Magnetic Minerals Research Articles

Renewable Water Filtration Innovation From Palm Oil Mill Effluent Waste

Indonesia is the largest palm oil producing country in the world. According to data from the North Sumatra BPS in 2021, Palm Oil production was 5,311,884 tons. Every palm oil factory disposes of its liquid waste which results in waste pollution becoming a very crucial issue to be addressed immediately because it has many negative impacts. POME is rich in minerals and carbon, but POME waste is currently not fully utilized optimally. The purpose of this research is to produce the latest innovation in water filtration to realize SDGs 2045 on clean water and sanitation and to study the effectiveness of magnetic which will be applied as clean water filtration by utilizing POME waste and natural sand containing ?-Fe2O3, alumina (Al2O3) and magnetic minerals with well water as samples in this study. The combination of POME waste and natural sand with chemical synthesis and calcination methods at a temperature of 500oC as activation of activated carbon and magnetic metals. The results of the synthesis of POME and natural iron sand obtained solids in the form of black powder. In the VSM test, the magnetization versus magnetic field data of Fe3O4/activated carbon POME obtained a magnetic saturation value of 10.13 emu/g. In the XRD test results of activated carbon materials, composites of activated carbon iron oxide and iron oxide and the synthesis results have diffraction patterns similar to the XRD database from JCPDS and in the COD and BOD tests, it proves a decrease in COD and BOD levels in well water before and after filtration with a large range, this indicates the success of the filtration process. In the AAS test as an identification of Fe metal in well water samples, Fe metal becomes <0.00206 (mg/L) starting from 0.01 (mg/L).

Magnetic response and bioaccessibility of toxic metal pollution in outdoor dustfall in Shanghai, China

Toxic metal content testing, environmental magnetic monitoring and in vitro bioaccessibility experiments each have their own advantages and are often used independently for environmental monitoring, but there are few studies that combine the three to evaluate the hazards of toxic metals to humans. This paper investigated the total content, magnetic properties and bioaccessibility of nine potentially toxic metal elements (Zn, Sn, Pb, Cu, Fe, Ni, Cr, Sr, Mn) in dustfall from different functional zones in Shanghai, China, and systematically compared the related results. The results show that these nine metal elements have different degrees of contamination and enrichment in outdoor dustfall, and their content distribution shows the following trend: Zn>Sn>Pb>Cu>Fe>Ni>Cr>Sr>Mn. Magnetic characteristics χlf and SIRM are mostly positively correlated with the metal elements, indicating that the higher the content of magnetic minerals in the sample, the higher the concentration of metal elements. It was also found that χlf, SIRM, and χARM can well reflect the characteristics of dustfall pollution. The magnetic minerals have a certain degree of enrichment, and the particle size of the magnetic minerals is relatively coarse, mainly in the form of coarse multi-domain and pseudo-single-domain particles, which are largely derived from anthropogenic pollution. The χlf and PM10 concentrations in the precipitation show relatively similar spatial trends, so χlf, SIRM, and χARM can be used as air pollution indices to facilitate the evaluation of metal elements pollution in dustfall. The overall trend in gastric bioaccessibility is Pb>Zn>Mn>Cu>Cr. Due to the increase in the pH of digestive fluid, the bioavailability of toxic metals decreases significantly from the gastric stage to the intestinal stage. χlf, SIRM, and χARM/SIRM are all related to the bioaccessibility of toxic metals in the intestinal stage, so they can be used as toxicity indicators to evaluate the bioaccessibility of toxic metals in dustfall.

