Orals: Wed, 6 May, 16:15–18:00 | Room -2.31
In recent years, there have been reports suggesting the possibility of the West Pacific Anomaly existing in East Asia during the 16th century. To verify whether the anomaly existed in other ages, reliable archeomagnetic intensity (archeointensity) measurements from fired archeological materials in East Asia are necessary. Therefore, we conducted a study on archeointensity and rock magnetism using several Japanese pottery fragments from the Yayoi period, which were made in three stages. Thermomagnetic analysis revealed that the induced magnetization curve in air was more reversible than that in vacuum. Based on these results, we conducted the Tsunakawa-Shaw method with heating in air. As a result, we obtained archeointensities from 18 out of 20 specimens belonging to 4 out of 6 pottery fragments, which were made in three stages. When the average values of the three stages are arranged in chronological order, from 250 BCE to 50 BCE, the archeointensity remained nearly constant at 39.4 ± 4.2 µT to 38.6 ± 5.0 µT, and from 50 BCE to 50 CE, an increase in archeointensity was observed, from 38.6 ± 5.0 µT to 46.8 ± 2.0 µT. We constructed a reference curve from -530 CE to 1725 CE using a total of 30 archeointensity data from the present study and recent studies in Japan and South Korea. In this reference curve, two minima and two maxima were observed. Among these, we newly discovered a minimum around 150 BCE. The time intervals between the minimum and minimum, as well as between the maximum and maximum, were both approximately 900 years. Besides, this suggests the possibility that the West Pacific Anomaly occurred in East Asia at approximately 900-year intervals. This indicates that the reversed flux patch that causes the West Pacific Anomaly may recur at intervals of ~900 years at the core-mantle boundary near East Asia. The characteristic time-interval of approximately 900 years is similar to the recurrence time-interval of the South Atlantic Anomaly, which implies that the common cause (e.g., planetary gyre) may modulate both anomalies.
How to cite: Yoshimura, Y., Ahn, H.-S., Kato, C., Yamamoto, Y., Anai, C., Tajiri, Y., Hatakeyama, T., and Ohno, M.: Regional archeointensity curve from 600 BCE to 1700 CE for East Asia and possible recurrence of the weak field intensity, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2876, https://doi.org/10.5194/egusphere-egu26-2876, 2026.
Reliable paleointensity estimates are crucial for understanding past behavior of the Earth’s magnetic field but remain difficult to obtain using traditional methods. Conventional thermal Thellier paleointensity experiments often have low success rates for volcanic samples, as repeated heating can induce alteration. Heating can be avoided by using the pseudo-Thellier method, in which samples are magnetized using alternating fields. However, pseudo-Thellier experiments intrinsically yield only relative paleointensities.
Over the past years, several attempts have been made to calibrate pseudo-Thellier results to absolute paleointensities for lavas by relating laboratory-induced anhysteretic remanent magnetizations (ARMs) to the thermally acquired natural remanent magnetizations (NRMs). Because magnetization depends on factors such as magnetic grain size, shape, and minerology, simple linear models struggle to consistently predict paleointensities across varied datasets.
Here, we present LAVA (Learning Absolute paleointensities from Volcanic ARMs), a machine learning approach that predicts absolute paleointensities from pseudo-Thellier data. Machine learning methods are well suited to model highly non-linear and complex relationships between ARM and NRM. LAVA was calibrated and tested using two datasets: a synthetic laboratory-induced datasets and a dataset of recently cooled volcanic products from diverse volcanic settings and geographic locations whose natural remanent magnetizations span the full range of observed geomagnetic field strengths. LAVA outperforms existing pseudo-Thellier interpretation techniques, by predicting the paleointensity for every volcanic site in the natural dataset within 5.6 μT and with an average error of 1.3 μT. These results demonstrate that LAVA provides a robust new tool for recovering absolute paleointensities from volcanic rocks.
How to cite: van Grinsven, L., van der Molen, D., de Groot, B. M., Langelaar, S., and de Groot, L. V.: LAVA: A machine learning method for predicting absolute paleointensities from pseudo-Thellier data , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11884, https://doi.org/10.5194/egusphere-egu26-11884, 2026.
A robust reconstruction of geomagnetic field intensity requires careful evaluation of spatial sampling strategies and latitude reduction methods, especially in regions strongly influenced by non-dipolar field components. In this work, we systematically investigate the statistical stability and spatial and temporal sensitivity of regional geomagnetic intensity estimates as a function of three fundamental variables: the radius of the spatial region used to represent a point of interest, the number of sites sampled within the region of interest and the number of independent site samples. Using the global geomagnetic field models CHAOS-8.1 and COV-OBS.x2, we simulated controlled statistical experiments in which field intensity values are randomly sampled in circular regions centered on previously defined locations of interest. Five locations were analyzed, including two fixed points (Paris and São Paulo cities) and three time-varying reference points associated with the minimum, maximum and average values of the paleosecular variation index (Pi). The statistical performance of the regional estimates was quantified using the normalized root-mean-square (RMS) error, calculated relative to the local reference intensity at a specific epoch. Five approaches were tested: (i) without latitude correction; (ii) latitude correction considering only the axial dipole term (g10); (iii) latitude correction including the axial dipole and quadrupole terms (g10 + g20); (iv) latitude correction including axial dipole, quadrupole and octupole terms (g10 + g20 + g30); and (v) the eccentric dipole (ED) approximation. Our results show that the sampling radius is the dominant parameter in controlling the error. The effectiveness of the latitude corrections strongly depends on the region and epoch analyzed. Axial latitude corrections perform better in contexts close to a dipolar configuration, while no latitude correction or ED approach are more effective in regions dominated by non-dipolar contributions, such as the South Atlantic Anomaly (SAA).
How to cite: Marum, V., Hartmann, G., Terra-Nova, F., Amit, H., Yue, Y., Puente-Borque, M., and Trindade, R.: Testing the Geomagnetic Axial Dipole hypothesis at the South Atlantic Anomaly region, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13078, https://doi.org/10.5194/egusphere-egu26-13078, 2026.
The South Atlantic Anomaly (SAA) is the most prominent low-intensity feature of the modern geomagnetic field. Its origin is debated between hypotheses invoking (i) a deep-mantle controlled flux system beneath southern Africa at the edge of the African Large Low-Shear Velocity Province (LLSVP), and (ii) models proposing an eastward origin in the Indian Ocean followed by westward migration into the South Atlantic. Discriminating between these scenarios requires well-dated Southern Hemisphere paleomagnetic records, which remain sparse.
