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Abstract Holocene evolutionary history of the Banni Plain in the Great Rann of the Kachchh Basin is reconstructed from a subsurface sediment core of ca 50 m. Detailed data on textural and lithofacies variations, grain‐size analysis, environmental magnetism and accelerator mass spectrometry 14C dates on seven samples were generated on the sediment core retrieved from the Banni Plain near Berada. A high‐resolution record extending back to 10 ka has been reconstructed from the top ca 40 m of the core section comprising shallow marine sediments. The core is divisible into five depositional units. The basal part is a fluvial depositional unit followed upward by estuarine, sub‐tidal, intertidal and supra‐tidal environments. The sediment accumulation rate is highest in the sub‐tidal to intertidal facies (1.9 cm year−1) and decreases towards the supra‐tidal facies to 0.09 cm year−1. Environmental magnetic analysis, χlf coupled with the S‐ratio, indicates high magnetic mineral concentrations during the Early Holocene, suggesting a wet period accompanied by high monsoon precipitation. This is followed by the onset of semi‐arid conditions in the Great Rann of the Kachchh Basin as indicated by the low values of the χlf and S‐ratios. A westward and northward shift in the shoreline towards the deeper part of the basin is suggested during the Late Holocene, which is coupled with aridity and reduced monsoonal conditions. The change in depositional pattern from the retrogradational deposit of fluvial (Unit 1) to estuarine sediment (Unit 2), progressing to sub‐tidal (Unit 3), is attributed to sea‐level transgression followed by regressive intertidal (Unit 4) to supra‐tidal deposition (Unit 5), culminating in complete withdrawal of the sea, aided by tectonic uplift, during the Late Holocene. The results reveal that the sediment accumulation rates and depositional environments changed over time in response to changes in sea level from minima to maxima and then eventually to the present level.

Detailed and systematic analyses of the magnetic and grain-size properties of the Weihe River sediments were conducted to explore effective proxies that could reflect variations in the runoff. Ultimately, the magnetic parameter χARM/χlf was considered a reliable proxy owing to the close relationship with grain-size fraction larger than 63 μm, with a correlation coefficient of 0.90. By combining accelerator mass spectrometry radiocarbon (AMS 14C) dating, a timescale ranging from 12,900 year BP to the present was established for the section. Accordingly, the reconstructed runoff variations showed that, from 12,900 to 9,600 year BP, the hydrodynamic force of the river was relatively strong, and the runoff was large. From 9,600 to 7,500 year BP, these two parameters varied from weak to strong, and the trend continued to increase from 7,500 to 5,300 year BP. At 5,300 year BP, the sediments shifted from the fluvial to the continental environment, indicating a marked decrease in the runoff. Although the resolution and pattern of this reconstruction were rough, this is a significant analysis among the historical runoff studies based on floodplain sediments, and the results showed trends that to some extent coincide with the variations in the intensity of the East Asian Summer Monsoon. HIGHLIGHTS An integrated study of Weihe River sediments using environmental magnetism and particle size analysis.; Establishing a chronological framework for the Weihe sedimentary profile using AMS14C dating.; The magnetic ratio parameter χARM/χlf is extracted as an effective proxy for indicating river runoff.; The results show that the runoff process of the Weihe River is mainly controlled by the East Asian summer winds.;

Abstract We report the first complete loess–paleosol record spanning the last 130 kyr from the southern extremity of the Hunshandake Sandy Land (HSL) in central‐eastern Mongolia. Our combined mineral magnetic and geochemical results demonstrate that during the last interglacial, the front of the East Asian summer monsoon (EASM) extended to central‐eastern Inner Mongolia, consistent with modern observations of climate change. However, during the last glacial, typical magnetic parameters (e.g., magnetic susceptibility and anhysteretic remanent magnetization and their ratios), which have been successfully adopted to denote the EASM variations on the Chinese Loess Plateau (CLP), show only muted temporal variations and cannot be readily correlated with equivalent records from the main body of the CLP. Remarkably, the Zr/Rb ratio, a robust geochemical indictor of the winter monsoon, is positively correlated with saturation isothermal remanent magnetization and saturation magnetization during the last glacial, demonstrating the strong control of wind vigor on high‐field magnetization signals dominated by lithogenic ferrimagnetic minerals. In contrast to the variable response of magnetic parameters to regional paleoclimatic fluctuations, the Rb/Sr and Ba/Sr ratios (two summer monsoon indicators) faithfully track weak chemical weathering processes and fine‐scale monsoon oscillations, especially during the last glacial. Additionally, we found that higher proportions of pedogenic high‐coercivity magnetic minerals were formed during the last interglacial, which may reflect relatively low rainfall but higher evapotranspiration in the southern extremity of the HSL compared with the CLP. We therefore attribute this complex magnetic record to a threshold response to the EASM variations in eastern Inner Mongolia.

Abstract Effective moisture (EM) distribution in the Indian summer monsoon (ISM) region is strongly related to regional topography. An understanding of climate change and the interactions between climate variables can help predict future climate variations. Here, we reconstruct a stack EM record for Southwest China over the past 90 kyr using environmental magnetism in lake sediment. The EM in Southwest China at the orbital scale was closely linked to precession‐induced change in North Hemisphere solar insolation, as well as the ISM variability. However, at the glacial‐interglacial scale, it was decoupled with ISM intensity, being wetter during glacial periods (weakened ISM) and drier during interglacial periods (enhanced ISM). Combined with modern meteorological observations, we suggest that the topographical barrier effect and temperature induced dryness are responsible for the decoupling between ISM intensity and EM. The terrestrial topography and temperature strongly influence EM distribution by altering the dynamics of onshore airflow and evapotranspiration.

High-temperature susceptibility (HT-χ) data are routinely measured in Earth, planetary, and environmental sciences to rapidly identify the magnetic mineralogy of natural systems. The interpretation of such data can be complicated. Whilst some minerals are relatively unaltered by heating and are easy to identify through their Curie or Néel temperature, other common magnetic phases, e.g., iron sulphides, are very unstable to heating. This makes HT-χ interpretation challenging, especially in multi-mineralogical samples. Here, we report a review of the HT-χ data measured primarily at Imperial College London of common magnetic minerals found in natural samples. We show examples of “near pure” natural samples, in addition to examples of interpretation of multi-phase HT-χ data. We hope that this paper will act be the first reference paper for HT-χ data interpretation.

Abstract In well‐buffered modern soils, higher annual rainfall is associated with enhanced soil ferrimagnetic mineral content, especially of ultrafine particles that result in distinctive rock magnetic properties. Hence, paleosol magnetism has been widely used as a paleoprecipitation proxy. Identifying the dominant mechanism(s) of magnetic enhancement in a given sample is critical for reliable inference of paleoprecipitation. Here, we use high‐resolution magnetic field and electron microscopy to identify the grain‐scale setting and formation pathway of magnetic enhancement in two modern soils developed in higher (∼580 mm/y) and lower (∼190 mm/y) precipitation settings from the Qilianshan Range, China. We found that both soils contain 1–30 μm aeolian Fe‐oxide grains with indistinguishable rock magnetic properties, while the higher‐precipitation soil contains an additional population of ultrafine (

