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Abstract The South Qiangtang block of the Qinghai‐Tibet Plateau represents an area critical to understanding the late Paleozoic and early Mesozoic history of the Tethyan realm, but its drift history remains poorly constrained. Here we report a new quantitative paleogeographic constraint for the South Qiangtang block from a paleomagnetic study of Late Triassic volcanic rocks of the Xiaoqiebao Formation. A characteristic remanent magnetization isolated from 25 sites passes both fold‐ and reversal tests, and likely represents a primary magnetization. On the basis of these data, we estimate that the South Qiangtang block occupied a paleolatitude of 30.1 ± 4.6°N at ca. 222 Ma. When combined with existing paleomagnetic constraints, these new results indicate that the South Qiangtang block (and other “Cimmerian” blocks) moved rapidly northward (in true latitude) between the middle Permian and Late Triassic. Our new data further suggest that the southern branch of the Paleo‐Tethys (Longmuco‐Shuanghu Ocean) likely closed by the mid‐Late Triassic.

This paper presents the results of microprobe, paleomagnetic, and rock magnetic studies on peats from the Tyapka peat section (Khabarovsk krai) up to the turn of 4 ka BP. The alternating field demagnetization of peats yielded a horizon of 57–109 cm (1833–3083 cal. BP) with negative inclination values of the magnetization vector corresponding to the geomagnetic Etrussia excursion. The relative paleointensity estimates obtained for peats for the first time are consistent with the literature archeomagnetic data on the western part of Eurasia. According to the results of this study, the Etrussia excursion took place against the background of increased values of the Earth's magnetic field and lasted for ~1200 years. [ABSTRACT FROM AUTHOR]

Magnetic fabric, paleomagnetic, and petrophysical studies were conducted on rocks in the Tafresh area of the central Urumieh-Dokhtar magmatic arc in Iran. The samples included Late Triassic dark gray sandstone, a mafic dyke, diorites, and a felsic dyke in the Zaghar region. Hydrothermal alteration in the Spid intrusion was investigated to understand the effects of alteration on magnetic fabric patterns. The AMS measurements support the theory that the Nayband Formation was constructed under a crustal extension regime. Magnetic susceptibility anisotropy in a microdioritic dyke indicates compression from the NNE-SSW, likely due to tectonic activity. AMS results from diorites in Zaghar suggest intrusions were emplaced in extensional spaces between the Tafresh and Chaghar thrust faults. The Spid intrusion's magnetite is the primary carrier of magnetic susceptibility, but hydrothermal alteration has partly converted it into hematite, resulting in lower susceptibility and higher porosity in altered diorites. This process leads to a bimodal distribution of magnetic lineation trends. The Spid and Zaghar massifs underwent a northward tilt of about 30 degrees around an east-west axis following the Early Miocene. Post-Eocene rotations in the area are typically within ±20 degrees. This study demonstrates how magnetic properties can provide new insights into the evolution of tectono-magmatic processes and structural controls within a magmatic arc. [ABSTRACT FROM AUTHOR]

Ancient magnetization(s), often recorded by hematite (Fe2O3), provide key paleomagnetic constraints on plate interactions through time. Primary remanent magnetizations may be modified or overprinted by secondary processes that complicate interpretations of paleomagnetic data. Hematite (U‐Th)/He (hematite He) dating has the potential to resolve when secondary magnetizations were acquired. Here, we compare hematite He data and paleomagnetic results in Paleoproterozoic crystalline rocks, meters below a major nonconformity in the Colorado Front Range, USA. Prior work and new rock magnetic data indicate that pervasive hematite alteration records a secondary chemical remanent magnetization (CRM) during the Permo‐Carboniferous Reverse Superchron, coincident with the Ancestral Rocky Mountain orogeny. We target minor hematite‐coated faults cutting basement for (U‐Th)/He analyses because they are of sufficient hematite purity to yield geologically meaningful dates. Two samples yield overlapping and scattered individual hematite He dates ranging from ∼138 to 27 Ma (n = 33), significantly younger than the age of the late Paleozoic CRM. Scanning electron microscopy, electron probe microanalysis, and Raman spectroscopy indicate that aliquots have variable grain size distributions and fluorocarbonate impurities. Thermal history models support hematite on fault surfaces mineralized coeval with CRM acquisition during the late Paleozoic, and hematite He data scatter reflects variable He loss during Mesozoic burial owing to differences in grain size distribution from fault slip comminution and in chemistry among aliquots. Our results underscore the differences in temperature sensitivity and sampling requirements between paleomagnetic and hematite He investigations and illustrate that hematite He dates will usually be younger than preserved remanent magnetizations. Plain Language Summary: Minerals such as hematite are capable of recording the direction of the Earth's magnetic field during formation and this paleomagnetic information helps geoscientists estimate the age of rocks and the past motions of tectonic plates. During geologic events like mountain‐building, primary paleomagnetic signatures in rocks may be modified or replaced by new, secondary paleomagnetic recordings. Such secondary magnetizations can be challenging to interpret, especially if the age of these magnetizations is unknown. (U‐Th)/He analysis, a form of radiometric dating, may aid paleomagnetic studies by revealing the age of minerals that carry secondary magnetizations. In this study, we compare hematite (U‐Th)/He data and a secondary magnetization carried by hematite from Colorado's Front Range and find that (U‐Th)/He dates are scattered and considerably younger than the reported age of the secondary magnetization. We interpret the variability of hematite (U‐Th)/He dates to reflect differences between aliquots relating to crystal size and the presence of non‐hematite minerals. Our results suggest that the (U‐Th)/He system was partially to fully reset by a more recent phase of burial and associated reheating that was not hot enough to fully reset the paleomagnetic system. We conclude that (U‐Th)/He and paleomagnetic investigations in hematite may not record the same geologic events. Key Points: We compare new hematite (U‐Th)/He dates with previously published paleomagnetic data from the same exposure of crystalline basement rockHematite (U‐Th)/He dates are younger than the inferred timing of magnetization and imply partial He loss since magnetization acquisition(U‐Th)/He dates may not relate to remanence acquisition because of differences in sampling requirements and temperature sensitivity [ABSTRACT FROM AUTHOR]

Red Ereño is a red-stained ornamental and construction limestone with characteristic white fossil shells. Although exploited since Roman times, marketed worldwide and that the rock itself and its outcrop areas have been included in geological heritage inventories, the origin of its characteristic reddish colour remained unresolved. The aim of this work is to deepen the scientific knowledge of Red Ereño as a basis for understanding the characteristics of this stone and to make this information available for geoconservation actions. The mineralogical and petrological study, mainly based on optical and electron microscopy, X-ray diffraction, and rock magnetism and paleomagnetic techniques, concluded that the red-staining mineral is pigmentary hematite. Moreover, the analysis stated that hematite precipitated after sedimentation but prior to burial diagenesis and before alpine inversion. Based on palaeomagnetic studies, it can be stated that mineralisation occurred during the Late Cretaceous. This work illustrates how scientific research on this potential heritage stone provides key information for geoconservation. [ABSTRACT FROM AUTHOR]

The Sangdanlin section in southern Tibet represents a geologic Rosetta stone to constrain the initiation of the India--Asia collision from its sedimentary and paleomagnetic records. However, geoscientists have arrived at fundamentally divergent interpretations surrounding the age of the strata and its paleomagnetic record. Here, we report paleontologic, petrographic, and paleomagnetic data from the Sangdanlin section that recognize the sequence as a thrust complex containing interlaced Barremian--Albian (Early Cretaceous) and Paleocene strata, each separated by thrust faults. Recognizing two complexly interwoven formations of distinctly different ages contradicts a continuous stratigraphic superposition. Assigning an Early Cretaceous, instead of Paleocene, age to the units collected for paleomagnetic data revises paleogeographic models thereby supporting a large (2,000 to 3,000 km) extent of Greater India, with collision initiating at 55 ± 5 Ma in the western Himalayas. A contiguous plate in the Neotethys Ocean precludes that Asia's southern margin was built through a succession of accreted terrains. [ABSTRACT FROM AUTHOR]

