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The minerals carrying the magnetic remanence in geological samples are commonly a solid solution series of iron‐titanium spinels known as titanomagnetites. Despite the range of possible compositions within this series, micromagnetic studies that characterize the magnetic domain structures present in these minerals have typically focused on magnetite. No studies systematically comparing the domain‐states present in titanomagnetites have been undertaken since the discovery of the single vortex (SV) structure and the advent of modern micromagnetism. The magnetic properties of the titanomagnetite series are known to vary strongly with composition, which may influence the domain states present in these minerals, and therefore the magnetic stability of the samples bearing them. We present results from micromagnetic simulations of titanomagnetite ellipsoids of varying shape and composition to find the size ranges of the single domain (SD) and SV structures. These size ranges overlap, allowing for regions where the SD and SV structures are both available. These regions are of interest as they may lead to magnetic instability and "partial thermal remanent magnetization (pTRM) tails" in paleointensity experiments. We find that although this SD + SV zone occupies a narrow range of sizes for equidimensional magnetite, it is widest for intermediate (TM30‐40) titanomagnetite compositions, and increases for both oblate and prolate particles, with some compositions and sizes having an SD + SV zone up to 100s of nm wide. Our results help to explain the prevalence of pTRM tail‐like behavior in paleointensity experiments. They also highlight regions of particles with unusual domain states to target for further investigation into the definitive mechanism behind paleointensity failure. Plain Language Summary: Rocks that record Earth's magnetic field often contain the mineral magnetite. The crystal structure of magnetite allows titanium atoms to substitute for iron, giving rise to a range of minerals known as titanomagnetites. The internal magnetic structure of titanomagnetite particles in rocks, known as the "domain structure," controls the ability of that particle to record magnetic fields. Particles with certain kinds of domain structure are unstable magnetic recorders, which can cause problems for experiments trying to determine Earth's magnetic field strength in the past (paleointensity experiments). Although the domain structures in magnetite are well understood, there are no recent studies which describe them in titanomagnetites. In this paper, we simulate the domain structures in small titanomagnetite particles and map these out as a function of size, shape and chemical composition. In doing so, we identify types of magnetic particles with multiple possible domain structures that may give rise to unstable magnetizations. Our results indicate that some titanomagnetite particles may have unstable magnetizations over a much larger range of sizes than has previously been seen in magnetite. This wide range of sizes could explain the high failure rates of paleointensity experiments. Key Points: We systematically map out the domain states in titanomagnetite as a function of shape and compositionOur results highlight ranges of compositions, shapes and sizes which contain unreliable paleomagnetic recordersFor certain shapes and compositions, these regions span hundreds of nanometers, representing a significant proportion of remanence carriers [ABSTRACT FROM AUTHOR]

The identification of the Grenvillian‐age ophiolite suites in the Yangtze block in recent years suggested that the northern Yangtze subblock (NYB) and the southern Yangtze subblock (SYB) were once separated by an ocean in late Mesoproterozoic. Although some paleogeographic models advocated the Pre‐Grenvillian connections between the south China blocks and Laurentia, none of them has been paleomagnetically tested. Here we report the new paleomagnetic results obtained from the ∼1,270 Ma purplish‐red muddy dolomite beds of the Luanshigou Formation, Shennongjia Group, NYB, providing new constraints for reconstructing the paleogeographic positions of the south China blocks in late Mesoproterozoic. A total of 447 samples underwent stepwise thermal demagnetization. Two components were identified. The low‐temperature component is interpreted as the recent viscous remnant magnetization. The high‐temperature component was obtained from 64 samples below 580°C and from 177 samples below 690°C, directed northeast‐up or southwest‐down, antipodally, positioning the paleomagnetic pole at 18.5°S, 74.4°E (dm/dp = 2.5/1.6°). Rock magnetic results demonstrate that the magnetic carriers in purplish‐red dolomite and pale‐pink dolomite are predominated by hematite and magnetite, respectively. The data quality is supported by an inverse baked contact test, a B‐class reversal test, and the paleomagnetic pole is distinct from any younger poles of the region. Based on the paleomagnetic results, aided by geological evidence, we propose a reconstruction in which the NYB was juxtaposed to southwestern Laurentia in the late Mesoproterozoic and suggest that the late Mesoproterozoic Miaowan‐Shimian ophiolite zone in the Yangtze block was likely an extension of the Grenville belt of Laurentia. Plain Language Summary: The south China block was traditionally subdivided into the Yangtze block to the northwest and the Cathaysia block to the southeast, which were separated by an early Neoproterozoic ocean. Recently published geological data further suggest that the Yangtze block contains two subblocks, the NYB and the SYB, which were separated by a late Mesoproterozoic ocean. Several paleogeographic models proposed the Mesoproterozoic relationships between the south China blocks and Laurentia, but none has been paleomagnetically tested. Here we report a new paleomagnetic pole obtained from the ∼1,270 Ma purplish‐red dolomite beds of the Luanshigou Formation, Shennongjia Group in the NYB. The data quality is assured by the positive paleomagnetic field tests. Our results combing with the geological evidence suggest that the NYB was located in a low‐latitudinal position and connected to southwestern Laurentia in the late Mesoproterozoic. The late Mesoproterozoic ophiolite zone in the southern margin of the NYB was likely an extension of the Grenville belt. Key Points: A new paleomagnetic pole (18.5°S, 74.4°E, dm/dp = 2.5/1.6°) was obtained from the late Mesoproterozoic Luanshigou Formation of the Shennongjia Group in south ChinaThe northern Yangtze subblock (NYB) was connected to southwestern Laurentia at the late MesoproterozoicThe late Mesoproterozoic Miaowan‐Shimian suture zone in the southern margin of the NYB was likely an extension of the Grenvillian orogenic belt [ABSTRACT FROM AUTHOR]

Abstract—We present the results of detailed paleomagnetic studies of six Permian–Triassic boundary sections in the central part of the East European Platform, which are located in the lower reaches of the Vetluga River: Astashikha, Voskresenskoe, Znamenskoe, Prudovka, Sosnovka, and Sukhoborka. The paleomagnetic data, which meet the modern quality standards for laboratory processing, together with the results of biostratigraphic studies, make it possible to develop and substantiate the magnetostratigraphic scales for each section, as well as to correlate them and to compile a composite magnetic polarity scale for the Permian–Triassic sedimentary complex of the Vetluga River. Rock-magnetic characteristics are determined for each of the studied sections, and paleomagnetic poles of the East European Platform are calculated for the Late Permian and Permian–Triassic boundary. [ABSTRACT FROM AUTHOR]

Northern Anatolia has been the subject of many studies due to its complex tectonic structure. Here we report on a paleomagnetic study sampled from upper Cretaceous to middle Miocene sedimentary and volcanic rocks at 54 sites running along the traces of the North Anatolian Fault in the Pontides, Northern Türkiye, to define the post-late Cretaceous tectonic evolution of the area. The results were evaluated together with previously published paleomagnetic data around the Kırşehir Block and the Pontides. The rotational pattern showed distinct phases in the Pontides after the late Cretaceous. A predominant late Cretaceous-middle Eocene clockwise rotation up to 38.1° ± 17.4° probably occurred due to the progressive collision between the Pontides and the Kırşehir Block from west to east. The ongoing deformation continued along the İzmir-Ankara-Erzincan Suture Belt during the middle Eocene-middle Miocene time as evidenced by the paleomagnetic rotation pattern, while no significant rotations were observed further north of the suture zone at this time period. On the other hand, middle Miocene paleomagnetic sites showed a counterclockwise rotation, reflecting the westward escape of the Anatolian microplate, while local fault-bounded vertical block rotations were apparent in places. [ABSTRACT FROM AUTHOR]

The depositional ages and provenance of the Paleozoic Araba and Naqus Formations along the northern Gondwanan margin in Egypt have remained uncertain due to a lack of index fossils. Resolving this issue is crucial for understanding regional geology during deposition and subsequent tectonic development. We integrate detailed facies analysis, anisotropy of magnetic susceptibility (AMS), paleomagnetism, and mineralogical data to elucidate the genesis and depositional ages of the Araba and Naqus Formations. Petrographic analyses identified seven distinct facies types, providing insights into sedimentary textures, maturity, and sources, with contributions from igneous and metamorphic sources indicated by heavy minerals. X-ray diffraction (XRD) analysis identified accessory minerals such as quartz, goethite, kaolinite, hematite, and anatase. Paleomagnetism isolated two magnetic components (CA and CN) providing the first robust paleo pole positions at Lat. = 70.8° N, Long. = 308.2° E and Lat. = 37.8° N, Long. = 233.1° E, indicating Cambrian and Carboniferous ages for the Araba and Naqus formations, respectively. Thermal demagnetization constrained these dates using established polarity timescales. Mineralogical data indicated that the Araba Formation originated from an igneous source, while the Naqus Formation had a mixed metamorphic-igneous provenance. The integrated AMS and paleomagnetic data reveal evidence of post-depositional deformation. Specifically, the clustering of maximum AMS axes in the NW–SE direction for both formations, suggests the initial presence of a primary depositional fabric. However, prevalent tectonic activity during the Cenozoic appears to have overprinted and modified this fabric through deformation related to rifting of the Gulf of Suez region. Through this novel multi-proxy approach, we have resolved long-standing uncertainties regarding the formations' depositional ages. Our study thereby provides the first chronostratigraphic framework for these strategically important sedimentary units, significantly advancing understanding of regional Paleozoic geology. [ABSTRACT FROM AUTHOR]