Provenance and sediment dispersal in Pearl River Estuary, southern China unraveled by magnetic properties

The Pearl River Estuary (PRE), with eight outlets supplied by multiple tributaries, is an excellent study area for reconstructing sediment provenance and transport pathways of a multi-sourced sediment-routing system. However, it less known the sediment source to sink dispersal model. This study aimed to estimate the PRE sediment budget by comparing the magnetic characteristics of estuarine surface sediments with those of all potential sources. In the bottom sediments of PRE and adjacent region, magnetic minerals, mainly magnetite and hematite, have a characteristic terrigenous signature. Source and sink comparison for magnetic parameters shows that the possible input of southwestern Taiwan rivers can be excluded, whereas the possibility of sediment contribution from nearby rivers, including Han, Rong, and Jiulong rivers, to the estuary could not be ruled out. Quantitative provenance analysis indicates that West River-sourced sediment dominates the western side of the estuary, the East River-sourced sediment is most important in the eastern side of the estuary, whereas sediment supplied by the North River is high only close to the outlets. A mixed-sediment contribution to the estuary is suggested, with a fluvial-dominated sediment input around the west river outlets and a tide-dominated sediment dispersal in the eastern side of the estuary. Overall, our study demonstrates the importance of fingerprinting changes in sediment supply using sediment magnetic properties and provides new insights into the PRE sediment-routing system.

A Northgrippian sedimentary magnetic enhancement along the western margin of India

Sedimentary magnetic records of shelf region contains complex environmental evolution information, necessitating records from various global regions to accurately interpret its significance. A sediment core (SSD-39/GC-01) retrieved from the eastern Arabian Sea was analyzed to elucidate the geologic and climatic controls on the sediment rock magnetic and grain size properties. We report the first record of high energy sediment deposits linked with intense monsoon phases, sea level variations, and extreme natural events during the Northgrippian period (8.27 ka to 4.20 ka). The compilation of magnetic susceptibility profiles of six sediment cores from the western margin of India revealed the presence of multiple sedimentary intervals of enhanced magnetic susceptibility and most likely reflect periods of high sedimentation events controlled by the regional geologic and climatic processes. We identified two anomalous sedimentary magnetic zones (Z-II, Z-IV) marked by an elevated magnetite content and sediment grain size, which reflect the periods of high-sedimentation events on the shelf off Goa. A shift in the magnetic mineral composition, clastic grain size, calcium carbonate, and organic carbon content at ~1.8 ka (Z-I) indicate a abrupt change in monsoon intensity. The elevated organic content within Z-I indicate efficient preservation of labile organic matter which survived oxidation due to rapid sediment deposition. End-member modeling of rock magnetic and grain size properties enabled us to discriminate and quantify the contributions of terrigenous fluxes and post-depositional mineral phases to the bulk magnetic mineral assemblage. We demonstrate that rapid scanning of magnetic susceptibility of sediment cores has the potential to precisely detect the periods of increased continental (magnetic flux) inputs into the marine shelf system. The proposed magnetic mineralogical approach has wider scope to constrain the understanding of how shelf sedimentation responded to past geological and climatic conditions globally.

Biomagnetic monitoring of the spatial distribution of atmospheric particulate matter in an industrialized city in Japan: Case study at Muroran

<p>Japan has 111 active volcanoes, supplying a great amount of magnetically-enhanced fly ashes. Such fly ashes likely mask anthropogenic magnetic signals; therefore, only a few magnetic biomonitoring studies have been reported in active volcanic regions, including Japan. The environmental magnetic results are reported for the materials deposited on Sasa Kurilensis, also known as dwarf bamboo, in the vicinity of the industrialized Muroran city center in Japan. The dust on the ten leaves at 105 sites was wiped off with a commercial wipe sheet, and their rock magnetic properties were analyzed. Room- and low-temperature magnetic analyses indicate that the major magnetic mineral in the dust is partially oxidized magnetite, ranging from single to pseudo single domain size, and the magnetic mineralogy on the leaves’ surface remains consistent throughout the study area. Much higher saturation isothermal remanent magnetization intensities are observed in the city’s eastern parts. The dominant wind directions in Muroran city are northwest, indicating that the steel companies in the city center are the major source of the fine-grained magnetic minerals on the dwarf bamboo leaves. These results indicate that using the leaves of dwarf bamboo for magnetic biomonitoring can be a non-destructive and rapid method to study the spatial distribution of atmospheric particulate matter from local industrial activities, even in active volcanic areas.<strong></strong></p>

Forensic-geology-based magnetic analysis of beach sediments from the Shimokita Peninsula, Japan.