Paleomagnetic statistical inference is underpinned by a family of parametric null hypothesis tests. In many cases, however, paleomagnetic data do not meet the distributional assumptions of these tests, which can lead to spurious inferences. Earlier studies have proposed the bootstrap as a nonparametric alternative for paleomagnetic analysis, which can be applied even when the distributional form of the data is unknown. Key among these approaches is the bootstrap test for a common mean direction, which relies on assessment of the overlap of estimated confidence regions. In its current form, the bootstrap test for a common mean paleomagnetic direction does not consider a null hypothesis and can yield outcomes that cannot be interpreted in terms of a statistical significance level. To resolve these issues, we use recent advances to place such bootstrap tests within a null hypothesis significance testing framework, and unify them with the existing family of paleomagnetic statistical tests. Furthermore, using numerical experiments we demonstrate the applicability of such a nonparametric approach to moderately sized paleomagnetic data sets typical of modern and legacy studies. Finally, we demonstrate how a confidence region can be estimated for the common mean of two sets of directions and how known directions, such as the expected field produced by a geocentric axial dipole, can be compared to that mean. Plain Language Summary: Statistical inference is the process of using observations to infer the properties of an unobserved population. An example of this process in paleomagnetism (the study of Earth's ancient magnetic field based on information preserved in geological materials) is a test of whether two sets of field directions have a common mean. Traditional statistical methods used to address this question make assumptions about the properties of the observations, which are known to be invalid in many cases. An alternative approach is so‐called bootstrapping, which relaxes assumptions about the observations and can then be applied more widely. In this study, we show how bootstrapping can be applied to paleomagnetic observations within the interpretational structure of existing paleomagnetic statistics, thus, providing a consistent inference framework. Furthermore, using numerical experiments we investigate how many paleomagnetic observations are required for bootstrapping to yield reliable results. Key Points: Advances in bootstrapping directional data are consideredThe number of directions needed for bootstrap‐based inference is assessedA bootstrap common mean direction test (CMDT) for paleomagnetic directions is presented [ABSTRACT FROM AUTHOR]

Progress of relative paleointensity (RPI) estimations using marine sediments has greatly contributed to better understanding of the behavior of the past geomagnetic field. To enhance further the reliability of RPI estimations, we must overcome the problem that climatically induced variations of magnetic‐mineral assemblages in sediments may influence RPI records. Two major constituents of magnetic‐mineral assemblages in marine sediments are magnetofossils and detrital magnetic minerals, and the latter consists of silicate‐hosted magnetic inclusions and unprotected magnetic minerals. It is necessary to understand different RPI recording efficiencies among those constituents to tackle the problem, but previous evaluations were inconclusive. We studied this issue using a sediment core taken from the southeast Pacific Ocean. Rock‐magnetic investigations revealed that the magnetic mineral assemblage of this core during the last ∼900 Kyr is a mixture of low‐coercivity magnetofossils and middle‐coercivity detrital unprotected partially oxidized magnetite. Natural remanent magnetization versus isothermal remanent magnetization demagnetization diagram showed strong convex curvature, and RPI signals carried by the two components could be separated by calculating RPI from the gradients of 20–40 and 70–160 mT segments. We confirmed that RPI recording efficiency of magnetofossils is lower than that of detrital unprotected magnetites/maghemites. Because of the marginal overlap between the coercivity ranges of the two components, changes in their relative abundance do not influence RPI estimations. This condition is ideal for RPI estimations, and the resulted RPI curve closely coincides with that of the PISO‐1500 stack despite changes in the relative abundance of the two components. Plain Language Summary: Marine sediments potentially preserve records of geomagnetic field intensity variations in the past (paleointensity), which may be important for life on the Earth to shield influx of high‐energy particles from the universe. A serious problem recognized by previous studies is that paleointensity records from sediments sometimes include artificial changes induced by sediment lithology changes reflecting varying depositional environments. Two major constituents of magnetic minerals in sediments, which records paleointensity variations, are magnetites produced by magnetotactic bacteria, called magnetofossils, and inorganic magnetic minerals originated from weathering of rocks on land or materials of volcanic eruptions. Our study using a sediment core taken from the southeast Pacific Ocean revealed that magnetofossils yield lower paleointensity values than inorganic magnetic minerals. This implies that temporal changes in the relative abundance of magnetofossils and inorganic magnetic minerals in sediments may cause the artificial paleointensity variations. We could obtain a reliable paleointensity record from the studied sediments by evaluating separately the magnetizations carried by the two magnetic‐mineral components, which utilized the observations that the two magnetic‐mineral components have different resistance to an external magnetic field. Key Points: Magnetofossil and detrital partially oxidized unprotected magnetite are the major constituents of magnetic mineral assemblageLittle overlap in coercivity distribution of the two components enabled separate evaluation of relative paleointensity (RPI) recording efficiencyRPI recording efficiency of magnetofossil is lower than that of detrital unprotected magnetite/maghemite [ABSTRACT FROM AUTHOR]

New geostructural, petro-geochemical, U–Pb geochronological and paleomagnetic data for sills of metagabbro-dolerites of the Severobyrranga and Yasnenskiy complex specify the paleotectonic position of the Faddey terrane of the Central Taimyr accretionary belt. The structural position of the sills in the rocks of the Oktyabr and Zhdanov formations is indicative of their intrusion before deformations caused by the accretion of the Central Taimyr belt. The U–Th–Pb age of crystallization for the metagabbro-dolerites has been established as 1357 ± 9 Ma. The primary paleomagnetic record reflecting the time of intrusion has not been preserved, but two metachronous components have been identified. The first one corresponds to crust formation processes at ca. 840 Ma due to collision, probably of continent – island arc type involving the cratonic block that included the Faddey and Mamont-Shrenk terranes. These collisional events took place several hundreds of kilometers from the Siberian margin. The second component corresponds to thermal events on the Paleozoic-Mesozoic boundary and reflects the strike-slip deformation in the Kara orogen. [ABSTRACT FROM AUTHOR]

Vertically accreted, cyclic tidal rhythmites—laminated, fine-grained sandstones, siltstones and mudstones—occur in the late Cryogenian glaciogenic Elatina Formation (ca 635 Ma) and early Cryogenian Sturt Formation (ca 660 Ma) in the South Flinders Ranges region of the Adelaide Rift Complex within the Adelaide Superbasin, and in Cryogenian strata from Nicholson 2 drill hole in the eastern Officer Basin, South Australia. The rhythmites provide insights into Cryogenian littoral environments. The Elatina rhythmite was deposited during an interstadial and the Sturt rhythmite during early glacial advance, whereas the Nicholson 2 rhythmite is assigned to interglacial beds. The resultant raised sea levels and drowned valleys provided the tidal inlets, ebb-tidal deltas, estuaries and fjords favouring rhythmite deposition. The rhythmites display semidiurnal and diurnal (lunar day) tidal laminae grouped in fortnightly neap–spring cycles and record the semiannual tide. Periods of 26.2 ± 0.9 neap–spring cycles displayed by the Elatina rhythmite and ∼27 neap–spring cycles by the Nicholson 2 rhythmite mark the non-tidal annual variation of sea level, which results from seasonal surface winds and changes in atmospheric pressure and temperature acting on the waters of marine shelves and marginal seas. The strong annual signals and absence of dropstones in the Elatina and Nicholson 2 rhythmites indicate that respective marine shelves and marginal seas were ice-free during rhythmite deposition. The Sturt rhythmite, by contrast, shows a weak annual period of ∼27 neap–spring cycles and contains dropstones and till pellets, indicating that the adjacent marine shelf and sea were largely ice-covered. Paleotidal data for the Elatina rhythmite have illuminated Earth's late Cryogenian paleorotation and the Moon's orbit, and paleomagnetic studies of the Elatina rhythmite indicated a low paleolatitude for late Cryogenian glaciation. Contrary to recent modelling by others, strong tides existed at shallow-water continental margins during Cryogenian glaciations. Cyclic tidal rhythmites are associated with early and late Cryogenian (ca 660 and ca 635 Ma) glaciogenic successions and interglacial beds in South Australia. Rhythmite deposition occurred when raised sea levels provided the coastal environments favouring rhythmite deposition. The rhythmites display semidiurnal and diurnal tidal laminae grouped in fortnightly cycles, and record the semiannual tide and the non-tidal annual variation of sea level. Strong tides existed at shallow-water continental margins during early and late Cryogenian low-latitude glaciations and the interglacial interval. [ABSTRACT FROM AUTHOR]