This paper contributes to an understanding of the tectono‐sedimentary evolution of the South Pyrenean foreland system by reviewing the chronostratigraphic framework of the basin infill in its eastern sector. Six sections are analysed and cross‐correlated to build a 6.5 km thick composite magnetostratigraphy that represents the complete record of the Cadí Nappe in the Ripoll Syncline. New and previous magnetostratigraphic sections are integrated with available biostratigraphy to provide a new age calibration of the sedimentary succession of the Cadí Nappe, encompassing from Palaeocene to Middle Lutetian age. The proposed correlation with the Geomagnetic Polarity Time Scale aims at best reconcile magnetostratigraphic data with the regional biochronology built on the marine Shallow Benthic Zonation (SBZ biozones), the continental mammalian biochronology (MP levels) and the newly collected charophyte data. A subsidence analysis was performed on the calibrated composite succession, resulting in two well‐defined intervals bounded by a hiatus. A Palaeocene to Early Eocene interval with low (11–21 cm/kyr) total subsidence rates, and an Early to Middle Eocene interval, characterised by high (70–75 cm/kyr) total subsidence rates. The detailed trends in both subsidence and sedimentation mark the development and evolution of the foreland depozones, from distal foreland depozones to foredeep and wedge‐top depozones, relative to the emplacement of the Pedraforca Nappe and Cadí Thrust Nappe. The most pronounced sedimentary shift in the Cadí Nappe occurred at 49 Ma, with the rapid drowning of the carbonate platforms and its transition into talus and deep basinal environments. Carbonate platforms collapsed and resedimented on the talus of the elongated trough, newly formed parallel to the orogenic front. This marked the onset of tectonic subsidence triggered by the submarine emplacement of the Lower Pedraforca Nappe. The emersion of the orogenic wedge drove the entry of siliciclastics, lagged by 1 Myr, into the Ripoll Trough. The foredeep filled rapidly (5.5 km thickness in less than 7 Myr) compared to other South Pyrenean regions, favoured by its semi‐enclosed palaeogeography. The emplacement of the Vallfogona Thrust as early as the Middle Lutetian (43 Ma) brought the Cadi Nappe into a wedge‐top setting. However, the Ripoll growth syncline continued acting as a temporary sink for alluvial sedimentation while a foredeep developed further south in the autochthonous Ebro Basin. The flexural response of the Iberian plate to the tectonic thickening of the Axial Zone counterbalanced for a period the local uplift of the Cadi Nappe, providing accommodation space for the top sediments filling the Ripoll Syncline. [ABSTRACT FROM AUTHOR]

Paleosecular variation analysis is a primary tool for characterizing ancient geomagnetic behavior and its evolution through time. This study presents a new high‐quality directional data set, paleosecular variation of the Paleogene (PSVP), with and without correction for serial correlation, compiled from 1,667 sites from 45 different localities from the Paleogene and late Cretaceous (84–23 Ma). The data set is used to study the variability, structure, and latitude dependence of the geomagnetic field during that period by varying selection criteria and PSV models. Modeled values for the equatorial virtual geomagnetic pole (VGP) dispersion have over‐lapping uncertainty intervals within their uncertainty bounds between 8.3° and 18.6° for the past 250 Ma. We investigate the suitability of two descriptive models of PSV, Model G‐style quadratic fits and covariant Giant Gaussian Process models, and find that both styles of model fail to satisfactorily reproduce the latitude dependent morphology of PSV, but suggest that estimates of the equatorial VGP dispersion may still robustly characterize aspects of Earth's long‐term field morphology. During this time where the PSV behavior has not changed substantially, the reversal frequency has varied widely. The lack of a clear relationship between PSV behavior and reversal frequency is not trivially explained in the context of published findings regarding numerical geodynamo simulations. Plain Language Summary: The geomagnetic field is saved in volcanic rocks, which can be used to study the direction and intensity of this field millions of years later. The magnetic field is formed in the geodynamo in the Earth's outer core. The study of geomagnetic field changes through time gives us information on the changes in the Earth's outer core, lower mantle and inner core. In this study, all the data from the Paleogene and Late Cretaceous were gathered (84–23 million years ago) and studied to see how much the geomagnetic field changed through that time. With this study we now have information on the variability of the field for the entirety of the past 320 million years. We see that during the last 250 million years, the directional variability of the field seems to have varied little, even though the frequency of reversals varied massively. Some numerical simulations of the dynamo process occurring in Earth's core had previously suggested that both of these two things were directly correlated to the magnitude of heat flowing from the outer core to the mantle. Our new results suggest a more complex, nuanced picture. Key Points: A new data set, paleosecular variation of the Paleogene, comprising 1,667 paleomagnetic directions from 45 different localities of volcanics aged between 84 and 23 MaMedian equatorial dispersions of virtual geomagnetic poles have overlapping uncertainty bounds since 250 MaLarge fluctuations in the reversal frequency are not associated with large fluctuations in the inferred median axial dipole dominance [ABSTRACT FROM AUTHOR]

The article reports on the discovery of ceramic kilns in the archaeological complex of Atzompa in Monte Albán, Oaxaca. These kilns have similar characteristics to those of the ethnographic tradition of Atzompa and it is believed that they were used to produce large gray ceramic pots. An archaeomagnetic study conducted on one of the kilns indicates that it was used after the supposed abandonment of Monte Albán, suggesting that the inhabitants of Atzompa continued to manufacture ceramics. Additionally, evidence of specialization in ceramic production in Atzompa and a permanent relationship between Atzompa and Monte Albán were found. The study was funded by the CONAHCyT CF19-1761 project and UNAMDGAPA PAPIIT IN100224. [Extracted from the article]

The Qaidam Block, located at the northern Qinghai–Tibet Plateau, is a pivotal area in unraveling the closure time of the Kunlun Ocean basin which might have recorded the transformation process between the Proto-Tethys and Paleo-Tethys Ocean basins. However, the late Triassic position of the Qaidam Block remains enigmatic, largely due to the scarcity of paleomagnetic data essential for quantitatively determining its paleolatitude. The widespread presence of the Elashan formation, particularly along the southern periphery of the Qaidam block, presents good material for conducting paleomagnetic work. Nevertheless, the primary magnetic carriers preserved within the Elashan formation might be influenced by multiple tectonic thermal events, particularly those associated with collisions between southern blocks and the Qaidam Block. Here we present rock magnetism and magnetic fabrics studies to identify the content and composition of magnetic minerals within the Elashan formation. The rock magnetic and petrologic results show that the magnetic carriers in the samples from the Elashan formation are dominated by magnetite with a small amount of goethite, pyrrhotite, and hematite. The results of Anisotropy in Magnetic Susceptibility indicate that the south of the Longwalangku section might not be obviously influenced by the tectonic events. Our results also provided guidance for future paleomagnetic research, emphasizing the importance of conducting further sampling away from adjacent faults, particularly in the southern Longwalangku area. [ABSTRACT FROM AUTHOR]

Currently, the climatic implications associated with the Cenozoic tectonic history and growth mechanisms of the Tibetan Plateau lack consensus and remain controversial. This is due in part to chronological uncertainties and few paleoelevation records distributed in the central to northern Tibetan Plateau, which we address here with the development of a robust chronology (using magnetostratigraphy, biostratigraphy, detrital zircons, and regional radiochronologic dating) and a paleoelevation reconstruction for the Tuotuohe Basin (central-northern Tibet). We refined the age of the Tuotuohe Formation (37-33 Ma), Yaxicuo Formation (33-23.6 Ma), and Wudaoliang Formation (23.6-19.7 Ma). We estimated early Oligocene (ca. 29 Ma) paleotemperatures of the Tuotuohe Basin from 11 °C to 16.1 °C, which correspond to paleoelevations of 2.9 km (±0.4 km) when the relative humidity is 64% and 2.5 km (±0.5 km) when this value is 75%, using various methods including ostracod assemblages, gastropods, charophytes, branched glycerol dialkyl glycerol tetraether analysis, regional empirical formulas, and climate model simulation. Paleoelevation data and existing geological evidence in the vicinity indicate that late Eocene to late Oligocene uplift was associated with upper-crustal shortening. Since the middle Miocene, uplift has been associated with convective removal of lithospheric mantle and/or lower-crustal flow beneath the Hoh Xil Basin. [ABSTRACT FROM AUTHOR]

[Display omitted] • The S-shaped form of the ARSZ has formed since the late Miocene. • The difference in rotation rate between blocks controls the evolution of ARSZ. • The outwardgrowth of Tibet induced relative motion of blocks. The Ailaoshan–Red River shear zone (ARSZ), which is ∼ 1000 km long and one of the largest boundary strike-slip fault zones in the southeastern margin of the Tibetan Plateau, provides valuable insights into the growth process of the southeastern Tibetan Plateau since the India-Asia collision. During the Late Miocene to Early Pliocene, the ARSZ underwent a kinematic transition from left-lateral strike-slip to right-lateral strike-slip motion. To reveal the mechanism of this kinematic transition and its relationship with the growth process of the southeastern Tibetan Plateau during the Cenozoic, we conducted paleomagnetic and tectonic deformation analyses on both sides of the ARSZ. The results show that the formation of the S-shaped bending and kinematic transition of the ARSZ were controlled by the changes in clockwise rotation rates of the Chuandian Fragment and the Indochina Block. This suggests that since the Oligocene, the growth of the southeastern Tibetan Plateau progressively extended outward from the southern margin of the Lhasa Terrane to the southeastern margin of the Tibetan Plateau, resulting in the sequential initiation of the clockwise rotation of the Shan-Thai Block, Indochina Block, and Chuandian Fragment since the Late Oligocene, and in variations in the rotational rates of these blocks. The different rotational movement of these blocks controlled the tectonic evolution of strike-slip fault systems on the southeastern margin of the Tibetan Plateau. [ABSTRACT FROM AUTHOR]