The occurrences of various illegal activities on beaches require effective geological and environmental investigation methods. Among these methods, the room-temperature magnetic analysis of soils and sediments represents a nondestructive investigation method for various amounts, types, and grain sizes of magnetic minerals. Here, to verify the usefulness of magnetic analysis in forensic geology research, beach sediment samples from nine sites in the Shimokita Peninsula, Japan, were measured using magnetic analysis to determine the correlations between their concentration-dependent magnetic parameters and actual regional characteristics. The results revealed that the values of various parameters, namely the low-field magnetic susceptibility, anhysteretic remanent magnetization, and isothermal remanent magnetization (IRM), were relatively higher at sites near Ti and Fe sedimentary ore deposits. Further, thermomagnetometry results revealed that magnetite was the main magnetic carrier of the sediments. Moreover, pyrrhotite was detected around Ti-Fe mine sites. Furthermore, the results of the investigated parameters reflected the regional characteristics of the amount of magnetic minerals in the beach sediments. Low-temperature IRM curves and the magnetic grain size parameter also displayed sample-site-reflective characteristics. Thus, we believe that magnetic analysis represents an effective method for estimating the provenance of beach sediments in forensic geology research.

Field‐based estimation of cation exchange capacity using induced polarization methods

AbstractThis study investigates the potential of field‐based induced polarization (IP) methods to provide in‐situ estimates of soil cation exchange capacity (CEC). CEC influences the fate of nutrients and pollutants in the subsurface. However, estimates of CEC require sampling and laboratory analysis, which can be costly, especially at large scales. Induced polarization (IP) methods offer an alternative approach for CEC estimation. The sensitivity of IP measurements to the surface properties of geological materials ought to make them more appropriate than DC resistivity and electromagnetic induction methods, that are sensitive to bulk electrical properties . Such abilities of IP are well demonstrated in the laboratory; however, applications are lacking at field scales. In this work, the ability of field‐based IP to characterize the CEC of floodplain soils is assessed by implementing a methodology that allows for direct comparison between IP and soil parameters. In one field, soil polarization and CEC exhibited the expected positive correlation; but multi‐frequency measurements showed no clear advantage over single‐frequency measurements. In another field, coarser soils (with low CEC) exhibited a high polarization. These coarser soils were characterized by anomalous magnetic susceptibility values, and hence the polarization was attributed to the presence of magnetic minerals. Although better than order‐of‐magnitude estimates of CEC were possible in soils without substantial magnetic minerals, better characterization of porosity, saturation, cementation and saturation exponents, and pore fluid conductivity would improve predictions. However, the measurement of these parameters would require similar efforts as direct CEC measurements. This study contributes to bridging the gap between laboratory‐derived relationships and their applicability in field applications. Overall, this work provides valuable insight for future studies seeking to understand polarization mechanisms in soils at the field scale.

Magnetic Fabrics in Laminated Rocks of the Ilímaussaq Igneous Complex, Southern Greenland