SK-2 borehole in Songliao Basin provides unprecedented geological materials for investigating the Early Cretaceous continental paleoenvironment and paleoclimate in northeastern China. The lacustrine successions of the lower Shahezi (K1sh) Formation at the depth from 4,542 to 5,695 m was systematically studied using environmental magnetism and cyclostratigraphy in this study. Magnetic analysis reveals an inverse correlation between magnetic susceptibility (MS) and lithological ranks in fine clastic sediments, with the highest values in mudstones and the lowest in sandstones. The main magnetism carriers in the lower K1sh are pseudo-single-domain (PSD) and/or multi-domain (MD) magnetite with minor presence of hematite. MS was used to further explore the genesis of the environmental and climatic variations through cyclostratigraphic analysis. Sedimentary cycles of 113 m, 34 m, 13 m and 6 m can be identified in the power spectrum, which were interpreted as long and short eccentricity, obliquity, and precession cycles, demonstrating the impact of astronomical cyclicity on sedimentary rhythmicity. Floating astronomical time scale (FATS) of 4,090 kyr and 4,148 kyr were established by tuning the inferred long and short eccentricity cycles to the artificial 405-kyr and 105-kyr orbital eccentricity curves respectively. The estimated sediment accumulation rate around 28 cm/kyr confirms the rapid deposition process within the faulted lacustrine basin. Based on this study, the lake level oscillations in Songliao Basin are assumed to be shaped by long and short eccentricity, precession and semi-precession cycles during Early Cretaceous. This study also indicates that the sand-mudstone alternations deposition in K1sh is most likely driven by the seasonal discrepancies of summer insolation during semi-precession periods.

As an important global water vapor source, the Western Pacific warm pool (WPWP) influences precipitation changes in middle and low latitudes. The low-latitude water cycle is a key climate parameter at different time scales, as it contributes to various feedback processes. However, at present, indicators of precipitation variability in the equatorial western Pacific are limited. In this work, we used the sedimentary record of the southern margin of the WPWP to study the precipitation variability over the western equatorial Pacific since MIS8. The age framework based on plankton-foraminifera δ18O was used to analyze changes in geochemical elements, clay minerals, and magnetic parameters of a marine sediment core H10. As new precipitation records, our precipitation records (TiO2, χ, and SIRM concentration without carbonate base) are closely related to monsoon and Intertropical Convergence Zone and generally in inverse phase with the oxygen isotope records of stalagmites from caves in China. A spectral analysis showed an obvious precession period. The southern margin of the WPWP water cycle is closely related to the East Asian monsoon in the last four climate cycles, and is influenced by both high and low latitudes.

Uplift of the Tibetan Plateau, expansion/shrinkage of the Paratethys Sea, and global climate are three major forcings for central-east Asian climatic and environmental variations during the Cenozoic. However, knowledge of expansion/shrinkage history of the Paratethys Sea is much less well known in comparison with the other two forcings. Here, we present a first multiple-parameter environmental magnetic and diffuse reflectance spectroscopy study of the Eocene eolian Red Clay deposits (∼51–40 Ma) in the Xorkol Basin of the northeastern Tibetan Plateau, which is near the easternmost maximum boundary of the Eocene Paratethys Sea. The first detailed Eocene expansion/shrinkage history of the Paratethys Sea was reconstructed based on the hematite content of the Eocene Red Clay, which shows remarkable consistency with the previous low-resolution Paratethys Sea paleowater depth record in the southwestern Tarim Basin. These results demonstrate that the Paratethys Sea experienced a three-stage (shrinkage-expansion-shrinkage) evolution between ∼51 and 40 Ma, with boundaries at ∼46.2 and 42 Ma. Superimposed on this framework, the Paratethys Sea experienced four times of rapid shrinkages at the expansion phase (shows 400-kyr cycles) during ∼44–42 Ma modulated by eccentricity forcings. These new results are of great significance to evaluate respective role of Tibetan uplift, global climate, and Paratethys Sea area variations in Asian climate and environmental change over the Eocene.

Abstract Children's exposure to air pollution affects both their health and learning skills. Fine and ultrafine particulate matter (PM2.5, PM1), notably issued from traffic sources in urban centers, belong to the most potential harmful health hazards. However their monitoring and the society's awareness on their dangers need to be consolidated. In this study, raising teacher and pupil involvement for air quality improvement in their schools environment is reached through developing a passive monitoring technique (bio‐sensors made of tree bark). The experiment was implemented in two urban elementary schools situated close to a main traffic road of the city of Toulouse (South of France). Magnetic properties, carbonaceous fraction measurements, and scanning electronic microscopy (SEM‐EDX) investigations were realized both on passive bio‐sensors and filters issued from active sampling. We find that traffic is the main PM1 source for both outdoors and indoors at schools. Higher levels of outdoor PM in the school's environments compared to urban background are reached especially in the cold period. The schools proximity to a main traffic source and lack of ventilation are the main causes for observed PM1 accumulation in classrooms. The co‐working experiment with educational teams and pupils shows that the use of bio‐sensors is a driver for children empowerment to air pollution and therefore represents a potential key tool for the teachers though limiting eco‐anxiety. As PM accumulation is observed in many scholar environments across Europe, the proposed methodology is a step toward a better assessment of PM impact on pupil's health and learning skills.

The Indian monsoon is an important part of the global monsoon system, allowing important transfers of moisture at a large geographical scale and deeply affecting human populations and economic prosperity of regions. The tropical summer monsoon in the Northern Hemisphere is generally considered to be driven by low latitude solar radiation. Therefore, the summer monsoon strength is near zero-phase to the maximum of Northern Hemisphere Summer Insolation (NHSI). However, records from the Arabian Sea and some other parts of the Indian Ocean (e.g., Andaman Sea) show that a ∼8 kyr phase difference exists between the Indian summer monsoon (ISM) strength and the northern Hemisphere Summer Insolation maxima, which is obviously different from the records of stalagmites in the East Asia and other marine sediments (e.g., Bay of Bengal). This leads to the “sea-land precession phase paradox” in indian summer monsoon research. This paper systematically summarizes the Indian monsoon variability on orbital scale indicated by various records from the Indian monsoon regions (including oceans and continents) since the late Quaternary. The orbital forcing of Indian monsoon, the potential phase difference between indian summer monsoon and northern Hemisphere Summer Insolation and its possible forcing mechanism(s) are further discussed. The observed phase lag between indian summer monsoon and northern Hemisphere Summer Insolation may be controlled by the Atlantic Meridional Overturning Circulation (AMOC), latent heat transfer between the southern Indian Ocean and the Asian continent, or caused by the lack of tightly coupling between the Arabian Sea summer monsoon proxies and the monsoon intensity. In addition, it is still unclear whether previous monsoon proxies can provide a strong constraint on the intensity of summer monsoon. Environmental magnetism has been widely used in high-resolution dating and the analysis of paleoclimate variabilities in marine and terrestrial sediments, due to its high sensitivity on the rainfall and temperature. Therefore, in order to solve these issues, it is necessary to combine magnetic parameters with geochemical and paleontological parameters for more systematic work in the future.

This study presents new evidence for long-term variability in the late Holocene North American Monsoon (NAM), Pacific coast of Mexico. We have carried out a rock magnetic study on two deep-sea sediment cores from the Pacific coast Pescadero Basin. The magnetic intensities estimate total magnetic material and are a proxy for total clastic sediment. Ratios of magnetic intensities estimate the grain size of magnetic material. The rock magnetic data show a decimeter scale, multi-decadal oscillation with fourteen cycles (A-N) over the last 1200 years. These oscillations reflect alternating intervals of stronger/coarser magnetic/clastic flux to the coastal ocean and intervals of weaker/finer magnetic flux. We think these variations are caused by variations in long-term dominance of the NAM; summer (wet) monsoons produce rainy conditions (with runoff) while winter (dry) monsoons produce significant offshore winds, increased upwelling/biological productivity. We can correlate our variability to two other published studies southeast of Pescadero Basin, coastal lake sediments in Laguna de Juanacatlan and a Juxtlahuaca Cave stalagmite. Both of these studies estimate local rainfall. We see evidence of the same pattern of multi-decadal rainfall-runoff variability in these records as we see in Pescadero Basin, which is synchronous to within ±25 years over the last 1200 years. The multi-dacadal pattern of hydrologic variability in all three records varies in cycle duration from ~90-years wet/dry cycles in the Little Ice Age (1400–1850 AD) to ~60-years cycles in the Medieval Climate Optimum (1100–1400 AD). This variability in cycle duration suggests some chaotic nature to the regional NAM climate pattern or some long-term non-linear forcing (PDO?).