The rich and extensively studied archaeological record of the Near East provides an opportunity to develop a comprehensive archaeomagnetic dataset for exploring the behavior of the geomagnetic field with high precision. The Levantine archaeomagnetic curve (LAC) project is an ongoing effort to develop a continuous high‐resolution geomagnetic intensity curve for the Levant and Mesopotamia. The first version of the LAC covered the period between 3000 and 550 BCE. Here, we report archaeointensity data from 169 samples compiled into 32 groups dating between the 7th and the 1st centuries BCE aiming at extending the LAC up to the end of the first millennium BCE. Twenty‐two groups are assembled from storage jar handles bearing different types of royal seal impressions, which were used in Judah as part of a taxation administrative system. These groups are combined with 10 other groups of pottery assemblages, three of which are from Hellenistic destruction layers dated using radiocarbon and coins. The new curve shows that the Levantine Iron Age Anomaly (LIAA) spanned 550 years (1100 ‐ 550 BCE) and that the rate of decline during the last spike around 600 BCE could have reached ∼0.6 μT/year. During the 6th century, the virtual axial dipole moment (VADM) dropped from 160 ZAm2 to 125 ZAm2 after which field intensity only slightly increased to 135 ZAm2, until another considerable decline to ∼90 ZAm2 during the 3rd to the 1st centuries BCE. We highlight the archaeomagnetic implication of the new curve in inferring the relative chronological relationship between different stamp types. Plain Language Summary: The Earth's magnetic field is continuously changing both in time and space in an unpredictable manner. A detailed description of how the magnetic field has changed throughout Earth's history offers constraints on our understanding of the mechanism generating the field in Earth's core. In this study, we reconstruct the intensity of the past field using an assemblage of well‐dated archaeological materials from Israel, dated to the Assyrian, Babylonian, Persian, Hellenistic and Hasmonean periods. This work is part of an ongoing effort to procure a high‐resolution curve describing the changes in field intensity for the Levant and Mesopotamia over the past several millennia. With the new data, we calculate the curve for the first three millennia BCE. The curve provides further details on an anomalous behavior of the field between 1100 BCE and 550 BCE, termed the Levantine Iron Age Anomaly (LIAA), during which the field intensity and its rate of change were significantly higher than today's. In addition, the curve forms the basis for an archaeomagnetic dating tool, which can be especially useful for periods when traditional archaeological dating methods fail to provide precise ages due to large uncertainties in radiocarbon dates. Key Points: Archaeomagnetic intensity data from 32 groups of pottery in Israel dated between the 7th and the 1st centuries BCEThe second generation of the Levantine Archaeomagnetic Curve (LAC.v.2.0) covering the last three millennia BCEThe new data constrain the duration of the Levantine Iron Age Anomaly (LIAA) from 1100 BCE to 550 BCE [ABSTRACT FROM AUTHOR]

Volcanic rocks are considered reliable recorders of past changes in the Earth's magnetic field. Recent flows, however, sometimes fail to produce the known magnetic field at the time of cooling. Previous research on Mt. Etna suggests paleomagnetic data might not be accurately recorded. Here we test the accuracy of paleomagnetic data obtained from Mt. Etna lavas by comparing paleomagnetic data from historical flows to direct measurements of the magnetic field above the current topography. The inclinations and intensities in both data sets are biased toward lower values, while there is no such trend for the declination. Inclinations are on average 2.9° lower than expected; intensities are on average 8.8 µT lower. The deviations from the expected values depend on the height above the flow. Moreover, the inclinations and intensities vary as a function of topography. Both are higher above ridges and lower in gullies; the variations within a site are up to 14.1° in inclination and 12.9 µT for intensity. To suppress this paleomagnetic data bias it is important to take samples several meters apart and from different parts of the flow whenever possible. While this leads to a higher degree of scatter in paleodirections, the results better represent the Earth's magnetic field at the time of cooling. This emphasizes the importance of reporting paleomagnetic sampling strategies in detail. Plain Language Summary: Paleomagnetic data from lavas is routinely used in the Earth Sciences to for example, reconstruct the past behavior of the Earth's magnetic field, or make models of past plate motions. Very young flows for which the ambient magnetic field at the time of cooling is known, however, sometimes fail to produce the known reference values. Lava flows from Mt. Etna are extensively studied in the past and the paleomagnetic data obtained does often not agree with the known magnetic field value in which the lavas cooled. Here we show that the topography of volcanic terrain may influence the magnetic signal of new, overlying, flows, and we make recommendations for sampling strategies that suppress these terrain effects as much as possible. Key Points: Paleomagnetic data from Mt. Etna does often not reproduce the known geomagnetic field wellLocal magnetic anomalies explain bias in paleomagnetic data as function of topographyOptimizing the paleomagnetic sampling strategy may suppress this bias in paleomagnetic data [ABSTRACT FROM AUTHOR]

Magnetic records from meteorites provide valuable information about the formation and evolution of the solar system and planets. The parent planetesimals of chondrites are typically considered to be undifferentiated based on their primary chemical composition and texture. However, recent paleomagnetic investigations of various chondrites indicate that they carry a primary remanence generated by a dynamo, suggesting partial differentiation of their parent planetesimals. The presence of a dynamo within the parent planetesimal of LL chondrites remains uncertain due to the ambiguous origin of the remanent magnetism. Here, we report petrographic, paleomagnetic, and rock magnetic properties for the novel LL6 chondrite NWA 14180. The high metamorphic temperature experienced by NWA 14180 could have removed the pre‐accretionary remanence. The fusion crust baked‐contact test suggests that NWA 14180 preserves primary magnetic information about its parent body. Alternating field demagnetization results from interior subsamples reveal distinct low‐ and medium‐coercivity components that may represent a viscous remanent magnetization acquired in the geomagnetic field. No natural remanent magnetization was unblocked in the high coercivity range, implying that NWA 14180 cooled in zero‐field conditions. Therefore, we suggest that the parent body of NWA 14180 did not have a dynamo. Furthermore, this result suggests that the LL chondrite parent planetesimal accreted later and was smaller in size than other chondrite classes. Plain Language Summary: Chondrites contain primary material that formed during the first few million years of the solar system. Their parent bodies are believed to have had a concentric structure with gradually increasing metamorphic temperature from surface to center that did not differentiate to form a metallic core. However, several recent paleomagnetic measurements suggest that chondrites may record a stable extraterrestrial remanence attributed to a dynamo magnetic field, indicating that the parent body may be partially differentiated with a convective metallic core inside and unmelted chondritic material on the surface. But whether the LL chondrite parent body featured a dynamo is unknown. Our study shows that a dynamo field did not exist during LL6 chondrite NWA 14180 cooling on its parent planetesimal. Therefore, our results suggest that the LL chondrite parent planetesimal formed later than other chondrite bodies. Key Points: The fine‐grained tetrataenite in NWA 14180 can record paleomagnetic signals if its parent planetesimal has a dynamoPaleomagnetic results for NWA 14180 indicate that it cooled in a zero‐field environment, and no parent planetesimal dynamo existedWe suggest that the LL chondrite parent planetesimal accreted later in the early solar system relative to other chondrites [ABSTRACT FROM AUTHOR]

The North Hebei Plain is a typical example of a deep-covered area, with a thickness of more than 200 m Quaternary loose sediments. Previous studies have tried various stratigraphic classification methods but lack an effective combination of geophysical methods. Based on the analysis of rock strata and dating tests, combined with geophysical well-logging data, shallow seismic reflection, and paleomagnetic dating, the Quaternary strata of the deep-covered area in the Hebei Plain was divided into the Lower Pleistocene series, the Middle Pleistocene series, the Upper Pleistocene series, and the Holocene series. By observing the cores of the Quaternary borehole QHJ02, this paper focused on dividing its loose sediments into eight lithological sections, according to the lithology, sediment colour, sedimentary assemblage, and sedimentary environment. The geomagnetic polarity belt is divided according to the paleomagnetic inclination of the paleomagnetic sample in borehole QHJ02. The results of the paleomagnetic test show that the interval of 0–101.3 m is Brunhes normal polarity chron, the interval from 101.3 to 219.5 m is Matuyama reversed polarity chron, and the interval from 219.5 to 350 m is Gauss normal polarity chron. The amplitude of the geophysical logging curve shows a good correspondence with the lithology of the QHJ02 borehole. The lithology changes can be identified through the abrupt abnormal positions of logging curves such as gamma ray, resistivity, and magnetization to analyze the sedimentary environment combination and determine the formation boundary. According to the combination of paleomagnetic, shallow seismic reflection, and geophysical well logging methods, we can determine the bottom boundaries of the Quaternary and middle Pleistocene are 219.5 m and 101.3 m, respectively. According to the combination of geophysical well-logging, lithostratigraphic assessment, dating experiment of Accelerator Mass Spectrometry 14C (AMS 14C), and Optically Stimulated Luminescence (OSL), we can determine the bottom of the upper Pleistocene and the lower limit of Holocene to be at 45.4 m and 21.4 m, respectively. Based on a comprehensive analysis of rock stratigraphic characteristics and well-logging curves, this study investigated the paleoenvironmental characteristics of borehole QHJ02 at different ages. The Upper Neogene was characterized by branch channels and river floodplains, with localized occurrences of alluvial fans, avulsion fans, and inter-channel lowlands. During the Early Pleistocene, branch channels and inter-channel lowlands dominated, with localized river floodplains. The Middle Pleistocene witnessed alternating branch channels and river floodplains as the main paleoenvironments. In the Late Pleistocene, branch channels and inter-channel lowlands were prevalent. The Holocene saw a combination of natural levees and river flood-plain environments. These findings enhance our understanding of the geological evolution and paleoenvironmental changes in the North Hebei Plain. [ABSTRACT FROM AUTHOR]