Here, we present new full-vector paleomagnetic data from volcanic products on Réunion Island and Bali (Indonesia), providing constraints on Holocene field behavior on both sides of the Indian Ocean. At Réunion, Bayesian paleosecular-variation curves based on our new data reveal a pronounced intensity maximum around ~1400 CE followed by a sharp decline to ~29 µT at ~1550 CE. This high-to-low transition indicates that Réunion did not experience persistent low fields prior to the devolpment of the SAA. This is inconsistent with models proposing an origin under the Indian Ocean and an east-to-west migration from there. Instead, the Réunion record documents the onset of low-field behavior only after ~1400 CE, in agreement with the hypothesis that the SAA originated below, or slightly to the east of the African continent and is probably linked to the presence of the African LLSVP.
The Indonesian paleointensity records from Bali reveal earlier low-intensity episodes (~1000–1300 CE), but these are temporally disconnected from the Réunion minimum and are best interpreted as expressions of independent or recurrent (West) Pacific or Indian Ocean anomalies rather than precursors of the SAA. Together, the data indicate that while low-field patches may likely recur in the Indian Ocean realm, the modern SAA originated beneath southern Africa and moved westwards from its point of inception. These results support a top-down control on the geodynamo driving the occurence of the SAA and provide new data to create the next-generation geomagnetic field models optimized to track the origin, and. evolution of the South Atlantic Anomaly through time.
How to cite: de Groot, L., Meyer, R., Pratama, A., Fadillah, A., and van Grinsven, L.: Full-vector Holocene records from Réunion and Bali constrain the origin of the South Atlantic Anomaly, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17232, https://doi.org/10.5194/egusphere-egu26-17232, 2026.
Sediment cores recovered from the Playa Adamito Grande (PAG) claypan in the hyperarid core of the Atacama Desert (Chile) show a sequence of three main lithological units. Here we focus on the lowest unit, which was found below 29.2 m to the bottom of the core at a depth of 52 m. The silty-clayey sediment is frequently interspersed with gypsum-rich layers and is interpreted as a palaeo-lake deposit. At the top of this unit an erosion unconformity was identified at ca. 29.5 m depth. Two U/Pb zircon ages obtained from tephra layers provide chronological data at 31.49 m (16.27 ± 0.09 Ma) and 29.22 m (15.54 ± 0.03 Ma) sediment depth. Below, none of the various dating methods employed yielded results. The timing and duration of the lake phase in the Atacama, were therefore attempted to be determined more precisely using magnetic polarity stratigraphy. The mineral magnetic association is composed of partially maghemised magnetite and Ti-magnetite in domain states that allow for retention of the magnetic signal over long geological time scales. However, the sediment sequence mainly exhibits normal polarity, interrupted only by thin layers with reversed polarity. Therefore, it is not readily possible to specify age constraints for the lake phase by correlation with the geomagnetic polarity time scale (GPTS). Some of the layers with reversed polarity coincide with layers rich in gypsum. Therefore, we discuss the nature of these short-lived reversed sections, considering possible post-depositional overprinting of the magnetic signal or the occurrence of hiatuses. However, our considerations show that the palaeomagnetic signal most likely represents a high-resolution record of field instabilities during the Miocene. This interesting case study thus provides new evidence for the occurrence of geomagnetic excursions during the Subchron C5Cn.1n (Middle Miocene).
How to cite: Scheidt, S., Wennrich, V., Albert, R., Leicher, N., Hasberg, A., McLin, S. D., Diederich-Leicher, J. J., Zeeden, C., and Melles, M.: Interpretation of palaeomagnetic signals from palaeo-lake sediments of the Atacama (Chile) – evidence of geomagnetic excursions in C5Cn.1n?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21857, https://doi.org/10.5194/egusphere-egu26-21857, 2026.
The paleomagnetic record from sedimentary rocks is often ambiguous, limiting the recovery of reliable paleomagnetic data, particularly when compared to paleomagnetic data obtained from igneous rocks. We explore the potential of a novel type of paleomagnetic recorder in sedimentary rocks: fossil micrometeorites. Micrometeorites (MM) are small cosmic particles (50 μm-2mm) which account for a significant portion of the approximately 40,000 tons of extraterrestrial material that arrives on Earth annually. Many MMs melt during atmospheric entry, at altitudes of 80-90 km and transform into cosmic spherules (CS). CS have long been recognised as magnetic and can be extracted from sedimentary rocks. During melting and formation of CS, MM oxidise and form new minerals, particularly wüstite and magnetite. Subsequently, the cosmic spherules quench within a few seconds. This rapid cooling through the Curie temperature leads to the formation of thermoremanent magnetisations within CS. Diagnostic features such as metal beads and vesicles inside a proportion of CS make it possible to determine their flight trajectory, which can be combined with the magnetisation to reconstruct the polarity of EMF. While modern CS from Antarctica have already been shown to be good recorders of the geomagnetic field1, the deep-time paleomagnetic records of CS remain unexplored. We present the results of a paleomagnetic study of anthropogenic magnetite spherules that resemble iron-type (I-type) CS, as well as several Paleozoic I-type CS. We demonstrate that individual spherules are measurable using existing paleomagnetic methods and equipment, while computed tomography (NanoCT) scanning enabled reliable reconstruction of the fall trajectory of a Paleozoic CS. We show that fossil CS with sizes of 50-300 μm are a promising, novel class of paleomagnetic recorder, accessible with existing techniques and capable of opening a new window on the ancient geomagnetic field.
1Suavet, C., Gattacceca, J., Rochette, P. & Folco, L. Constraining the terrestrial age of micrometeorites using their record of the Earth’s magnetic field polarity. Geology 39, 123–126 (2011).
How to cite: van der Boon, A., de Boer, R., de Groot, B., Nakrem, H. A., Krämer Ruggiu, L., Goderis, S., and de Groot, L.: A promising novel recorder of Earth’s ancient magnetic field: fossil micrometeorites as paleomagnetic archives, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18433, https://doi.org/10.5194/egusphere-egu26-18433, 2026.
Paleomagnetic studies of marine sediments often assume that the remanence acquisition process occurs via torque from the Earth's magnetic field called a depositional remanent magnetization (DRM), which implies that paleomagnetic recording is time-transgressive. However, magnetic minerals can also grow authigenically in the sediment, leading to a chemical remanent magnetization (CRM), which is not necessarily time-transgressive. Not only are the physics of the DRM and CRM acquisition processes different, but their remanence lock-in times are likely non-contemporaneous, potentially leading to misinterpretations of the magnetic signal. The question arises how to distinguish the two? The hallmark of a detrital remanence can be expressed by the anisotropy of remanence. Since single domain prolate grains should be distributed statistically parallel to the magnetic field direction, the maximum anisotropy axis should also be in the magnetic field direction, as suggested by our theoretical models and confirmed by our experimental data. But what about CRM? To test this, we applied a wide range of experiments using anhysteretic methods with the automated SushiBar system on Bruhnes-Matuyama-aged marine sediments from the Bermuda Rise (ODP Site 1063). Previous work assumed the remanence in these sediments was carried solely by magnetite; however, we found evidence for a gyroremanent magnetization (GRM), which is commonly attributed to greigite. Of interest is that these samples, as well as neighboring samples or other intervals that do not show evidence for GRM, yield distinctly different characteristics either in their remanence anisotropy parameters and/or in their partial anisotropy spectra. We present new methodology that helps identify potential CRM-bearing horizons that was overlooked by existing techniques.