Quantifying the contributions of distinct mineral populations in bulk magnetic experiments greatly enhances the analysis of environmental and rock magnetism studies. Here, we develop a new method of parametric unmixing of susceptibility components in hysteresis loops. Our approach is based on a modified Gamma‐Cauchy exponential model that accounts for variable skewness and kurtosis. The robustness of the model is tested with synthetic curves that examine the effects of noise, sampling, and proximity (similar coercivities) of susceptibility components. We provide a Python‐based script, the Hist‐unmix, which allows the user to adjust a forward model of up to three ferromagnetic components as well as a dia/paramagnetic contribution. Optimization of all the parameters is achieved through least squares fitting (Levenberg‐Marquardt method), with uncertainties of each inverted parameter calculated through a Monte Carlo error propagation approach. For each ferromagnetic component, it is possible to estimate the saturation magnetization (Ms), saturation remanent magnetization (Mrs) and the mean coercivity (Bc ${B}_{c}$). Finally, Hist‐unmix was applied to a set of weakly magnetic carbonate rocks from Brazil, which typically show distorted hysteresis loops (wasp‐waisted and potbellied). For these samples, we resolved two components with distinct coercivities. These results are corroborated by previous experimental data, showing that the lower branch of magnetic hysteresis can be modeled by the presented approach and might offer important mineralogical information for rock magnetic and paleomagnetic studies. Plain Language Summary: Rocks contain magnetic minerals that record Earth's varying magnetic field morphology and intensity and provide information on our planet's evolution, as well as the ancient environmental conditions where the rocks formed. To study these magnetic minerals, we need to identify and quantify them, but this is challenging because of the complex mixture of such minerals that a rock may contain. Magnetic hysteresis curves are a simple and quick measurement that provide information on the magnetic properties of a rock, reflecting the combined effects of different minerals. In this paper, we propose a mathematical model that can separate the individual contributions of each magnetic population. We also provide an open‐source Python script for users to apply our model to their own data. Key Points: A new method for the parametric unmixing of magnetic hysteresis data based on a modified Gamma‐Cauchy exponential model is presentedThe model accounts for curves with variable skewness/kurtosis, allowing the separation of dia/para and ferromagnetic contributionsAn open‐source Python script (Hist‐unmix) allows users to import, process and model their data via a friendly interface [ABSTRACT FROM AUTHOR]

Relative Caribbean‐North American plate motion is partitioned over the trench and intra‐Caribbean plate faults that bound large scale tectonic blocks. Quantifying the kinematic evolution of this tectonic corridor is challenging because much of the region is submarine. We present an extensive regional paleomagnetic data set (1,330 cores from 136 sampling locations) from Eocene and younger rocks of the northern Lesser Antilles, the Virgin Islands, and Puerto Rico, and use a statistical bootstrapping approach to quantify vertical axis block rotations. Our results show that the Puerto Rico–Virgin Island (PRVI) block and the Northern Lesser Antilles (NoLA) block formed two coherently rotating domains that both underwent at least 45° counterclockwise rotation since the Eocene. The first ∼20° occurred in tandem in late Eocene and Oligocene time, after which the blocks were separated in the Miocene by the opening of the Anegada Passage. The last 25° of rotation of the PRVI block ended in the middle Miocene, whereas the NoLA block rotated slower, until the latest Miocene. The boundary between the NoLA block and a non‐rotated Southern Lesser Antilles was likely the Monserrat‐Harvers fault zone. These results require hundreds of kilometers of intra‐Caribbean motions with oroclinal bending of the trench or forearc sliver motion along the curved plate boundary as endmembers. These data invite a critical re‐evaluation of the kinematic reconstruction of Caribbean‐North American plate motion. The consequent changes in paleogeography may provide a new view on the enigmatic eastern Caribbean paleo‐biogeography and the Paleogene dispersal of South American mammals toward the Greater Antilles. Key Points: Since the late Eocene the Puerto Rico‐Northern Lesser Antilles block underwent ≃45° of counterclockwise rotationDuring the Miocene the opening of the Anegada Passage split this block in two and accommodated part of their differential rotation rateOur results imply intraplate motion of a forearc sliver over 500 km with profound effects on Paleogene Caribbean paleogeography [ABSTRACT FROM AUTHOR]

We present a multidisciplinary study based on Differential Scanning Calorimetry (DSC), paleomagnetic analysis, and numerical modeling to gain information on the timescales of syn‐ and post‐depositional ductile deformation of the strongly welded and rheomorphic Green Tuff ignimbrite (GT; Pantelleria, Italy). DSC measurements allow the determination of glass fictive temperatures (Tf; i.e., the parameter accounting for the cooling dependence of glass structure and properties). Using a Tf‐based geospeedometry procedure, we infer the cooling rate (qc) experienced by the glassy phases in different lithofacies within the GT formation. Glass shards from the basal pumice fall deposit record a fast qc of ∼10°C/s. In contrast, the ignimbrite body returns slow qc values depending on the stratigraphic position and lithofacies (basal/upper vitrophyres, fiamme‐rich and rheomorphic layers), ranging from ∼10−2 to ∼10−6 °C/s. Moreover, paleomagnetic analyses of the natural remanent magnetization of ignimbrite matrix and embedded lithic clasts indicate an emplacement temperature higher than 550–600°C. By integrating calorimetric and paleomagnetic datasets, we constrain a conductive cooling model, describing the ignimbrite's temperature‐time‐viscosity (T–t–η) evolution from the eruptive temperature to below Tf. Outcomes suggest that the upper and basal vitrophyres deformed and quenched over hours, indicating that the entire GT underwent intense syn‐depositional ductile deformation. Furthermore, the central body remained above Tf for a much longer timespan (>1 month), enabling post‐emplacement rheomorphic flow. Lastly, we discuss the critical role of mechanisms such as shear heating and retrograde solubility of volatiles, in locally controlling the rheological behavior of the GT. Plain Language Summary: Pyroclastic density currents (PDCs), one of the most dangerous occurrences caused by volcanic eruptions, are hot mixtures of ash, gas, and rocks that travel rapidly and propagate around the volcanoes. In some conditions, favored by the high temperature of the erupted material, the associated deposit (ignimbrites) may continue to deform viscously during and after deposition, experiencing welding (sintering and compaction of pyroclasts) and rheomorphism (formation of pervasive lava‐like structures). Studying rheomorphic ignimbrites can improve our knowledge of the hazard posed by the emplacement of PDCs. Here we constrain the timescales at which this type of ductile deformation occurs, focusing on the pantelleritic Green Tuff ignimbrite emplaced during the 45 ky eruption at Pantelleria Island (Italy). Distinct experimental approaches (i.e., calorimetry and paleomagnetism) allow constraining a model to describe the cooling history of this deposit. We define different deformations regimes experienced by the ignimbrite, highlighting that intense viscous deformation occurred at timescales like those of deposition (hours), and rheomorphic flow can also continue for a longer time (months) after the PDC deposition. Finally, we discuss the possible causes that lead to the formation of the observed rheomorphic structures. Key Points: A multidisciplinary approach provides information on the cooling history of the highly welded and rheomorphic Green Tuff ignimbriteExperimentally constrained cooling model describes the timescale of syn‐ and post‐emplacement deformations undergone by the depositCalorimetric and paleomagnetic proxies mark out different rheological thresholds controlling ignimbrite emplacement and rheomorphism [ABSTRACT FROM AUTHOR]