Paleomagnetic records of middle Neoproterozoic (820 to 780 Ma) rocks display high amplitude directional variations that lead to large discrepancies in paleogeographic reconstructions. Hypotheses to explain these data include rapid true polar wander (TPW), a geomagnetic field geometry that deviates from a predominantly axial dipole field, a hyper‐reversing field (>10 reversals/Ma), and/or undiagnosed remagnetization. To test these hypotheses, we collected 1,057 oriented cores over a 85 m stratigraphic succession in the Laoshanya Formation (Yangjiaping, Hunan, China). High precision U‐Pb dating of two intercalated tuff layers constrain the age of the sediments between 809 and 804 Ma. Thermal demagnetization isolates three magnetization components residing in hematite which are not time‐progressive but conflated throughout the section. All samples possess a north and downward directed component in geographic coordinates at temperatures up to 660°C that is ascribed to a Cretaceous overprint. Two components isolated above 660°C reveal distinct directional clusters: one is interpreted as a depositional remanence, while the other appears to be the result of a mid‐Paleozoic (460 to 420 Ma) remagnetization, which is likely widespread throughout South China. The high‐temperature directions are subtly dependent on lithology; microscopic and rock magnetic analyses identify multiple generations of hematite that vary in concentration and distinguish the magnetization components. A comparison with other middle Neoproterozoic paleomagnetic studies in the region indicates that the sudden changes in paleomagnetic directions, used elsewhere to support the rapid TPW hypothesis (ca. 805 Ma), are better explained by mixtures of primary and remagnetized components, and/or vertical axis rotations. Plain Language Summary: Paleomagnetic directions recorded in 820 to 780 million year old rocks from South China exhibit large amplitude changes that vary rapidly, which have been interpreted to indicate extraordinarily fast motion of Earth's crust and mantle, up to 90° within a 5 million year span, with respect to the spin axis of the core. This hypothetical phenomenon, called rapid true polar wander (TPW), could be responsible for dramatic global environmental change at that time. To test this theory, we collected over 1,000 samples from a well exposed section where the incongruous directions are found. Our measurements suggest that some of the rocks acquired a new magnetic signal during a pervasive remagnetization event in South China around 440 million years ago, long after original deposition of the rocks. New hematite growth has a demagnetization spectrum that partially overlaps or completely obscures the original magnetic signal, which was previously unrecognized. This implies that rapid TPW is likely an artifact of magnetic overprinting in ancient rocks from South China. Our results suggest that South China was in a relatively stable position at high latitudes 809 to 804 million years ago. We find no evidence to support exceptionally fast continental drift or an abnormal geomagnetic field geometry during that time. Key Points: High‐precision ID‐TIMS U‐Pb dating yields deposition ages of the Laoshanya Formation (Yangjiaping, South China) between 809 and 804 MaDiscordant paleomagnetic directions in the red beds are a conflation of three temporally distinct field records residing in hematiteOur results do not support rapid true polar wander or abnormal magnetic field geometry around 805 Ma [ABSTRACT FROM AUTHOR]

Changes in Earth's magnetic field during the Cretaceous Normal Superchron (CNS) spanning ∼121 Ma to ∼84 Ma hold important clues about the geodynamo evolution. Canonical models predict a persistently strong geomagnetic field with low variability during CNS, which, however, has not been observed in the available absolute paleointensity data and seafloor marine magnetic anomaly (MMA) records. The lack of relative paleointensity (RPI) data across CNS further impedes tests of model predictions. Here, we present a ∼9‐Myr (∼94–∼85 Ma) RPI record from a Turonian to Santonian hemipelagic succession from IODP Site U1512 offshore southern Australia. Detailed paleomagnetic and rock magnetic analyses demonstrate that the ratio of natural remanent magnetization (NRM) demagnetized at 20 mT over magnetic susceptibility (MS), that is, NRM20mT/MS, as a reliable proxy for the RPI of the Upper Cretaceous succession. The new RPI record shows marked changes in both intensity and variability at ∼90.8 Ma. Also, the 6 Myr‐long (∼94–∼88 Ma), near‐continuous, ∼1.2 kyr‐resolution RPI record exhibits a strong positive correlation between field intensity and variability. Assuming this correlation holds for the entire CNS, an extrapolated RPI curve for the entire CNS is obtained by integrating the positive correlation with field variability estimates from the MMA data. The extrapolated RPI curve shows a strong and highly variable field in the middle CNS but a weak and stable field at its beginning and ending. These features imply a much more dynamic geodynamo than previously thought, and provide crucial benchmarks for unraveling the geodynamo evolution during CNS. Plain Language Summary: Cretaceous Normal Superchron (CNS, ∼121 to ∼84 million years ago) marks a nearly 40 million years interval of almost constant normal geomagnetic polarity. Changes in Earth's magnetic field during CNS hold important clues about the evolution of the geodynamo, by which the geomagnetic field was generated. However, whether the geomagnetic field was persistently strong and stable during CNS has been controversial based on estimates from snapshot recordings of igneous rocks and marine magnetic anomaly data. Here, we report a high‐resolution near continuous relative paleointensity (RPI) record of the ∼88–94 million years old interval from a hemipelagic sedimentary succession at IODP Site U1512. The new RPI record documents salient changes in both intensity and variability of the geomagnetic field at ∼90.8 million years ago and a positive correlation between these two parameters toward the ending of CNS. These features imply that the geomagnetic field was strong and highly variable in the middle CNS, but weak and stable at its beginning and ending. These findings indicate much more dynamic geodynamo behavior during the CNS than previously thought, and thus provide important benchmarks for "ground truthing" model simulations to unravel the geodynamo evolution during CNS. Key Points: We report a ∼9 Myr high‐resolution RPI record for the late stage (∼94–∼85 Ma) of CNS from IODP Site U1512 coresThe new RPI record shows a marked change in intensity and variability at ∼90.8 Ma and a positive correlation between these two parametersSalient changes in geomagnetic field's strength and variability imply a much more dynamic geodynamo than previously thought during CNS [ABSTRACT FROM AUTHOR]

Recovering ancient records of Earth's magnetic field is essential for determining the role of the magnetosphere in protecting early Earth from cosmic radiation and atmospheric escape. We present paleomagnetic field tests hinting that a record of Earth's 3.7‐billion‐year (Ga) old magnetic field may be preserved in the northeastern Isua Supracrustal Belt as a chemical remanent magnetization acquired during amphibolite‐grade metamorphism in the banded iron formation. Multiple petrological and geochronological lines of evidence indicate that the northernmost part of Isua has not experienced metamorphic temperatures exceeding 380°C since the Eoarchean, suggesting the rocks have not been significantly heated since magnetization was acquired. We use "pseudo" baked contact tests (intrusions emplaced 3.26–3.5 Ga ago) and a fold test (folding 3.6 Ga ago) to demonstrate that some samples preserve a ca. 3.7 Ga record of the magnetic field. We recover a field strength of >15 µT. This suggests that Earth's magnetic field may have been weak enough to enhance atmospheric escape during the Archean. Plain Language Summary: Recovering ancient records of Earth's magnetic field is challenging because the magnetization in rocks is often reset by heating during tectonic burial over their long and complex geological histories. We show that rocks from the Isua Supracrustal Belt in West Greenland have experienced three thermal events throughout their geological history. The first event was the most significant, and heated the rocks up to 550°C 3.7‐billion‐years‐ago. The subsequent two events did not heat the rocks in the northernmost part of the area above 380°C. We use multiple lines of evidence to test this claim, including paleomagnetic field tests, the metamorphic mineral assemblages across the area, and the temperatures at which radiometric ages of the observed mineral populations are reset. We use these lines of evidence to argue that an ancient, 3.7 billion year old record of Earth's magnetic field may be preserved in the banded iron formations in the northernmost part of the field area. The magnetization was acquired during mineral transformation associated with the first thermal event and therefore only a lower limit on the strength of the ancient magnetic field was constrained. However, we are able to conclude that the ancient magnetic field was likely comparable with the strength of Earth's magnetic field today. Key Points: The north‐eastern part of the Isua Supracrustal Belt experienced two metamorphic events at 3.69 Ga and 2.85 Ga and one hydrothermal event at 1.5 GaBanded iron formations acquired a chemical remanent magnetization during the first thermal event that was not entirely overprinted by subsequent eventsPaleomagnetic results hint that a record of the Eoarchean geomagnetic field is preserved in the Isua Supracrustal Belt [ABSTRACT FROM AUTHOR]

The Cracked Mountain edifice is a basaltic subglacial volcano (i.e. tuya) situated in southwest British Columbia, Canada. The edifice is dominated by subaqueously deposited, massive to poorly stratified, variably palagonitized lapilli tuffs intruded by syn-eruptive dikes and lobes of peperitic pillow-lavas (15–20 vol.%); minor stacks of pillow-lava are found on the margins of the edifice. Here, we present mineralogical, textural, and physical property data for 134 sample cores from the palagonitized volcaniclastic deposits. Our sample suite includes three specific field environments defined by proximity to intrusive heat sources: (i) proximal (< 1 m) deposits (ENV1), (ii) deposits within 1–5 m of intrusions (ENV2), and (iii) deposits far removed (> 5 m) from discernible heat sources (ENV3). The dataset comprises mineralogy and measurements of density, porosity, permeability, P-wave velocity, uniaxial compressive strength, and paleomagnetism. Increased palagonitization is marked by increases in authigenic mineral abundance (smectite and analcime), density, strength, and P-wave velocity and concomitant decreases in porosity and permeability. Paleomagnetic data show a common pole direction recorded by all volcanic deposits indicating volcanism occurred within a single paleomagnetic moment (< 200 years). Palagonitization of the volcaniclastic deposits is driven by heat supplied by syn-eruptive intrusions and is most intense in ENV1, where dikes raised temperatures (> 150 °C) for a prolonged duration (< 1 year), and weakest in ENV3 deposits reheated to lower temperatures (< 150 °C). The timescale of palagonitization was short and coincident with the emplacement and cooling of syn-eruptive intrusions. The mapped intensity of palagonitization and thermal modelling are used to define a ‘palagonite window’ as a function of time and distance from heat sources (i.e. dikes). [ABSTRACT FROM AUTHOR]