How to cite: Gilder, S., Wack, M., Roud, S., Ostermeier, F., Jezek, J., and Finn, D.: Identifying chemical remanent magnetization in marine sediments via anhysteretic magnetization: Case study from the Bermuda Rise, North Atlantic Ocean , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12826, https://doi.org/10.5194/egusphere-egu26-12826, 2026.
Drift sediments in the North Atlantic accumulated rapidly (≥10 cm/kyr) over the past ~3.6 Ma, enabling high-resolution reconstructions of geomagnetic field behavior. Previous scientific drilling expeditions (e.g., ODP Leg 162, IODP Exp. 306) from the North Atlantic refined the Quaternary Geomagnetic Instability Time Scale (GITS; 0–2.58 Ma) by revealing short-lived geomagnetic instabilities like the Iceland Basin Excursion (~188 ka). Here, we aim at further refining the GITS by studying newly collected cores in the same area.
Between 2020 and 2023, the International Ocean Discovery Program (IODP) Expeditions 384, 395C, and 395 targeted six sites: five along a transect east of the Mid-Atlantic Ridge (20–30°W, ~60°N) and one west of Greenland. These expeditions targeted the volcanic basement that forms the V-shaped ridges/troughs on the Reykjanes Ridge and the overlying sediments that record deepwater current evolution. Shipboard age models are based on paleomagnetic and microfossil data, but a robust and reliable paleomagnetic record extends up to 11 Ma.
We present results from Expeditions 384/395C/395 sediments that capture most GITS magnetic events (excursions and reversals) within the Matuyama chron. These records hold potential to extend the GITS backward in time, bolstering magnetic instabilities as geochronologic tools and refining models of Earth's ancient geomagnetic variations.
How to cite: Di Chiara, A., Satolli, S., Friedman, S., Dwyer, D., Acton, G., Karatsolis, B. T., Dunkley Jones, T., Pearson, P. N., Suzuki, T., Briais, A., Parnell-Turner, R., LeVay, L., and 395 Science Party, E.: Paleomagnetic records of Matuyama chron and beyond from North Atlantic drift sediments: IODP Expedition 384/395C/395 sites, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11479, https://doi.org/10.5194/egusphere-egu26-11479, 2026.
The Wilson Creek Formation, exposed around Mono Lake in east-central California, is comprised of interbedded lacustrine sediments and tephra that were deposited during higher stands of Mono Lake (Lake Russell) in the late Pleistocene. A prominent paleomagnetic excursion recorded in this formation led to the recognition and naming of the ~33 ka Mono Lake geomagnetic excursion (MLE). However, recent direct radiometric dating of key tephra layers bracketing this event have shown that this excursion is instead the Laschamps geomagnetic excursion (~41 ka). This has prompted a recommendation (e.g., Laj et al., 2014) that the MLE be renamed the "Auckland excursion," based on a reliably dated and well-documented paleomagnetic record for a ~33 ka excursion in New Zealand, casting doubt on the presence of the MLE at its namesake site.
Nevertheless, close inspection of paleomagnetic profiles from two pioneering studies suggest that there may be a second, less prominent, paleomagnetic anomaly above the Laschamps. The striking lateral continuity of the Wilson Creek Formation and its prominent tephra layers facilitates the identification and resampling of the intervals of interest. We carried out high-resolution paleomagnetic sampling of three trenches bracketed by key dated tephra, focussing on the interval between Ash 8 (~34 ka) and Ash 7 (~26 ka), the location of the potential second anomaly, with one trench extending below Ash 15 (~42 ka) to capture the Laschamps excursion. Thermal demagnetization revealed that the lacustrine sediments of Mono Lake are excellent paleomagnetic recorders, with well-behaved remanence directions. Below Ash 15, the sediments contain a sharp and well-defined excursion consistent with the Laschamps excursion. Most significantly, all the trenches reveal a coherent pattern of significantly reduced inclinations between Ashes 8 and 7, with values dipping below 20° without full polarity reversal. This pattern, present in all three trenches, is defined by a double-dip inclination structure and westward-shifting declinations. These findings show that while the original excursion identified at Mono Lake is instead the Laschamps excursion, the MLE is indeed recorded at Mono Lake with an age of ~33 ka consistent with current estimates. Moreover, the enhanced resolution afforded by high sedimentation rates may be capturing previously underappreciated complexity in the geomagnetic field behavior during this excursion.
How to cite: Jensen, B., Ibarra, D., Reyes, A., Buryak, S., Evans, M., and Kravchinsky, V.: Revisiting the Mono Lake Excursion Type Section with High-Resolution Paleomagnetic Records, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15660, https://doi.org/10.5194/egusphere-egu26-15660, 2026.
The atmospheric production rate of cosmogenic 10Be is inversely related to the geomagnetic field strength. This leads to variable deposition rates of 10Be in environmental archives, such as ice or sediment cores. 10Be records from these archives can, therefore, be used to reconstruct past intensities of the geomagnetic field. Recent 10Be production and atmospheric mixing models, however, suggest that the sensitivity of 10Be records to changes in the geomagnetic field intensity depends on the latitude. This impacts the use of single-site 10Be records for reconstructing global 10Be production rates and, therefore, geomagnetic field intensities.
Here, we quantitatively assess the latitudinal sensitivity of 10Be deposition to geomagnetic field changes. We present new authigenic 10Be/9Be data from a sediment core from the Bay of Bengal (IODP U1446) and compile additional 10Be data from ice and sediment cores. Our analysis focuses on 10Be deposition changes during the Laschamps geomagnetic field intensity minimum at different latitudes. We compare 10Be deposition changes with changes in modeled 10Be production from geomagnetic field reconstructions (LSMOD.2, GGFSS70, Black Sea, GLOPIS-75) and the GEOS-Chem atmospheric mixing model.
Our findings reveal that 10Be deposition changes are larger in the tropics (tropical enhancement) and diminish at higher latitudes (polar bias), indicating incomplete mixing of cosmogenic beryllium, consistent with atmospheric mixing models. This latitudinal sensitivity needs to be taken into account when reconstructing variations in global geomagnetic field intensity from 10Be.
How to cite: Loftfield, J., Wall, V., Zheng, M., Stübner, K., Lachner, J., Rugel, G., and Adolphi, F.: Latitude-dependent sensitivity of 10Be records to variations in geomagnetic field intensity, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17477, https://doi.org/10.5194/egusphere-egu26-17477, 2026.