A comprehensive paleomagnetic study of the La Mora Formation fluvial sediments, presumably deposited during the Late Triassic-Early Jurassic, over the Mixteca terrane, allows us to document the most likely Early Mesozoic paleoposition of the Acatlán-Oaxaquia block among the mosaic of peri-Gondwanan blocks just before and during Pangea break-up. The oxide microscopy and the rock magnetic studies confirm that the magnetic carrier is titanomagnetite, hematite partially to almost totally replacing titanomagnetite (maghemite), and pigmentary hematite, in varying proportions related to dominant facies along the sedimentary sequence. Paleomagnetic results indicate that chemical remanent magnetization was acquired at during a time-lapse from the last steps of deposition to the burial and weakly deformation stage during the Late Jurassic (ca. 160 Ma). The mean paleolatitudes in flattening, unflattening, and geographic coordinate inclinations are: 7.6°N ± 1.6°, 9.8°N ± 1.7° and 11.1°N ± 1.6°, in comparison to the current latitude that is 18°N. However, a southern paleoposition of the La Mora Formation for the Late Triassic, is indicated from detrital zircon provenance ages from Amazonian craton sources, suggesting that the Acatlán-Oaxaquia block was juxtaposed to the northwestern Gondwana corner (i.e. NW South America), close to 7°S ± 2°. Therefore, we reported ca. 1800 ± 220 km of northward transport of the Acatlán-Oaxaquia block during the Late Triassic to Late Jurassic Pangea break-up. Last, the magnetic anisotropy susceptibility (AMS) indicates a primary origin magnetic fabrics with a slight syn-sedimentary tectonic overprint that agree with the Amazonian westward paleo-fluvial system. [ABSTRACT FROM AUTHOR]

The Paleoproterozoic Svecofennian Central Finland Granitoid Complex (CFGC) has been regarded as an area of low mineralisation potential. The Hiekkapohja area, 20km north-east of the town of Jyväskylä, host a concentration of variable metalliferous showings. Samples from mineralised boulders and outcrops display variable combinations of anomalously high concentrations of Cu, Mo, Zn, Pb, W, Pb, Ag, As, and Au. The area is composed mainly of peraluminous and ferroan granitoids. The dominant porphyritic Hiekkapohja granodiorite (~1.88 Ga) is cross-cut by the equigranular Soimavuori granite of similar age. The porphyritic Lehesvuori granite on the western side of the study area represents marginally older (~1.89 Ga) magmatism. The paragenetic sequence of the ore minerals shows that the Hiekkapohja area has been affected by at least two separate stages of hydrothermal activity. The first mineralisation stage was widespread, crystallising typically chalcopyrite, pyrrhotite, sphalerite, galena, arsenopyrite, magnetite and Ag-bearing minerals. After the first stage, a low temperature oxidising phase formed hematite and marcasite. The second mineralisation stage enclosed low temperature minerals, such as marcasite and native Ag and Ag-minerals, as inclusions inside chalcopyrite, pyrite, pyrrhotite, sphalerite, and arsenopyrite. The mineralised samples typically display signs of K-metasomatism and less commonly signs of propylitic alteration. During the second mineralisation stage the fluid flow was controlled by the dominant 120°–135° trending shear zones. Both the hydrothermal activity and the regional geology indicate that porphyry type ore forming processes have occurred in the Hiekkapohja area. Paleoproterozoic resetting of the remanent magnetisation is further evidence for the role of the hydrothermal system.

Magnetostratigraphy has become increasingly popular among geologists worldwide, as evidenced by recent scientific publications. This article reviews the role and place of magnetostratigraphy in general stratigraphic studies. The problem of developing a magnetostratigraphic scale of the Brunhes epoch based on paleosecular variation in the direction or intensity of the geomagnetic field was discussed. Nowadays, the above method has been actively pursued by researchers. Some hitherto little explored problems related to it were considered. Special attention was paid to the applicability range of the local magnetostratigraphic scale on the Earth’s surface. Three methods for estimating this parameter were proposed. Possible causes for the bias of paleomagnetic records in lava flows were analyzed: displacement of a recording medium during the recording process or later, magnetic anisotropy of two types, as well as the distortion of the geomagnetic field due to uneven surface magnetism, unevenly cooling lava magnetism, magnetism of surrounding rocks, or magnetohydrodynamic properties of flowing lava. The issues addressed here are important for improving the quality and reliability of paleomagnetic data.

Miocene igneous rocks of southern Kamchatka have remained poorly studied, so an expedition was organized in September-October, 2022, as part of a project for young scientist supported from the Russian Science Foundation. Main part of the expedition was carried out using maritime transport. The outcrops in the cliffs of the Beregovoi ridge on the Pacific coast side were studied. Part of the field works were close to Petropavlovsk-Kamchatsky, Vilyuchinsk cities, in the valley of the Paratunka river, in the basement of Vilyuchinsky pass, on the Zavoiko peninsula with involvement of vehicles. The presented work describes the sampling points and shows photographs of the outcrops. Paleomagnetic and isotope-geochemical characteristics of the samples are supposed to be obtained, which will be used to create a model of formation of magmatic complexes of southern Kamchatka.

We present two robust and well‐dated paleomagnetic poles from upper Eocene and Oligocene volcanics in the Urumieh‐Dokhtar magmatic arc, Central Iran. These two poles place Iran ∼3.7°–3° of latitude south of its present position between ca. 40 and 23 Ma. Our new paleomagnetic declination data indicate that the Central Iran block may have experienced a ∼11.6° clockwise rotation since the Late Eocene. We integrated our new data with the retrodeformed margins of the Zagros collision zone and contemporaneous Arabia positions to better constrain the age and configuration of the Arabia and Eurasia assembly process. In our model, the Arabia‐Eurasia collision occurred first in the western Main Zagros suture between ca. 35 and 30 Ma and then diachronously spread eastwards. Our paleogeographic reconstruction and initial continental collision timing supports the Arabia‐Eurasia collision as a first‐order driver of global cooling, Red Sea rifting, and Mediterranean extension. Plain Language Summary: The demise of the Neo‐Tethyan ocean and accompanied continent‐continent collisions created the thick crust and the low relief surfaces of the Iran Plateau and Tibetan Plateau. The onset timing and configuration in the Zagros collisional belt are critical for understanding the uplift of the Iran Plateau, tectonic evolution of the Mediterranean and Zagros regions, as well as the associated Cenozoic climate change. However, the age and configuration of the Arabia‐Eurasia continental collision are hotly debated. Previous works generated competing collision timing estimates ranging from Late Cretaceous to Pliocene, with most estimates from Eocene to Miocene. By conducting geochronology and paleomagnetism on the Eocene‐Oligocene volcanic rocks in Central Iran, we show that the Arabia‐Eurasia collision occurred first in the western Main Zagros suture at the Eocene/Oligocene boundary, and then diachronously spread eastwards. We suggest the Arabia‐Eurasia collision facilitates the slowing of Africa, the opening of the Red Sea, the extension in the Mediterranean, and the Eocene/Oligocene global cooling. Key Points: Our paleomagnetic results indicate a ∼3.7°–3° of latitude south of the present position of Central Iran during ca. 40–23 MaCentral Iran has experienced ∼11.6° clockwise rotation since ca. 40 MaArabia‐Eurasia collision began at the Eocene/Oligocene boundary in the western Main Zagros suture and diachronously spread eastwards [ABSTRACT FROM AUTHOR]

We investigate the amplitude and frequency of directional geomagnetic change since 15 ka in the Northern North Atlantic (∼67°N) using five "ultra‐high" resolution continental shelf sediment cores deposited at rates greater than 1 m/kyr. The ages of these cores are constrained by 103 radiocarbon dates with reservoir ages assessed through tephra correlation to terrestrial archives. Our study aims to address many of the uncertainties that are common in sedimentary paleomagnetic studies, including signal attenuation in low to moderate resolution archives and difficulty to demonstrate reproducibility in higher resolution archives. The "ultra‐high" accumulation rates of our cores reduce "lock‐in" and smoothing uncertainties associated with magnetic acquisition processes. Abundant radiocarbon dates along with an objective alignment algorithm provide a test of signal reproducibility at sub‐millennial timescales. The paleomagnetic secular variation (PSV) signal, evaluated as individual records and as a new stack (GREENICE15k), validates prior results, but provides stronger geochronological constraints, demonstrates a reproducible PSV signal and amplitude, and extends through the abrupt Bølling–Allerød and Younger Dryas climate transitions of the latest Pleistocene. While broadly consistent with time‐varying spherical harmonic models and varve dated records from Northern Europe, we demonstrate greater variance and higher amplitudes—particularly at sub‐millennial timescales. This robust variability on centennial timescales is rarely observed or discussed, but is likely important to our understanding of some of the most intriguing aspects of the geodynamo. Plain Language Summary: Our study used mud from the seafloor to investigate changes in Earth's magnetic field in the Northern North Atlantic region over the past 15 thousand years. Magnetic minerals eroded from rocks and deposited on the seafloor can preserve a record of the geomagnetic field, like little compass needles suspended in mud. We obtained sediment cores from areas near land with very high accumulation rates, which are rare in the modern ocean, that can record short magnetic field variations that occur on the timescale of centuries. We used radiocarbon dating to determine the ages of the sediment samples and a new alignment algorithm to verify the accuracy and consistency of the magnetic signal we observed. Understanding these short geomagnetic field variations is challenging, but it is key to unlocking many mysteries about the past and future of Earth's magnetic field. Key Points: Sediment cores with ultra‐high accumulation rates are used to study directional changes in the Northern North Atlantic's geomagnetic fieldStudy addresses uncertainties in sedimentary paleomagnetic research, such as signal attenuation, chronology, and reproducibilityStudy reveals robust variability on centennial timescales with greater variance than generally observed over the last 15,000 years [ABSTRACT FROM AUTHOR]