Abstract—To describe secular geomagnetic variation on geological timescales, statistical models have been widely used in recent decades. Currently, the most popular among these is the TK03 model (Tauxe and Kent, 2004). As other statistical models, TK03 numerically characterizes the amplitude of secular geomagnetic variation and the shape of the distribution of paleomagnetic directions which are thought to directly reflect the directions of the geomagnetic field on the considered interval of geological time. For this purpose, three main parameters are used: the scatter Sb (or S) of the virtual geomagnetic poles, the elongation E of the distribution of paleomagnetic directions, and the elongation direction of the distribution of paleomagnetic directions. The correct use of these parameters to describe paleosecular variation requires the fulfillment of certain, sometimes rather strict conditions. These conditions for parameters Sb and E were considered in a number of previous publications, while the limits and conditions of application of have not been studied in detail so far. The results of mathematical modeling presented in this paper allow us to evaluate the stability of the calculated parameter values as a function of sampling latitude, the number of samples used to determine this parameter, the length of the time series from which this parameter is estimated, as well as the inclination shallowing and the degree of averaging if is estimated from sedimentary rocks. We also consider the extent to which the parameter can be sensitive to the presence and characteristics of the equatorial dipole component in the total geomagnetic field. [ABSTRACT FROM AUTHOR]

The remarkable uplift of the Tibetan Plateau in the Neogene had great impacts on the climate and environment of East Asia and even the world. Therefore, establishment of the Neogene stratigraphic framework of the Tibetan Plateau is of great significance to research in various fields of geosciences. Based on marine sediments, the international chronostratigraphic system of the Neogene is divided into six stages in the Miocene and two stages in the Pliocene. Since the beginning of the Cenozoic, the share of terrestrial strata on continents has increased rapidly. By the Neogene, it had far exceeded that of marine strata, and almost all deposits on the Tibetan Plateau and its surrounding areas were terrestrial strata. In China, the Miocene includes five stages and the Pliocene includes two stages. Except for the Tunggurian of the Miocene, which has a lower boundary at 15 Ma, the other stages have the same paleomagnetic definitions and time intervals as the corresponding international marine stages. Mammalian fossils play a very important role in the division and correlation of Cenozoic terrestrial strata, and rodent, carnivore, proboscidean, perissodactyl and artiodactyl fossils are especially important in Neogene terrestrial biostratigraphy. There are many basins with well-exposed strata and abundant mammalian fossils in the Tibetan Plateau. The lower boundary stratotype sections of the Neogene Xiejian and Bahean stages are located respectively in the Xining and Linxia basins, and there are precise paleomagnetic dates in coordination with mammalian fossils. The lower boundary stratotypes of other stages can also be effectively determined in the Tibetan Plateau. Many first appearing mammalian genera in East Asia also appeared in the Tibetan Plateau and its surrounding areas, especially in the Linxia Basin on the northeast margin and in the Siwaliks on the southwest margin. Among them, Prodeinotherium first appeared at the bottom of the Miocene in the Siwaliks, and the earliest Hipparion of the Old World first appeared at the bottom of the Bahean Stage in the Linxia Basin. Carbon and oxygen isotope analysis of enamel and paleosols of Cenozoic sediments and mammal fossils in the Tibetan Plateau and its surrounding areas have been used to reconstruct the climate, environment and vegetation development characteristics, and revealed that these changes were not only related to global change, but also had regional features. Evidence of the Late Miocene C4 plant expansion event based on carbon isotope changes comes from the southern margin of the Tibetan Plateau, but in sharp contrast, δ13C indicates that there was still no clear or significant C4 plant signal on the northern margin of the Tibetan Plateau until the end of the Neogene. The δ18O analysis shows that there were several major climate change events in the Cenozoic, especially in the Late Miocene at about 7 Ma, when positive drift of δ18O indicates that the northern and southern sides of the Tibetan Plateau were changing to drier environments. The strong uplift of the Tibetan Plateau in the Late Miocene strengthened the thermal contrast between sea and land, which strengthened monsoon circulation and led to the expansion of C4 vegetation in South Asia. However, the East Asian summer monsoon, which can bring atmospheric precipitation and a climate suitable for C4 plants to northern China, was not enough to affect the northern Tibetan Plateau. The Tibetan Plateau on the whole rose to an altitude of about 3000 m in the Miocene, becoming a barrier to mammalian migration; it reached its modern altitude of more than 4000 m in the Pliocene, thus forming a cryosphere environment, which led to the emergence of ancestral types of the Ice Age fauna. [ABSTRACT FROM AUTHOR]

This article discusses the paleomagnetism of the Acraman-Bunyeroo meteorite impact ejecta zone in the South Flinders Ranges region of South Australia. The study confirms that the Acraman impact structure is the source of the ejecta, and examines the directional changes between the red and green shale beds in the ejecta zone. The green shale is found to contain goethite, which formed during the Early Jurassic period. The authors suggest that the goethite may have resulted from downward movement of meteoric waters from a now-removed Early Jurassic weathering profile. [Extracted from the article]

The Neotectonic period of deformation in Anatolia has been embraced by a location between the complex interaction of Afro-Arabian and Eurasia plates. During this ongoing deformation, the eastern part was under the continuing influence of subduction by the Neotethyan Ocean in the Eastern Mediterranean Region resulting in the indentation of the Arabian Plate into Anatolia. As the Red Sea opened deformation became increasingly focused on a fault system comprising the Dead Sea, North Anatolian, and East Anatolian fault systems. To help constrain the age and deformation history of this last phase we have conducted a paleomagnetic study from a total of 28 sites at Lower-Middle Miocene Mazgirt volcanic rocks and Pliocene Karakoçan basalts in the Anatolian Plate, and the Quaternary Cizre basalts of the Arabian Plate. The mean paleomagnetic direction in Early-Middle Miocene time identifies a clockwise rotation of 12.38° ± 5.1° in the Anatolian Plate. In contrast, counterclockwise rotation of 19.2° ± 6.1° and 14.8° ± 5.7° is obtained in the Middle Miocene-Pliocene and Quaternary periods in the Anatolian and Arabian Plate, respectively. According to our findings, we point to the importance of two distinct tectonic events. The first phase defines a period between Lower Miocene to Pliocene which is defined by a clockwise rotation of 31.5°. It is concluded that during this time interval, the collision between Arabia and Eurasia and the motion of Arabia in the northeast direction gave rise to the clockwise rotation of Anatolia. The North Anatolian Fault (NAF) is thought to be inactive, while the East Anatolian Fault (EAF) was not generated in this time interval. In the second phase, the northwest-directed movement of the Arabian Plate led to counterclockwise rotations both in the Anatolian and Arabian Plate. We suggest that the North Anatolian Fault provided a contribution to this movement in the Pliocene, while the East Anatolian Fault accompanied this tectonic westward escape of the Anatolian Plate after the Quaternary. [ABSTRACT FROM AUTHOR]

Magnetic signals in igneous rocks arise from assemblages of iron‐oxide bearing minerals that differ in for example, size, shape, and chemistry. Paleomagnetic measurements on bulk samples measure millions of such grains simultaneously, producing a statistical ensemble of the magnetic moments of the individual grains. Scanning magnetometry techniques such as the Quantum Diamond Microscope (QDM) measure magnetic signals on micrometer scales, allowing the identification of magnetic moments of individual grains in a sample using for example, Micromagnetic Tomography (MMT). Here we produce a grain‐size distribution of iron‐oxides in a typical Hawaiian basalt from the superparamagnetic threshold (∼40 nm) to grains with a diameter of 10 µm. This grain‐size distribution is obtained by combining FIB‐SEM and MicroCT data from sister specimens, and normalizing them to the mineral surface area of non‐magnetic minerals. Then we use this grain‐size distribution to determine the contributions of individual magnetic carriers to bulk magnetic measurements and surface magnetometry. We found that measurements on bulk samples are sensitive to relatively small grain sizes in the realm of single domain or vortex states (<200 nm), while signals in surface magnetometry arise mainly from larger grains with diameters >1 µm. This implies that bulk measurements cannot be compared straightforwardly to signals from surface magnetometry from the same sample. Moreover, our observations explain why MMT results are insensitive to the presence of many small grains in a sample that intuitively should hamper their outcome. Plain Language Summary: Magnetic grains in lavas acquire a magnetic signal while cooling in presence of Earth's magnetic field. However, not all grains preserve the signal well, meaning that both good and bad recorders are present. Classical paleomagnetic techniques measure the magnetic signal of all recorders together, that is, the bulk signal. New scanning magnetometry techniques such as Micromagnetic Tomography acquire the signal from individual recorders in the lava, enabling the selection of potentially good recorders and the rejection of signals from bad recorders. Here we found that these two types of magnetic measurements do not measure the same grains that are present in the sample: classical techniques emphasize small grains (<200 nm), while signals in surface magnetometry arise mainly from larger grains with diameters >1 μm. This means that measurements from both techniques performed on the same sample material cannot be compared straightforwardly. Furthermore, our results explain why Micromagnetic Tomography results often are successful, even when many small magnetic grains that intuitively should hamper this technique are present in a sample. Key Points: We determine contributions of individual magnetic carriers to bulk magnetic measurements and surface magnetometryMeasurements on bulk samples are sensitive to small grains (<200 nm); surface magnetometry emphasizes signals from larger grains (>1 μm)Our observations explain why undetected ghost grains in MMT experiments have an unintuitively low impact on the accuracy of MMT results [ABSTRACT FROM AUTHOR]