Palaeomagnetic measurements provide the most robust, quantitative constraints on vertical axis rotations from outcrop scale blocks to entire tectonic plates. Vertical axis rotations are typically shown on maps as vectors representing local palaeodeclinations or individual rotations to a reference at the site level. When dealing with large and noisy datasets, however, this approach struggles to pick out underlying spatial patterns or finer scale regional displacements, especially when the data has variable density across regions.
These limitations are compounded in areas where several rotations events have been recorded across multiple scales or are poorly recorded in the palaeomagnetic record. As a result, both the visualisation and interpretation of complex rotation fields are hindered.
Here, we introduce PyRotate: a robust and scalable, end-to-end workflow for integrating and analyzing locality-level palaeomagnetic data from multiple sources. This framework allows users to curate and clean data through custom parameters, and to apply bootstrap techniques to determine the rotation of selected blocks and plates. Novel tools include kriging of rotations by age to simplify areas of highly variable rotation amounts and estimate interpolations between sites, giving an overlain interpolated rotation field as a visualisation tool, as well as automated outlier detection and labelling through cluster analysis. In addition, outputs are compatible with both PmagPy (Tauxe et al., 2016) and PyGPlates (Mather et al., 2024) as the basis of further analysis.
To illustrate the capabilities of PyRotate, we analyse a curated paleomagnetic dataset from Japan, and multiple-source datasets directly obtained from the Magic database. This analysis tests the ability of the workflow to deal with noisy and unevenly distributed datapoints. The tools introduced in PyRotate enable easier identification of areas needing additional sampling, synthesis of disparate datasets, and interpretation of the rotation of blocks through time.
How to cite: Ross, O., Leite Mendes, B., Vaes, B., and Pastor-Galán, D.: PyRotate: An automated framework for the analysis, visualisation, and interpretation of tectonic rotations using palaeomagnetic data, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6999, https://doi.org/10.5194/egusphere-egu26-6999, 2026.
This work studies focuses on periods of dramatic temperature changes during the early Eocene hyperthermal events ETM3 (~52.8 Ma), ETM2 (~54 Ma), and the PETM (~56 Ma). We aim at developing a refined age model for IODP Site U1514 (Mentelle Basin) and carry out a suite of rock magnetic measurements as proxies for paleoclimatic changes. On 234 sediment samples from 248.2 to 324.68 m CSF-A we performed new magnetic measurements including AF demagnetization, AMS (Anisotropy of Magnetic Susceptiblity), bulk susceptibility, IRM (Isothermal Remanent Magnetization) acquisition and demagnetization, and ARM (Anysteretic Remanent Magnetization) acquisition and demagnetization. The integration of these new data with the previously available shipboard datasets allows us to characterise magnetic mineral assemblages, remanence carriers, and sedimentary processes at a resolution not previously available for this site. The new high-resolution paleomagnetic (Inclination only) data allow a clearer identification of polarity boundaries and reduce uncertainties in the placement of chron transitions. This improved temporal control enables a more precise determination of the depths and thicknesses of ETM3, ETM2, and the PETM. Variations in ARM/k ratios, IRM acquisition curves, and susceptibility reveal changes in magnetic grain size and concentration that align with intervals of elevated temperature. Applying Fourier transforms to continuous magnetic property curves, constructed from magnetic parameters, allowed us to detect statistically significant cyclicity consistent with short and long eccentricity. These Milankovic oscillations provide independent constraints on sedimentation rates and help refine accumulation histories surrounding the hyperthermal intervals. The orbital pacing observed in the background sedimentation also strengthens the reliability of the new age model. By combining the refined magnetostratigraphy, magnetic property analyses, and orbital cyclicity, we produce a high-quality framework to identify and correlate ETM3, ETM2, and the PETM. This improved temporal and stratigraphic resolution clarifies the relative timing between warming, environmental shifts, and changes in sediment properties.
How to cite: Bonilla-Alba, R., Di Chiara, A., Florindo, F., and De Michelis, P.: Tracking the ETM3, ETM2, and PETM hyperthermal events: New Age Model and Magnetostratigraphic Study , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20144, https://doi.org/10.5194/egusphere-egu26-20144, 2026.
High-altitude lakes on the Tibetan Plateau preserve sensitive records of hydroclimate and atmospheric circulation, but establishing robust chronologies is often hindered by core-recovery artifacts, section-to-section discontinuities, and uncertainties in radiocarbon dating. Here we present a paired paleomagnetic strategy based on sediment cores from two high-altitude Tibetan lakes, Taro Co and Nam Co, to develop reproducible geomagnetic tie points for inter-core and inter-basin correlation.
For Taro Co (31°07′53.89″N, 84°07′50.65″E; ~4,566 m a.s.l; ~474 km²; max depth 130 m; catchment ~7,423 km²), we target two 8 m long parallel sediment cores spanning ~25 kyr. In parallel, we apply the same workflow to sediments recovered by the ICDP NamCore project from the central basin of Nam Co (30°30′–30°56′N, 90°16′–91°03′E,~4,718 m a.s.l.,~2,017 km², catchment ~10,680 km²,max depth ~99 m), enabling a comparison between independent sedimentary archives from the Tibetan Plateau.
We perform stepwise alternating-field demagnetization of the natural remanent magnetization (NRM) and determine characteristic remanent magnetization (ChRM) directions using principal component analysis (PCA). The datasets include inclination, relative declination, maximum angular deviation (MAD), and median destructive field (MDF), measured at 1 cm stratigraphic resolution. A key methodological focus is quality control across core sections and overlaps in both records: we assess directional stability and evaluate consistency between overlapping intervals to maximize recovery of the paleomagnetic secular variation (PSV) signal. Initial results from Taro Co show strong agreement in inclination between the two parallel cores, supporting the reproducibility of the PSV signal across holes.
The resulting PSV curves from Taro Co and Nam Co provide an independent stratigraphic framework to (i) test and refine radiocarbon-based chronologies, (ii) strengthen correlations between parallel holes/sections within each lake, and (iii) identify shared directional highs and lows between lakes. Ultimately, our goal is to build a preliminary inter-lake PSV stack for the SW/central Tibetan Plateau, improving regional synchronization and helping separate geomagnetic variability from site-specific recording effects.
How to cite: Otero, S., Wang, J., Zhu, L., Ma, Q., Ju, J., Henderson, A., Clarke, L., Adolph, M.-L., Vogel, H., St-Onge, G., and Haberzettl, T.: Towards a regional Late Pleistocene and Holocene Paleomagnetic Secular Variation stack for the Tibetan Plateau, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7190, https://doi.org/10.5194/egusphere-egu26-7190, 2026.
