structures (in present-day coordinates). Within the passive margin of Baltica the collision resulted in the formation of a lateral series of fold-and-thrust structures. They started from the Main Uralian Fault westward, with possible gradual termination of this process towards the Pre-Uralian Foredeep. Paleomagnetic results of this research work support these assumptions.

The metamorphosed iron ore volcanogenic–sedimentary strata of the Karsakpai series in the eastern Ulutau Precambrian terrane of Central Kazakhstan are studied. The crystallization age of 745 ± 3 Ma is first dated for the andesidacitic tuffs by the U–Th–Pb (SIMS) method, which indicates their formation at the end of the Tonian period of the Neoproterozoic Era.

Статья посвящена истории возникновения и развития геофизических исследований, проводимых в Институте геологии УФИЦ РАН. Основными направлениями деятельности лаборатории геофизики в последние годы являются геотермические и палеомагнитные исследования. Представлены основные результаты, полученные по этим направлениям научной деятельности. В геотермии – это изучение природы аномалий теплового потока, реконструкция изменений климата по измерениям температуры в скважинах, введение палеоклиматических поправок в измеренный тепловой поток на Урале. Палеомагнитные исследования направлены на решение фундаментальной проблемы эволюции Земли – воссоздание глобальной палеогеографии для различных интервалов времени. Получены новые палеомагнитные данные по отложениям верхнего рифея и венда на Южном Урале. По датированным вулканитам получен результат, уточняющий траекторию кажущейся миграции палеомагнитного полюса для палеоконтинента Балтика на сегменте поздний ордовик – ранний силур, где надёжные палеомагнитные данные отсутствовали. Получены новые палеомагнитные данные по породам девонского и нижнекаменноугольного возраста западной и центральной частей Магнитогорской зоны, позволяющие сравнить одновозрастные палеошироты Магнитогорской островной дуги и восточной окраины Восточно-Европейского континента и определить взаимные перемещения этих двух тектонических элементов. Также проведен анализ вторичных позднепалеозойских компонент намагниченности по всем тектоническим зонам Южного Урала, что позволяет проследить формирование складчатой структуры этой части мобильного пояса. The article is devoted to the history of the origin and development of geophysical research carried out at the Institute of Geology, UFIC RAS. The main areas of activity of the laboratory of geophysics in recent years are geothermal and paleomagnetic research. The main results obtained in these areas of scientific activity are presented. In geothermics, this is the study of the nature of heat flow anomalies, climate reconstruction in the Urals from geothermal data, the introduction of paleoclimatic corrections to the measured heat flow in the Urals. Paleomagnetic studies are aimed at solving the fundamental problem of the evolution of the Earth – reconstructing global paleogeography for different time intervals. New paleomagnetic data obtained by sediments of the Upper Riphean and Vendian in the Southern Urals. Based on dated volcanics, a rather high degree of reliability result was obtained that can clarify the trajectory of the apparent polar wander path (APWP) for the Baltica paleocontinent during the Late Ordovician–Early Silurian, where reliable paleomagnetic data are not available. New paleomagnetic data have been obtained on the Devonian and Lower Carboniferous rocks from the western and central parts of the Magnitogorsk zone, allowing one to compare the coeval paleolatitudes of the Magnitogorsk island arc and the eastern edge of the East European Craton and determine the mutual displacements of these two tectonic structures. Analysis of secondary magnetization components (Late Paleozoic remagnetization) has been also performed for all tectonic zones of the Southern Urals, which makes it possible to trace the formation of the folded structure of this part of the mobile belt.

Abstract—In order to determine the Earth’s magnetic field intensity in the Devonian, a collection of rocks of the Baymak-Buribay formation of the Buribay volcanic complex in the West Magnitogorsk Zone—Southern Urals, Khvorostyanka section, has been studied. The complex dates back to the Late Emsian of the Early Devonian (D1e2, 408–393 Ma), based on the conodont fauna. A full set of experiments to study the magnetic and thermomagnetic properties of rocks and to assess the domain structure of magnetic grains have been performed; micromagnetic and X-ray studies have been carried out. It is shown that the carriers of the characteristic component of natural magnetization are single-domain and small pseudo-single-domain grains. The (Banc) paleointensity has been determined by the Thellier-Coe method and the Wilson express method. Ultra-low Banc values = (2.01–7.07) μT have been obtained in 8 samples (24 duplicates) from two sites. The average values of the virtual dipole moment (VDM) for both sites are close to each other and equal to ≈1×1022 Am2, which is almost an order of magnitude less than its current value of 8 ×1022 Am2. The new Banc determinations confirm the hypothesis that there was a period of very weak field in the Devonian, which again raises questions about the time of the Earth’s solid core formation and the geometry of the geomagnetic field during periods of a very weak field intensity. The new Banc determinations are consistent with the already obtained data on paleointensity in the Devonian, indicating a high probability that there was a long period of a weak field at this time, the intensity of which is close to the intensity of the nondipole components of the current field. This fact raises the question about the actual geometry of the field at that time—was it dipole or multipole?