Plain Language Summary: Nearly synchronous global changes in geomagnetic polarity give both a detailed irregular pacing to geological time and provide a glimpse into heat transfer processes across the core—mantle boundary which drives the Earth's geodynamo. Although the Late Carboniferous is characterized by some well‐studied reversals, details of the tempo of polarity changes in the Early Carboniferous are unknown. This work addresses this by providing a detailed record of polarity changes over a ∼2 million year interval at around 334.5–332.5 million years ago‐from the Trowbarrow Quarry section in NW England. We demonstrate that these limestones likely preserve magnetization from close to their time of formation and record at least 31 polarity reversals. These observations support the idea that the Earth's dynamo was in a hyperactive reversing state similar to those sustained for tens of Myr in the Late Jurassic, parts of the Cambrian and the Late Ediacaran. It further corroborates a ∼200 Myr cyclicity in paleomagnetic field behavior since the Precambrian, potentially linked to variable core heat flow forced by mantle convection. The pattern of geomagnetic polarity changes during the Early Carboniferous (Mississippian) is not known in detail. This information sparsity is addressed by determining a magnetostratigraphy from the late Asbian (late Visean at ∼333 Ma) in Trowbarrow Quarry, UK. This is the stratotype section of the late Asbian and has a detailed foraminiferal zonation based on the same set of paleomagnetic samples, establishing a detailed biostratigraphy. The 195 m‐thick section was sampled at an average spacing of 1.1 m, yielding a detailed magnetostratigraphy comprising nine major magnetozone couplets, and seven submagnetozones. The section dataset has a 78% bias to normal polarity determined from 177 sampling levels. The magnetization is carried by a mixture of hematite and detrital magnetite, with 68% of specimens dominated by hematite magnetizations. The primary magnetization passes a fold test showing its age was prior to the latest Carboniferous. The hematite is inferred to be largely of detrital, eolian origin, although some reddened levels are associated with emergent surfaces, suggesting that a small fraction of hematite is associated with platform emergence. The Mississippian age magnetization is partly overprinted with Kiaman Superchron‐age and Brunhes‐age magnetizations. Using the duration of the section based on astrochronology indicates a reversal frequency of 15.7 ± 0.75 Myr−1, indicating that the geodynamo was in a hyperactive reversing state between 335 and 333 Ma. Key Points: A 195 m section, representing ∼2 Myr, yields a magnetostratigraphy comprizing nine major magnetozone couplets and seven submagnetozonesPrimary magnetizations are predominantly carried by hematite with lesser important detrital magnetite. Data pass regional fold testsA reversal frequency of 15.7 ± 0.75 Myr−1 is calculated, suggesting that the geodynamo was in a hyperactive state at ∼333 Ma [ABSTRACT FROM AUTHOR]

Abstract Dating young lava flows is essential for understanding volcano's eruption frequency, yet challenging due to methodological limitations of commonly used dating techniques. Ruapehu (Aotearoa New Zealand) produced many lava flows during the Holocene, but constraints on the timing of these eruptions are scarce. Here, we use paleomagnetic dating to deliver new eruption ages of 18 lava flows with uncertainties ranging between 500 and 2,700 years (at the 95% confidence level). Comparison between lava flows' paleomagnetic directions and a local paleosecular variation record indicates that the large lava flow field located on the Whakapapa area was emplaced during at least three distinct eruptive episodes between 10600 and 7400 BP. Two of these episodes closely followed a large collapse event that affected Ruapehu's northern area and generated large volumes of lava between 10600 and 8800 BP, with the third episode producing less voluminous lava flows between 8100 and 7400 BP. Following a smaller collapse of the southeastern sector of the edifice at ca. 5300 BP, several low‐volume lava flows were emplaced during at least two distinct eruptive episodes prior to ca. 1000 BP, which supplied the Whangaehu valley with lava. The youngest age inferred from our data represents the youngest eruption age provided for a lava flow outside Ruapehu's summit region. This research provides greater detail to the Holocene effusive chronology at Ruapehu, shedding light on partial cone reconstructions after edifice collapses during the Holocene, and the time relationships between trends observed in its effusive and explosive activity.

Abstract The ability of rocks to hold a reliable record of the ancient geomagnetic field depends on the structure and stability of magnetic domain‐states contained within constituent particles. In paleomagnetic studies, the Day plot is an easily constructed graph of magnetic hysteresis parameters that is frequently used to estimate the likely magnetic recording stability of samples. Often samples plot in the region of the Day plot attributed to so‐called pseudo‐single‐domain particles with little understanding of the implications for domain‐states or recording fidelity. Here we use micromagnetic models to explore the hysteresis parameters of magnetite particles with idealized prolate and oblate truncated‐octahedral geometries containing single domain (SD), single‐vortex and occasionally multi‐vortex states. We show that these domain states exhibit a well‐defined trend in the Day plot that extends from the SD region well into the multi‐domain region, all of which are likely to be stable remanence carriers. We suggest that although the interpretation of the Day plot and its variants might be subject to ambiguities, if the magnetic mineralogy is known, it can still provide some useful insights about paleomagnetic specimens' dominant domain state, average particle sizes and, consequently, their paleomagnetic stability.

Paleomagnetic data enables the global reconstruction of the geomagnetic field, allowing the investigation of significant events like polarity reversals and excursions. When compared to prior polarity reversals, the most recent one, the Matuyama-Brunhes (MB), is the best recorded reversal in terms of number of available paleomagnetic data. Nevertheless, several of these data have poor age control, and they are not distributed equally worldwide. Few global models have been presented for the MB; the most recent is the GGFMB (Global Geomagnetic Field Model for the MB reversal). Limitations imposed by input data and subjective assumptions about the data that are made in modelling restrict the resolution and reliability of these models. This study presents a suite of eight additional global models that reconstruct the magnetic field during the interval 700–900 ka ago, including the MB reversal and Kamikatsura (KKT) excursion. Through model comparisons, the robustness of the models in resolving MB reversal characteristics is assessed. The majority of models indicate that the reversal was mainly driven by the axial dipole field contribution gradually decreasing, while non-dipole parts slightly increased. At the core-mantle boundary, two high-latitude reverse flux patches appear at the beginning of the reversal, and it seems like a few precursors in the form of regionally seen transitional field occurred, related to variations in the decaying dipole moment. The main global polarity change occurred close to 778 ka, with the axial dipole quickly strengthening in the opposite direction in the following, completing the full polarity transition. All the models confirm the previously reported asymmetry of slow dipole decay and fast recovery, and indicate that the dipole moment was clearly lower in the late Matuyama than the early Brunhes. The whole reversal process occurred on average between 800 and 770 ka, with a duration of approximately 30 kyr. Out of four apparent excursions discovered in some of the models between 900 and 800 ka, the KKT excursion (890–884 ka), can be confirmed as a robust magnetic field feature. Additional, well dated paleomagnetic records in particular from the southern hemisphere are required to confirm several details suggested by the models that should only be interpreted with caution so far.

Abstract Crustal deformation and hydrothermal percolation related to the India‐Asia collision have caused extensive remagnetization of the Tethyan Himalaya Terrane (THT). The present work identified three phases of regional remagnetization during 62.3–50.0 Ma for the east‐central THT. Consequently, a model of three‐stage India‐Asia collision was proposed. The east‐central THT first collided with the southward migrated southern margin of the Lhasa Terrane (LT) at 5.4 ± 0.9°N during 62.3–60.9 Ma. Subsequently, the THT continuously moved northward and pushed the southern margin of the LT back to its original position prior to the initiation of fore‐arc and back‐arc extension on both sides of the Gangdese magmatic arc. Since the final suturing of the THT with Asia at ∼10°N during 59.8–58.0 Ma, the east‐central THT remained stationary until India collided with it at 10.9 ± 5.1°N at ∼50.0 Ma.

The magma source for mafic dykes from South Rewa Basin (SRB) in central India is invariably linked to Rajmahal volcanism (117 Ma) for Damodar, Raniganj-Jharia, and Bengal basin (Permian - Quaternary) to the east, and Deccan volcanism (66 Ma) for Satpura Basin to the west of SRB. However, the magmatic events linked to the SRB are not explicit. To ascertain the dyke association with these volcanic events, we performed a comprehensive paleomagnetic study on the exposed dykes and basalts from Shahdol region in SRB. Rock magnetism indicate that magnetite or titano-magnetite is the main remanence carrier mineral in these dykes. The measured directions produce a mean declination (Dm) of 338° and mean inclination (Im) of - 35° (α95= 8.4°, k = 25.3, N = 13), is close to Deccan normal directions. The calculated Pole position (λp) is at 42.02°N, and (Lp) is at 289.33°E, suggesting that the studied dykes are emplaced simultaneously along with Deccan Traps (36.96°N/78.70°W) and not of Rajmahal Traps (11.37°N/297.58°E). These dykes can be the result of multiple Deccan magma intrusions along the Narmada-Tapti lineament and intra-basinal faults in the SRB of central India.