Instrumental observations highlight that intertropical Africa is one of the areas with the most rapid changes in the modern geomagnetic field. The secular variation beyond the last centuries is poorly known due to lack of data, this large region representing only 0.7% of the GEOMAGIA50 database. The resulting large uncertainties in global geomagnetic models in this area make in particular the history of the present South Atlantic anomaly unclear. Here, we present archaeomagnetic studies in Southern Benin, Northern Togo, Eastern Senegal and Northeastern Ethiopia. In order to study the full geomagnetic vector, most fieldworks focus on in-situ archaeological structures sampled using the plaster cap technique, one oven in Ethiopia (mid 2nd mill. BCE), 11 iron furnaces in Senegal (500 BCE – 800 CE), 5 iron furnaces in Benin (13-15th c. CE) and 7 iron furnaces in Togo (18-20th c. CE). In Benin, we also sampled displaced baked clays associated to iron metallurgy (kiln walls, tuyeres, potteries).
Archaeodirections were determined after thermal demagnetization. We obtained 13 average directions, one in Ethiopia, 5 in Benin and 7 in Togo). The Senegalese structures provided scattered directions, probably because of tilting of the structure walls after the last heating. Archaeointensities were acquired using the classical Thellier-Thellier protocol with anisotropy and cooling rate corrections. The relatively high success rate (75% on average) allowed us to obtain 21 new average data, one on the Ethiopian oven, ten on the Beninese furnaces, 7 on the Togolese ones and 3 preliminary data on the Senegalese structures. The most recent 19-20th c. CE data from Togo are in very good agreement with the local predictions of the geomagnetic global models. At earlier periods, the new data are in agreement with, if any, already published data as in the 13-15th c. CE in West Africa. They highlight faster changes than the models, highlighting their importance to improve our knowledge of the secular variation of the geomagnetic field over the last 4 millennia.
How to cite: Hervé, G., Khalidi, L., Robion-Brunner, C., Serneels, V., van Toer, A., Wandres, C., Bakrobena, L., Delqué-Kolic, E., Harena, P., Mantenant, J., Mayor, A., N'Dah, D., Ricci, G., and Walmsley, A.: Secular variation of the geomagnetic field in Sub-Saharan Africa over the last millennia: new archaeomagnetic data from West Africa and Ethiopia., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8220, https://doi.org/10.5194/egusphere-egu26-8220, 2026.
The strategic geographical position of Cyprus at the crossroads of civilizations in the eastern Mediterranean provides a unique opportunity to investigate past geomagnetic field variations and to fill the spatial gap between Eastern Europe and the Levant. In this study, we present new archaeointensity data obtained from well-dated ceramic assemblages from the ancient Kingdom of Idalion, one of the most significant archaeological sites on the island. A comprehensive palaeomagnetic and rock magnetic investigation, combined with Thellier-type experiments modified after Coe, was conducted to assess the magnetic mineralogy, thermal stability, and reliability of the remanent magnetization carried by the pottery sherds. A total of 186 specimens from 55 independent ceramic fragments were analyzed, and reliable archaeointensity estimates were obtained after correction for magnetic anisotropy and cooling-rate effects. The resulting field intensity values range between 50 and 80 µT, providing evidence for the occurrence of significant and rapid geomagnetic field variations in the eastern Mediterranean during the early first millennium BCE. These results are consistent with the Levantine Iron Age Anomaly (LIAA), previously documented in the Middle East. Our new data demonstrate the key role of Cypriot ceramics in constraining the spatial and temporal evolution of the LIAA and contribute to a more detailed regional reconstruction of geomagnetic secular variation. Furthermore, the pronounced and rapid intensity fluctuations recorded during the Iron Age highlight the potential of archaeomagnetic intensity as a robust dating tool for ceramic materials, offering a valuable alternative in periods affected by the Hallstatt radiocarbon plateau.
How to cite: Tema, E., Morales, J., Goguitchaichvili, A., and Gaber, P.: Iron Age Geomagnetic Intensity Variations in the Eastern Mediterranean: New Evidence from Cyprus, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10115, https://doi.org/10.5194/egusphere-egu26-10115, 2026.
Polarity reversals are among the most relevant events in Earth’s magnetic field evolution and are crucial to understand the dynamics within the outer core. During a reversal, the geomagnetic field deviates from an axial dipole, with non-dipolar components becoming dominant and resulting in a more complex spatial geometry. Therefore, paleomagnetic models based on Spherical Harmonic Analysis (SHA) have become an essential tool for analyzing the spatial and temporal features of the geomagnetic field during these events. However, to date, only the most recent magnetic field reversal, the Matuyama-Brunhes (MB) reversal (780 kyr BP), has been modeled.
Here we present and discuss our first SHA model of the second most recent reversal, the Gauss-Matuyama (GM), constructed from a recent compilation of high-quality paleomagnetic sediment records spanning from 2.4 to 2.7 Myr BP . Our model is based on 19 sediment cores, that have been carefully checked for independent age information, data quality and, where possible, regional consistency of the records. This provides a global distribution that allows us to analyze the spatial and temporal geometry of the GM worldwide. We further compare the field characteristics during the GM reversal to those of the MB reversal and to the present-day field. We discuss similarities and differences between the two geomagnetic field reversals.
How to cite: Rivera, P., Korte, M., Mahgoub, A., Panovska, S., and Shinu, S.: First Global Paleomagnetic model including the Gauss-Matuyama reversal, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10782, https://doi.org/10.5194/egusphere-egu26-10782, 2026.
Understanding geomagnetic variations observed at the Earth’s surface requires knowledge of processes occurring in the Earth’s interior that are associated with the geodynamo. Because these processes occur at inaccessible depths, numerical models are used to simulate the expected conditions within these regions. On the other hand, data-based reconstructions provide constraints in terms of the field morphology at the Earth’s surface and at the core-mantle boundary. Such models are constrained by direct measurements for recent periods and by indirect data for older intervals. For the time span covering the last few centuries to approximately 50 ka, the available paleomagnetic data are unevenly distributed in both space and time, with a strong bias toward the Northern Hemisphere and more recent periods. These data limitations influence the reliability of geomagnetic model predictions, particularly in poorly sampled regions such as South America. In recent years, new paleomagnetic data have been obtained from ocean-floor sediments off the southern coast of Brazil. However, integrating paleomagnetic data from geographically close locations, together with reliable age and sedimentation rate models, remains a major challenge and limits the reproducibility of records from nearby sites. To address this issue, we applied a machine-learning approach based on Gaussian process regression to construct inclination and relative paleointensity curves using data from three sediment cores collected in this region (29°S, 47°W). This method allows for the estimation of a modeled curve that integrates data from the three cores, which have irregular time intervals between samples, and provides associated uncertainties. The resulting inclination and relative paleointensity curves were compared with predictions from the GGF100k geomagnetic model. Overall, the results show good agreement with model predictions, although some discrepancies are observed in both inclination and intensity over the studied interval. These findings demonstrate that Gaussian process regression is a robust and effective tool for integrating paleomagnetic data from oceanic sediment cores.
