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Abstract—The collection of paleomagnetic samples of the Lower Devonian Frænkelryggen Formation from the northwest of Spitsbergen is studied. The main carrier of the natural remanent magnetization of the studied rocks is hematite. Based on the component analysis results, the prefolding, bipolar components of the natural remanent magnetization with a positive reversal test are identified. The sequence of the magnetozones of the studied section is compared with the existing world data for Lower Devonian. [ABSTRACT FROM AUTHOR]

Paleomagnetic dating of the Bolshesyrsky igneous area, a thick intraplate igneous complex of Khakassia, was carried out. The complex has not been dated due to the peculiarities of the stratigraphy and the lack of suitable rocks for applying the methods of absolute geochronology. The use of the paleomagnetic method has shown that the paleomagnetic pole of the red beds, which are intruded by sills and dikes of the Bolshesyrsky area, is close to the Silurian paleomagnetic poles of Siberia and Tuva and differs sharply from the Ordovician paleomagnetic poles of these areas. That is, red-colored rocks are Silurian, and subvolcanic rocks are post-Silurian. The sharp unconformable overlapping of the red-colored and volcanic strata with the Middle Devonian sedimentary trough without igneous rocks indicates that the age of the Bolshesyrsky complex is limited to the Silurian-Early Devonian interval. The genesis of the rocks of the Bolshesyrsky magmatic area was associated with the activity of the Early Devonian Minusinsk plume.

This article presents the results of a detailed paleomagnetic study of five sections of the Permian-Triassic sedimentary rocks from the southeastern part of the Volga-Ural anteclise in the East European Platform (Orenburg region, Russia): Boevaya Gora, Vyazovka, Sambulak, Krasnogor, and Vozdvizhenka. The magnetic fabric determined by magnetic susceptibility anisotropy indicates that the rocks accumulated under the conditions of intense hydrodynamic activity. This makes it possible to reconstruct a predominantly submeridional transport of detrital material. The rocks of the Boevaya Gora section have a bipolar distribution of the characteristic component of their remanent magnetization, while other sections show a reversed polarity. In the Vyazovka section, the E/I method was used to calculate the inclination shallowing coefficient of the rocks (f = 0.79). The regional fold test yielded positive results, suggesting that the rocks of the studied sections were displaced after the deposition. For each section, paleomagnetic poles were calculated, with the poles of the Boevaya Gora and Vyazovka sections being the most reliable. The mean paleomagnetic pole coordinates of the studied sections, except the Sambulak section, are as follows: slat = 51.7°, slong = 55.8°, n = 4, plat = 48.5°, plong = 173.4°, α95 = 3.4°, paleolat = 23.4°.

Giant mafic dykes are the key markers of the Earth’s evolution in the Precambrian and have been the subject of extensive research. This article presents the results of the paleomagnetic, rock-magnetic, and paleointensity Banc studies of the Great Dyke of the Kola Peninsula (2.68 Ga). The mean paleomagnetic direction of the characteristic magnetization component and the paleomagnetic pole of the Murmansk craton were calculated using the data from 5 sites (n = 41 samples): D = 117.6°, I = 77.1°, K = 40.9, α95 = 12.1°, slat = 69.265°, slong = 34.35447°, plat = 51.5°, plong = 70.7°, dp/dm = 21.1°/22.6°, and paleolat = 65°. The rocks under study were thoroughly examined for their thermomagnetic properties, revealing that the main carriers of remanent magnetization are single-domain or small pseudo–single-domain (group A) or multidomain (group B) magnetite. The paleointensity values Banc = (6.16 ± 0.92) μT were obtained for 12 samples from group A by the Thellier–Coe method. The corresponding mean virtual dipole moment VDM2.68Ga = (0.85 ± 0.13)×1022 Am2 was determined. These new findings align with previous results on the Archean and Proterozoic objects, indicating that the Earth’s magnetic field was remarkably weak in the Late Archean.

The use of a magnetic compass in paleomagnetic studies of highly magnetic rocks (for instance, basalts) can lead to large errors in the orientation of paleomagnetic samples. On the other hand, alternative methods of orientation are relatively time-consuming, and in the case of using a solar compass, they also require sunny weather – a condition that is rarely met, especially when sampling at high and subpolar latitudes. This often leads to the fact that researchers in their work rely on the results of magnetic compass measurements, while assuming that the resulting errors are of a random nature and, with sufficiently good statistics, are averaged. In this study, numerical modeling is performed, which allows us to verify this assumption and assess how much orientation errors associated with the use of a magnetic compass can affect the final results of paleomagnetic studies, such as determining the position of the paleomagnetic pole and the amplitude of ancient geomagnetic variations. As a result of the work performed , it is shown that: 1) the amplitudes of paleosecular variations and the positions of paleomagnetic poles are weakly sensitive to moderate and even relatively large errors in the orientation of paleomagnetic samples associated with the use of a magnetic compass; 2) very large errors in the orientation of samples lead to a significant increase in the within-site scatter of paleomagnetic directions, which makes it possible to detect and exclude the corresponding sites with a large (for instance >15°) value of the α95; 3) the influence of distortions associated with the use of a magnetic compass on the accuracy of determining the position of the paleomagnetic pole and the amplitude of ancient geomagnetic variations depends on latitude. At near-equatorial latitudes, this effect is maximal, at medium latitudes – minimal.