ABSTRACT Nepheline syenites from the ∼1.2 Ga Ilímaussaq Complex of southern Greenland are examined to assess the utility of anisotropy of magnetic susceptibility (AMS) fabrics as proxies for silicate petrofabrics. Mineral lamination is a relatively common structural feature in cumulate rocks, including in the Ilímaussaq intrusion, but there is little consensus on the process (or processes) responsible for its formation. The Ilímaussaq AMS data are combined with rock magnetic experiments and electron backscatter diffraction (EBSD) measurements to characterize the magnetic mineralogy and compare the magnetic fabrics obtained to the silicate petrofabric. The data show that Na-amphibole (arfvedsonite) is most likely the dominant control on the AMS fabrics in the coarse-grained nepheline syenites (referred to as kakortokites), and that the AMS fabric is inverse relative to the observed silicate fabric. The EBSD data for a kakortokite sample suggests that the petrofabric is defined by arfvedsonite and is wholly planar, with evidence of only weak cross-lineation of c axes. The fine-grained nepheline syenites (lujavrites), two of which have a well-developed lamination carried by Na-pyroxene (aegirine), appear to have composite AMS fabrics that are considered to be a consequence of a mixed aegirine (normal) and arfvedsonite (inverse) response. The combined datasets shed light on the mechanisms of fabric acquisition in both lithologies. In the kakortokites, the AMS fabrics and silicate crystallographic preferred orientations, as well as the lack of observed microstructural evidence for subsolidus intra-crystal deformation, support models invoking gravitationally controlled crystal mats in the development of the macro-rhythmic layering of these rocks. In the lujavrites, the strong planar fabrics revealed by both the AMS and EBSD datasets, with some evidence of subsolidus deformation, point to fabric formation and perhaps even aegirine crystallization at the postcumulus stage. The combination of EBSD and AMS fabric datasets is a powerful means of deciphering the processes responsible for mineral alignment in igneous cumulates.

Paleomagnetic study of Tres Vírgenes Volcanic Complex, Baja California, Mexico

While the great majority of paleomagnetic studies come from Central Mexico (Trans Mexican Volcanic Belt), still few works are available from Baja California peninsula. Twelve lava and domes from the Tres Vírgenes Volcanic Complex were sampled, and 96 standard paleomagnetic cores were analyzed. Available isotope ages range from 22 ka to 300 ka. Magnetic mineralogy analysis indicates that titanium-poor titanomagnetite is the main carrier of remanent magnetization, although some sites also contain Ti-rich titanomagnetites commonly observed in recent volcanic eruptions. Nine of the studied lavas yielded normal polarity magnetization with site mean declination ranging D=349°−28.1° and inclination I=32.4°−55.4° as expected for the Bruhnes chron. Mean paleodirections show remarkable coincidence with previously reported data from the nearby San Quintín volcanic field. The scatter parameter of the virtual geomagnetic poles SB=15.1213.8716.60 agrees, under uncertainties, with the latitude-dependent G Model of paleosecular variation for the Bruhnes chron. Both Thellier double heating and Tsunakawa-Shaw absolute paleointensity methods were applied, however, the success rate was relatively low with 4 reliable values ranging from 21.46μTto56.4μT. One of the lava domes that we dated at 253 ± 24 ka using the U-Th systematics demonstrated the worldwide observed Calabrian Ridge 0 short-lived geomagnetic event.

Redox Sensitive Mineral Magnetic Signatures of Seafloor Massive Sulfide Deposits

AbstractSeafloor massive sulfide (SMS) deposits in different geological settings can have variable magnetic mineralogy, but the mechanism and implications of their spatiotemporal diversity are poorly understood. Based on seabed shallow drilling and surficial sampling of the Yuhuang hydrothermal field, Southwest Indian Ridge, we investigate here whether ubiquitous oxidative weathering affects the magnetic properties of SMS deposits. Microscopic observation and ferrous iron concentrations reveal that seafloor SMS deposits are extensively oxidized; subseafloor SMS deposits are relatively fresh, but oxidation initiates immediately after sample recovery. Negative frequency dependence of magnetic susceptibility likely due to measurement eddy currents is observed for fresh samples but not for oxidized ones, which suggests that oxidative weathering reduces the electromagnetic detectability of SMS deposits in geophysical investigations. Pyrrhotite (and probably other magnetic iron sulfide minerals), magnetite, and hematite are recognized as dominating magnetic (ferromagnetic, sensu lato) minerals in SMS deposits. Electron and quantum diamond microscope observations reveal pyrrhotite mineralization from high‐temperature reducing hydrothermal fluids, while iron‐oxides are mostly oxidation products of primary sulfides. Oxidative weathering modifies paleomagnetic records of SMS deposits. Bulk magnetic parameters vary systematically with enhanced oxidation degree. Temperature‐dependent magnetic measurements are useful tools for distinguishing the oxidation state of SMS deposits. Overall, these findings explain magnetic mineral variability in SMS deposits, linking mineral magnetic properties with seafloor geophysical investigations. Mineral magnetism can also be a redox state proxy for tracing natural and artificial environmental fluctuations in seafloor hydrothermal fields, inspiring novel interdisciplinary research to understand interactions in the dynamic Earth System.