How to cite: Frigo, E., Gomes Gonçalves, Í., Francisco Savian, J., Yesid Suárez-Ibarra, J., Panovska, S., André Hartmann, G., Azzolini Pontel, C., Trindade Lopes, C., Alejandra Gómez Pivel, M., Carlos Coimbra, J., Monticelli Petró, S., Leonhardt, A., and Ivan Ferreira da Trindade, R.: Paleomagnetic variations along the Southern Coast of Brazil from 46.06-5.36 ka BP using a Gaussian Process Technique, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11365, https://doi.org/10.5194/egusphere-egu26-11365, 2026.
The Geomagnetic Polarity Time Scale (GPTS) is the backbone of the time scale for at least the last ~84 Myr (Late Cretaceous–Quaternary). Astronomically calibrated ages for the Cenozoic portion (C-Sequence) of the GPTS are provided as part of the Cenozoic Global Reference benthic foraminifer carbon and oxygen Isotope Dataset (CENOGRID1), but not for the late Cretaceous portion of the C-Sequence. We aim to provide astronomically calibrated age for the late Cretaceous magnetic Chron boundaries. We generated preliminary magnetic polarity stratigraphy data and bulk carbon stable isotope data from a series of deep-sea drilled record recovered in the South Atlantic Ocean: Ocean Drilling Program (ODP) Site 1267 2 (Leg 208), Deep Sea Drilling Project (DSDP) Site 5253 (Leg 74), and International Ocean Drilling Project (IODP) Site U15764 (Exp. 391) from Walvis Ridge, and DSDP Site 5165 (Leg 72) from the Rio Grande rise. The sampled records are generally characterized by a stable magnetic remanence with either normal (up-pointing) or reverse (down-pointing) inclination of the remanence vector. The integration of magneto- and carbon isotope-stratigraphy will be used to calibrate the GPTS from the top of Chron C34n to the base of Chron C30n. To achieve this, we will use a new approach based on the correlation of the obtained magnetostratigraphy to an astronomically tuned reference by using the bulk carbonate stable carbon isotope data. This effort represents the first step toward a fully astronomically calibrated C-sequence of the GPTS that is consistent with CENOGRID.
References
1 Westerhold, T. et al. An astronomically dated record of Earth’s climate and its predictability over the last 66 million years. Science (1979) 369, 1383–1388 (2020).
2 Zachos, J. C., Kroon, D. & Blum, P. Site 1267. Proceedings of the Ocean Drilling Program, 208 Initial Reports 208, 1–77 (2004).
3 Chave, A. D. Lower Paleocene–Upper Cretaceous magnetostratigraphy, Sites 525,527, and 529, Deep Sea Drilling Project Leg 74. in Deep Sea Drilling Project preliminary report, Vol. 74 (eds. Moore, T. C. & Rabinowitz, P. D.) 525–531 (DSDP, Washington DC, USA, 1984). doi:10.2973/dsdp.proc.74.1984.
4 Sager, W. et al. Site U1576. International Ocean Discovery Program: Preliminary Reports 391, 1–65 (2023).
5 Barker, P. F., Carlson, R. L., Johnson, D. A. & Al., E. Site 516. Deep Sea Drilling Project preliminary report, Vol. 72 (1983).
How to cite: Dallanave, E., Westerhold, T., and Villa, A.: Astronomical tuning of the Late Cretaceous geomagnetic polarity time scale (from top Chron C34n to base Chron C30n), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11382, https://doi.org/10.5194/egusphere-egu26-11382, 2026.
The present-day geomagnetic field is characterized by a region of weak intensity over the South Atlantic, known as the South Atlantic Anomaly (SAA). Over the past few hundred years, there is evidence for possible persistence of the SAA. In addition, another less pronounced surface intensity minimum has appeared below the West Pacific, known as the West Pacific Anomaly (WPA). Since 2008, the SAA has split with a new local minimum appearing in Africa. This split introduces a challenge for characterizing the time dependence of a pair of minima, particularly in terms of their respective areas.
In this work, we propose a new topological algorithm to calculate the time dependent areas and centers of complex field configurations with multiple local surface intensity minima enclosed by the same threshold value. The algorithm relies on the identification of saddle points, which further enables the subdivision of the SAA area into sub-regions associated with different minima. In addition, the analysis considers contours of null intensity gradient, which do not require setting an arbitrary threshold value.
Based on the analysis of a modern geomagnetic field model, we find that the sub-region area associated with the weaker South American minimum decreases, whereas that of the African minimum increases. Both minima drift westward with negligible north-south displacement. The global minimum is located at a lower latitude than both local minima. The proposed method can be applied to paleo-magnetic field models, in which more complex patterns are observed.
In addition, analysis of the distribution of the null meridional intensity gradient over the period 1000–1950 reveals localized hemispheric asymmetry with relatively subdued activity in the Pacific hemisphere and stronger variability in the Atlantic, particularly in the Southern Hemisphere. The null intensity azimuthal gradient exhibits an order-2 signature suggestive of mantle control on the geomagnetic field.
How to cite: Yue, Y., Amit, H., Terra-Nova, F., Marum, V., Wang, Y., and Wei, Y.: Time dependence of multiple geomagnetic surface intensity minima, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12741, https://doi.org/10.5194/egusphere-egu26-12741, 2026.
The Aptian-Albian interval represents a key phase in Earth history, characterized by greenhouse climate conditions, major perturbations in oceanic redox state and significant changes in geomagnetic field behavior leading to the establishment of the Cretaceous Normal Superchron (CNS). Here we present an ongoing paleomagnetic and rock magnetic study of the Monte Cucco (“Hill 991”) section, located on the western margin of the Umbria–Marche Apennines. The section belongs to the Umbria–Marche Succession and preserves a continuous upper Aptian–lower Albian stratigraphy record within the Marne a Fucoidi Formation, a cyclic marly–calcareous characterized by alternating marls, clay-rich marls, and calcareous levels, including organic-rich horizons and black shales associated with Oceanic Anoxic Events (OAE), particularly OAE1b. The dataset includes stepwise alternating field and thermal demagnetization to isolate the characteristic remanent magnetization, complemented by rock magnetic analyses such as magnetic susceptibility, anhysteretic remanent magnetization (ARM), isothermal remanent magnetization (IRM), and coercivity component analysis. These analyses are currently in progress and will be completed to constrain magnetic mineralogy, grain-size distribution, and environmental controls on the magnetic signal across lithological cycles and OAE-related intervals. Preliminary paleomagnetic results indicate stable characteristic remanent magnetization components. Hysteresis parameters and IRM acquisition curves suggest a mixed magnetic assemblage dominated by low-coercivity magnetite, with grain sizes ranging from single-domain (SD) to pseudo-single-domain (PSD) and a subordinate contribution of multi-domain (MD) grains. The assemblage is predominantly detrital, with local variations suggesting a relative enrichment in finely grained magnetite. The final dataset will be integrated with existing Poggio le Guaine (PLG), a Aptian-Albian complete record located approximately 20 km from Monte Cucco and compared with magnetostratigraphic data from South Atlantic marginal basins, particularly the Brazilian Equatorial Margin. This approach aims to strengthen interbasinal correlations between the Tethyan realm and Gondwanan margins and to refine constraints on geomagnetic field behavior and paleoenvironmental variability during the Aptian–Albian transition.