The study of the geomagnetic field evolution on minor timescales, in particular of such significant events as geomagnetic reversals and excursions, has acquired particular relevance nowadays due to the increased attention of mankind to the environment. The question of how exactly abrupt changes in the characteristics of the geomagnetic field affect the climate and biosphere remains largely debatable; the idea of the speed and dynamics of these changes is also very vague. "Classical" geological objects and existing methods provide limited opportunities for highly detailed reconstructions of geomagnetic field variations; therefore, paleomagnetologists are looking for new objects and approaches to solve this problem. The research that we have begun involves the use – for the first time in Russia – of speleothems to study secular variations of the geomagnetic field.This brief communication presents paleomagnetic records of two drill-cores from the flowstone from Vorontsovskaya cave, located on the western flank of the Caucasus Mountains in the valley of the river Kudepsta. Preliminary results indicate the presence of a geomagnetic excursion record in both drill-cores. Further study of the samples from Vorontsovskaya cave will make it possible to compare the discovered event with known excursions, as well as to clarify its age, duration, and dynamics.

Abstract Speleothems are ideal archives of environmental magnetism and paleomagnetism, since they retain continuous magnetic signals in stable conditions and can be used for reliable radiometric dating using U-series and radiocarbon methods. However, their weak magnetic signals hinder the widespread use of this archive in the field of geoscience. While previous studies successfully reconstructed paleomagnetic signatures and paleoenvironmental changes, the time resolutions presented were insufficient. Recently emerging scanning SQUID microscopy (SSM) in this field can image very weak magnetic fields while maintaining high spatial resolution that could likely overcome this obstacle. In this study, we employed SSM for high spatial resolution magnetic mapping on a stalagmite collected at Anahulu cave in Tongatapu Island, the Kingdom of Tonga. The average measured magnetic field after 5 mT alternating field demagnetization is ca. 0.27 nT with a sensor-to-sample distance of ~ 200 µm. A stronger magnetic field (average: ca. 0.62 nT) was observed above the grayish surface layer compared to that of the white inner part (average: ca. 0.09 nT) associated with the laminated structures of the speleothem at the submillimeter scale, which scanning resolution of the SSM in this study is comparable to the annual growth rates of the speleothem. The magnetization of the speleothem sample calculated from an inversion of isothermal remanent magnetization (IRM) also suggests that the magnetic mineral content in the surface layer is higher than the inner part. This feature was further investigated by low-temperature magnetometry. Our results show that the main magnetic carriers of the speleothem under study are magnetite and maghemite and it can contain hematite or ε-Fe2O3. The first-order reversal curve (FORC) measurements and the decomposition of IRM curves show that this speleothem contains a mixture of magnetic minerals with different coercivities and domain states. The contribution from maghemite to the total magnetization of the grayish surface layer was much higher than the white inner part. Such differences in magnetic mineralogy of the grayish surface layer from that of the inner part suggest that the depositional environment shifted and was likely changed due to the oxidative environment.

The cave system in the Sierra de Atapuerca holds one of the most important archaeological sites for the understanding of early human occupation in Europe. Among the different cavities and galleries, the Gran Dolina cave yielded a new hominin species coined as Homo antecessor of an Early Pleistocene age. Encouraged by our previous results in Gran Dolina, we carried out a study to extend and deepen our rockmagnetic investigation of the paleoenvironmental reconstruction of the upper Gran Dolina cave based on experiments that include composition, relative concentration, and grain size of the magnetic iron oxides present in the sediments. Based on the rockmagnetic experiments, we identified magnetite, hematite, goethite, and possibly maghemite in changeable amounts along the profile, which allows us to complement the existing shortage in the literature on the palaeoenvironmental reconstruction of the site. We tentatively interpret the rockmagnetic changes recorded in the cave sediments in terms of glacial/interglacial conditions, furnishing the base for a better understanding for the formation conditions of this unprecedented archaeological site.

Thick sediments from foreland basins usually provide valuable information for understanding the relationships between mountain building, rock denudation, and sediment deposition. In this paper, we report environmental magnetic measurements performed on the Miocene sediments in the Subei Basin, northeastern Tibetan Plateau. Our results show two different patterns. First, the bulk susceptibility and SIRM, ARM, and HIRM mainly reflect the absolute-concentration of magnetic minerals; all have increased remarkably since 13.7 Ma, related to provenance change rather than climate change. Second, the ratios of IRM100mT/SIRM, IRM100mT/IRM30mT, and IRM100mT/IRM60mT, together with the redness and S ratio, reflect the relative-concentration of hematite, being climate-dependent. Their vertical changes correlate in general with the long-term Miocene climatic records of marine oxygen isotope variations, marked by the existence of higher ratios between 17 and 14 Ma. This may imply that global climate change, rather than uplift of the Tibetan Plateau, played a dominant role in the long-term climatic evolution of the Subei area from the early to middle Miocene.

Magnetic measurement was combined with geochemical analysis to investigate the trace metal pollution of atmospheric dustfall from rural areas of Inner Mongolia and urban regions of Hebei province in northern China. It is found that the type of magnetic mineral within atmospheric dustfall samples in Inner Mongolia is similar to those found in Hebei province, but the atmospheric dustfall samples in Inner Mongolia have lower magnetic mineral concentrations and finer particles. Linear multiple regression analyses show that the relationship between magnetic parameters and trace metals is found to vary between the contrasting rural and urban areas, and is controlled by the different source magnetic minerals. The concentration- and type-dependent magnetic properties of the particles correlated strongly with the concentrations of trace metals derived from natural processes, and the grain size-dependent magnetic parameters correlated negatively and significantly with the concentrations of trace metals derived from anthropogenic activities.

In this study, dustfall samples were systematically collected in various regions of Shanghai before and after the occurrence of COVID-19 in December 2019 and December 2020. The magnetic response, content and pollution status of relevant heavy metal elements in the samples were analyzed using environmental magnetism, geochemistry, scanning electron microscopy (SEM) and the enrichment factor (EF) method. The results show that the magnetic particles in the dustfall samples are mainly pseudo-single-domain (PSD) and multi-domain (MD) ferrimagnetic minerals, and Fe, Zn, Cr, and Cu are mainly concentrated in the districts with intensive human activities. Due to restrictions on human activities following the COVID-19 epidemic, both the values of magnetic parameters and the heavy metal pollution level in 2019 are more significant than those in 2020, which is consistent with the Air Quality Index (AQI) results. In addition, magnetic susceptibility (χlf), non-hysteresis remanence (χARM) and saturation isothermal remanence (SIRM) have different degrees of correlation with heavy metal elements, and the correlations with Fe, Pb, Cr and Zn are extremely prominent. The magnetic parameters can effectively and quickly reflect the level of particulate matter pollution, making them a useful tool for monitoring urban air quality.