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]

Some rocks contain multiple remanence "components," each of which preserves a record of a different magnetic field. The temperature ranges over which these remanence components unblock can overlap, making it difficult to determine their directions. We present a data analysis tool called Thermal Resolution Of Unblocking Temperatures (TROUT) that treats the process of thermal demagnetization as a function of temperature (or alternating field demagnetization as a function of coercivity). TROUT models the unblocking temperature/coercivity distributions of components in a demagnetization experiment, allowing these distributions to overlap. TROUT can be used to find the temperatures/coercivities over which paleomagnetic directions change and when two directional components overlap resulting in curved demagnetization trajectories. When applied to specimens given multi‐component Thermoremanent Magnetizations (TRMs) in the laboratory, the TROUT method estimates the temperature at which the partial TRMs were acquired to within one temperature step, even for specimens with significant overlap. TROUT has numerous applications: knowing the temperature at which the direction changes is useful for experiments in which the thermal history of a specimen is of interest (e.g., emplacement temperature of pyroclastic deposits, re‐heating of archaeological artifacts, reconstruction of cooling rates of igneous bodies). The ability to determine whether a single component or multiple components are demagnetizing at a given temperature is useful for choosing appropriate ranges of temperatures to use in paleodirection/intensity experiments. Finally, the width of the range of temperature overlap may be useful for inferring the composition, grain size and domain state of magnetic mineral assemblages. Plain Language Summary: Rocks can contain records of multiple magnetization events or "components," which can tell researchers about their history. For example, if a cooled lava flow was later reheated by another lava flowing over the top of it, it will have two magnetic components for each of the cooling events. Sometimes, these components can be hard to separate from one another correctly, making it difficult to reconstruct the rocks' history. In this paper, we present a data analysis tool called Thermal Resolution of Unblocking Temperatures (TROUT) which can analyze experimental data and automatically pick out the different components. We tested TROUT on several data sets where rocks were given multiple magnetic components in the laboratory, and it accurately picks out the correct components in most cases. These test cases indicate that TROUT will be useful as an automatic tool for many applications where researchers want to know about the history of rocks they are studying. Key Points: Multi‐component demagnetization experiments can exhibit curved demagnetization data which may be difficult to interpretThermal Resolution of Unblocking Temperatures (TROUT) is a method for resolving the temperature/coercivity distributions, directions and magnitudes of components in demagnetization dataTROUT accurately estimates the temperature specimens were reheated to in laboratory experiments with curved demagnetization data [ABSTRACT FROM AUTHOR]

Previous models of strike‐slip basins do not consider the rotation of the basin itself; however, we show that the Tanakura transtensional basin in Japan was rotated and propose that this basin rotation was related to rifting caused by back‐arc spreading. The Tanakura Basin was formed by displacement along the Tanakura Fault Zone, one of the major active transform faults during the opening of the Sea of Japan. We carried out paleomagnetic analyses and U–Pb dating of the Neogene Tanakura Basin fill rocks. We present a revised, high‐precision stratigraphic record for the Neogene Tanakura Basin fill sequence shows that vertical‐axis counter‐clockwise rotation occurred between ∼17.2 and ∼16.6 Ma. Comparison with paleomagnetic data from adjacent areas shows that rotation was restricted to the basin. In addition, the timing of basin rotation corresponds to the rifting phase of the Tanakura Basin, suggesting that rapid basin subsidence owing to rifting and rapid basin rotation owing to strike‐slip faulting occurred simultaneously. The Tanakura Basin has the characteristics of both rift and transtensional basins that have experienced rotation. This study reveals the detailed relationships between the development and rotation of the Tanakura Basin: rifting‐related subsidence accompanied by basin rotation. Rifting owing to back‐arc spreading may have been accompanied by tectonic basin rotation in Northeast Japan, leading to variations in the magnitude and age of rotation, as the rifting occurred at different times in different locations. Key Points: We demonstrate the vertical‐axis rotation of blocks in the strike‐slip Tanakura transtensional basin, JapanBasin rotation coincided with basin riftingRifting owing to back‐arc spreading may have been accompanied by tectonic basin rotation in Northeast Japan [ABSTRACT FROM AUTHOR]

The paleogeography of the Tethyan Himalaya (TH) during the Mesozoic is vital to constrain the evolutionary history of the Neo‐Tethys Ocean, but reliable paleomagnetic data from Jurassic rocks in this area are scarce. Here, we report the first high‐quality paleomagnetic results from the Middle Jurassic (∼175–173 Ma) Lanongla Formation limestones in the Nyalam area of the TH. For most specimens, stepwise thermal or hybrid demagnetization reveals two well‐defined magnetization components. A low‐temperature component, which is isolated between natural remanent magnetization and 200–300°C, is consistent with the present geomagnetic field direction. A high‐temperature component, which is isolated between 300–350°C/10–25 mT and 500–580°C/60–120 mT, passes fold tests at the 95% and 99% confidence level, indicating a prefolding primary magnetization. The tilt‐corrected site‐mean direction for 28 paleomagnetic sites is Ds = 331.0° and Is = −49.9° with α95 = 2.7°, which provides a Fisherian site‐mean paleopole at 23.7°N, 292.9°E with A95 = 2.8° and a paleolatitude of 31.7 ± 2.8°S for the Nyalam study area (28.6°N, 86.1°E). A comparison between the reliable Middle Jurassic‐Early Cretaceous poles obtained from the TH and those observed from the Lhasa terrane reveals that the Neo‐Tethys Ocean for the reference point (29.1°N, 86.1°E) had a latitudinal width of 3,500 ± 1,000 km at ∼174 Ma, reached its greatest width of 7,000 ± 1,000 km at ∼137 Ma, and had an average latitudinal spreading rate of ∼10.4 cm/year during ∼174–137 Ma. Plain Language Summary: The Neo‐Tethys Ocean here refers to the prehistoric ocean that existed between the Lhasa terrane to the north and the Indian plate to the south during the much of the Mesozoic and early Cenozoic. Knowledge of the development of the Neo‐Tethys Ocean is crucial to understanding the evolution of the Himalayas and Tibetan Plateau. However, the opening of the Neo‐Tethys Ocean remains controversial. In this work, we report what we consider is the first high‐quality Middle Jurassic age paleopole from the Tethyan Himalaya, which shows that the Nyalam area was located at 31.7 ± 2.8°S at ∼174 Ma and that the Neo‐Tethys Ocean was at least ∼3,500 km wide in a N–S direction at that time. Key Points: The Nyalam area of the Tethyan Himalaya (TH) was located at 31.7 ± 2.8°S at ∼174 MaThe Neo‐Tethys Ocean opened a latitudinal width of ∼3,500 km at ∼174 Ma and reached its greatest width of ∼7,000 km at ∼137 MaThe Neo‐Tethys Ocean had an average latitudinal spreading rate of ∼10.4 cm/year during ∼174–137 Ma [ABSTRACT FROM AUTHOR]