Abstract We document an apparent downward displacement of the Matuyama‐Brunhes magnetic reversal by ∼20 m at Scotia Sea International Ocean Discovery Program Site U1538 (Pirie Basin) by comparison with the well‐defined paleomagnetic record at nearby Site U1537 (Dove Basin). Detailed stratigraphic correlation between the two sites is possible due to similar lithologic variations. However, the two sites have distinctly different porewater geochemistry. Notably, Site U1538 indicates a greater demand for electron acceptors to oxidize organic carbon and Fe2+ enrichment below the depth of SO42− depletion. Magnetic parameters indicate enrichment of an authigenic magnetic mineral with strong remanence properties around the depth of SO42− depletion (∼46 m at Site U1538) relative to magnetic parameters at correlative depths at Site U1537. Fe2+ enrichment below the depth of SO42− depletion is not predicted based on the energetically favorable order of electron acceptors for microbial respiration but is documented here and in other depositional settings. This indicates Fe2+ production exceeds the production of H2S by SO42− reduction, providing a geochemical environment that favors the production and preservation of ferrimagnetic remanence‐bearing iron sulfides over paramagnetic pyrite and, thus, a mechanism for deep chemical remanent magnetization acquisition at depths of tens of meters. The influence of authigenic ferrimagnetic iron sulfides on paleomagnetic signals can be difficult to demonstrate with magnetic properties alone; therefore, this finding has implications for evaluating the fidelity of magnetostratigraphic records with complementary geochemical data. Such situations should be considered in other depositional environments with similar porewater Fe2+ accumulation below the SO42− reduction depth.

Abstract Micromagnetic modeling allows the systematic study of the effects of particle size and shape on the first‐order reversal curve (FORC) magnetic hysteresis response for magnetite particles in the single‐domain (SD) and pseudo‐single domain (PSD) particle size range. The interpretation of FORCs, though widely used, has been highly subjective. Here, we use micromagnetics to model randomly oriented distributions of particles to allow more physically meaningful interpretations. We show that one commonly found type of PSD particle—namely the single vortex (SV) particle—has far more complex signals than SD particles, with multiple peaks and troughs in the FORC distribution, where the peaks have higher switching fields for larger SV particles. Particles in the SD to SV transition zone have the lowest switching fields. Symmetrical and prolate particles display similar behavior, with distinctive peaks forming near the vertical axis of the FORC diagram. In contrast, highly oblate particles produce “butterfly” structures, suggesting that these are potentially diagnostic of particle morphology. We also consider FORC diagrams for distributions of particle sizes and shapes and produce an online application that users can use to build their own FORC distributions. There is good agreement between the model predictions for distributions of particle sizes and shapes, and the published experimental literature.

Abstract Construction of regional geomagnetic secular variation curves for the last several tens of thousands of years is important for understanding the behavior of non-dipole fields and applications to geochronology. Around Japan, secular variation records of older than 10 ka was scarce, in particular for relative paleointensity (RPI). Here, we conducted a paleomagnetic study of a sediment core covering the last ~ 40 kyr taken from a small basin in the Nankai Trough. The core consists of homogenous hemipelagic sediments except for turbidites and volcanic ashes. The age model was constructed based on seven 14C datings and two volcanic ashes. Turbidites and volcanic ashes were excluded from the construction of secular variation curves because of geologically instantaneous deposition. It was revealed that the magnetization of this core is carried largely by detrital magnetic minerals, although magnetofossils are also contained. Bulk magnetic properties show some temporal changes in magnetic concentration and grain size, but still homogeneous enough for reliable RPI estimations except for turbidites and volcanic ashes. The resultant RPI shows no correlation with the normalizer, anhysteretic remanent magnetization, of the RPI estimations or with a proxy for a magnetic grain size and/or the proportion of magnetofossils to detrital magnetic minerals. The obtained RPI record shows a long-term increasing trend since ~ 40 ka, which coincides with global stack curves. On the other hand, there are some differences in shorter timescale variations, which may reflect non-dipole fields. This study demonstrated that hemipelagic sediments in the Nankai Trough have potential for recovering high-quality RPI records when turbidites and volcanic ashes were excluded and are useful for accumulating records to construct a regional master curve. Graphical abstract

Abstract Despite being essential in determining absolute paleomagnetic field intensity (API) with high fidelity over Earth science research topics, API determination still suffers little quantitative success. This is due to common nonideal magnetic behaviors in experiments using natural rocks caused by physiochemical changes in the magnetic minerals contained. Although linking rock-magnetic parameters to API results may be fundamental, negligible effort has been made using the Tsunakawa–Shaw (TS) API method despite its potentially high experimental success rate in overcoming nonideal magnetic effects. Here, we explore the relationships between rock-magnetic parameters retrieved using relatively rapid and widely pre-conducted measurements and TS API results from late Cenozoic basaltic rocks. We selected rock-magnetic parameters quantified from strong-field high-temperature thermomagnetic curves, magnetic hysteresis loops, and back-field isothermal remanent magnetization demagnetizations. We provide new data pairs of rock-magnetic parameters and TS API results for 41 basaltic rock samples from 8 sites (cooling units) in Northeast China. Then, by compiling them with published data of similar quality, we compiled 133 pairs of rock-magnetic and TS API data at the sample level (38 sites). Using this data compilation, the following topics of interest were identified: Magnetic coercivity (Bc) and remanence coercivity (Bcr) among the hysteresis parameters, and the thermomagnetic parameter ITC|m| (an index of thermal change quantifying an average of the differences in saturation magnetization at a full temperature range of during a single heating–cooling run) allow meaningful and efficient discrimination between data subsets divided by “success” or “failure” in the API results. We propose sample preselection criteria for the TS experiment: a minimal set of Bc ≥ 13 mT (or Bcr ≥ 26 mT) and ITC|m|≤ 0.15. Moreover, extended consideration based on the preselection criteria may allow the screening of potentially biased specimen/sample-level API estimates in the site-averaged determination of such a site with a large within-site API dispersion. Graphical Abstract

This study examined the applicability of R. Fischer’s approach to the analysis of sample directions in the flow of eruptive rocks. A test of the hypothesis that all samples share a common direction of the ancient field was proposed.

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

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°.

Remote sensing techniques provide crucial insights into ancient settlement patterns in various regions by uncovering previously unknown archaeological sites and clarifying the topological features of known ones. Meanwhile, in the northern part of the Southern Levant, megalithic structures remain largely underexplored with these methods. This study addresses this gap by analyzing the landscape around Rujm el-Hiri, one of the most prominent Southern Levantine megaliths dated to the Chalcolithic/Early Bronze Age, for the first time. We discuss the type and extent of the archaeological remains identified in satellite images within a broader context, focusing on the relationships between landscapes and these objects and the implications of their possible function. Our analysis of multi-year satellite imagery covering the 30 km region surrounding the Sea of Galilee reveals several distinct patterns: 40–90-m-wide circles and thick walls primarily constructed along streams, possibly as old as Rujm el-Hiri itself; later-period linear thin walls forming vast rectangular fields and flower-like clusters of ~ 20 m diameter round-shaped fences found in wet areas; tumuli, topologically linked to the linear walls and flower-like fences. Although tumuli share similar forms and likely construction techniques, their spatial distribution, connections to other archaeological features, and the statistical distribution in their sizes suggest that they might serve diverse functions. The objects and patterns identified may be used for further training neural networks to analyze their spatial properties and interrelationships. Most archaeological structures in the region were reused long after their original construction. This involved adding new features, building walls over older ones, and reshaping the landscape with new objects. Rujm el-Hiri is a prime example of such a complex sequence. Geomagnetic analysis shows that since the entire region has rotated over time, the Rujm el-Hiri’s location shifted from its original position for tens of meters for the thousands of years of the object’s existence, challenging theories of the alignment of its walls with astronomical bodies and raising questions regarding its possible identification as an observatory.

Magnetic fields in protoplanetary disks are thought to play a prominent role in the formation of planetary bodies. Acting upon turbulence and angular momentum transport, they may influence the motion of solids and accretion onto the central star. By searching for the record of the solar nebula field preserved in meteorites, we aim to characterize the strength of a disk field with a spatial and temporal resolution far superior to observations of extrasolar disks. Here, we present a rock magnetic and paleomagnetic study of the andesite meteorite Erg Chech 002 (EC002). This meteorite contains submicron iron grains, expected to be very reliable magnetic recorders, and carries a stable, high-coercivity magnetization. After ruling out potential sources of magnetic contamination, we show that EC002 most likely carries an ancient thermoremanent magnetization acquired upon cooling on its parent body. Using the U-corrected Pb-Pb age of the meteorite's pyroxene as a proxy for the timing of magnetization acquisition, we estimate that EC002 recorded a field of 60 ± 18 µT at a distance of ~2 to 3 astronomical units, 2.0 ± 0.3 My after the formation of calcium-aluminum-rich inclusions. This record can only be explained if EC002 was magnetized by the field prevalent in the solar nebula. This makes EC002's record, particularly well resolved in time and space, one of the two earliest records of the solar nebula field. Such a field intensity is consistent with stellar accretion rates observed in extrasolar protoplanetary disks. [ABSTRACT FROM AUTHOR]

Evaluating the stratigraphy of the North Pacific is the first step towards understanding the role of this region in climate variability in the past. This region has been notoriously difficult to work in due to the presumed low sedimentation rates (<0.1 cm/kyr), which would likely be inadequate to capture glacial-interglacial cycles of the Late Pleistocene (∼500,000 years). These low sedimentation rates have been estimated from magnetostratigraphy and biostratigraphy, but those techniques are only minimally constrained during this geologically recent time period. Here, we reconstruct average sedimentation rates for the last 500 kyr across the deep (>3000 m) North Pacific using 230Th depth profiling, which is based on the exponential radioactive decay of 230Th and is one of only a few chronological tools applicable to sediment within this relatively calcium carbonate deficient region. Sedimentation rates are indeed low (<0.25 cm/kyr) within the subtropical gyre, especially between 20 and 30°N, but sedimentation rates greater than 0.5 cm/kyr are observed between 30 and 40°N, particularly west of 200°E. Sedimentation rates are higher underneath the Asian dust plume, and no water depth dependence is observed below 4000 m. Sedimentation rates from 230Th depth profiling generally agree with other methods, but they may be more representative of the average sedimentation rates for the last 500 kyr compared to other proxies that operate on much shorter (e.g., radiocarbon) or much longer (e.g., magnetostratigraphy) timescales. Overall, the efficacy of 230Th chronology is a promising tool for further investigation into the history of the North Pacific in the past. [ABSTRACT FROM AUTHOR]