Abstract The sedimentological, geochemical, physical and magnetic properties of 40 surface and basal sediment samples of box cores collected throughout the Canadian Arctic Archipelago (CAA) from the Canadian Beaufort Shelf to Lancaster Sound were analyzed to determine the sedimentary processes that operate within the CAA during the pre‐ and post‐industrial periods (i.e., before and after 1900 Common Era or CE). In addition, the chronology of seven selected regional cores was established using 210Pb measurements, where the base is dated between 1550 and 1820 CE. These cores provide an opportunity to robustly compare post‐1900 sedimentary conditions with those of the colder Little Ice Age period (LIA; ∼1500–1900 CE). The different properties combined with multivariate statistical analyses result in the identification of three regional provinces with distinct sedimentary characteristics: (a) the West province (Mackenzie Shelf/Slope, west Banks Island and M'Clure Strait) typified by detrital associations (Fe‐Rb‐Ti‐Zn), high organic matter inputs, dominance of magnetite and low‐coercivity minerals and high aluminosilicate contents; (b) the Intermediate Zone (Amundsen and Coronation gulfs) distinguished by Si‐Al‐Zr‐Sr‐K associations, Mn oxyhydroxides precipitation, constant high magnetic grain concentrations and a mixture between marine and terrigenous organic matter; and (c) the East Province (Queen Maud Gulf, Victoria and Barrow straits, and Lancaster and Eclipse sounds) described by high detrital carbonate inputs, marine organic matter, a dominance of high‐coercivity minerals and high magnetic concentrations in pre‐industrial samples. Our results confirm that the pre‐ and post‐industrial sedimentary dynamics are controlled by sediment supplies from the river discharges in the West and Intermediate provinces, whereas the East province is more influenced by sea ice and coastal erosion. Basal sediment samples from the seven 210Pb‐dated cores suggest an intensification of the Mackenzie, Coppermine, and Ellice rivers runoff, extensive sea‐ice cover and consequently sediment transport by the latter during the LIA period.

Abstract Magnetic detection and classification of magnetofossils have been proposed as potential tools for paleoenvironmental studies. Magnetosomes in bacterial species living in different environmental conditions exhibit different grain morphologies and chain configurations, which determine their magnetic properties. Recently, abundant magnetofossils have been reported from unfossiliferous pelagic red clay. However, little is known about their geometry and magnetic properties. Here we report very low coercivity biogenic magnetite in red clay from Ocean Drilling Program (ODP) Site 777 in the northern Mariana Basin. Analyzed sediment showed non‐interacting, stable single‐domain‐like magnetic behaviors. Acquisition of isothermal remanence was decomposed into five components, and a component with mean coercivity below 10 mT accounted for around 25 % of the remanence in some samples. Based on comparisons with semi‐quantitative transmission electron microscopy observations of magnetic extracts, this component appears to be carried by octahedral grains with size and shape very similar to biogenic magnetite in red clay from other sites. Micromagnetic calculations indicated that isolated maghemite octahedra may be responsible for the observed low coercivity component. Based on these results, we conclude that the low coercivity component represents non‐chained biogenic magnetite that has been oxidized to maghemite. The crystal morphology, geological setting, and lithology do not suggest unusual environmental conditions for ODP Site 777, so the relative amount of chained versus non‐chained grains may represent subtle environmental differences. We suggest that non‐chained magnetofossils may be widespread in deep‐sea sediments. Some methods could overlook the presence of non‐chained magnetite, affecting the identification and quantification of magnetofossils.

Abstract Sedimentary rocks of the Itararé Group, deposited during the Late Paleozoic Ice Age in the Paraná Basin of South America, were collected throughout the state of São Paulo, Brazil, for an anisotropy of magnetic susceptibility (AMS) and rock‐magnetic study. A recent paleomagnetic study conducted on the same samples had determined that these rocks were largely remagnetized during the Cretaceous; however, rock‐magnetic experiments demonstrate that the AMS is dominantly carried by paramagnetic minerals and therefore is unaffected by the secondary magnetic overprints. AMS data are analyzed in terms of their shape and orientation, and according to the relationship between the q‐value (magnetic lineation/foliation) and the imbrication angle (β) of the minimum susceptibility axes with respect to bedding (q–β diagram). Using multiple lines of evidence, we demonstrate that AMS records primary sedimentary fabrics that reflect the depositional environments and paleocurrent conditions in which these rocks were deposited. The magnetic fabrics consistently record a SE‐NW paleocurrent orientation, with dominant direction of transport to the NW throughout the entire state of São Paulo, in agreement with ice flow and sediment transport directions reported from limited numbers of sites possessing sedimentary structures and ice‐kinematic indicators.

The type-section of the Blackwater Draw Formation (BDF) consists of a series of five paleosol horizons developed on eolian deposits and an overlying surficial soil. Previous work has shown that magnetic properties (e.g., χ, ARM, and IRM) as a function of depth in this type-section, display both magnetically enhanced and magnetically depleted signals for different paleosols. To better understand the magnetic mineralogy responsible for these varying responses, various rock-magnetic experiments, scanning electron microscopy, and Mössbauer spectroscopy were conducted on representative samples from the six soil units which constitute the BDF type-section. Our results show that sub-micron hematite [with a minor contribution from single-domain sized hematite (Hc = ∼500 mT) dominates all the soils in terms of weight percent concentration. Whereas, low coercivity (Hc = ∼35 mT or less) magnetite/maghemitized-magnetite grains, largely in the PSD state (Mr/Ms=∼0.14 +/– 0.03588, Hcr/Hc=∼2.68 +/– 0.298789), dominate the magnetic signal. Magnetically depleted soils show a relatively higher proportion of goethite, while magnetically enhanced soils show an increased contribution from SP/SSD magnetite/maghemite phases.By combining our data-set with geochemically-derived climofunctions, we have correlated the magnetically preserved, depleted, and enhanced sections of the type-section to three distinct environmental phases (I-III). The basal sediments of Phase I displays relatively homogenous (neither enhanced nor depleted) magnetic properties due to relatively arid conditions and minimal alteration of southerly derive eolian sands. Conversely, Phase II-III represents a change in weathering intensities and provenance, resulting in a mix of southerly derived sands and northerly derived silts. Phase II, experienced greater precipitation levels, resulting in the dissolution of Fe-oxide phases and thus magnetic depletion. The uppermost Phase III experienced intermediate precipitation intensities resulting in magnetic enhancement.Using previously published age models we tentatively interpret these changing environmental conditions to be influenced by the Middle-Pleistocene Transition (1.2-0.7 Ma), where the Earth’s climatic cycles shifted from a ∼41 kyr to ∼100 kyr cycles. However, ambiguities persist due to uncertainties in the currently published age model. Due to the complexity of the magnetic signal, we recommend future studies utilize a holistic approach, incorporating rock-magnetic, geochemical, and microscopy observations for more accurate reconstruction of regional paleoenvironments.

Hematite concentration is an important climatic proxy for environmental (climatic) studies of soils and sediments. However, the accurate quantification of naturally occurring hematite has always been a difficult question, especially for those areas with lower hematite concentrations. Diffuse reflectance spectroscopy (DRS) is an effective method for hematite identification and quantification with lower detection limits. In this study, we synthesized a set of samples with well-determined concentrations to explore the exact detectable range of hematite and propose the most effective transfer function between the DRS proxy and hematite concentration. In addition, natural sediments from Inland Asia and the Western Pacific Ocean were used to further test the feasibility of the new transfer function. Results show that the lowest DRS detection limit for hematite could reach ~0.00078%, but is affected by the natural matrix. We also find that the second derivative of the Kubelka–Munk (K–M) function is monotonically correlated with the hematite concentration (0.00078%–100%), but ambiguities exist for the first derivative. Therefore, the second derivative of the K–M function is highly suggested for the hematite quantification, especially when concentration exhibits a wide range of variations. This study provides important references for the application of hematite proxy and promotes the popularization and development of the DRS method.