The growth history of the Tibetan Plateau provides a valuable natural laboratory to understand tectonic processes of the India–Asia collision and their impact on and interactions with Asian and global climate change. However, both Tibetan Plateau growth and Asian paleoenvironments are generally poorly documented in pre-Pliocene times and reflect limited temporal coverage for different parts of the plateau. In this paper, the 238 m thick Cenozoic sediments in the Hongzhuang section of the Xunhua Basin were tested and analyzed via paleomagnetic and environmental magnetic methods. The formation age was determined, and the evolution history of the regional climate environment was analyzed. The magnetostratigraphy study shows that the sediments record a continuous sequence of geomagnetic polarity changes from C5ACn to C10r, which spans an interval of approximately 30~14.3 Ma from the early Oligocene to the middle Miocene. The magnetic susceptibility of the Hongzhuang section is basically similar to the deep-sea oxygen isotope fluctuation, indicating that the monsoon climate change indicated by the magnetic susceptibility is affected by global temperature. It is worth noting that at ~27 Ma and ~15 Ma, there is a negative correlation between magnetic susceptibility and deep-sea oxygen isotope, and magnetic susceptibility lags behind the increase in deep-sea oxygen isotope. Combined with the change in the sedimentary rate curve, we explain the asynchrony between the magnetic susceptibility and the deep-sea oxygen isotope around ~27 Ma and ~15 Ma. As the uplift of the plateau leads to the enhancement of the East Asian summer monsoon, the soil formation in the region is strengthened, resulting in an increase in magnetic susceptibility. At the same time, the rapid uplift of the plateau caused the erosion of the surrounding mountains to strengthen, and the input of near-source materials may promote the increase in magnetic susceptibility. [ABSTRACT FROM AUTHOR]

Bending of ribbon continents or arcs is an important tectonic process for reconstructing central Asia. Formation of the striking Tuva‐Mongol Orocline by closure of the Mongol‐Okhotsk Ocean (MOO) has long been proposed, but coupling of the two geological events has not been well illustrated, hindering our understanding of tectonic evolution of central Asia. In order to constrain age of initial closure of the MOO in its western segment and formation of the Tuva‐Mongol Orocline, we performed paleomagnetic studies on the Late Triassic clastic rocks in the Amuria Block (AMB; 17 sites) and the Tarvagatay Block (TVB; 10 sites) of the western Mongolian blocks (WMB) on both sides of the Mongol‐Okhotsk Suture. Rock magnetic investigations show hematite and magnetite as main magnetic carriers of the characteristic remanent magnetization (ChRM). The ChRM directions from both regions pass fold and/or reversal tests and can be considered as primary remanent magnetization. Combining the overlapped new paleomagnetic poles (AMB: λ/φ = 70.4°N/233.8°E, A95 = 4.6°; TVB: λ/φ = 70.5°N/248.2°E, A95 = 9.0°) with geological evidence, we propose that the bending of the WMB following its collision with the Siberia Craton resulted in the Late Triassic closure of the MOO in its western segment, and initiated the formation of the Tuva‐Mongol Orocline. Plain Language Summary: The Mongol‐Okhotsk Ocean (MOO) was a triangle‐shaped ocean between Mongolia and Siberia about 150 million year ago. A scissor‐like progressive closure of this ocean from the west to the east has been proposed. However, it is still controversial when this ocean began to close in its western segment. In this study, we report coeval Late Triassic paleomagnetic poles from continental blocks on both sides of the suture to constrain when the MOO closed initially. The new data indicate an initial closure of the MOO in the Late Triassic that was caused by bending of the western Mongolian blocks, which also initiated the formation of the Tuva‐Mongol Orocline. This study provides the first paleomagnetic evidence for a Late Triassic initial closure of the MOO. Key Points: Coeval Late Triassic paleomagnetic poles were obtained from both sides of the Mongol‐Okhotsk SutureThe Tarvagatay and Amuria Blocks on both sides of the Mongol‐Okhotsk Suture show consistent paleolatitudes in the Late TriassicBending of western Mongolian blocks led to the Late Triassic closure of the Mongol‐Okhotsk Ocean and formation of the Tuva‐Mongol Orocline [ABSTRACT FROM AUTHOR]

The Cenozoic strata of the Xining Basin, NE Tibet, have provided crucial records for understanding the tectonic and palaeo‐environmental evolution of the region. Yet, the age of the lower part of the sedimentary stratigraphy and, consequently, the early tectonic evolution of the basin remain debated. Here, we present the litho‐ and magnetostratigraphy of various early Eocene sections throughout the Xining Basin independently constrained by the U–Pb radiometric age of a carbonate bed. Our study extends the dated stratigraphy down to 53.0 Ma (C24n.1r) and reveals highly variable accumulation rates during the early Eocene ranging from 0.5 to 8 cm/ka. This is in stark contrast to the low but stable accumulation rates (2–3 cm/ka) observed throughout the overlying Palaeogene and Neogene strata. Such a pattern of basin infill is not characteristic of flexural subsidence as previously proposed, but rather supports an extensional origin of the Xining Basin with multiple depocentres, which subsequently coalesced into a more stable and slowly subsiding basin. Whether this extension was related to the far‐field effects of the subducting Pacific Plate or the India–Asia collision remains to be confirmed by future studies. [ABSTRACT FROM AUTHOR]

• An integrated record of the Mio-Pliocene transition in the Eastern Paratethys is provided. • A >2000 m thick exposed section reveals events in unprecedented detail. • Integration of magnetostratigraphy, sedimentology, mollusks and ostracods. • A distinct behavior of the Eastern Paratethys during the Messinian Salinity Crisis is evidenced. Well-documented, high-resolution sedimentary sections are critical to our understanding of the often eventful evolution of semi-isolated basins that form during the final stages of continent–continent convergence, as exemplified by the Mediterranean-Paratethys system. Due to its nearly land-locked position in the Late Miocene, the Mediterranean experienced the renowned Messinian Salinity Crisis. At the same time, the equally restricted Eastern Paratethys to the north-east evolved in a potentially related, but very distinctive way. The events of this period are fully recorded in the sediments deposited during the Pontian regional stage in the Dacian Basin, part of the Eastern Paratethys, which we here investigate in detail in the best available section. The studied interval of the Slănicul de Buzău section is more than 2 km thick and almost continuously exposed. It is analyzed for paleomagnetism, mollusks, microfauna and sedimentary facies. This allows us to refine previous results from nearby but less complete sections, with particular improvements concerning resolution, biostratigraphy and sedimentology. The marine incursion just below the base of the Pontian (6.1 Ma) is shown to significantly predate the early Pontian highstand. The biostratigraphically defined onset of the middle Pontian (6.0 Ma) coincides with the highstand and slightly predates the major regression (5.9–5.6 Ma) for which the middle Pontian is best known. In the here-investigated section, the transgression at the beginning of the late Pontian (5.6 Ma) is followed by a regressive trend culminating between 5.4 and 5.2 Ma around the Mio-Pliocene boundary (5.33 Ma). The late Pontian sedimentation then becomes relatively stable and the fauna gradually transitions (4.8 Ma) into assemblages characteristic for the Dacian stage of the Dacian Basin, while overall significantly diverging from the rest of the Eastern Paratethys. Finally, we discuss several factors that could affect accuracy and applicability of the updated chronostratigraphy, warranting some caution. [ABSTRACT FROM AUTHOR]

Alkaline dikes from the Santos-Rio de Janeiro coast, SE Brazil, mainly from São Sebastião and Búzios islands, yielded a Late Cretaceous paleomagnetic pole (SR) located at 319.7°E 81.2°S (N = 44, A95 = 3.0°, k = 44). This pole includes some sites of alkaline stocks from São Sebastião Island of the same age and supersedes the previous pole for this island. To match the available radiometric ages and the prevailing normal polarity remanence of the rocks with the geomagnetic polarity time scale, the SR pole is placed at 84 Myr. Another group of alkaline rocks, dikes located mainly in Rio de Janeiro, was assigned an age of less than 70 Myr. The ages of the Poços de Caldas, Itatiaia, and Passa Quatro paleomagnetic poles are also discussed based on available radiometric data. Assuming a rigid plate, the SR pole indicates the southward movement of about 7° with virtually no rotation between 100 and 84 Myr. From approximately 84 to 70 Myr, a clockwise rotation of 8° is postulated, with slight variation in latitude. [ABSTRACT FROM AUTHOR]

