PANDA – 100 Myr paleomagnetic data gap: Investigating anomalous behaviour of Earth’s magnetic field in the middle Paleozoic

• Boon, Annique van der & Dowding, Elizabeth May (2026). Drawing Maps in the Dark: Devonian Palaeomagnetic Uncertainty and the Illusion of Robust Palaeogeography. Geological Society Special Publication. ISSN 0305-8719. 565(1). doi: 10.1144/gslspecpub2026-69. Full text in Research Archive Show summary

  Palaeomagnetic data are the most important quantitative basis for palaeogeographic models, on which a significant proportion of geoscientific research depends. Many of the key palaeomagnetic datasets were collected between the 1970's and 1990's; despite persistent gaps, the last 20 years brought few new data for global palaeogeographic reconstructions. Some intervals, notably the Devonian, remain particularly poorly constrained. This strongly affects palaeogeographic reconstructions, which are now commonly used to model palaeoclimate and investigate mass extinctions and other biotic crises. Although the scarcity of reliable Devonian palaeomagnetic data is well known within palaeomagnetism, its implications are less appreciated by users of Global Plate Models and dependent palaeoclimate models. Here, we highlight these implications, examine problems with Devonian palaeomagnetic data, compare alternative palaeogeographic models for this interval, and evaluate how these models influence climate reconstructions. We show that sparse palaeomagnetic constraints and often non-transparent datasets promote artificial convergence among reconstructions, obscuring large underlying uncertainties. We encourage explicit recognition of the substantial uncertainties within Devonian palaeogeographic models, particularly in climate simulations, and we outline how expanded, FAIR palaeomagnetic datasets and transparent model construction can improve future palaeogeographic reconstructions and research.

• Boon, Annique van der; Schubert, Brian; Hagopian, William Martin; Domeier, Mathew Michael & Jahren, Anne Hope Florine (2026). High-resolution carbon isotope record from Svalbard reveals elevated atmospheric CO2 during the Middle Devonian Taghanic crisis. Palaeogeography, Palaeoclimatology, Palaeoecology. ISSN 0031-0182. 691. doi: 10.1016/j.palaeo.2026.113747. Full text in Research Archive
• Grappone, Michael; Boon, Annique van der; Fu, Roger & Biggin, Andy (2025). Evidence for an Exceptionally Weak Cambrian Geomagnetic Field: New Paleointensity Estimates From the Florida Mountains, New Mexico. Geochemistry Geophysics Geosystems. 26(7). doi: 10.1029/2025GC012234. Full text in Research Archive Show summary

  The timing of the formation of the Earth's inner core remains a major mystery in the history of Earth's deep interior, with estimates ranging from >1 billion years to <500 million years. Inner core nucleation is expected to be characterized in the paleomagnetic record by a drop in magnetic field strength prior to inner core nucleation, followed by a sharp increase in strength after nucleation. Paleointensity data from the 1 Ga–500 Ma age range are, however, exceptionally sparse (with fewer than a dozen studies), which largely prevents any definitive conclusions. This study presents new paleointensity results from whole rocks aged 510 ± 5 Ma from the Florida Mountains in southwestern New Mexico. Exceptionally low paleointensity estimates (<2 μT) were measured from three sites in granite and syenite outcrops of the southwestern portion of the Florida Mountains. Detailed rock magnetic and imaging investigations, including Quantum Diamond Microscopy, suggested that the two were unreliable because their remanence was unlikely a pure thermoremanent magnetization. The third site is more trustworthy and gave an estimate of 1.2 ± 0.2 μT (N = 5) corresponding to a virtual dipole moment of 0.4 × 1022 Am2, which is of a similar magnitude to the lower bound of estimates from the Ediacaran (635–541 Ma). Such a low estimate at 510 Ma appears inconsistent with recent claims that the field strengthened rapidly following inner core nucleation in the late Ediacaran. Nevertheless, the risk of this single estimate being unrepresentative of the long-term field should be recognized alongside the urgent need for more paleointensity data spanning the interval 540–440 Ma.

• Lloyd, Simon; Biggin, Andrew J.; Domeier, Mathew Michael; Lundmark, Anders Mattias & Boon, Annique van der (2025). Low Geomagnetic Paleointensity in the Mid‐Part of the Kiaman Superchron. Journal of Geophysical Research (JGR): Solid Earth. ISSN 2169-9313. 130(1). doi: 10.1029/2024JB030314. Full text in Research Archive Show summary