In mid-latitude Eurasia, loess-paleosol sequences (LPS) provide the most widespread sedimentary records of Quaternary paleoenvironmental evolution. In the Middle Danube Basin (MDB), these archives cover at least the last million years of climate history, and occasionally contain archeological findings. The studied Zemun LPS is located on the right bank of the Danube in Northern Serbia. The site was declared as a protected site, based on Paleolithic artifacts found on the riverbank and stemming from unknown stratigraphic levels of the loess cliffs exposed along the Danube. The present study aims to provide a stratigraphic, paleoenvironmental, and temporal context for the Zemun LPS by means of environmental magnetic and colorimetric methods. Our investigations result in a chronostratigraphic scheme allowing direct comparison with other well-established reference records in the MDB and elsewhere. Two potential tephra layers tentatively assigned to the so-called L2 and Bag tephras, which are both widespread in the MDB and beyond were investigated for their bulk magnetic properties. The resulting integrated age model suggests that the Zemun LPS records a detailed history of a quasi-continuous accumulation of mineral dust from Marine Oxygen Isotope Stage (MIS) 11–5a (c. 430–60 ka). The outcome of our integrative approach indicates a continuous aridification over the last four interglacial/glacial cycles and we discuss potential changes in seasonality over time.

We describe here a multiproxy dataset (grain size, environmental magnetism, stable carbon isotope, total nitrogen, and total organic carbon) generated on a ~116 cm long trench profile from the high altitude alpine Badnikund lake in the Central Himalaya. The dataset also includes environmental magnetic and organic geochemistry data on catchment soils of the Bednikund lake. The presented data is related to the research article “Middle Holocene Indian summer monsoon variability and its impact on cultural changes in the Indian subcontinent” [1]. The chronology of the Bednikund lake trench (BBK) profile is well established with seven AMS 14C dates. The multiproxy data is provided in tabular format in an excel file along with ages in Mendeley Data Repository. The multiproxy data can be significantly utilized for regional correlation of Indian summer monsoon (ISM) variability during the middle Holocene as well as for correlation of global climatic events. The data can also be reutilized in paleoclimate modelling for precipitation change over the past ~6000 years.

Fe-bearing minerals are a tiny fraction of the composition of speleothems. They have their origin in the karst system or are transported from the drainage basin into the cave. Recent studies on the magnetism of speleothems focused on the variations of their magnetic mineralogy in specific time intervals and are usually limited to a single sample. In this study, we describe a database of environmental magnetism parameters built from 22 stalagmites from different caves located in Brazil (South America) at different latitudes, comprising different climates and biomes. The magnetic signal observed in these stalagmites is dominated by low-coercivity minerals (∼20 mT) whose magnetic properties resemble those of the magnetite formed in pedogenic environments. Also, a comparison with few samples from soils and the carbonate from cave’s walls shows a good agreement of the magnetic properties of speleothems with those of soil samples, reinforcing previous suggestions that in (sub-)tropical regimes, the dominant magnetic phase in speleothems is associated with the soil above the cave. Spearman’s rank correlation points to a positive strong correlation between magnetic concentration parameters (mass-normalized magnetic susceptibility, natural remanent magnetization, anhysteretic remanent magnetization, and isothermal remanent magnetization). This implies that ultrafine ferrimagnetic minerals are the dominant phase in these (sub-)tropical karst systems, which extend across a diverse range of biomes. Although the samples are concentrated in the savannah biome (Cerrado) (∼70%), comparison with other biomes shows a higher concentration of magnetic minerals in speleothem underlying savannahs and lower concentration in those underlying moist broadleaf forests (Atlantic and Amazon biome) and dry forests (Caatinga). Thus, rainfall, biome, and epikarst dynamics play an important role in the concentration of magnetic minerals in speleothems in (sub-)tropical sites and indicate they can be an important target for paleoenvironmental research in cave systems.

At the Willendorf site Upper Paleolithic archeological layers associated to early Aurignacian cultures were found. The environmental conditions of the associated society, potentially co-existing with Neanderthal groups, is still not fully understood. Here, we report on environmental magnetic analyses including anisotropy of the magnetic susceptibility (AMS) carried out on loessic aeolian sediments at the Willendorf site. Data on lineation, foliation and the degree of anisotropy were used to assess depositional and post-depositional magnetic fabric properties and to deduce site-specific environmental processes. Overall, the loess is of aeolian origin and shows magnetic enhancement and magnetic fabric properties similar to those of other European loess geoarchives, but the magnetic mineralogy differs from many ‘dry’ loess sites, insofar as it shows a higher susceptibility during heating. We infer an enhanced neoformation of magnetite during heating due to the presence of organic matter. While at face value the AMS properties are indicative of pure aeolian loess consistent with previous studies, imbrication suggests post-depositional slope movement toward the Danube, which obscures inferences on palaeo-wind direction. It is well possible that these post-depositional magnetic fabric alterations occur at other localities with similar geomorphological settings.

Quantum diamond microscope (QDM) magnetic field imaging is a recently developed technique capable of mapping magnetic field sources in geologic samples at 1 micrometer resolution. Applying QDM imaging to speleothems can provide high‐resolution time series of detrital input into the cave environment, which, in turn, can yield useful paleoenvironmental information. Here we map the magnetic field over a speleothem from midwest Brazil over a 174 year timespan with annual to sub-annual resolution and perform backfield remanence acquisition experiments to quantify changes in the magnetic grain population through time. We find that magnetic particles occur in highly enriched layers of 10–100 µm thickness that sample the same detrital source population. Combined with petrographic observations and electron microprobe mapping of Mg and Ca, we conclude that detrital enrichment in our sample is caused by drier conditions leading to slow or halted speleothem growth. This interpretation is compatible with oxygen isotopic data and implies that speleothem magnetism can be used to infer the past occurrence of drought and potentially quantify their duration. Future high-resolution magnetic imaging of speleothems may provide additional insight into the mechanism of detrital enrichment and establish their role as a proxy for local moisture and infiltration.

Unambiguous magnetic mineral identification in sediments is a prerequisite for reconstructing paleomagnetic and paleoenvironmental information from environmental magnetic parameters. We studied a deep-sea surface sediment sample from the Clarion Fracture Zone region, central Pacific Ocean, by combining magnetic measurements and scanning and transmission electron microscopic analyses. Eight titanomagnetite and magnetite particle types are recognized based on comprehensive documentation of crystal morphology, size, spatial arrangements, and compositions, which are indicative of their corresponding origins. Type-1 particles are detrital titanomagnetites with micron- and submicron sizes and irregular and angular shapes. Type-2 and -3 particles are well-defined octahedral titanomagnetites with submicron and nanometer sizes, respectively, which are likely related to local hydrothermal and volcanic activity. Type-4 particles are nanometer-sized titanomagnetites hosted within silicates, while type-5 particles are typical dendrite-like titanomagnetites that likely resulted from exsolution within host silicates. Type-6 particles are single domain magnetite magnetofossils related to local magnetotactic bacterial activity. Type-7 particles are superparamagnetic magnetite aggregates, while Type-8 particles are defect-rich single crystals composed of many small regions. Electron microscopy and supervised magnetic unmixing reveal that type-1 to -5 titanomagnetite and magnetite particles are the dominant magnetic minerals. In contrast, the magnetic contribution of magnetite magnetofossils appears to be small. Our work demonstrates that incorporating electron microscopic data removes much of the ambiguity associated with magnetic mineralogical interpretations in traditional rock magnetic measurements.