How to cite: Gewehr de Mello, R., Francisco Savian, J., Gonçalves Leandro, C., Frontalini, F., Di Chiara, A., Azzolini Pontel, C., Coccioni, R., and Casadei, N.: Preliminary Paleomagnetic and Rock Magnetic Results from the Aptian–Albian Marne a Fucoidi Formation at Monte Cucco (Hill 991), Italy, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15640, https://doi.org/10.5194/egusphere-egu26-15640, 2026.
The Western Upper Peninsula of Michigan (WUP), located in the north-central United States, is part of the Paleoproterozoic North American Continent accreted onto the ~2.6 Ga Superior craton. The WUP is intersected by several generations of diabase dikes associated with the ~1.1 Ga North American Mid-Continent Rift system (MCR). In addition to these dikes, recent aeromagnetic and geological surveys of the WUP have revealed multiple sets of dikes in the southeastern and north-northeastern portions of the region that trend either perpendicular or obliquely to the MCR rift axis. Geological relationships derived from stratigraphic field studies, along with paleomagnetic and geochemical analyses, suggest that these dikes predate the Keweenawan dikes of the main-stage MCR, likely dating to the early Mesoproterozoic to late Paleoproterozoic. The dikes in the southeastern part of the WUP intrude the Archean Carney Lake Gneiss Complex (CLGC) and can be subdivided into several small but distinct swarms with varying orientation and geomagnetic polarities. These findings point to a possible circumferential dike structure (Buchan and Ernst, 2019)1 of middle Paleoproterozoic age at the locus of the CLGC. A set of dikes located directly North of the CLGC, in the Neoarchean Dickinson Group, were also sampled to test this theory and constrain the region’s metamorphic conditions. Meanwhile, newly obtained geochemical data from dikes belonging to three distinct swarms in the north-central to northeastern portion of the region provide support for previous paleomagnetic interpretations linking these swarms to the earliest stages of hotspot activity which indicate the onset of the MCR. Further, new paleomagnetic and geochemical data collected from north-south trending dikes of the Huron Mountains in the northernmost portion of the northeast WUP, were analyzed to determine if they are constituent to the ~2.1 Ga Marathon dike swarm in Ontario, Canada, or evidence of fault-fracture infilling caused by the onset of the main stage MCR volcanism. We will present new results of geochemical, paleomagnetic, and rock-magnetic investigations of the pre-MCR dikes in the WUP and discuss their implications to the regional tectonic history.
[1] Buchan, K.L., Ernst, R.E. (2019). Giant Circumferential Dyke Swarms: Catalogue and Characteristics. In: Srivastava, R., Ernst, R., Peng, P. (eds) Dyke Swarms of the World: A Modern Perspective. Springer Geology. Springer, Singapore. https://doi.org/10.1007/978-981-13-1666-1_1
How to cite: Ahrendt, G., Mol, M., Surovitskii, L., and Smirnov, A.: Building upon the paleomagnetic history of mafic intrusions in the pre-North American Mid-Continent Rift system, Western Upper Peninsula of Michigan., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15642, https://doi.org/10.5194/egusphere-egu26-15642, 2026.
Tectonic opening of the Equatorial Atlantic Gateway (EAG) and its impact on Ocean–Atmosphere dynamics has global implications. Rifting between South America and Africa drove a transition from continental–lacustrine to evaporitic, and ultimately marine, environments, although the timing and duration of these changes remain debated. Over the same period, Earth’s magnetic field remained in a stable polarity state for ~38 Myr, a phase referred to as the Cretaceous Normal Superchron (CNS). In northeastern Brazil we have key sedimentary sections for this period, such as the Araripe Basin. The studied interval within the basin is notable for recording the evolution from restricted marine sequences to the complete opening of the EAG. Here, we present a preliminary paleomagnetic study of key sedimentary sections from Araripe Basin, in northeastern Brazil, covering the Aptian-Albian ages. Stepwise alternating field (AF) and thermal (TH) demagnetizations were used to isolate the primary remanent component. Magnetic remanence and rock magnetic parameters, such as magnetic susceptibility (χ), anhysteretic remanent magnetization (ARM) and isothermal remanent magnetization (IRM), were measured. Rock magnetic measurements indicate that the primary magnetic remanence carriers are low-coercivity magnetite and/or titanomagnetite and high-coercivity hematite. Our magnetoestratigraphy records reveal a long interval of normal polarities associated with the CNS, with isolated short intervals of reversed polarities that could be further investigated in the future. The results illustrate the potential of paleomagnetic records for best understanding the Earth’s magnetic field in the equatorial region during the Aptian-Albian to better understanding the age and tectonic evolution of the EAG.
How to cite: Savian, J., Ramos, J., Pontel, C., Lacerda, J., Kuchle, J., Silva Jr, R., de Mello, R., Lopes, C., Nunes, S., Almeida, G., and Figueiredo, M.: Paleomagnetic preliminary results from the Aptian-Albian Araripe Basin, northeastern Brazil, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15717, https://doi.org/10.5194/egusphere-egu26-15717, 2026.
Posters virtual: Mon, 4 May, 14:00–18:00 | vPoster spot 1a
EGU26-8141 | ECS | Posters virtual | VPS29
A Late Holocene Paleomagnetic Record from Lago del Desierto, Southern Patagonia (Argentina)Mon, 04 May, 14:27–14:30 (CEST) vPoster spot 1a
Lago del Desierto (49°02′S, 72°51′W) is located in a climatically sensitive sector near the Southern Patagonian Ice Field (Argentina). Three sediment cores collected from two sites in the lake were analyzed using a multi-proxy approach to reconstruct past environmental variability (Kastner et al., 2010). Numerous turbidites were identified in the sedimentological record. After excluding these event layers, a new age–depth model was developed for the first 3 sections of the core DES05-3 (289 cm), and paleosecular variations (PSV) were reconstructed for the interval between ~1000 and 3500 cal. BP.