The improvement of the archaeomagnetic dating method requires compiling new and older data of the Earth's magnetic field (EMF) variations for the last millennia. Combustion events from fumier sequences have been proposed as good directional EMF recorders. However, they are subjected to diverse taphonomical processes and how these affect the archaeomagnetic record has not yet been studied. In order to evaluate it, here we report the first archaeomagnetic and rock-magnetic results on samples from experimentally recreated fumiers since 2014 under controlled conditions. A facies description with unprecedent resolution was used to study the variation of magnetic properties in depth. Rock-magnetic analyses indicate a homogenous magnetic mineralogy dominated by pseudo-single domain magnetite as main carrier in all facies, with not very high and similar contribution of the finest (superparamagnetic) grains. The low values of anisotropy of magnetic susceptibility (AMS) indicate that the studied sample set is mainly isotropic. The directional behaviour in well-preserved burned facies (here described as G, LM and DGB), are jointly characterized by highly reversible thermomagnetic curves, high Koenigberger (Q n) ratio values and intense, univectorial and normal polarity orthogonal NRM demagnetization diagrams. On the contrary, specimens affected by mechanical alteration processes are less magnetic and show anomalous directional behaviours. The high thermomagnetic reversibility of ashes indicates that they reached ca. 600–700 °C, in line with the thermocouples' data. Temperatures of 460 °C were obtained for the DGB facies (subyacent black carbonaceous facies). Sampling of ashes located on the top of these combustion events should be avoided for archaeomagnetism. Being just beneath the last stabling episode they are the most prone to undergo mechanical alterations and do not preserve well the Earth's magnetic field direction. Despite their unlithified nature and the multiple taphonomic processes that fumier sequences may undergo, under certain quality criteria, they are valid geomagnetic field recorders providing both information of archaeological and geophysical interest. [ABSTRACT FROM AUTHOR]

The article summarizes paleomagnetic data for Tuva, Mongolia, and Eastern China, which showed that in the central part of the Central Asian Fold Belt, areas with different paleomagnetic characteristics are distinguished. These are areas located north of the Mongol–Okhotsk mobile belt, the western and eastern parts of Southern Mongolia, and Eastern China. The areas located north of the Mongol–Okhotsk mobile belt were part of the structure of the Siberian continent from the Ordovician and experienced movement similar to the Siberian continent. The regions of the western part of Southern Mongolia have been part of the structure of the Siberian continent since the Late Carboniferous. The geological complexes of the eastern part of Southern Mongolia and blocks of Eastern China in the Middle Paleozoic and Early Mesozoic were located in a latitudinal interval close to the North China block and experienced similar latitudinal movements and rotations. The large difference between the paleolatitudes of coeval strata in western and eastern Mongolia and Eastern China south of the Mongol–Okhotsk mobile belt suggests the existence of a tectonic boundary that separated blocks formed at paleolatitudes along the 107° E meridian, close to Siberia and North China. To the west of the 107° E meridian, the paleolatitudes of the formation of Late Carboniferous–Permian strata are close to the paleolatitudes of Siberia, and east of the meridian, to the paleolatitudes of North China. The width of the Mongol–Okhotsk Ocean in the Late Paleozoic–Early Mesozoic was 30°–40° E (~3000–4000 km). The southern limit of the Mongol–Okhotsk Ocean was segmented and consisted of terranes of various genesis and structure. The closure of segments of the Mongol–Okhotsk Ocean occurred as a result of collision of terranes with the Siberian continent from the Late Carboniferous (in the west) to the Jurassic (in the east). [ABSTRACT FROM AUTHOR]

Abstract—In 394 samples characterizing 266 stratigraphic levels in four Turonian–Santonian sections of the Southwestern Crimea, characteristic remanent magnetization components (ChRM) acquired at the stage of diagenesis are identified. The obtained data fix the record of the paleosecular geomagnetic variation of high amplitude (root mean square deviation S = 25.9° with a fixed cut-off angle of 45°, which is about twice as high as the model S for this latitude) in the sediments formed during ~5–6 Myr and is interpreted as anomalous behavior of the geomagnetic field in the Turonian, Coniacian, and Santonian. [ABSTRACT FROM AUTHOR]

The Kotuy intrusive complex was identified from the geological survey of the western slope of the Anabar Massif in the middle reaches of the Kotuy River. It is represented by dolerite–gabbrodolerite sills and dikes of Vendian age (556 ± 28 Ma). A number of sills are characterized by 30–80 m thickness, and dikes often have a length of a few dozen kilometers. The distribution area of the complex is a few hundred square kilometers. However, the geodynamic evidence for the formation of extensive intrusive bodies in the northern part of Siberia in the Vendian is not clear. We present new geochronological, geochemical, and paleomagnetic data indicating that at least part of the Kotuy magmatic complex intrusions in the middle reaches of the Kotuy River should be attributed to the ~1500 Ma Kengede magmatic complex (Kuonamka large igneous province). In this light, the very existence of Vendian intrusive magmatism on the western slope of the Anabar massif appears questionable. [ABSTRACT FROM AUTHOR]

We present the first results of a detailed rock magnetic and paleomagnetic research of the Mga marine interglacial sediments of the Mikulino (Eemian) Interglacial (the Upper Pleistocene) in the Etalon section (former Sverdlov Factory, Leningrad Region). The Blake geomagnetic excursion was determined in the upper part of the Mga formation according to a shallow inclination of the characteristic remanent magnetization (ChRM) component. Age of the Blake excursion was obtained as 117 ± 7 ka applying optically stimulated luminescence (OSL) dating. The results obtained are in good agreement with other Blake Event records. The ChRM in the Mga sediments is related to syngenetically formed biogenic greigite produced by magnetotactic bacteria. [ABSTRACT FROM AUTHOR]

As demonstrated by a three-dimensional geodynamo model, during reversals and excursions of the geomagnetic field, with small amplitudes of heat sources, there occurs attenuation not only of the dipolar magnetic field but also of the high harmonic field. In this scenario, the Earth's magnetosphere can be significantly smaller than previously expected, and correspondingly, the amount of radiation that penetrates the Earth could be greater. [ABSTRACT FROM AUTHOR]

In this study we use micromagnetic modeling to show that the magnetizations of magnetically single‐vortex particles rotate toward the stress axis on the application of a differential compression stress. This is the exact opposite response to magnetically single‐domain particles, which previously provided the theoretical underpinning of the effect of stress on the magnetic signals of rocks. We show that the magnetization directions of single‐vortex and equant single‐domain particles are altered by much lower stresses than previously predicted, c.f., 100 versus 1,000 MPa; where a change in magnetization is defined as a rotation of >3° after the removal of stress. The magnetization intensity of assemblages also drops by ∼20%–30% on the application and removal of stress of ∼100 MPa. Given that single‐vortex particles are now thought to dominate the magnetization of most rocks, future studies should account for paleomagnetic directional uncertainties and potential underestimation of the ancient magnetic field intensity. Plain Language Summary: Magnetic minerals in rocks can record and retain magnetic information for millions of years. This magnetic information helps us to understand processes like plate tectonics and geomagnetic field behavior in the past. When rocks experience compressional forces, these affect the magnetization of the magnetic minerals within them, potentially altering this magnetic information. Previous theoretical studies of the affect of stress on magnetization used analytical theory, and predicted that stresses of >1,000 MPa are required to alter a rock's otherwise stable magnetization. We show that much lower stresses of only ∼100 MPa are required to compromise magnetic recordings in rocks. The reason for this is a change in our understanding of rock magnetic systems. Previous analytical models were for elongated particles <100 nm in size, as these were thought to be the primary carriers of stable magnetization in minerals. We now know that larger particles can retain stable magnetic recordings to high temperatures over geological time. This study shows that the magnetization of these particles are less stable than smaller particles when stresses are applied. This suggests that common geological processes such earthquakes might provide sufficient near‐surface stress to remagnetize rocks close to the fault zone, leading to a paleo‐stress recording. Key Points: Single‐vortex particles' net magnetization rotates toward the compression axis when subjected to differential stressSingle‐vortex particles display the opposite response to compressional stress compared to single‐domain particlesStress fields of only ∼100 MPa are required to alter paleomagnetic signals, lower than previously predicted [ABSTRACT FROM AUTHOR]

Paleomagnetism is the most important source of information for determining the position of tectonic plates in the geological past. Over the last few decades significant advancements have been made in improving the reliability of paleomagnetic data, ranging from analytical methods to statistical assessments. Here I present the first version of PmagDiR, an R-based open-source package which displays, assesses the reliability, and, when possible, corrects given paleomagnetic directions distributions. The main functions of the package are to: plot paleomagnetic directions, their averages and confidence boundaries; apply different direction cut-offs to identify and filter outliers; perform a test for antipodality; compare the distribution shape with the one predicted by a widely accepted paleosecular variation model; correct flawed distributions for paleomagnetic inclination flattening; and correct for strain-derived paleomagnetic directions deviations when the strain fabric is known. Furthermore, directions can be converted in virtual geomagnetic poles and plotted on a spherical projection for comparison with reference apparent polar wander paths. All main functions of the PmagDiR package return results as comma separated value text files as well as vector graphic files (pdf), optimized for publication purpose with minimal manipulation. [ABSTRACT FROM AUTHOR]