Abstract We document magnetic mineral diagenesis with high‐resolution magnetic susceptibility, hysteresis, isothermal remanent magnetization, and other rock magnetic measurements through a shallow sulfate‐methane transition (SMT) at Perseverance Drift—a high‐accumulation rate Holocene biosiliceous Antarctic marine sediment deposit. The structure of the SMT is defined with porewater measurements from the same core, allowing direct comparison. Dissolution of the detrital (titano)magnetite assemblage, with preferential dissolution of stochiometric magnetite, occurs in the upper SMT. Higher coercivity magnetic minerals dissolve more slowly, continuing to dissolve through the entire SMT and could be a source of ferric iron for microbial respiration following exhaustion of porewater sulfate, as suggested by accumulation of porewater ferrous iron below the SMT. Superparamagnetic ferrimagnetic mineral enrichment/depletion occurs in three phases through the SMT and is coupled tightly to the availability of dissolved ferrous iron relative to dissolved sulfide. High concentrations of authigenic remanence‐bearing iron sulfides, including greigite and hexagonal 3C pyrrhotite, which can be detected using remanence parameters but not in‐field concentration dependent parameters, accumulate in a transient horizon at the base of the SMT during this early diagenesis, where sulfide is present but limited relative to dissolved ferrous iron. Formation of this remanence‐bearing iron sulfide horizon is likely facilitated by continued iron reduction through the SMT. Nonsteady state perturbations that shift the porewater profile, such as changes in carbon flux or sedimentation rate, can lead to preservation of these transient horizons, much like well documented preservation of manganese oxide layers in marine sediments following similar shifts to porewater profiles.

The paleowind direction in the Chinese Loess Plateau (CLP) was studied using anisotropy of magnetic susceptibility (AMS) data. Magnetic fabrics were examined for the last glacial loess (L1) and last inter-glacial paleosol (S1) in the southern and central CLP along a present day precipitation zone of 600 mm per year. Statistical analyses of AMS ellipsoid orientations indicate that strong rainwater events may cause random distributions in the maximum axis of the AMS azimuth, but with no deviation in the vertical plane for the average minimum axis. As high rainfall can distort paleowind determinations, it is challenging to conduct paleowind studies on the southern CLP - a topography with high precipitation density.

Abstract We test the use of magnetic measurements of evergreen needles as a proxy for particulate matter pollution in Salt Lake City, Utah. Measurements of saturation isothermal remanent magnetization indicate needle magnetization increases with increased air pollution. Needle magnetization shows a high degree of spatial variability with the largest increases in magnetization near roadways. Results from our magnetic measurements are corroborated by scanning electron microscopy of needle surfaces and by inductively coupled plasma mass spectrometry of metal concentrations in residues collected from sampled needles. Low‐temperature magnetic analysis suggests the presence of small (

Abstract In Northern France, land use is dominated by agriculture. Erosion by runoff results in heavy loss of fertile soil into surface waters. There is a need for cost‐effective tools to trace the sediment flux in catchments. This study highlights the potential of environmental magnetism to provide rapid non‐destructive parameters to characterize the spatiotemporal runoff versus bedload signal in a watershed. Between 2015 and 2017, within the Canche River watershed, several spatiotemporal sampling campaigns of suspended particulate matter (SPM) were undertaken and two distinct “snapshot campaigns” of flood events were conducted at key locations acquiring, in addition, hydrodynamical observations (discharge, turbidity, sediment load, etc.). Agricultural soils and SPM within the watershed have similar values for bulk magnetic concentration (isothermal remanent magnetization, IRM). The magnetic mineral assemblage of the SPM is dominated by soft ferromagnetic (sensu lato) minerals during low water conditions and is enriched in high‐coercivity phases during high water stages associated with rainfall events. Low‐temperature remanence experiments identified goethite and hematite as the high‐coercivity phases. IRM acquisition component analysis of the room temperature results quantify the relative input of high‐ versus low‐coercivity components focused on a given confluence site. Results from snapshot campaigns highlight the link between the enhanced runoff input of high‐coercivity particles during flood events and show that the S ratio parameter is an effective tool to trace erosion of topsoils.

Abstract Sedimentary archives of the westerlies‐influenced Pamir Plateau in Tajikistan, a climatically sensitive region in arid central Asia, provide information on past climatic changes and the tectonic evolution of the northern Tibetan Plateau. However, due to the scarcity of meteorological stations, knowledge of the recent precipitation history of the region is limited. We conducted a detailed rock magnetic investigation of 34 surface loess samples from the western Pamir Plateau. The results show that on the windward side, below an altitude of 2,000–2,200 m above sea level, the concentration of magnetic minerals initially decreases and then begins to increase with increasing altitude. Below 2,000–2,200 m above sea level, the surface soils are enriched in multidomain magnetite particles, suggesting a detrital origin of the magnetic minerals, whereas above this altitude the samples are enriched in fine superparamagnetic magnetite/maghemite grains of pedogenic origin. The inferred variations in pedogenic intensity, combined with analysis of the available meteorological data and the content of organic matter and clay, support the occurrence of an altitudinal threshold separating a predominantly detrital control on surface soil magnetic mineral assemblages from a predominantly pedogenic control. Within the plateau interior, the surface loess samples exhibit low and uniform values of magnetic concentration parameters and organic matter and clay content, which is attributed to the decreased supply of moisture from westerly sources because of the rain shadow effect. Our results indicate that rock magnetic investigations can be used to define a critical climatic boundary in arid central Asia.

Abstract Magnetic mineral inclusions in silicates are widespread in sediments as well as in igneous rocks. Because they are isolated from surrounding environment, they have potential to preserve original magnetic signature even in chemically altered sediments. Such inclusions may provide proxies to help differentiating the source of the host silicate. We measure magnetism of quartz and feldspars separated by chemical digestion of pelagic red clay. The samples are from the upper 15 m of sediments recovered at Integrated Ocean Drilling Program Site U1366 in the South Pacific Gyre. The quartz and feldspars account for 2.3–22.7 wt% of the samples. X-ray diffraction analyses detect both plagioclase feldspar and potassium feldspar. Plagioclase is albite-rich and abundant in the top ~ 7.4 m of the core. Potassium feldspar mainly occurs below ~ 10.4 m. The dominance of albite-rich plagioclase differs from a previous investigation of coarser fraction of sediments from the South Pacific. Saturation isothermal remanence (SIRM) intensities of the quartz and feldspars are 7.45 × 10−4 to 1.98 × 10−3 Am2/kg, accounting for less than 1.02% of the SIRM of the untreated bulk samples. The depth variations of the silicate mineralogy and the previously reported geochemical end-member contributions indicate that quartz and/or plagioclase above 8.26 m is likely to be Australian dust. In contrast, the relative abundance and the magnetic properties of quartz and feldspars vary below 10.42 m, without clear correlation with geochemical end-member contributions. We consider that these changes trace a subdivision of the volcanic component. Our results demonstrate that magnetism of inclusions can reveal additional information of mineral provenance, and chemical separation is an essential approach to reveal the environmental magnetic information carried by magnetic inclusions.