Scanning Electron Microscopy and Magnetic Characterization of Iron Oxides in Suspended Sediments

<p class="Abstract"><span lang="EN-US">River sediment is the product of a sedimentation process in the river environment that originates from the weathering of bedrock or erosion processes, organic materials, particles, or anthropogenic substances. Previous research shows the magnetic mineral content in the sediments of the Citarum River and its tributaries. Suspended sediment was collected from the Citarum River and its tributaries in West Java, Indonesia, for mineralogical and granulometric analysis. The aim of this research is to distinguish between magnetic mineral sources, a scanning electron microscope equipped with energy dispersive X-ray spectroscopy (SEM-EDX), and rock magnetism. The hysteresis parameter verifies that the XRD measurement results show that the main magnetic minerals in suspended sediments are ferrimagnetic minerals such as magnetite (Fe<sub>3</sub>O<sub>4</sub>). According to the results of the SEM-EDX investigations, the magnetic granules in the Citarum River and its tributaries derive from two distinct sources: pedogenic and anthropogenic. The Citarum River and its tributaries’ magnetic granules are generally octahedral or angular in shape, with broken corners, indicating a pedogenic origin</span></p>

Environmental changes and historical occupation at Oued Laksar (Ksar Seghir), Morocco

Laksar is a small river near the village of Ksar Seghir, located between Tangier and Ceuta (Morocco), strategic points to control the Strait of Gibraltar over centuries. The river outlets at the western part of a sandy beach that can block the fluvial discharge in years of low precipitation/river flow.The area is densely occupied since the 5th century BC, during the roman period and Early Middle Age in the archaeological site of Dhar d’Aseqfane, located around 1 km from the mouth of the river. The coastal town of Ksar Seghir was founded on the eastern margin and was used as a shipyard for Moroccan dynasties after the 12th century. During the 15th and 16th centuries, Portugal occupied Ksar Seghir to control the Strait and to increase its power in North Africa. After the Portuguese left the site remained abandoned. The present-day Moroccan village developed in the 20th century, first expanding on the western river slope and gradually encompassing the archaeological site.This work aims to i) characterize the environmental evolution of the Laksar River; ii) identify potential records of extreme events such as floods or tsunamis; and iii) explore the relationship between the landscape dynamics and human occupation.To achieve these goals, a ∼5.4 m long sediment core - KS1 - was studied applying high-resolution multiproxy analyses (X-Ray, magnetic susceptibility, sedimentology, organic chemistry and micropalaeontology) together with 14C dating to establish a chronological model.The sedimentary sequence corresponds to intercalations of fine sand and mud. Results point to deposition in subtidal conditions between the core base (ca. 2500 cal BP) and the 15th century AD (388 cm below surface). The dominance of marine foraminifera assemblages with high number of juveniles and high diversity index suggests an environment under open marine conditions during this period. Conversely, the low δ13C values, coupled with the presence of charophytes and Cretaceous, Paleogene and Neogene reworked calcareous nannofossils reflect the contribution of fluvial processes. The sedimentary record underscores fluctuations in fluvial discharge, beach morphology and marine influence. The accumulation of magnetic (heavy) minerals at the core base is the likely result of at least one high-energy event.Following the onset of Portuguese occupation of Ksar Seghir (15th century), the sedimentation rate increases, silting-up the channel margins. Deposition occurs under low subtidal to intertidal conditions. Foraminifera assemblages point to a low salinity environment; coarse materials are mostly constituted by minerogenic particles transported by the fluvial network. Changes in the sedimentary succession (heavy-minerals accumulation, higher marine influence and rip-up clasts) were detected between 219 cm and 140 cm depth below surface that, according to the age-model, overlap temporally with the Lisbon 1755 AD tsunami event (Great Lisbon earthquake).