The results of paleomagnetic and rock magnetic studies of the upper Permian red beds from the Sukhoborka and Sosnovka sections of the south-eastern of the Moscow syneclise on the right bank of the Vetluga River in Nizhny Novgorod Region, Russia, are presented. The arguments in favor of the primary nature of the characteristic magnetization component are indicated. The first late Permian (254 Ma) paleomagnetic pole dated precisely for the sedimentary Permian–Triassic complex in the eastern part of the East European Platform is calculated: 56.731° N, 45.748° E, N = 44, plat = 55.3°, plong = 158.1°, dp/dm = 3.5°/5.1°, paleolat = 34.6°. [ABSTRACT FROM AUTHOR]

Abstract—The paper presents the results of paleomagnetic, rock magnetic, and cyclostratigraphic studies of continental red beds that compose the Permian-Triassic boundary interval of the Staroe Slukino section in the Vladimir Region, Russia. Based on the directions of the characteristic components of the natural remanent magnetization of the studied rocks in the sampled stratum, the intervals of normal and reversed polarity related to the regional magnetozones r2RnP, r3RnP, and N3P-T were identified. Within the r3RnP zone, there is an interval of anomalous paleomagnetic directions, which has similar characteristics to those identified earlier in the coeval intervals of the Nedubrovo, Zhukov Ravine, and Okskiy Siyezd sections. Revising the biostratigraphy allows us to assume that the two zones of anomalous paleomagnetic directions in the composite magnetic polarity scale of the upper Permian of the Russian Platform are a reflection of the same epoch of an anomalous geomagnetic field configuration. It is estimated by the cyclostratigraphic method that the studied 16 m interval of the Staroe Slukino section took 900 ± 20 thousand years to accumulate, which limits the duration of the geomagnetic field anomalous state near the Permian-Triassic boundary to ~110 thousand years. A new Permian-Triassic (~252 Ma) paleomagnetic pole of the East European Platform is calculated: plat = 36.3°; plong = 155.0°; dp/dm = 2.8°/4.8°. [ABSTRACT FROM AUTHOR]

Abstract—The paper presents the results of paleomagnetic studies of the Silurian and Devonian strata of Tuva. The paleomagnetic pole for the Silurian strata is characterized by Φ = 5°, Λ = 147°, А95 = 4.8°, n = 57. The paleomagnetic pole for the Middle Devonian rocks is characterized by Λ = –14°, Φ = 103°, А95 = 6.7°, n = 63. Rocks of some Middle Devonian sections have anomalous declination of magnetization. It is assumed that these strata were rotated relative to Siberia as a result of shear movements in Tuva in the Late Devonian. The strata of the lower and upper parts of the Upper Devonian accumulated at different paleolatitudes. The paleomagnetic pole for the lower part of the Late Devonian section is Φ = 4°, Λ = 139°, А95 = 9.3°, n = 37, for the upper part of the Late Devonian section—Φ = 48°, Λ = 135°, А95 = 14°, n = 33. Generalization of paleomagnetic data for Tuva and Mongolia showed that the curves of latitudinal displacement of Siberia, Tuva, and northern Mongolia differ insignificantly and, possibly, these geological blocks, starting from the Ordovician, moved as a single geological body. South of the Mongol-Okhotsk suture to the west of the 107° meridian, the paleolatitudes of the formation of the Late Carboniferous-Permian strata are close to the 'Siberian' ones, and to the east of the meridian—to the North Chinese ones. The wide variations in the declination of the magnetization of sequences located south of the Mongol-Okhotsk suture could possibly be associated with strike-slip displacements that were active in southern Mongolia during different periods of the Late Phanerozoic. The regions of Tuva and Mongolia differ sharply in the set of components of the natural remanent magnetization of Phanerozoic rocks. Permian remagnetization of rocks by a magnetic field of reversed polarity is widespread in Mongolia. In Tuva, the Permian remagnetization is practically not detected, but a wide distribution of randomly directed secondary magnetization has been established. [ABSTRACT FROM AUTHOR]

Paleomagnetic poles used to compute apparent polar wander paths (APWPs) are strongly dispersed, which was recently shown to cause a large fraction (>50%) of these poles to be statistically distinct from the APWP to which they contributed, suggesting that current statistical approaches overestimate paleomagnetic resolution. Here, we analyze why coeval paleopoles are so dispersed, using the paleopoles behind the most recent global APWP and a compilation of paleomagnetic data obtained from <10 Ma volcanic rocks (PSV10). We find that paleopoles derived from sedimentary rocks, or from data sets underrepresenting paleosecular variation (PSV), are more dispersed and more frequently displaced. We show that paleopoles based on a smaller number of paleomagnetic sites are more dispersed than poles based on larger data sets, revealing that the degree to which PSV is averaged is an important contributor to the pole dispersion. We identify as a fundamental problem, however, that the number of sites used to calculate a paleopole, and thus the dispersion of coeval paleopoles, is essentially arbitrary. We therefore explore a different approach in which reference poles of APWPs are calculated from site‐level data instead of paleopoles, thereby assigning larger weight to larger data sets. We introduce a bootstrap‐based method for comparing a collection of paleomagnetic data with a reference data set on the same hierarchical level, whereby the uncertainty is weighted against the number of paleomagnetic sites. Finally, our study highlights that demonstrating smaller tectonic displacements requires larger paleomagnetic data sets, and that such data sets can strongly improve future APWPs. Plain Language Summary: Apparent polar wander paths (APWPs) are widely used to reconstruct the position of continents relative to the Earth's rotation axis. These paths are typically calculated by averaging paleomagnetic poles obtained from rocks of similar age. Although these poles are expected to be tightly grouped, they are strongly scattered. Notably, this causes >50% of the poles used in recent APWPs to be statistically different from the APWP itself. Here, we investigate to what extent errors in these poles may explain the observed scatter. We find that poles derived from sedimentary rocks are more scattered than those derived from igneous rocks. Also, poles based on smaller data sets are more dispersed than those based on larger data sets. Our analysis shows that the amount of paleomagnetic data used to determine a pole is often arbitrary. To overcome the subjectivity in pole calculation, we propose a new approach in which an APWP is calculated from individual data points instead of from paleopoles. This allows comparing paleomagnetic data on the same statistical level, and the development of APWPs in which larger data sets have larger weight. Our study thus emphasizes the value of collecting large paleomagnetic data sets, which may improve future APWPs. Key Points: Paleopoles do not average "out" paleosecular variation, which forms a first‐order contributor to the dispersion of coeval paleopolesThe number of sites used to compute a paleopole and the number of paleopoles calculated from a given data set is essentially arbitraryCalculating apparent polar wander paths from site‐level data instead of poles allows the weighting of uncertainties and the amount of data [ABSTRACT FROM AUTHOR]

