-We report results of a systematic paleomagnetic study of the Abinskaya Group of the Kuznetsk depression, including a typical volcanic complex that reflects important features of the evolution of the Permian-Triassic Siberian large igneous province (LIP). Four zones of magnetic polarity have been established in the group's deposits. We revise the correlation of the volcanic sheets of the Mal'tsevo Formation (Fm.) at the base of the group with the Ivakinsky Fm. of the Norilsk region, which is linked to the initiation of trap magmatism. The beginning of the eruption of the Saltymak complex volcanic rocks in the Kuznetsk area corresponds to the boundary between subchrons LT1n.1n and LT1n.1r (251.2 Ma) within the Kedrovka sub-formation of the Mal'tsevo Fm. This boundary was traced in the magnetostratigraphic sections of the Maimecha-Kotui, Koltogor-Urengoy, Western Taimyr, and Norilsk regions of the Siberian LIP and suggests a correlation of the Mal'tsevo Fm. volcanic rocks with the upper part of the undifferentiated interval of the Onkuchak - Tyvankit (?) fms., the base of the Korotchaev Fm., the Verkhnetam Fm. and the top of the Samoed Fm. The duration of this main pulse of volcanism in the Kuznetsk depression did not exceed 0.1 Myr. The volcanic sheets of the second, significantly weaker pulse of the Yamin Fm. are compared with the Maimecha Fm. of the Maimecha-Kotui area and the top of the Korotchaev Fm. of the Koltogor-Urengoy area. Thus, the accumulation of the entire Abinskaya Group, including the sedimentary complex of the Sosnovka Fm., lasted no more than 1.5 Myr. Except for the initial stage, this coincided with the eruption of most of the Maimecha-Kotui and Koltogor-Urengoy trap sections. The early magmatism of the Ivakinsky time and its analogs in other areas of the Siberian province during the Permian-Triassic boundary in the Kuznetsk depression probably corresponds to the break between the Taylugan Fm. and the Abinskaya Group. The mean paleomagnetic pole (PLat = 59.0 degrees, PLon = 160.3 degrees, A95 = 5.7 degrees, N = 33) calculated for the entire studied section reflects the paleogeography of the Kuznetsk depression and can be considered a reference pole for the Permian-Triassic boundary.

Data on the absolute value of the geomagnetic field intensity at the beginning of the Cretaceous Normal Superchron (C34n) was obtained from basalts of Hooker Island of the Franz Josef Land archipelago (FJL). These basalts are considered as one of the manifestations of the High Arctic Large Igneous Province. The record of the ancient geomagnetic field in the studied Early Cretaceous basalts was preserved well due to the presence of pseudo-single domain grains of primary magmatic titanomagnetite. The paleointensity, obtained by the Thellier–Coe method, satisfies the generally accepted reliability criteria, taking into consideration other necessary evidence. This information indicates that 125 Ma, during the formation of the FJL traps, the intensity of the geomagnetic field was four times lower than today. Our estimates show that the mean value of the virtual dipole moment was 1.7 × 1022 Am2. These results support the views about the low paleointensity at the Barremian–Aptian boundary and indicate a correlation between the intensity of the geomagnetic field, the frequency of reversals, and the formation of mantle plumes.

We report new estimates of the intensity of the geomagnetic field strength for the Permian–Triassic boundary. Amid predominantly low virtual dipole moment values for that time in the Global Paleointensity Database, episodes of increased VDM up to 8.9 × 1022 Am2 were recorded in the sections of the trap formation of the Kuznetsk depression, which do not conform to the Mesozoic Dipole Low concept. Analysis of data on changes in the value of the virtual dipole moment during the formation of the Siberian Large Igneous Province within the framework of modern magnetostratigraphic correlations indicates a persistently weak geomagnetic field only at the initial stage, when most of its Norilsk area was formed. A change in the geomagnetic mode is noted after 800 thousand years at the level of subchron LT1n.1r (251.2–251.1 Ma) of the General Magnetostratigraphic Scale and was recorded in the basaltic andesite lava sheets of the Kuznetsk area. Low virtual dipole moment values from this time correspond to episodes of reversals, while the overall intensity was on average only slightly lower than today. Thus, the drop in paleointensity at the very beginning of the Triassic period was not caused by a major long-term change in the geodynamo, but was short-term and related to plume activity.