The Pleistocene Tawanouchi basalt of SW Japan formed as a lava lake in an explosion crater within granitic basement. Volcanic activity in the Tawanouchi area started with a phreatomagmatic eruption, based on the lithofacies present near the crater and between the granite basement and the lava. The Tawanouchi basalt lava lake forms an inverted elliptical frustum with upper dimensions of approximately 340 m × 550 m, tapering downward to a depth of more than 170 m. Thermal history was evaluated based on differences in sizes and shapes of columnar joints from the margins of the lava to its interior. The vent lay near the center of the lava mass, based on deformation and trends of columnar joints in lava associated with clastic deposits. Lava repeatedly upwelled and flowed back into the vent. Mg/(Mg + Fe) ratios of some groundmass clinopyroxenes in the basalts overlap those of phenocryst cores, suggesting that less-differentiated lava was injected into more differentiated and semi-solidified lava. Paleomagnetic data show that the basement granite was heated to 530 °C or more 90 cm - 155 cm away from the contact with the lava. Numerical simulation of the thermal effect on the basement granite from the lava indicates that the lava lake with an initial temperature of 1150°C took more than 20 years to cool below 1100 °C. [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]

A thermodynamically consistent model for soft deformable viscoelastic magnets is formulated in actual space (Eulerian) coordinates. The possibility of a ferro-paramagnetic-type (or ferri-antiferromagnetic) transition exploiting the Landau phase-transition theory as well as mechanical melting or solidification is considered, being motivated and applicable to paleomagnetism (involving both thermo- and isothermal and viscous remanent magnetization) in rocks in Earth's crust and to rock-magma transition. The temperature-dependent Jeffreys rheology in the deviatoric part combined with the Kelvin-Voigt rheology in the spherical (volumetric) part is used. The energy balance and the entropy imbalance behind the model are demonstrated, and its analysis is performed by time discretization, proving existence of weak solutions. [ABSTRACT FROM AUTHOR]

The objective of the Psyche Magnetometry Investigation is to test the hypothesis that asteroid (16) Psyche formed from the core of a differentiated planetesimal. To address this, the Psyche Magnetometer will measure the magnetic field around the asteroid to search for evidence of remanent magnetization. Paleomagnetic measurements of meteorites and dynamo theory indicate that a diversity of planetesimals once generated dynamo magnetic fields in their metallic cores. Likewise, the detection of a strong magnetic moment (> 2 × 10 14 Am 2 ) at Psyche would likely indicate that the body once generated a core dynamo, implying that it formed by igneous differentiation. The Psyche Magnetometer consists of two three-axis fluxgate Sensor Units (SUs) mounted 0.7 m apart along a 2.15-m long boom and connected to two Electronics Units (EUs) located within the spacecraft bus. The Magnetometer samples at up to 50 Hz, has a range of ± 80 , 000 nT , and an instrument noise of 39 pT axis − 1 3 σ integrated over 0.1 to 1 Hz. The two pairs of SUs and EUs provide redundancy and enable gradiometry measurements to suppress noise from flight system magnetic fields. The Magnetometer will be powered on soon after launch and acquire data for the full duration of the mission. The ground data system processes the Magnetometer measurements to obtain an estimate of Psyche's dipole moment. [ABSTRACT FROM AUTHOR]

Paleolatitude evolution could provide a general paleo-location framework for explaining the paleoclimate change and tectonic deformation in geological time. Strengthening the paleolatitude study of the Tuotuohe Basin is important for understanding the history and mechanism of the tectonic uplift process in the north-central Tibetan Plateau. In this study, we introduced the magnetostratigraphy for the Tuotuohe-D (TTH-D) section in the Tuotuohe Basin, central-northern Tibetan Plateau, in order to constrain the chronology and to reconstruct the paleolatitude of the basin during the deposition of the Tuotuohe Formation. The results indicated that the Tuotuohe Formation in the TTH-D section was deposited between 38.5 and ~36.7 Ma. Combining this age with the results from the Tuotuohe section indicates that the age of the Tuotuohe Formation spans the interval from >38.5 Ma to ~33 Ma. Additionally, other paleomagnetic data of the Tuotuohe Formation from the Tuotuohe section, combined with the data from this study, indicate that the paleolatitude of the Tuotuohe Basin during the late Eocene was 25.9 ± 4.2°. That means that the Tuotuohe Basin was located in a subtropical anticyclonic zone and that the paleoenvironment during the late Eocene might be controlled by subtropical high pressure. Additionally, paleomagnetic results from the Qiangtang terrane and the bordering regions are combined with the results of our study, which suggest that the paleolatitude of the Tuotuohe Basin at ~26 Ma coincides well with the Eurasian apparent polar wander path for that interval, and that the N-S India–Asia convergence was reduced or ceased at ~26 Ma in the Tuotuohe Basin. [ABSTRACT FROM AUTHOR]

Under the influence of the far-field effect of the India-Asia convergence, the Tianshan Mountains have become a typical area of Cenozoic resurrection orogeny, a natural laboratory for continental geodynamics. However, the study of its uplift exhumation history is still controversial. Based on a detailed magnetostratigraphic study of sediments in a 501.29 m deep drill core, located in the Yili Basin that is sandwiched between the Northern and Southern Tianshan Mountains, a total of 202 samples were used to establish magnetostratigraphy. Characteristic remnant magnetization with both normal (N1–N7) and reversed (R1–R7) polarity was isolated by thermal demagnetization. The maximum age can be obtained at the bottom of the borehole profile is 1.95 Ma. Our results show that a significant increase in sedimentation rate as well as notable shift in depositional environment occurred at ~ 0.99–0.78 Ma, which represents the uplift of the northwest Tianshan Mountain and one subsequent rapid uplift event in early Pleistocene time. [ABSTRACT FROM AUTHOR]

Geomagnetic excursions are short‐lived episodes when Earth's magnetic field deviates into an intermediate polarity state. Understanding the origin, frequency, amplitude, duration, and field behaviour associated with excursions is a forefront research area within solid Earth geophysics. Excursion events typically last a few thousand to tens of thousands of years; unlike full reversals, excursions are generally not recorded around the globe. We present here a new palaeomagnetic record (Geomagnetic excursions) from a lacustrine sediment sequence (at times, punctuated by undersized horizons of the gravels) with extraordinarily stable signals. Palaeomagnetic and rock magnetic investigations were performed on a 17‐m‐thick profile of unconsolidated sediments from Bagwalipokar palaeolake (Lat. 29°43′18″; Long. 79°28′42″; altitude 4167 ft), Binta Basin in the Kumaun Lesser Himalaya, situated in the zone of the active North Almora Thrust (NAT). A total of 540 oriented palaeomagnetic samples from 108 horizons (five samples per horizon) were collected from the section. The extrapolation of the optically stimulated luminescence (OSL) date indicates that the whole section was deposited between 45 and 2.5 ka. Magnetic remanence is predominantly carried by magnetite alone. Virtual Geomagnetic Pole (VGP) latitudes were determined using mean declinations and inclinations. Two geomagnetic excursions were observed at younger levels [11.6–10.5 m (15.5–14.7 ka) and 15–11.7 m (8.0–2.85 ka)]. These geomagnetic excursions correlate with the recently reported younger Hawaiian lava flow excursions. The youngest excursion from 8 ka may be attributed to the climatic event beginning at 8.2 ka cooling event of an oxygen isotope record of biogenic carbonate from palaeolake Riwasa in north‐western India that provides a history of the Indian Summer Monsoon (ISM) from ∼11 to 6 ka BP and also the North Atlantic glacial outburst flood and the slowdown of Atlantic meridional overturning circulation. However, further work is needed to verify this interpretation. [ABSTRACT FROM AUTHOR]

Abstract Ancient magnetization(s), often recorded by hematite (Fe2O3), provide key paleomagnetic constraints on plate interactions through time. Primary remanent magnetizations may be modified or overprinted by secondary processes that complicate interpretations of paleomagnetic data. Hematite (U‐Th)/He (hematite He) dating has the potential to resolve when secondary magnetizations were acquired. Here, we compare hematite He data and paleomagnetic results in Paleoproterozoic crystalline rocks, meters below a major nonconformity in the Colorado Front Range, USA. Prior work and new rock magnetic data indicate that pervasive hematite alteration records a secondary chemical remanent magnetization (CRM) during the Permo‐Carboniferous Reverse Superchron, coincident with the Ancestral Rocky Mountain orogeny. We target minor hematite‐coated faults cutting basement for (U‐Th)/He analyses because they are of sufficient hematite purity to yield geologically meaningful dates. Two samples yield overlapping and scattered individual hematite He dates ranging from ∼138 to 27 Ma (n = 33), significantly younger than the age of the late Paleozoic CRM. Scanning electron microscopy, electron probe microanalysis, and Raman spectroscopy indicate that aliquots have variable grain size distributions and fluorocarbonate impurities. Thermal history models support hematite on fault surfaces mineralized coeval with CRM acquisition during the late Paleozoic, and hematite He data scatter reflects variable He loss during Mesozoic burial owing to differences in grain size distribution from fault slip comminution and in chemistry among aliquots. Our results underscore the differences in temperature sensitivity and sampling requirements between paleomagnetic and hematite He investigations and illustrate that hematite He dates will usually be younger than preserved remanent magnetizations.