The nearly 2000 m-thick Ikakern Formation is the basal sedimentary unit in the Argana basin of Morocco, consisting of fluvial red and purple conglomerates in the lower part and interbedded red conglomerates, sandstones, siltstones and mudstones in the upper part. It unconformably overlies deformed and metamorphosed Variscan basement rocks and is unconformably overlain by the finer grained lacustrine to fluvial sediments of the?Early to Late Triassic Timesgadiouine Formation. Vertebrate fossil and chronostratigraphic constraints indicate a post-Kiaman, Late Permian age for at least the sampled upper member (t2) of the Ikakern Formation. A stable, high unblocking temperature dual polarity characteristic magnetization that passes a local fold test gives a paleomagnetic pole for 14 sites at 48.8°N 246.3°E A95 = 7.2° after correction for inclination flattening and indicates a paleolatitude of 14°N for the nominal sampling location at 30.75°N 9.10°W. The Ikakern pole agrees well with poles of similar age deemed reliable in a recent assessment of published data from South America, Africa, Adria, and Australia, which together (N = 7) provide a mean Gondwana pole for an age bin centered on 260 Ma at 52.2°N 239.8°E A95 = 5.0° (NW Africa coordinates). In conjunction with a robust mean 260 Ma pole form Laurasia, these results confirm a Pangea A configuration for the Late Permian. This is in contrast to some recently published interpretations of paleomagnetic data from the Gondwanides of South America that would prolong the existence of a Pangea B configuration from the Late Carboniferous-Early Permian through the Late Permian but which instead probably reflect effects of remagnetization or local rotation. Unlabelled Image • Paleomagnetic study of Late Permian Ikakern Formation red beds from Morocco. • Prefolding dual polarity characteristic magnetizations are of late Kiaman-Illawara age. • Results support 260 Ma Gondwana APW mean pole and Pangea-A by Late Permian. [ABSTRACT FROM AUTHOR]

Abstract—This paper presents the results of paleomagnetic studies of the Proterozoic sedimentary and igneous rocks composing the structure of sections of the Olenek and Udzha uplifts. Carbonate rocks of the upper unit of Khaipakh formation have been studied within the Olenek uplift, and terrigenous and volcanic-sedimentary rocks of the Udzha and Unguokhtakh formations and the Early Mesoproterozoic igneous complex have been investigated within the Udzha uplift. Within the Olenek uplift, the carbonate rocks of the upper unit of the Khaipakh formation have been studied; within the Udzha uplift–terrigenous and volcanogenic-sedimentary rocks of the Udzha and Unguokhtakh formations, and the Early Mesoproterozoic magmatic complex. The results of the paleomagnetic study (1) indicate that the upper unit of Khaipakh formation of the Olenek uplift and the Udzha formation of the Udzha uplift have different sedimentation age, which contradicts the currently accepted correlation scheme of the Proterozoic sections in the northern Siberian platform; (2) support the existence of two stages of the Proterozoic magmatism in the territory of the Udzha uplift, with a more ancient stage having an age of ~1500 Ma according to the paleomagnetic data; (3) show that from ~1500 to 1110 Ma ago, the Siberian platform was located in the equatorial and subequatorial latitudes. [ABSTRACT FROM AUTHOR]

Apparent polar wander paths (APWPs) calculated from paleomagnetic data describe the motion of tectonic plates relative to the Earth's rotation axis through geological time, providing a quantitative paleogeographic framework for studying the evolution of Earth's interior, surface, and atmosphere. Previous APWPs were typically calculated from collections of paleomagnetic poles, with each pole computed from collections of paleomagnetic sites, and each site representing a spot reading of the paleomagnetic field. It was recently shown that the choice of how sites are distributed over poles strongly determines the confidence region around APWPs and possibly the APWP itself, and that the number of paleomagnetic data used to compute a single paleomagnetic pole varies widely and is essentially arbitrary. Here, we use a recently proposed method to overcome this problem and provide a new global APWP for the last 320 million years that is calculated from simulated site-level paleomagnetic data instead of from paleopoles, in which spatial and temporal uncertainties of the original datasets are incorporated. We provide an updated global paleomagnetic database scrutinized against quantitative, stringent quality criteria, and use an updated global plate motion model. The new global APWP follows the same trend as the most recent pole-based APWP but has smaller uncertainties. This demonstrates that the first-order geometry of the global APWP is robust and reproducible. Moreover, we find that previously identified peaks in APW rate disappear when calculating the APWP from site-level data and correcting for a temporal bias in the underlying data. Finally, we show that a higher-resolution global APWP frame may be determined for time intervals with high data density, but that this is not yet feasible for the entire 320–0 Ma time span. Calculating polar wander from site-level data provides opportunities to significantly improve the quality and resolution of the global APWP by collecting large and well-dated paleomagnetic datasets from stable plate interiors, which may contribute to solving detailed Earth scientific problems that rely on a paleomagnetic reference frame. • New paleomagnetic reference frame for the last 320 million years. • Global apparent polar wander path computed from site-level data rather than poles. • First-order geometry similar to previous models but with smaller uncertainties. • Peaks in apparent polar wander may result from a temporal bias in the data. • Future improvement of the reference frame requires new, high-quality data. [ABSTRACT FROM AUTHOR]