Standard paleomagnetic measurements (alternating-field demagnetization) were performed on 125 samples from the same core. In addition, rock-magnetic measurements, including Anhysteretic Remanent Magnetization (ARM, 100 mT peak AF, 0.05 mT DC field), Isothermal Remanent Magnetization (IRM, acquisition up to 1.5 T and backfield curves), hysteresis loops and thermomagnetic analyses, were applied to extract complementary paleoenvironmental information from the sediment cores.
Rock-magnetic measurements indicate that the magnetic mineralogy is dominated by a low-coercivity component (magnetite-type), accompanied by a secondary high-coercivity fraction (hematite/goethite-type). This downcore distribution mirrors the paleoenvironmental shift described by Kastner et al. (2010): the lower part of the sequence shows an enhanced contribution of high-coercivity Fe oxides, consistent with more stable and chemically weathered catchment conditions. In contrast, the upper part shows an increasing dominance of detrital magnetite, indicating strengthened minerogenic supply and enhanced erosion, matching the onset of warmer conditions and glacier retreat during the Medieval Climate Anomaly as inferred from geochemical and lithological proxies. This agreement between magnetic and non-magnetic sediment parameters suggests coherent changes in the provenience of the sediment and in catchment dynamics over the last millennia. As expected from the catchment instability and the numerous turbidites in the upper part of the sequence, this interval could not be used for PSV reconstruction due to its discontinuous directional record. In contrast, samples from the lower part (~1000–3500 cal. BP) provided a continuous sequence suitable for paleosecular variation analysis. Although samples from this unit were not completely demagnetized at 100 mT, due to the presence of a high-coercivity component, magnetization directions consistently decayed toward the origin with high precision. Characteristic remanent magnetization (ChRM) directions were determined using principal component analysis, with maximum angular deviation (MAD) values below 2.5° for all non-turbidite samples. The resulting PSV record compares well with geomagnetic field models and other Patagonian paleomagnetic reconstructions. Inclination values range from −40° to −70°, displaying coherent directional variability over the last ~3500 years.
References:
Kastner, S., Enters, D., Ohlendorf, C., Haberzettl, T., Kuhn, G., Lücke, A., Mayr, C., Reyss, J.-L., Wastegård, S., & Zolitschka, B. (2010). Reconstructing 2000 years of hydrological variation derived from laminated proglacial sediments of Lago del Desierto at the eastern margin of the South Patagonian Ice Field, Argentina. Global and Planetary Change, 72(3), 201-214. https://doi.org/10.1016/j.gloplacha.2010.04.007
How to cite: Achaga, R. V., Gogorza, C. S. G., Irurzun, M. A., Ohlendorf, C., Haberzettl, T., and Zolitschka, B.: A Late Holocene Paleomagnetic Record from Lago del Desierto, Southern Patagonia (Argentina), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8141, https://doi.org/10.5194/egusphere-egu26-8141, 2026.
EGU26-8852 | Posters virtual | VPS29
High-resolution magnetic record of environmental changes during Middle – Late Pleistocene from a loess-palaeosol sequence in NE Bulgaria – pilot data from the LOEs-CLIMBE projectMon, 04 May, 14:30–14:33 (CEST) vPoster spot 1a
Continental sedimentary sequences of alternating loess and palaeosol horizons preserve detailed records of past global climate changes during the Pleistocene. Obtaining deeper and genuine knowledge on the history of past climates using proxy data depends on interdisciplinary approaches, novel techniques and thinking “out-of-the-box”. The LOEs-CLIMBE team members gather around this concept and present here the first pilot magnetic data from the Kolobar loess-palaeosol section in NE Bulgaria. The 25 m thick section is exposed in an active quarry and was sampled at 2-cm-resolution, covering the Holocene soil, seven palaeosol units and loess horizons L1 to L7 of varying thicknesses. New high resolution magnetic susceptibility data, delineates palaeosol horizons with high values of mass specific magnetic susceptibility except the special case of fourth palaeosol S4, showing no magnetic enhancement as compared to the underlying thin loess. Such depletion of pedogenic magnetic enhancement in paleosol units from the Lower Danube area is rarely reported. This phenomenon will be further examined by detailed magnetic and colorimetric methods. The strongest pedogenic magnetic signal is observed in the three youngest palaeosol units S1, S2 and S3, tentatively related to the interglacial stages MIS 5, MIS 7 and MIS 9. The weakest magnetic susceptibility is typical for the younger part of the loess unit L2, punctuated by the signal of a tephra layer, which is a widespread chronostratigraphic marker in the region. This research is carried out and financed within the framework of the second Swiss Contribution MAPS, LOEs-CLIMBE project № IZ11Z0_230102.
How to cite: Jordanova, D., Georgieva – Ishlyamska, B., Veres, D., Baykal, Y., Robu, M., Jordanova, N., Hambach, U., Ishlyamski, D., Dimov, D., Trott, A., and Wiesenberg, G.: High-resolution magnetic record of environmental changes during Middle – Late Pleistocene from a loess-palaeosol sequence in NE Bulgaria – pilot data from the LOEs-CLIMBE project, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8852, https://doi.org/10.5194/egusphere-egu26-8852, 2026.
EGU26-14934 | ECS | Posters virtual | VPS29
Effects of the Historical Geomagnetic Field on Earth's Energetic Particle Environment: Magnetic Anomalies and Auroral RegionsMon, 04 May, 14:33–14:36 (CEST) vPoster spot 1a
Three centuries ago, auroral emissions could be observed over the Korean sector, where the West Pacific Anomaly (WPA) coexisted with the South Atlantic Anomaly (SAA). To investigate this phenomenon, the present study builds upon our recent numerical simulations of the inner proton radiation belt [Girgis et al., JSWSC (2021), Girgis et al., SW (2023,2024)], in which we examined the effects of space weather on the near-Earth particle environment. Here, we extend our modeling framework to explore the historical distribution and state of the radiation environment. A key aspect of this research is the incorporation of a geomagnetic field configuration representative of the year 1650, and the comparison of the resulting particle environment with that derived from contemporary magnetic field models. The primary objective is to model the near-Earth particle environment in a manner that enables future coupling with atmospheric models, while also accounting for the influence of external space weather conditions. A comprehensive understanding of both the present-day and historical particle dynamics in the near-Earth environment is essential for predicting radiation conditions relevant to low Earth orbit (LEO) missions and for assessing the potential impact on Earth’s atmosphere.
How to cite: Girgis, K., Arthus Schanner, M., Panovska, S., and Yoshikawa, A.: Effects of the Historical Geomagnetic Field on Earth's Energetic Particle Environment: Magnetic Anomalies and Auroral Regions , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14934, https://doi.org/10.5194/egusphere-egu26-14934, 2026.