—We report results of a detailed study of the paleomagnetic record in the sedimentary rocks of the Taseeva Group of the Yenisei Ridge in three typical sections in the lower courses of the Angara, Taseeva and Irkineeva rivers. Our results confirm that the geomagnetic field was in an anomalous state at the Precambrian–Phanerozoic boundary. It is well known that Ediacaran rocks in general have preserved several different paleomagnetic directions that do not conform to the geocentric axial dipole model. For example, Siberian sections display two equally valid groups of paleopoles that cause many debates over the geometry of the geomagnetic field and whether any of the components correspond to its dipole configuration. The paleomagnetic record we studied is unique in that the rocks of the Chistyakovka and Moshakovka formations have captured both these components, which is factual evidence of a synchronous existence of two sources. To explain these findings, we propose an original hypothesis in which the bipolar component that is widely present in the rocks and corresponds to the Madagascar group of paleomagnetic poles is associated to the field of the geocentric axial dipole. The less widespread monopolar component corresponding to the Australian–Antarctic group of poles is reflective of a stationary anomalous source. The recording of this source became possible due to the abrupt decrease in the strength of the virtual dipole moment that probably was at its lowest during the accumulation of the Chistyakovka and Moshakovka formations. The new paleomagnetic pole calculated for the bipolar component – 39.2°N, 61.1°E – plots on the apparent polar wander path for Siberia and can be considered a key determination for the age ~570 Ma.

Here we report the first data on the absolute intensity value of the geomagnetic field on the Permian-Triassic boundary from basalts of the Kuznetsk basin. The latter are considered as one of the manifestations of the initial stage of trap magmatism during the for-mation of the Siberian large igneous province. The good preservation of information on the ancient geomagnetic field in the Mal'tsevskaya Formation basalts is due to the presence of small single domain and pseudo-single domain grains of primary magmatic titanomagnetite in the groundmass. The paleointensity values obtained following the Thellier-Coe method correspond to the generally accepted criteria of reliability and indicate that the geomagnetic field intensity during the formation of the Kuznetsk basin traps on the Permian-Triassic boundary was almost an order of magnitude lower than the present-day one. Moreover, the mean values of the virtual dipole moment for the Kozhukhta and the Vlasov units in the lower and middle Mal'tsevskaya Formation ((1.9 +/- 0.6) . 10(22) A . m(2) and (1.1 +/- 0.7) . 10(22) A . m(2), respectively) are in good alignment with determinations of the paleointensity during the accumulation of the Ivakinsky Formation of the Norilsk Region in the Siberian province, which confirms the accuracy of traditional regional correlations.

Here we present reconstructions indicating the stationary position and paleogeography of the Iceland plume, as well as its direct connection to the Mesozoic–Cenozoic large igneous provinces of the northern Atlantic and the Arctic. The main evidence for the stationary position of the Iceland hotspot comes from paleomagnetic data for the trap formation of the Franz Josef Land archipelago. Our reconstructions show that the Barents Sea magmatic province included in these traps belongs to the trace of the Iceland plume and formed as part of the High Arctic Large Igneous Province during a single relatively brief event ca. 125 Ma. Older pulses of basaltic magmatism inferred previously for the Franz Josef Land archipelago for the Early and Middle Jurassic period do not have known analogs in adjacent territories of the present-day Arctic.

The possibility of reconstructing the geological chronicle by identifying the peculiarities in the variations of the Earth’s magnetic field associated with the reversals is one of the fundamental applications of paleomagnetism. The most detailed records of reversal events whose duration is, on average, one to ten thousand years have been recognized from the results of studying flood basalts of the large igneous provinces. At the same time, recent publications report the facts that are interpreted as a record of a geomagnetic reversal in the intrusion bodies. Inter alia, these data have been obtained for the relatively thin Ergalakh dolerite sills in the Norilsk region of the Siberian trap province which are supposed to have recorded the «Ivakinsky-Syverminsky» reversal corresponding to the Permian–Triassic boundary. The interpretation is based on the hypothesis of slow cooling of the intrusion during which its apical parts are magnetized during the Ivakinsky epoch of reversed polarity whereas the central parts acquire magnetization after the reversal during the Syverminsky time corresponding to normal polarity. In this paper, we consider the results of mathematical modeling to discuss the validity of these assumptions and the potential eligibility of subvolcanic intrusions as a source of information for studying geomagnetic reversals. It is shown that the duration of their cooling including the interval of the most probable magnetization is a few orders of magnitude shorter than the duration of the reversal transitions, whereas the presence of the components with normal and reversed polarity is most likely to be due to the effect of self-reversal.

The paper presents the first results of studying the anisotropy of magnetic susceptibility in the basalts from Hooker Island, associated with the direction of the melt movement, the location of the eruption centers and the morphology of magmatic bodies. The established features of the primary magnetic fabrics correspond to the trap mechanism of formation of the volcanic province of the Franz Josef Land Archipelago and are a reflection of the simultaneous action of numerous small eruption centers. Previously obtained conclusions about the long, during the Early Jurassic - Early Cretaceous, multi-stage history of magmatism are not confirmed.