The results of detailed paleomagnetic studies in seven Upper Permian and Lower Triassic reference sections of East Europe (Middle Volga and Orenburg region) and Central Germany are presented. For each section, the coefficient of inclination shallowing f (King, 1955) is estimated by the Elongation-Inclination (E-I) method (Tauxe and Kent, 2004) and is found to vary from 0.4 to 0.9. The paleomagnetic directions, corrected for the inclination shallowing, are used to calculate the new Late Permian-Early Triassic paleomagnetic pole for the East European Platform (N = 7, PLat = 52.1°, PLong = 155.8°, A95 = 6.6°). Based on this pole, the geocentric axial dipole hypothesis close to the Paleozoic/Mesozoic boundary is tested by the single plate method. The absence of the statistically significant distinction between the obtained pole and the average Permian-Triassic (P-Tr) paleomagnetic pole of the Siberian Platform and the coeval pole of the North American Platform corrected for the opening of the Atlantic (Shatsillo et al., 2006) is interpreted by us as evidence that ~250 Ma the configuration of the magnetic field of the Earth was predominantly dipolar; i.e., the contribution of nondipole components was at most 10% of the main magnetic field. In our opinion, the hypothesis of the nondipolity of the geomagnetic field at the P-Tr boundary, which has been repeatedly discussed in recent decades (Van der Voo and Torsvik, 2001; Bazhenov and Shatsillo, 2010; Veselovskiy and Pavlov, 2006), resulted from disregarding the effect of inclination shallowing in the paleomagnetic determinations from sedimentary rocks of 'stable' Europe (the East European platform and West European plate). [ABSTRACT FROM AUTHOR]

The rock magnetic and paleomagnetic results from the Upper Paleozoic sedimentary sequences composing the isles of the Novaya Zemlya Archipelago are presented. The recorded temperature dependences of the magnetic susceptibility, the magnetic hysteresis parameters, and the results of the first-order reversal curve (FORC) measurements suggest the presence of single-domain or pseudo-single-domain magnetite and hematite grains in the rocks. The Upper Paleozoic deposits overall are promising for unraveling the tectonic evolution of the Barents-Kara region. Together with the rock magnetic data, the positive fold and reversal tests testify to the primary origin of the indentified magnetization components. However, the interpretation of the paleomagnetic data should take into account the probable inclination shallowing. New substantiation is offered for the paleomagnetic poles for Early Devonian and Late Permian. For the first time, paleomagnetic constraints are obtained for the Late Carboniferous boundary. It is shown that the Early Cimmerian deformation stage within the Paikhoi-Novaya Zemlya region is associated with the sinistral strike slip displacement along the Baidaratskii suture during which the internal structure of the Southern Novaya Zemlya segment could undergo shear in addition to the nappe-thrust transformations. The Northern Novaya Zemlya segment, which is shifted northwest with respect to the Southern segment, was deformed in the thrusting mode with an overall clockwise rotation of this segment relative to the East European Craton. [ABSTRACT FROM AUTHOR]

Results of a systematic paleomagnetic study are reported based on Late Carboniferous to Early Permian sedimentary rocks on the north slope of the Tanggula Mountains, in the northern Qiangtang terrane (NQT), Tibet, China. Data revealed that magnetic minerals in limestone samples from the Zarigen Formation (CP^ z)are primarily composed of magnetite, while those in sandstone samples from the Nuoribagaribao Formation (P nr) are dominated by hematite alone, or hematite and magnetite in combination. Progressive thermal, or alternating field, demagnetization allowed us to isolate a stable high temperature component (HTC) in 127 specimens from 16 sites which successfully passed the conglomerate test, consistent with primary remnance. The tilt-corrected mean direction for Late Carboniferous to Early Permian rocks in the northern Qiangtang terrane is D =30.2°, I =- 40.9°, k =269.0, α =2.3°, N=16, which yields a corresponding paleomagnetic pole at 25.7°N, 241.5°E (d p/d m=2.8°/1.7°), and a paleolatitude of 23.4°S. Our results, together with previously reported paleomagnetic data, indicate that: (1) the NQT in Tibet, China, was located at a low latitude in the southern hemisphere, and may have belonged to the northern margin of Gondwana during the Late Carboniferous to Early Permian; (2) the Paleo-Tethys Ocean was large during the Late Carboniferous to Early Permian, and (3) the NQT subsequently moved rapidly northwards, perhaps related to the fact that the Paleo-Tethys Ocean was rapidly contracting from the Late Permian to Late Triassic while the Bangong Lake-Nujiang Ocean, the northern branch of the Neo-Tethys Ocean, expanded rapidly during this time. [ABSTRACT FROM AUTHOR]

Reliable paleomagnetic poles were calculated for 1.80-1.78 and 1.76-1.75 Ga as a result of the detailed paleomagnetic studies of the Late Paleoproterozoic igneous complexes and the North Ladoga region and Onega structure of the East European craton. According to the new paleomagnetic data, the final assembly of the Superior and Fennoscandia cratons in structure of the Paleoproterozoic Nuna/Columbia supercontinent began at 1.80-1.78 Ga and led to the formation of the Hudsonland megacontinent. Comparison of the coeval poles of 1.76-1.75 Ga of Fennoscandia and Volga-Sarmatia allows reconstruction of the oblique collision among these segments of the East European craton and substantiation of the final assembly at ~1.70 Ga. [ABSTRACT FROM AUTHOR]