The physico-chemical characteristics of particulate matter (PM) in African cities remain poorly known due to scarcity of observation networks. Magnetic parameters of PM are robust proxies for the emissions of Fe-bearing particles. This study reports the first magnetic investigation of PM2.5 (PM with aerodynamic size below 2.5 μm) in Africa performed on weekly PM2.5 filters collected in Abidjan (Ivory Coast) and Cotonou (Benin) between 2015 and 2017. The magnetic mineralogy is dominated by magnetite-like low coercivity minerals. Mass normalized SIRM are 1.65 × 10−2 A m2 kg−1 and 2.28 × 10−2 A m2 kg−1 for Abidjan and Cotonou respectively. Hard coercivity material (S-ratio = 0.96 and MDF = 33 mT) is observed during the dry dusty season. Wood burning emits less iron oxides by PM2.5 mass when compared to traffic sources. PM2.5 magnetic granulometry has a narrow range regardless of the site or season. The excellent correlation between the site-averaged element carbon concentrations and SIRM suggests that PM2.5 magnetic parameters are linked to primary particulate emission from combustion sources.

A test site located along a 12-lane motorway east of Montpellier, France, is used to evaluate the potential of biomagnetic monitoring on traffic-related particulate matter (PM) to parametrize a computational fluid dynamics (CFD) simulation of the local airflow. Two configurations were established on the site with three vegetated flat-top earth berms of a basic design, and a fourth one was located windward to the traffic roofed with a 4-m-high precast concrete wall. As a first step, PM deposition simultaneously on plant leaves, on low-cost passive artificial filters, and on soils was estimated from proxies supplied by magnetic and X-ray fluorescence measurements on both sides of the motorway. These latter revealed that traffic-related pollutants are present on soils samples highlighted with a clear fingerprint of combustion residues, and wears of breaks, vehicles, and highway equipment. Maximum PM accumulations were detected in the lee of the berm–wall combination, while no significant deposition was observed on both sides of the flat-top earth berms. These results are in line with measurements from PM µ-sensors operated by the regional state-approved air quality agency. Finally, we compared the experimental measurements with the outcomes of a computational fluid dynamics (CFD) modeling based on the Reynolds-Averaged Navier–Stokes (RANS) equations that consider the traffic-induced momentum and turbulence. The CFD modeling matches the experimental results by predicting a recirculated flow in the near wake of the berm–wall combination that enhances the PM concentration, whereas the flat-top berm geometry does not alter the pollutants’ transport and indeed contributes to their atmospheric dispersion.

The main objective of this research was the determination of the geochemical and mineralogical properties of particulate matter: TSP (total suspended particles) and, especially PM1 (particles with aerodynamic diameter not greater than 1 µm) suspended in the air of a selected urban area in southern Poland. Identification of the emission sources of metals and metalloids bound in TSP and PM1 as well as the assessment of potential risk of urban ambient air to human health using hazard indices was an additional aim of this investigation. The daily TSP and PM1 quartz fiber filters collected during heating season were subjected to mass magnetic susceptibility (χ) measurements, SEM (Scanning Electron Microscopy) observations and geochemical analyses. Obtained results revealed that the concentration of TSP and PM1 well correlated with their mass-specific magnetic susceptibility. The good relationship between the PM concentration and χ suggests that magnetic susceptibility measurements can be a good proxy of low-level atmospheric dust pollution. The rank order of potentially toxic elements (PTE) based on average concentration was Ba > Zn > Al > Fe > Pb > Mn > Ti > Cu > Cr > Ni >As > Cd > V > Tl, both for TSP and PM1. PM1/TSP ratios for PTE concentrations and χ were around or slightly above unity, which indicated that PM1 was the main carrier of PTE (with the exception of cadmium, copper and lead) and technogenic magnetic particles. The non-carcinogenic and carcinogenic risks were confirmed by very high values of human health indices.

We used a novel approach of applying magnetic analyses to investigate the material released from the receding glacier Werenskioldbreen on Spitsbergen, Svalbard, Arctic Norway. Surface sediments were taken from the bay Nottinghambukta and the Werenskioldbreen foreland, along two main proglacial streams. Magnetic analyses, namely the low-field mass magnetic susceptibility, anhysteretic susceptibility mass normalized and hysteresis parameters, served to determine magnetic properties and identify the magnetic composition of the study material. We selected two distinct types of sediments. The first group, consisting of magnetite and pyrrhotite, has more single-domain grains in comparison to the second one, containing only magnetite. In the second group, multi-domain particles dominate. Deposits from the north stream, glacier river and an area close to the estuary of Nottinghambukta include magnetite and pyrrhotite. Magnetite was found in the south stream and in the outside part of the bay. Magnetic composition reflects different source rocks of sediments. This study demonstrates the utility of the magnetic method in analysing the current state of glacier environments.

Bulk magnetic properties of soils and sediments are often sensitive proxies for environmental change but commonly require interpretation in terms of the different sources of magnetic minerals (or components) that combine to generate them. Discrimination of different components in the bulk magnetic record is often attempted through endmember unmixing and/or high resolution measurements that can require intensive measurement plans, assume linear additivity, and sometimes have difficulty in discriminating a large number of sources. As an alternative, magnetic measurements can be made on isolated sediment fractions that constitute the bulk sample. When these types of measurements are taken, heterogeneity is frequently observed between the magnetic properties of different fractions, suggesting different magnetic components often associate with different physical grain sizes. Using a particle size-specific methodology, individual components can be isolated and studied and bulk magnetic properties can be linked to, and isolated from, sedimentological variations. Deconvolving sedimentary and magnetic variability in this way has strong potential for increased understanding of how magnetic fragments are carried in natural systems, how they vary with different source(s), and allows for a better assessment of the effect environmental variability has in driving bulk magnetic properties. However, despite these benefits, very few studies exploit the information they can provide. Here, I present an overview of the different sources of magnetic minerals, why they might associate with different sediment fractions, how bulk magnetic measurements have been used to understand the contribution of different components to the bulk magnetic record, and outline how particle size-specific magnetic measurements can assist in their better understanding. Advantages and disadvantages of this methodology, their role alongside bulk magnetic measurements, and potential future directions of research are also discussed.

Serious pollution of alluvial soils by a wide range of potentially toxic elements is usually observed in the valleys with mining and metallurgical industry. To outline areas of increased risk elements inputs, measurements of soil magnetic susceptibility can be used. This method is based on the measurement of the concentration of ferrimagnetic minerals of anthropogenic origin, mainly iron oxides, which are closely associated with risk elements such as heavy metals. The aim of this study is to examine the link between magnetic susceptibility of poorly drained Litavka River alluvial soils located in the mining/smelting region of Příbram (Czech Republic) and the observed high concentration of risk elements in soils. Surface volume magnetic susceptibility and the vertical distribution of magnetic susceptibility in soil profiles were measured in situ. On the basis of field measurements, selected parts of soil cores were sampled for a detailed magnetic and chemical analysis. Our results demonstrate a statistically significant correlation between magnetic susceptibility and soil concentration of Cu, Pb, and Zn. The magnetically enhanced soil layer, relatively low frequency-dependent susceptibility, presence of Verwey transition, and scanning electron microscope observations suggested a prevalence of coarse magnetite/maghemite, likely of anthropogenic origin. However, the magnetic properties in-situ also reflected the natural soil conditions and soil processes. The high content of organic matter, varying reductive/oxidative condition, and vertical migration of magnetic phases were the main factors influencing the observed magnetic susceptibility values.