Abstract Quantifying the contributions of distinct mineral populations in bulk magnetic experiments greatly enhances the analysis of environmental and rock magnetism studies. Here, we develop a new method of parametric unmixing of susceptibility components in hysteresis loops. Our approach is based on a modified Gamma‐Cauchy exponential model that accounts for variable skewness and kurtosis. The robustness of the model is tested with synthetic curves that examine the effects of noise, sampling, and proximity (similar coercivities) of susceptibility components. We provide a Python‐based script, the Hist‐unmix, which allows the user to adjust a forward model of up to three ferromagnetic components as well as a dia/paramagnetic contribution. Optimization of all the parameters is achieved through least squares fitting (Levenberg‐Marquardt method), with uncertainties of each inverted parameter calculated through a Monte Carlo error propagation approach. For each ferromagnetic component, it is possible to estimate the saturation magnetization (Ms), saturation remanent magnetization (Mrs) and the mean coercivity (Bc). Finally, Hist‐unmix was applied to a set of weakly magnetic carbonate rocks from Brazil, which typically show distorted hysteresis loops (wasp‐waisted and potbellied). For these samples, we resolved two components with distinct coercivities. These results are corroborated by previous experimental data, showing that the lower branch of magnetic hysteresis can be modeled by the presented approach and might offer important mineralogical information for rock magnetic and paleomagnetic studies.

The present study aims dating the topmost 50 m of a 115 m-long core retrieved from a valley located in the Cadarache Area (Upper Provence, South East France). Based on burial dating by in situ produced cosmogenic nuclides (10Be, 26Al and 21Ne), and paleomagnetic analyses, a Tortonian age was determined for the sedimentary succession exhibited in the core. In addition, thin sections, grain size analyses and quartz morphoscopy were used to characterize a shallow marine environment and to correlate the sediment core to the surrounding exposed sections. When comparing the studied sedimentary record to global sea level estimates, we establish that the local Tortonian transgression was not synchronous with the global scale sea level high-stand, but happened more likely later, during a global regressive trend. The timing of the Tortonian flooding in Upper Provence was therefore most probably driven by regional tectonic forcing. Finally, the Tortonian shallow marine sediments are topped by lacustrine tight carbonates. These carbonates protect the marine sediments from the following major erosional events resulting from the Messinian sea level drop and from interglacial-glacial fluctuations that both yielded to the present-day valley topography.

Paleomagnetic observations provide valuable evidence of the strength of magnetic fields present during evolution of the Solar System. Such information provides important constraints on physical processes responsible for rapid accretion of the protoplanetesimal disk. For this purpose, magnetic recordings must be stable and resist magnetic overprints from thermal events and viscous acquisition over many billions of years. A lack of comprehensive understanding of magnetic domain structures carrying remanence has, until now, prevented accurate estimates of the uncertainty of recording fidelity in almost all paleomagnetic samples. Recent computational advances allow detailed analysis of magnetic domain structures in iron particles as a function of grain morphology, size, and temperature. Our results show that uniformly magnetized equidimensional iron particles do not provide stable recordings, but instead larger grains containing single-vortex domain structures have very large remanences and high thermal stability-both increasing rapidly with grain size. We derive curves relating magnetic thermal and temporal stability demonstrating that cubes (>35 nm) and spheres (>55 nm) are likely capable of preserving magnetic recordings from the formation of the Solar System. Additionally, we model paleomagnetic demagnetization curves for a variety of grain size distributions and find that unless a sample is dominated by grains at the superparamagnetic size boundary, the majority of remanence will block at high temperatures ([Formula: see text]C of Curie point). We conclude that iron and kamacite (low Ni content FeNi) particles are almost ideal natural recorders, assuming that there is no chemical or magnetic alteration during sampling, storage, or laboratory measurement.

Abstract A portable Global Positioning System (GPS) compass was devised for orienting paleomagnetic drill cores and field test measurements were conducted. Orientation of drill cores has been done by magnetic compasses, sun compasses, and backsighting using landmarks. We modified a lightweight marine GPS compass to be mounted on an orientation device and directly measure azimuths, and compared them to measurements made with a magnetic compass, sun compass, and backsighting. Tests on our campus for a site with open sky above showed a root-mean-squared (rms) error of $$0.39^\circ$$ 0 . 39 ∘ , which is less than what is noted on the specifications of the GPS compass, and a difference of $$-\,0.1^\circ \pm 1.1^\circ$$ - 0 . 1 ∘ ± 1 . 1 ∘ (average ± rms) between the GPS and sun azimuths for 11 direction measurements. However, the site between buildings showed an average deviation of $$11.4^\circ$$ 11 . 4 ∘ from the sun azimuth due to multipath effects. When tested on drill core sampling of historical lavas in a volcanic island, the GPS azimuths were deviated only by $$0.4^\circ \pm 2.3^\circ$$ 0 . 4 ∘ ± 2 . 3 ∘ from the sun azimuths at a flat coastal site with open sky above, indicating that the GPS azimuths are as accurate as the sun azimuths. On the other hand, the GPS compass could not provide azimuths at vertical outcrops in forests due to the small number of satellites captured and multipath effects. If other Global Navigation Satellite Systems (GNSS) satellites are captured and false signals caused by multipath are eliminated, portable GNSS compasses, which operate regardless of rock type, weather, or geographic situation, would replace other methods of orienting drill cores. Graphical Abstract

Abstract Cosmogenic radionuclide records (e.g., 10Be and 14C) contain information on past geomagnetic dipole moment and solar activity changes. Disentangling these signals is challenging, but can be achieved by using independent reconstructions of the geomagnetic dipole moment. Consequently, solar activity reconstructions are directly influenced by the dipole moment uncertainties. Alternatively, the known differences in the rates of change of these two processes can be utilized to separate the signals in the radionuclide data. Previously, frequency filters have been used to separate the effects of the two processes based on the assumption that millennial-scale variations in the radionuclide records are dominated by geomagnetic dipole moment variations, while decadal-to-centennial variations can be attributed to solar activity variations. However, the influences of the two processes likely overlap on centennial timescales and possibly millennial timescales as well, making a simple frequency cut problematic. Here, we present a new Bayesian model that utilizes the knowledge of solar and geomagnetic field variability to reconstruct both solar activity and geomagnetic dipole moment from the radionuclide data at the same time. This method allows for the possibility that solar activity and geomagnetic dipole moment exhibit variations on overlapping timescales. The model was tested and evaluated using synthetic data with realistic noise and then used to reconstruct solar activity and the geomagnetic dipole moment from the 14C production record over the last two millennia. The results agree with reconstructions based on independent geomagnetic field models and with solar activity inferred from the Group Sunspot number. Our Bayesian model also has the potential to be developed further by including additional confounding factors, such as climate influences on the radionuclide records. Graphical Abstract

Abstract Our understanding of Earth's paleogeography relies heavily on paleomagnetic apparent polar wander paths (APWPs), which represent the time‐dependent position of Earth's spin axis relative to a given block of lithosphere. However, conventional approaches to APWP construction have significant limitations. First, the paleomagnetic record contains substantial noise that is not integrated into APWPs. Second, parametric assumptions are adopted to represent spatial and temporal uncertainties even where the underlying data do not conform to the assumed distributions. The consequences of these limitations remain largely unknown. Here, we address these challenges with a bottom‐up Monte Carlo uncertainty propagation scheme that operates on site‐level paleomagnetic data. To demonstrate our methodology, we present an extensive compilation of site‐level Cenozoic paleomagnetic data from North America, which we use to generate a high‐resolution APWP. Our results demonstrate that even in the presence of substantial noise, polar wandering can be assessed with unprecedented temporal and spatial resolution.