Abstract: We report paleomagnetic data on precisely dated Mesoproterozoic sills, in zircon and baddeleyite 207Pb/206Pb ages of 1345±12 and 1353±14Ma respectively, intruding the Xiamaling and Wumishan formations in North China with an aim of evaluating how the North China Craton (NCC) was involved in the evolution of the Columbia supercontinent from ca. 1.78 to 1.35Ga. After systematic thermal demagnetization we isolate a high temperature characteristic remanence from 18 sites with a tilt-corrected site-mean direction of D =294.4°, I =−31.7° and α 95 =4.3°, corresponding to a mean paleomagnetic pole at λ =5.9°N, φ =359.6°E (N =18) with angular standard deviation of 10.0° and A 95 =4.3°. Rock magnetic experiments, light microscopy and scanning electron microscopy all indicate that the main magnetic minerals in the sampled sill rocks are medium sized titanomagnetites. The positive fold test and fresh titanomagnetite grains suggest that the characteristic remanence is likely to be a primary acquired at ca. 1.35Ga. The preliminary paleogeography reconstruction based upon the well-matched apparent polar wander paths between the Laurentia–Baltica–Siberia united block and the NCC supports the interpretation that the NCC may have drifted together with this united block before ca. 1.35Ga during the late history of the Columbia supercontinent. We argue that the NCC was located in low latitudes and kept tight connections with the Siberian and Indian cratons during the interval between ca. 1.8 and 1.35Ga, and that the ca. 1.35Ga sills widely developed in the Mesoproterozoic Xiamaling and Wumishan formations, as well as the ca. 1.3–1.2Ga magma events well-developed in Siberia and northern margin of the NCC, may represent the complete fragmentation of the NCC with the neighboring cratons. [Copyright &y& Elsevier]

Abstract: The kinematics of the Early Caledonian accretion process in the southwest (in modern coordinate) of the Siberian paleocontinent, and the structure of its active continental margin are debatable subjects. This paper contains a generalization of paleomagnetic data on island-arc terranes of the territories of the Altai–Sayan and Baikal–Vitim folded areas for the Late Vendian/Cambrian–Early Ordovician time interval, obtained mostly with the author’s participation during the last two decades. The large accumulated database finally allows one to find unambiguously interpretable patterns in the distribution of paleomagnetic poles for the analyzed terrane system and to justify numerically the kinematics of the Early Caledonian accretion. In particular, the analysis of paleomagnetic data proves our idea stating that the transformation of the active continental margin in the Cambrian consisted in its breakup and segmentation as well as in the detachment of fragments of the initially whole island arc along a system of sinistral strike-slips during the clockwise rotation of the craton and conform drift of the continental and oceanic lithospheric plates. It also validates the mostly oblique conditions of the subduction and subsequent accretion, which means a subduction-transform mode on the ocean–continent margin. We propose a complemented version of the paleotectonic reconstruction for the Cambrian evolution of the Siberian continent western margin, based on the kinematic scheme constructed from paleomagnetic data. [Copyright &y& Elsevier]

Abstract: In this paper we present the results of a generalization of paleomagnetic data for the territory of the Siberian craton and its folded framing that were obtained during the last fifteen years. We propose a new version of the apparent polar wander path for the Siberian continental plate, including the interval from the Mesoproterozoic–Neoproterozoic boundary up to the end of the Mesozoic. The constructed path forms the basis for new concepts on the tectonics of the Siberian paleocontinent and the paleooceans that surrounded it. We present a series of paleotectonic reconstructions based on paleomagnetic data, which not only displays the paleogeographic position of the Siberian continent, but also reveals the features of the tectonic evolution of its margins during the last billion years. In particular it has been established that large-scale strike-slip motions played an important role in the tectonic regime of the continental plate at all stages of its development. [Copyright &y& Elsevier]

Abstract: We present paleomagnetic data on the Cambrian volcanosedimentary complexes of the Bateni Ridge, which correspond to the evolution of the Kuznetsk Alatau island arc. The paleomagnetic poles which served as the basis for the apparent polar-wander path (APWP) were determined. The paleomagnetic data were compared with those on the Cambrian poles for other fragments of the Kuznetsk Alatau island arc. For example, the APWP of the Bateni fragment corresponds to that of the Kiya (Martaiga) fragment of the eastern slope of the Kuznetsk Alatau. The distribution of the paleomagnetic poles suggests that the relative drift of the Kuznetsk Alatau arc fragments and the entire island arc system resulted from large-amplitude strike-slips. In the Cambrian, this paleoarc moved from ∼10° N to ∼10° S and rotated more than 50° clockwise. In the paleomagnetic record, its accretion is reflected in the coincidence of the Late Cambrian–Early Ordovician poles on the eastern slope of the Kuznetsk Alatau with one another and the coeval poles for the Siberian craton. This coincidence also suggests that the general structure of the present Kuznetsk Alatàu formed as early as the Early Caledonian. Nevertheless, the differences in the position of the poles on the western and eastern slopes of the Kuznetsk Alatau suggest that strike-slip activity along the Kuznetsk–Altai deep fault (the major one in the region) continued in the Late Paleozoic and, probably, in the Mesozoic. [Copyright &y& Elsevier]