The work presents the first results on the anisotropy of magnetic susceptibility in Hooker Island basaltoids; this anisotropy is related to the direction of motion of the melt, the location of eruption centers, and the morphology of igneous bodies. The peculiarities of the primary magnetic fabric revealed correspond to a trap mechanism of formation of the Franz Josef Land igneous province and reflect the simultaneous effect of multiple small eruption centers. Earlier conclusions about the long-term (during the Early Jurassic–Early Cretaceous) multistage magmatism history have not been supported.

The possibility of reconstructing geologic events by identifying patterns in variations of the geomagnetic field related to reversals is one of the fundamental applications of paleomagnetism. The most detailed records of reversal events, whose duration averages 1–10 thous. years, are known from studies of flood basalts of large igneous provinces. At the same time, there have been recent publications presenting facts interpreted as records of geomagnetic reversals in intrusive bodies. Specifically, such data were obtained for relatively thin dolerite sills of the Ergalakh complex in the Norilsk region of the Siberian trap province that supposedly recorded the Permian-Triassic “Ivakin-Syvermin” reversal. This interpretation is based on the hypothesis of a slowly cooling intrusion, in which its apical parts magnetized in the Ivakin epoch of reversed polarity and the central parts—after the reversal in the Syvermin epoch of normal polarity. In this paper, using results of mathematical modeling, we discuss the validity of such assumptions and the potential attractiveness of subvolcanic intrusions for studies of geomagnetic reversals. We demonstrate that the duration of their cooling, including the most probable interval of magnetization is several orders of magnitude less than the duration of reversal transitions, and that the most probable cause of the occurrence of both polarities is the self-reversal effect.

We report new paleomagnetic and geochronological data for rocks of the Franz Josef Land archipelago and generalize available information about the paleomagnetism of the Barents Sea continental margin as applied to the issues of the Mesozoic Arctic tectonics. Specifically, the obtained age estimates are indicative of a brief episode of mantle plume magmatism at the Barremian–Aptian boundary (Early Cretaceous). The paleomagnetic data shows that intraplate magmatism formations in the High Arctic, including the Franz Josef Land traps, are nothing else than a trace of the Iceland plume on the migrating tectonic plates of the region. Thus, the Iceland plume was geographically stationary for at least the last 125 Myr. Our paleotectonic reconstructions suggest a direct connection of the intraplate strike-slip systems of the Eurasian continent with the configuration and subsequent evolution mode of Mesozoic marginal basins and spreading axes during the initial opening stage of the Arctic Ocean.

The results of the first paleomagnetic study of a late Neoproterozoic magmatic complex on the Siberian paleocontinent (Siberia) using U–Pb geochronological data are presented. The igneous rocks of the Zimoveyniy massif (block) of the South Yenisei Ridge formed in an active continental margin setting and recorded the initial thermoremanent magnetization. Our calculations let us determine with reasonable certitude that in the late Ediacaran Siberia was located in the subequatorial latitudes.

In this study, we present new palaeomagnetic and geological data obtained from Ediacaran and Cambrian sedimentary rocks of Argun terrane, which is traditionally considered a key element of the hypothetical Amuria composite continent. Since 1990, when Amuria was first proposed in palaeogeographic reconstructions, it became one of the principle members in the global palaeotectonic schemes. A scenario when collision of Amuria with Siberian margin resulted in formation of the Mongol-Okhotsk Ocean is universally accepted and supported by majority of researchers. However, time of Amuria's final assembly and relative position of the blocks within Amuria before the collision with Siberia is still a topic of debate. Questions about principal allocation of Argun terrane and its relation to Amuria during the late Neoroterozoic-Cambrian are addressed in this study. Palaeomagnetic poles for the Ediacaran-early Cambrian rocks of Argun terrane differ within an error from coeval poles from Siberia indicating that Argun terrane could have been located similar to its present-day position with respect to Siberia already at 560-525 Ma. This observation calls into question association of Argun terrane with Amuria, which in classic reconstructions is usually placed close to the North China Craton. It also questions our current understanding of the Amuria palaeocontinent and consequently, accuracy of global palaeogeographic reconstructions for the late Neoproterozoic-Cambrian in general, and those of the eastern part of the Central Asia in particular.

New data on paleomagnetism and isotope geochronology of Jurassic and Early Cretaceous basic igneous rocks on Franz Josef Land Archipelago (FJL) represented by flows and dikes are discussed. The first paleomagnetic data obtained for these rocks offer the opportunity to suggest a model of spatial changes in the FJL block position during the Jurassic‒Cretaceous. In the Early Jurassic, the block occupied a different position relative to Europe from the modern one. It was displaced in the northeasterly direction by a distance of approximately 500 km and rotated clockwise by about 40° relative to its modern position. By the Early Cretaceous, the FJL block occupied a position close to the present-day one avoiding subsequent substantial relative displacements. The data obtained are of principal significance for reconstructing the geodynamic evolution of Arctic structures in the Mesozoic and contribute greatly to the base of paleomagnetic data for the Arctic region, development of which is now in progress.