Magnetic susceptibility (MS) is employed among others magnetic parameters to investigate pollution along a high traffic density road. In this study, MS field survey and magnetic laboratory analyses were applied to five sites along the Via Salaria road in the northern districts of Rome. Scanning electron microscope and energy dispersive spectroscopy analyses have also been employed to reveal the nature of Fe rich particles of anthropogenic origin. In general, the soil samples revealed to contain low coercivity minerals (e.g., magnetite) with different grain size, Fe-oxides occurring in various forms (spherules, aggregates, octahedral crystals and angular particles) are typically found close to the road side border at some of the analyzed sites. Magnetic minerals concentration in proximity of the road border resulted higher at sites with higher traffic volume and, in general, decreases with the distance from it. Evidences of anthropogenic material in topsoils were found within the first 5 m from the road border. The study confirms that the in situ measurements of the magnetic susceptibility are a valuable tool to rapidly investigate variations in the magnetic susceptibility profile related to anthropogenic contribution.

Environmental magnetic proxies were analyzed in a relatively monotonous, ~25.3m thick alluvial sedimentary sequence drilled in the Añavieja Basin (NE Spain). Results from the core AÑ2 suggest that the concentrationdependent magnetic parameters mainly reflect variations in the content of detrital magnetite, sourced in the catchment rocks and soils of the basin, via changes in the dynamics of alluvial fans due to temperature changes in the northern hemisphere during the Late Pleistocene. The correspondence between the magnetic proxies and the temperature variations in the North Atlantic region (NGRIP curve) indicates that higher (lower) concentrations and finer (coarser) magnetite grains coincide with warm (cold) periods. We propose that during cold periods, a sparser vegetation cover favored the incoming of higher energy runoff bearing coarser sediments to the basin that are relatively impoverished in magnetite. In contrast, during warm periods, the wider distribution of the vegetation cover associated with the lower runoff energy lead to finer, magnetite-richer sediment input to the basin. Maghemite, presumably of pedogenic origin, appears to be present also in the studied alluvial sediments. Further studies are necessary to unravel its palaeoclimatic significance.

We present the first rock magnetic study of archeologically-relevant chert samples from the Basque-Cantabrian basin (BCB) and surrounding regions, which was conducted in order to test the usefulness of non-destructive magnetic properties for assessing chert quality, distinguishing source areas, and identifying heated samples in the archeological record. Our results indicate that the studied BCB cherts are diamagnetic and have very low amounts of magnetic minerals. The only exception is the chert of Artxilondo, which has a mean positive magnetic susceptibility associated with larger concentrations of magnetic minerals. But even in this case, the magnetic susceptibility is within the lower range of other archeologically-relevant cherts elsewhere, which indicates that the studied BCB cherts can be considered as flint. The similar mean values for all magnetic properties, along with their associated large standard deviations, indicates that rock magnetic methods are of limited use for sourcing different types of flint except in some specific contexts involving the Artxilondo flint. With regards to the identification of chert heating in the archeological record, our results indicate only a minor magnetic enhancement of BCB natural flint samples upon heating, which we attribute to the low amount of non-silica impurities. In any case, the diamagnetic behavior of most BCB natural flints, along with the local use only of the Artxilondo type, suggests that any flint tool within the core of the BCB with positive magnetic susceptibility values is likely to have been subjected to heating for improving its knapping properties. Further studies are necessary to better identify the type, origin and grain size of magnetic minerals in BCB natural flints, and to apply non-destructive magnetic properties to flint tools in order to identify the use of heat treatment in the BCB archeological record.

The red-clay sequence on the Chinese Loess Plateau (CLP) was deposited during the late Miocene-Pliocene and is encoded with important information of past climate changes. However, it has received much less study in comparison to the overlying Pleistocene loess-paleosol sequence. In this paper, we review recent progress in characterizing the environmental magnetic parameter-based paleoclimate history recorded by the red-clay sequence. Several key conclusions are as follows. 1) the red clay and the loess-paleosol sequences have similar magnetic enhancement mechanisms but magnetic minerals in the red clay sequence have experienced a higher degree of oxidation than in the loess-paleosol sequence. 2) The CLP experienced a cooling and wetting trend from 4.5 to 2.7 Ma, caused by ice sheet expansion and East Asian summer monsoon intensification, respectively. 3) The above conclusions benefit from backfield remanence curve unmixing and comparison of magnetic grain size/concentration records, which are particularly useful in separating the temperature from the precipitation signal. A clear need in future studies is to explore the concentration and the grain size variations of hematite and goethite in the red-clay sequence and their formation mechanisms. The payback would be a clear understanding of climate history during the late Miocene-Pliocene, a possible analog for future warmer climate.

Recently, air pollution alerts were issued in the Metropolitan Area of Aburrá Valley (AVMA) due to the highest recorded levels of particulate matter (PM2.5 and PM10) ever measured. We propose a novel methodology based on magnetic parameters and an epiphytic biomonitor of air pollution in order to improve the air pollution monitoring network at low cost. This methodology relies on environmental magnetism along with chemical methods on 185 Tillandsia recurvata specimens collected along the valley (290 km2). The highest magnetic particle concentrations were found at the bottom of the valley, where most human activities are concentrated. Mass-specific magnetic susceptibility (χ) reaches mean (and s.d.) values of 93.5 (81.0) and 100.8 (64.9) × 10−8 m3 kg−1 in areas with high vehicular traffic and industrial activity, while lower χ values of 27.3 (21.0) × 10−8 m3 kg−1 were found at residential areas. Most magnetite particles are breathable in size (0.2–5 μm), and can host potentially toxic elements. The calculated pollution load index (PLI, based on potentially toxic elements) shows significant correlations with the concentration-dependent magnetic parameters (R = 0.88–0.93; p < 0.01), allowing us to validate the magnetic biomonitoring methodology in high-precipitation tropical cities and identify the most polluted areas in the AVMA.

We present a review of the magnetic properties of NE Saharan dust that was conducted, following a source-to-sink approach, to unravel the paleoclimatic significance of environmental magnetic records from Eastern Mediterranean marine sediments. Our synthesis indicates that pedogenic hematite, which formed during past wetter Green Sahara periods (GSPs), is the most common magnetic mineral in Eastern Mediterranean marine sediments as a result of its eolian transportation, along with smaller amounts of lithogenic hematite, from the NE Sahara. Coupled with the limited impact of reductive sedimentary diagenesis on hematite abundances in Eastern Mediterranean Sea sediments, this indicates that hematite concentrations provide reliable quantitative estimates of NE Saharan dust supply. Our results indicate that variations in NE Saharan dust supply record an on-off mechanism in which a key control on eolian input is provided by the monsoon-driven spread and retreat of savannah vegetation through the Sahara. Magnetite/maghemite is also a common magnetic mineral in NE Saharan dust, and also formed mainly pedogenically during GSPs but in much smaller amounts compared to hematite. Limited production of magnetite/maghemite in the source area during GSPs, along with the later imprint of diagenetic processes, indicates that magnetite/maghemite abundances cannot be used to estimate dust inputs from the NE Sahara. Goethite cannot be used either to estimate variations in NE Saharan dust supply, because its occurrence in Eastern Mediterranean marine sediments also appears to be linked to fluvial inputs. Our results reinforce the view that a source-to-sink approach should be routinely conducted in environmental magnetic studies to understand the complex combination of processes involved in the production, transportation, sedimentation and diagenetic evolution of magnetic minerals in sedimentary environments.

The use of mineral magnetic concentration parameters (χLF, χARM and SIRM) as a potential particle size proxy for soil samples collected from the Isle of Man (British Isles) is explored as an alternative means of normalizing particle size effects. Comparison of soil‐related analytical data by correlation analyses between each magnetic parameter and individual particle size classes (i.e. sand, silt and clay), more discrete intervals within classes (e.g. fine sand or medium silt) and cumulative size fractions (e.g. clay + fine silt) are reported. Both χLF and χARMparameters reveal significant (p