Abstract: We summarize the results of paleomagnetic and sedimentological studies of the Neoproterozoic rhythmic terrigenous-carbonate rock unit in the Karagas Supergroup, which were carried out in the middle reaches of the Biryusa and Uda Rivers. The paleomagnetic data are presented along with a detailed description of the studied sections and the specific sedimentological characteristics of the studied deposits. The new data refine the position of Late Precambrian paleomagnetic poles in Siberia and mark the paleogeographic and facies features of the rock unit formation. They also show that the rock unit was deposited much more rapidly than it was supposed earlier, in the environment of shallow-water sea basin on the margin of the Siberian continent. The origin and evolution of the Karagas sedimentary basin was governed by both global and regional tectonic factors. We suppose that the onset of the basin can be linked to a tectonic event, namely, the opening of ocean in southern Siberia during the break-up of Rodinia. Regional tectonic processes controlled the position of the Karagas sedimentary basin and its evolution. The position of the mean paleomagnetic pole (Plat = 3.9°, Plong = 292.3°, A95 = 7.1°) confirms the corresponding interval of the Neoproterozoic trend of APWP in Siberia and proves the near-equatorial position of the continent in Karagas time. [Copyright &y& Elsevier]

Abstract: Rock complexes in Mongolia experienced two remagnetization events. Almost all secondary remanence components of normal polarity were acquired apparently in the Cenozoic, after major deformation events, and those of reverse polarity were associated with intrusion of bimodal magmas during the Late Carboniferous–Permian reverse superchron. Active continental-margin sequences in some areas of Mongolia were folded prior to the Late Carboniferous–Permian magnetic event. The primary origin of magnetization in Late Paleozoic and Mesozoic rocks has been inferred to different degrees of reliability. According to paleolatitudes derived from most reliable paleomagnetic data, the analyzed rocks were located far north of the North China block throughout the Late Paleozoic and Early Mesozoic. Mongolia, as well as Siberia, moved from the south to the north in the Paleozoic, back from the north to the south between the latest Triassic and the latest Jurassic, and remained almost within the same latitudes in Cretaceous and Cenozoic time. These paleolatitudes show no statistical difference from those for the Siberian craton at least since the latest Permian (275–250 Ma). Older Mongolian complexes (with ages of 290, 316, and 330 Ma) likewise may have formed within the Siberian continent, which makes their paleomagnetic determinations applicable to calculate the polar wander path for Siberia. The paleolatitudes of Early Carboniferous sediments in Mongolia differ significantly from those of Siberia, either because of overprints from the reverse superchron or because they were deposited away from the Siberian margin. [Copyright &y& Elsevier]

Abstract: We report a new paleomagnetic determination of Paleoproterozoic rocks from the Siberian craton which showed a positive baked contact test and a stable age of the high-temperature NRM component. The mean paleomagnetic pole of Siberia for ∼1730 Ma located at 42.9° S, 109.6° E (α95 = 5.3°) is compatible with the pole positions obtained recently for the middle and late Early Proterozoic. [Copyright &y& Elsevier]

The study of rock samples from the Upper Permian Khei-Yaga River section revealed an r- n- r- n- r magnetic polarity succession based on the prefolding characteristic component of natural remanent magnetization. With account for stratigraphic and previous magnetostratigraphic data on Lower Triassic rocks from the Khei-Yaga River section, the examined strata of the Pechora Group (Silova Formation) may be compared with magnetic zones R1P2u and N1P3t in the magnetostratigraphic scale of European Russia. The gap in the paleomagnetic record, which corresponds in the examined section to the interval of the mid-Severodvinian Stage to basal Induan Stage, Zone N1T included, is estimated to be 10 Ma long. It is assumed that this hiatus represents one of the local signs of the global Permian-Triassic crisis. [ABSTRACT FROM AUTHOR]

Abstract: The paper summarizes paleomagnetic results obtained from the Neoproterozoic rocks of the western margin of the Siberian craton. On the basis of the obtained paleomagnetic poles and available paleomagnetic data for the Precambrian of Siberia, a new version of the Neoproterozoic segment of the apparent polar wandering path (APWP) is proposed for the craton and is compared with the Laurentian APWP. The superposition of these paths suggests that in the Neoproterozoic the southern margin of the Siberian craton (in modern coordinates) faced the Canadian margin of Laurentia. Most likely, in the end of the Mesoproterozoic and during the Neoproterozoic the Siberian craton and Laurentia were connected to form the supercontinent Rodinia. At 1 Ga the western margin of the Siberian craton was a northern (in modern coordinates) continuation of the western margin of Laurentia. The available paleomagnetic data on Laurentia and continental blocks of Eastern Gondwana (Australia, Antarctica, India, South China) and the proposed APWP trend allowed a new model for the breakup of this segment of Rodinia. Analysis of a total of the data available suggests that strike-slip movements on the background of the progressive opening of the oceanic basin between Siberia and Laurentia were predominant in the south of the Siberian craton during the Neoproterozoic. Similar kinematics is typical of the western margin of Laurentia, where strike-slip motions are probably associated with the progressive opening of the ocean basin between Laurentia and eastern Gondwana. [Copyright &y& Elsevier]