Astronomical Calibration of the Ocean Anoxic Event 1b and Its Implications for the Cause of Mid‐Cretaceous Events: A Multiproxy Record

AbstractThe timing and duration of oceanic disturbances linked to Oceanic Anoxic Event (OAE) 1b, as well as the mechanisms driving anoxia and carbon burial during this period, remain subjects of debate. We conducted cyclostratigraphic analyses on magnetic susceptibility (MS) and elemental Ti and Fe series within the upper Aptian‐lower Albian interval of the Poggio le Guaine core in the Umbria‐Marche Basin, Italy. This interval provides a detailed sedimentary record, supported by variations in magnetic mineral content, Ti, Fe, and significant global shifts in the δ13C curve. Orbital control of MS, Ti, and Fe suggests a duration of 2.84 Myr for the OAE 1b event. Our chronostratigraphic analysis reveals ages of 114.07 ± 0.12 Ma for 113/Jacob, 113.28 ± 0.12 Ma for Kilian, 112.49 ± 0.12 Ma for the central age of the Monte Nerone cluster, 111.70 ± 0.12 Ma for Urbino, and 111.28 ± 0.12 Ma for Leenhardt sub‐events. Stable δ13C chemostratigraphy correlations enable the transfer of tiepoints across various sedimentary basins. Key features of the carbon isotope curves were identified, named, and dated using astrochronology. Our findings suggest that the organic‐rich layers associated with the OAE 1b event exhibit distinct characteristics influenced by several factors, including a warm climate driven by volcanic CO2 emissions, heightened precipitation, intense weathering, and marine transgressions. These factors amplify orbital forcings on paleoclimate changes, leading to oceanic‐atmospheric disturbances that promote deoxygenation and carbon burial during OAE 1b.

Petrophysical cobalt exploration indicators in Kuusamo, northern Finland

The increasing global demand for cobalt, a critical green transition metal, encourages the development of improved exploration workflows, as Co typically occurs as a by-product of other metals, and the exploration and processing methods are rarely optimised for it. This paper investigates the possibility of extracting geophysical cobalt exploration indicators from petrophysical properties in Kuusamo, one of the most prominent cobalt-enriched areas in the largest European Co producer, Finland. The study region hosts 20 Au–Co deposits and occurrences classified as orogenic gold deposits with atypical metal association. Two separate mineralization stages have been distinguished: a pyrrhotite-dominated Co-stage and a pyrite-dominated Au–Co stage. The assumption in this study was that Co-enriched samples could be distinguished from Au-enriched samples and host rocks in petrophysical data due to the mineral associations. The investigation used an extensive previously acquired petrophysical and geochemical drill hole dataset from six targets complemented with new thermomagnetic data for magnetic mineral phase detection. The samples were divided into ore classes for the petrophysical data analysis. The results indicate that cobalt’s association with monoclinic pyrrhotite is a key factor for geophysical applications: the high remanent magnetisation characteristic of monoclinic pyrrhotite suggests that Co-enriched ores should typically associate with magnetic anomaly sources. Co enrichment is also related to higher electrical conductivities in comparison to Au. The workflow applied in this study illustrates how key petrophysical parameters can be connected with ore-bearing minerals and rocks, and the results indicate how cobalt could be explored more directly and effectively in the study area.