Abstract —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.

Для проверки предположения о существовании эпизода «гиперактивности» магнитного поля на рубеже докембрия и фанерозоя выполнено повторное, более детальное палеомагнитное опробование наиболее полного непрерывного разреза красноцветов зиганской свиты венда из изученных ранее на Южном Урале, расположенного вдоль новой дороги Макарово -Кулгунино

The behavior and strength of the Late Ediacaran-Early Cambrian magnetic field may provide a unique background for unravelling controversial plate reconstructions, the nature of the inner core and even biological evolution. Recent studies suggest that the Ediacaran dipole field strength was extremely low and that the magnetic field was in a hyperactive reversing state (>4?6 R/Ma) well into the Cambrian. Data supporting hyperactive reversals are derived from numerous studies of sedimentary successions in Baltica including the 547 Ma Zigan formation in the Urals. Although some of the younger, Cambrian-age, sedimentary sequences have robust age control, estimates of reversal frequency in the Zigan Formation was based on average sedimentation rates. In this study, we returned to a thick (-75 m) section of the Zigan and sampled for both magnetostratigraphic and magnetic susceptibility at a finer scale (-20 cm). The magnetic susceptibility data were used to evaluate orbitally-forced frequency signals that my provide a higher resolution estimate of reversal frequency. In particular, the stable long eccentricity signal of 405 Kyr was recognized in a frequency analysis of magnetic susceptibility. The identification of this periodic signal allowed us to refine the estimate for reversal frequency in the section to 20 R/Ma. Although slightly smaller than an original estimate of 25 R/Ma, this rate is well above the Phanerozoic background reversal rate and 3?5 times higher than the cut-off for hyperactivity. Our study thus confirms the hyperactive reversal interval from at least the latest Ediacaran until sometime in Epoch 3 of the Cambrian. @& nbsp;2021 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.

В работе приведены результаты палеомагнитного изучения красноцветных известняков катавской свиты верхнего рифея, а также красноцветных песчаников подстилающих и перекрывающих ее зильмердакской и инзерской свит.Всего изучено более 500 ориентированных образцов из 4 разрезов.Лабораторные исследования выполнены в соответствии с общепринятой в настоящее время методикой, включающей в себя температурную магнитную чистку и компонентный анализ намагниченности.Во всех разрезах удалось выделить биполярную ВТК намагниченности, тесты складки и обращения по которой уверенно положительные.Направления намагниченности в разрезах Толпарово и Карамалы смещены приблизительно на 20° по склонению относительно направлений в разрезах Юрюзань и Галиакберово (а также многих других разрезов, изученных как авторами, так и другими исследователями).Возможно, такой результат связан с тектоническими перемещениями.Наблюдается закономерное смещение среднего направления ВТК намагниченности снизу вверх по разрезам в сторону уменьшения наклонения от низов катавской свиты до низов инзерской свиты, что является достаточно сильным аргументом в пользу первичности намагниченности пород катавской свиты.Доказательство первичности высокотемпературной компоненты (ВТК) намагниченности катавской свиты, считавшейся ранее метахронной, могло бы стать хорошим палеомагнитным репером в неопротерозойской истории Земли и дало бы важную информацию об особенностях поведения геомагнитного поля в позднем

This paper gives new paleomagnetic research results concerning Lower Carboniferous volcanics of the Central Magnitogorsk Zone in the South Urals, with the aim to independently assess geological ideas about the development history of the Magnitogorsk island arc. We studied 9 sections of effusive rocks with primarily basic composition in the Grekhovka and Berezovka Formations located in the meridional flow of the Ural River from the village of Kizilskoe on the north to the village of Ershovka on the south. Laboratory paleomagnetic investigations were conducted according to currently accepted methods, including thermal demagnetization and component analysis of the isolated magnetization directions. The mean direction of the high-temperature magnetization component obtained on 28 sites and the paleolatitude calculated therefrom virtually coincide with global data on the eastern margin of the paleocontinent Baltica. Consequently, according to paleomagnetic data the Central Magnitogorsk Zone was a part of the continent in the Early Carboniferous. A combined analysis of the new results on Lower Carboniferous rocks and our previous data on Devonian rocks suggest that paleomagnetic data and modern ideas about the evolution of the Uralian Orogen associated with the collision between the Magnitogorsk island arc and the passive continental margin do not contradict each other.