Abstract: We undertook a paleomagnetic investigation of Cretaceous red sandstones at 30 sites within the Yuanma Basin in western Hunan, central South China Block (SCB), China. The aim of this study is to further constrain the extent of the SCB that has been stable since the Cretaceous. We isolated the characteristic directions of higher temperature components (HTCs) with an unblocking temperature of ∼650 to 690 °C by progressive thermal demagnetization and principal component analysis. The optimal concentrations of global mean HTC directions calculated using the direction–correction tilt test were achieved at 92.7±59.1%, 87.9±25.0%, and 93.3±19.7% untilting indistinguishable from 100% untilting, for Early Cretaceous (K1, 13 sites), Late Cretaceous (K2, 17 sites) and K site groupings (K1+K2, 30 sites), respectively. This treatment yielded positive tilt tests, and the HTCs are considered to be primary magnetic components acquired before tilting of the sedimentary layers. Early (K1) and Late (K2) Cretaceous paleomagnetic poles calculated using the site mean directions untilted completely are located at similar positions; this suggests the absence of local rotations linked to Cretaceous strain within the study area. The Cretaceous (K1+K2) mean paleomagnetic pole calculated using virtual geomagnetic poles from all sites is in agreement with previously reported Cretaceous paleomagnetic poles from the eastern and western SCB. This indicates that the Hunan region has been part of the stable body of the SCB since the Cretaceous and that the tectonic influence of the India–Asia collision did not extend to within the stable body of the SCB. The reference Cretaceous pole position (latitude=80.1°N, longitude=204.1°E, A 95 =2.5°) calculated using eight Cretaceous poles from the stable body of the SCB is similar to those determined from stable Eurasia and the North China Block (NCB). This result indicates that the India–Asia collision caused no relative motion, as detected by paleomagnetic analysis, among stable Eurasia, NCB, and the stable body of the SCB. [Copyright &y& Elsevier]

Abstract: The apparent polar wander path (APWP) of the Pacific plate still has many uncertainties owing to the fact that paleomagnetic data are difficult to obtain for oceanic plates. After more than three decades of coring by the Deep Sea Drilling Project (DSDP) and Ocean Drilling Program (ODP) there are now a large number of reliably dated basalt cores recovered from the Pacific plate and this provides an opportunity to determine paleomagnetic poles based on igneous rock samples, considered by many scientists to be the most reliable data type. Cretaceous Pacific plate basalt core data were compiled, corrected using a standard technique, divided into groups based on age, and combined to calculate five mean paleomagnetic poles with ages of 80, 92, 112, 121, and 123Ma, the latter two being for two different coeval regions. In all pole analyses, the lack of azimuthal orientation for cored samples leads to large uncertainties in pole locations along a nearly east–west direction. This difficulty was mitigated by using declination data from magnetic anomaly inversions of dated Pacific seamounts for azimuth constraint. The two nearly same-age poles were calculated because paleocolatitudes from Ontong Java Plateau (OJP) are discordant compared to those from other Pacific locations. I interpret the discordant OJP results to indicate that the plateau is on crust that had an early history as an independent plate. The other poles (80, 92, 112, and 123Ma) fall on a northeast-trending line that suggests slow apparent polar wander during the Early and mid-Cretaceous, followed by rapid polar wander between 92 and 80Ma. Comparison of the 123Ma pole with previously published paleomagnetic data of Jurassic age implies southward apparent polar wander followed by a turnaround. Because the 123Ma pole is the farthest from the geographic pole, it implies the turnaround happened near that time and that the Pacific plate has moved ∼40° northward since then. The 80Ma pole stands ∼17° from the geographic pole, indicating that ∼60% of the northward drift occurred prior to that time and ∼40% afterwards. [Copyright &y& Elsevier]

Abstract: A combined paleomagnetic and 40Ar/ 39Ar study was carried out along eight stratigraphically overlapping sections in the Oligocene Afro-Arabian flood volcanic province in Yemen (73 sites). The composite section covers the entire volcanic stratigraphy in the sampling region and represents five polarity zones that are correlated to the geomagnetic polarity time scale based on 40Ar/ 39Ar ages from this and previous studies. The resulting magnetostratigraphy is similar to that of the conjugate margin in Ethiopia. The earliest basaltic volcanism took place in a reverse polarity chron that appears to correspond to C11r, while the massive rhyolitic ignimbrite eruptions correlated to ash layers in Oligocene Indian Ocean sediment 2700 km away from the Afro-Arabian traps, appear to have taken place during magnetochron C11n. The youngest ignimbrite was emplaced during magnetochron C9n. Both 40Ar/ 39Ar and paleomagnetic data suggest rapid &#60;1 Ma eruption of the basal basalt units and punctuated eruption of the upper silicic units over a duration potentially as long as 3 Ma with interspersed eruptive hiatuses. Eruption of the basal basalts may have preceded the Oi2 cooling event. The paleomagnetic pole λ =74.2°N, φ =249.1°E (A95=3.6°; N =48) is supported by a positive reversal test. Paleosecular variation, estimated as the angular standard deviation of the VGP distribution 14.2°+2.3°/−1.7°, is close to expected, suggesting that the paleomagnetic pole represents a time-averaged field. The pole is in excellent accord with the paleomagnetic poles obtained from the Ethiopian part of the Afro-Arabian province, after closure of the Red Sea. By analyzing Afro-Arabian paleomagnetic data in conjunction with contemporaneous paleomagnetic poles available from different latitudes we argue that the Oligocene paleomagnetic field was dominated by the axial dipole with insignificant non-dipole field contributions. [Copyright &y& Elsevier]