Magnetic Mineral Dissolution in Heqing Core Lacustrine Sediments and Its Paleoenvironment Significance

The magnetic parameters within lacustrine sediments serve as invaluable proxies for deciphering the paleoenvironmental and paleoclimatic conditions. However, the dissolution of magnetic minerals can significantly alter detrital magnetic mineral assemblages, thereby complicating their interpretation in paleoenvironmental reconstructions. In an effort to clarify the impact of this dissolution on the grain size of magnetic minerals in lacustrine sediments, we undertook a thorough analysis of the rock magnetic properties on samples from the interval characterized by low ARM (anhysteretic remanent magnetization)/SIRM (saturation isothermal remanent magnetization) values between 140 and 320 ka in the Heqing (HQ) lacustrine drill core, located in Southwest China. Temperature-dependent magnetic susceptibility and FORC diagrams revealed a predominance of single-vortex and pseudo-single domain (PSD) magnetite and maghemite within the sample. When compared to samples from both the glacial and interglacial periods, the high SIRM, elevated magnetic susceptibility, and low ARM/SIRM ratio intervals from 140 to 320 ka suggested a high concentration of magnetic minerals coupled with a relatively low concentration of fine-grained particles in the sediments. The reductive dissolution of the fine-grained magnetic oxides is responsible for the reduction in the fine-grained magnetic particles in this interval. Our findings indicate that pedogenic fine-grained magnetite and maghemite are the first to dissolve, followed by the dissolution of coarser-grained iron oxides into finer particles. This process underscores the complex interplay between magnetic mineral dissolution and grain size distribution in lacustrine sediments, with significant implications for the reliability of paleoenvironmental interpretations derived from magnetic parameters.

Manipulating three-dimensional magnetic particles motion in a rotating magnetic field

The application of rotating magnetic field can reduce the effect of agglomeration of fine-grained strong magnetic minerals in the sorting process. In this study, a three-dimensional finite element model of two spherical magnetic particles agglomerated in a rotating magnetic field is established, and a rotating magnetic field is constructed using a quadrupole magnet to verify the simulation results. The results show that the numerical simulation results can predict the experimental results more accurately, and the trajectories of the magnetic particles in the agglomeration process are centrosymmetric spiral curves. The utilization of the rotating magnetic field as well as increasing the rotating magnetic field speed, magnetic field strength, and the initial spacing of the magnetic particles will enhance the tendency of the magnetic particles to get rid of the agglomeration.

Calibrating lower-middle Miocene mammal faunas and unravelling climate change during the Miocene Climate Optimum: the Bardenas Reales de Navarra record (Ebro basin, NE Iberian Peninsula)

AbstractThe chronology of lower Miocene Iberian small mammal faunas is still poorly constrained given the scarcity of well dated sedimentary successions including small mammal fossil localities. Such scarcity has prevented also an accurate understanding of the response of European terrestrial ecosystem to global changes across the Miocene climate optimum (MCO), one of the best analogues of present-day global warming. Here we present an updated fossil small mammal record of the Bardenas Reales de Navarra (western Ebro basin, Spain), where an expanded lower to middle Miocene continental succession is superbly exposed. Previous and new magnetostratigraphic results from this succession have enabled us to propose, along with additional magnetostratigraphically-dated Iberian faunas, a new chronology for local zones Y to D (Mammal Neogene zones MN2 to MN5). In addition to that, the studied small mammal faunas point to a gradual increase in temperature and humidity conditions in SW Europe between 20 and 15.5 Ma, which appears to be coupled with the progressive shift towards warmer regional (Atlantic) and global conditions across the MCO, thereby pointing to gradual changes in oceanic circulation as the main driver of this period of global warmth. The evolution of sedimentary facies appears to indicate a threshold response of the Ebro basin hydrological balance to the MCO, whereas pedogenic formation of magnetic minerals seems to be linked to periods of enhanced climate variability. These results highlight the need of combining different paleoenvironmental indicators in order to obtain a reliable view of the response of continental ecosystems to global warming.