A paleomagnetic investigation was performed on the Cretaceous red sandstones collected at the eastern side of the South China Block (SCB), China, and attempted to establish the stable part of the SCB since the Cretaceous. Paleomagnetic specimens were collected at 39, 25 and 14 sites from three independent parts: the northern, central and southern regions of eastern SCB, respectively. Characteristic directions of higher temperature components (HTCs) with an unblocking temperature of ∼680 °C were isolated from 69/78 sites. The optimal concentrations of global mean HTC directions calculated using the direction-correction tilt test were achieved at 79±19%, 95±27%, 71±37% and 117±98% untilting for the Early Cretaceous sites from the northern part, Late Cretaceous sites from the northern, central and southern parts, respectively. This treatment gives positive tilt tests or brings the optimal concentration not far from being indistinguishable from positive tilt tests, although this observation can be due to imperfect separation of a primary component (HTC) from a secondary one (lower temperature component). We adopted completely (100%) untilted directions of the HTCs as the paleomagnetic field directions during the Cretaceous, because the mean directions after complete untilting were almost equal to each mean direction after incomplete untilting showing the optimal concentration. The mean paleomagnetic poles for three independent parts were located at almost the same positions and were indistinguishable from that for Sichuan, the western side of SCB at the 95% confidence level. This observation indicates that there is no relative movement between the eastern and western sides of SCB and implies that a large part of the SCB (excluding a 400-km-wide swath along the Red River Fault) has behaved as its coherent (stable) body since the Cretaceous. The Cretaceous paleomagnetic pole for the stable body of the SCB (latitude=80.0°N, longitude=206.7°E, A95=2.5°) is worth using as a reference Cretaceous paleomagnetic pole of the SCB and agrees strongly with the reference Eurasian paleomagnetic pole during the Cretaceous period. [Copyright &y& Elsevier]

We present new paleomagnetic and multi-model stereo photogrammetry data from lava sequences in the West Greenland part of the North Atlantic igneous province (NAIP). The joint analyses of paleomagnetic and photogrammetric data yield a well-defined paleomagnetic pole located at Lat=73.6°N, Long=160.5°E (N=44, α95=6.2°, K=13.1; age ∼61–55 Ma), which is statistically indistinguishable from a pole recently obtained for the Eurasian part of the NAIP on Faroe Islands [Riisager et al., Earth Planet. Sci. Lett. 201 (2002) 261–276]. Combining the two datasets we obtain a joint NAIP paleomagnetic pole in Greenland coordinates: Lat=71.1°N, Long=161.1°E (N=87, α95=4.3°, K=13.6; age ∼61–54 Ma). The results presented here represent the first study in which photogrammetry profiles were photographed at the exact same locations where paleomagnetic fieldwork was carried out, and a direct flow-to-flow comparison of the two datasets is possible. Photogrammetry is shown to be particularly useful because of (i) highly precise dip/strike measurements and (ii) detailed ‘field observations’ that can be made in the laboratory. Highly precise determination of the structural attitude of well-exposed Kanisut Mb lava sequences demonstrates that their apparently reliable in-field dip/strike measurements typically are up to ∼6° wrong. Erroneous dip/strike readings are particularly problematic as they offset paleomagnetic poles without affecting their confidence limits. Perhaps more important for large igneous provinces is the recognition of a variable temporal relationship between consecutive lava flows. We demonstrate how correct interpretation of paleosecular variation, facilitated by the detailed photogrammetry analysis, is crucial for the rapidly emplaced Vaigat Formation lavas. Inaccurate tectonic correction, non-averaged paleosecular variation and unrecognized excursional directions may, perhaps, explain why coeval paleomagnetic poles from large igneous provinces are often discordant. The difference between the joint NAIP paleomagnetitc pole and apparent polar wander path poles suggests that they may be less reliable than suggested by their confidence limits. [Copyright &y& Elsevier]

A paleomagnetic study was carried out in the carbonates and marls of the Liassic member of the Zarzaïtine Formation of the Illizi basin (SE Algeria) deposited in a continental environment. Two magnetization components were identified. The first, defined at relatively low blocking temperature, was isolated in five sites, and yields the following paleomagnetic pole (80.8°N, 20.1°E, K = 811 and A 95 = 2.2°). This magnetization is considered an overprint acquired during Cenozoic times. The second component was defined by both normal and reversed polarity. The normal polarity was identified in fourteen sites using both linear regression and great circles. The reversed one was inferred in four sites from the remagnetization circle and demagnetization path analyses. This component is mainly (it could be in part the primary magnetization) a late diagenesis magnetic overprint. It yields a new Liassic pole (71.8°S, 54.9°E, K = 91 and A 95 = 3.9°) for Africa.

Archean to Paleoproterozoic rocks potentially record the evolution of the geodynamo and the tectonic mode of the early Earth. The paleomagnetic intensity and direction data provide important information on the Earth's core–mantle revolution. Herein, we report the results of paleomagnetic and geochronological studies of a Proterozoic dolerite dyke from southern West Greenland. Clinopyroxene grains from the dyke yielded Ar–Ar plateau ages from 1808 to 1887 Ma (1816.0 ± 14.6 Ma; 2σ). The paleomagnetic direction of the dyke (D = 243.6°, I = 66.3°, α 95 = 3.9°) yielded a virtual geomagnetic pole (VGP) of 33.5 °N and 96.4 °W. This 1.8 Ga pole falls in a limited area where Paleoproterozoic poles between 2.5 Ga and 1.7 Ga for southern West Greenland are distributed. Comparison of the Paleoproterozoic poles of southern West Greenland with those of North America suggests that the North Atlantic Craton of southern Greenland could have been an independent stagnant tectonic block, different from the drifting Superior and Slave Cratons in the Early Proterozoic. Thellier experiments on 13 specimens yielded a mean paleointensity value of 14.8 ± 2.3 μT, indicating a virtual dipole moment of 2.88 ± 0.46 × 1022 Am2. This value is approximately one-third of the present-day Earth's field intensity, and is consistent with the value for the period between 1400 Ma and 2400 Ma. This small paleointensity value of the Proterozoic rocks is due to a gradual dipole moment change over a long period (∼1 Gyrs) since 4000 Ma. [ABSTRACT FROM AUTHOR]