First Late Cambrian Paleomagnetic Results From the Oulongbuluke Terrane, Northern Tibetan Plateau: Implications for the Paleogeography of the Proto‐Tethys Ocean

AbstractThe Early Paleozoic paleolatitudinal position of the terranes in the northern Tibetan Plateau is the key to unraveling the evolution of the Proto‐Tethys Ocean. We present the first Late Cambrian paleomagnetic results from the Oulongbuluke terrane (OT), in the northern Tibetan Plateau. The mean paleomagnetic direction for 16 sites is Ds = 196.2°, Is = −36.9° with κs = 31.5, α95 = 6.7°, corresponding to a paleopole at 68.2°S/51.9°E with dp/dm = 4.6°/7.8°. Rock magnetic and petrologic analyses demonstrate the primary origin of the magnetic mineralogy. This paleomagnetic result defines the Late Cambrian paleolatitude of the OT as 20.6 ± 4.6°S (reference point: 37.2°N/96.6°E). Combined paleomagnetic and geological evidence suggests that the terranes in the northern Tibetan Plateau were located to the northwest of the Indian plate of Gondwana during the Late Cambrian.

Mid to late Holocene Indian monsoon variability, aridification and civilization changes in the Deccan Plateau, India

Climate change has been a key driver throughout human history and has frequently been associated with the rise and fall of civilizations. Holocene settlement changes or population displacements were almost always preceded by changes in climate. A high-resolution sedimentary record from the western Bay of Bengal offers insights to centennial-scale mid- to late-Holocene Indian summer monsoon (ISM) variability and its role in the decline of chalcolithic human settlements on India's Deccan Plateau. Increased erosion in the Indian peninsula during the mid- to late-Holocene, due to aridification and agricultural expansion, is evidenced by higher sedimentation, more magnetic mineral content, coarser magnetic grain size, and increased sand content. The results from mineral magnetic and textural analyses reveal centennial-scale abrupt weak ISM during the Bond events in the core monsoon zone of India. The Deccan Chalcolithic civilizations flourished between ∼4.0–3.0 ka BP owing to the favorable climatic conditions, but most of the settlements were deserted after ∼3.0 ka BP. We argue that the abrupt weakening of ISM during Bond event 2 (∼3.1–2.8 ka BP) caused this collapse of Deccan Chalcolithic. The results from this study together with the published records of number of settlements and summed radiocarbon dates suggest a climate-culture link in the Deccan Plateau. The weak ISM periods in this study are coherent with the records of total solar irradiance and the percentage of hematite-stained grains from the North Atlantic and suggest solar control on these abrupt climatic events.

Susceptibility and Metallics Elements in Soil Struck by Lightning in West Kotawaringin Regency, Central Kalimantan

Abstract Magnetic susceptibility is a magnetic parameter that assesses a magnetic material’s susceptibility to external magnetic fields. Magnetic susceptibility values can determine the properties of magnetic minerals related to the elements they contain. This research aims to determine the value of magnetic susceptibility and metal element content in soil struck by lightning in West Kotawaringin Regency. Sample measurements were performed using the Bartington MS2B instrument to determine the magnetic susceptibility value and XRF (X-ray fluorescence) to determine the metal element content in the soil samples. The magnetic susceptibility value obtained for sample A with low frequency (<10 strikes per month) was 26.1 x 10−8 m 3/kg; for sample B with medium frequency (11–200 strikes per month), it was 538.4 x 10−8 m 3/kg; and for sample C with high frequency (>20 strikes per month), it was 24.4 x 10−8 m 3/kg. Fe (388,000 mg/kg) was the most prevalent metal element in samples B and C, while element V (300 mg/kg) was the least prevalent in sample A. The sample with the highest metal element content was Fe (388,0 mg/kg), while sample A had the lowest metal element content, V (300 mg/kg). The highest correlation value between magnetic susceptibility and metals is 0.9 (K); 0.96 (Cr); 0.98 (Fe); and 1.00 (Ca, Ni, Zn, and Re).