  The Kiaman Reversed Superchron (∼260–318 Ma) is the longest known period of single geomagnetic polarity in Earth history (∼55 million years). It is associated with anomalously low dispersion of virtual geomagnetic poles and some high estimates of Earth's dipole moment. However, many of these strong paleointensity data are of poor or unknown quality. Here we report full-vector paleomagnetic measurements from a series of mid-Kiaman (∼282–302 Ma) lamprophyre dykes from Orkney, Scotland. A total of 258 paleointensity experiments were performed alongside rock magnetic experiments and scanning electron microscopy. Eleven dykes produced virtual dipole moment estimates indicating that the field was weak (between 0.1 and 2.9 × 1022 Am2) at 302 Ma and only moderately stronger (between 2.7 and 7.1 × 1022 Am2) at 282 Ma. These new data challenge the paradigm of a uniquely strong field in the Kiaman superchron and are especially intriguing when considered alongside recent studies of geomagnetic field behavior during the later Cretaceous Normal Superchron (∼84–121 Ma). Average dipole moment may be marginally elevated and paleosecular variation moderately suppressed during the superchrons but, in other respects, the field can appear similar to that encountered during other times. The deep-Earth conditions allowing for the generation of a geomagnetic field that is capable of weak, unstable behavior and transitory polarity inversions, while nevertheless maintaining a dominant single polarity for tens of millions of years, is not yet clear. The challenge of explaining superchrons and their geodynamic origin motivates further study integrating paleomagnetic observations with predictions from geodynamo simulations.

• Boer, Rosa de; Groot, Lennart V. De; Dekkers, Mark J.; Königshof, Peter & Boon, Annique van der (2025). A missing palaeomagnetic signal in Middle Devonian pillow lavas. Geophysical Journal International. ISSN 0956-540X. 242(1). doi: 10.1093/gji/ggaf151. Full text in Research Archive Show summary

  The configuration of the Earth's magnetic field during the Middle Devonian (394.3–378.9 Ma) is poorly understood. The magnetic signals in Middle Devonian rocks are often overprinted during the Kiaman reverse superchron, obscuring their primary remanence. In other cases, available palaeomagnetic data are ambiguous, conflicting with tectonic reconstructions or dipolar geomagnetic field behaviour. Here, we study the palaeomagnetic signal of Middle Devonian pillow basalts from the Rhenish Massif in Germany. Our rock-magnetic experiments show that the pillow basalts can store and retain magnetizations over time. However, the pillow basalts have a somewhat low initial natural remanent magnetization (NRM), which is not expected based on their magnetite content. The palaeomagnetic directions determined from alternating field demagnetization, thermal demagnetization and a combination of both, fail to cluster around a common mean. Great circle analyses of these palaeomagnetic directions reveal traces of both Kiaman and present-day field overprints. Our palaeointensity measurements have a very low success rate of < 2 per cent, with only one sample yielding a result of 5.9 T. This low intensity might explain the low initial NRM of the samples and the lack of interpretable directional data in this study. However, given the very low success rate, this result does not convincingly represent the palaeointensity of the Middle Devonian field. All together, the lack of signal in our Middle Devonian pillow lavas could be a sign of an (ultra-)low, or non-dipolar or possibly even absent geomagnetic field during the time of formation.

• Niknam, Ali; Boon, Annique van der; Rezaeian, Mahnaz; Kaymakci, Nuretdin & Langereis, Cor G. (2024). Block Rotations in NW Iran in Response to the Arabia-Eurasia Collision Constrained by Paleomagnetism. Tectonics. ISSN 0278-7407. 43(8). doi: 10.1029/2023TC008139. Full text in Research Archive Show summary

  Northwest Iran is a seismically active region dominated by NW-SE trending strike-slip faults, such as the North Tabriz and Qosha Dagh faults, and smaller NNE-SSW striking faults. The Bozgush Mountains are shaped by these faults and divided into two domains that show a difference in strike. To quantify rotational tectonic deformation in NW Iran, we performed a paleomagnetic study along three transects of the Bozgush and Qosha Dagh Mountains with 127 sites. Our large new paleomagnetic data set shows that the Bozgush Mountains did not rotate as a single rigid block. In the western domain of the Bozgush Mountains, we find evidence for clockwise vertical axis rotations of ∼40°, while the eastern domain has rotated up to ∼80° clockwise. Declinations of the western Bozgush domain fit well with observed declinations in the Qosha Dagh Mountains. Fault patterns show that the eastern domain of the Bozgush Mountains is divided by a set of NNE-SSW striking sinistral strike-slip faults, which created domino-style blocks that accommodated the additional 40° of rotation. We estimate that these extra rotations have resulted in around 4 km of N-S shortening and more than 1.5 km of differential uplift.

• Boon, Annique van der; Naudé, Marjolein; Callegaro, Sara; Monsef, Iman; Rezaeian, Mahnaz & Niknam, Ali [Show all 11 contributors for this article] (2024). Propagating Neotethys slab break-off beneath Iran following Arabia-Eurasia collision. Lithos. ISSN 0024-4937. 482-483. doi: 10.1016/j.lithos.2024.107737. Full text in Research Archive Show summary

  The closure of the Paleo- and Neotethys resulted in a long history of subduction of oceanic crust and production of a large variety of Phanerozoic magmatic rocks in the region occupied by present day Iran. Adakitic rocks of varying ages are common in this area and have distinctive geochemical signatures that have been variably linked to slab break-off or melting of the lower continental crust. The geographic distribution and age of the adakitic rocks indicates a potential younging trend from northwest to southeast Iran, but this trend was interrupted by an older outlier in the area of Tafresh, in the central part of the Neotethys arc. We obtained new geochemical and U-Pb geochronological data for Eocene volcanic and Miocene intrusive rocks from this anomalous locality. Our results show that adakitic signatures are only present in younger Miocene intrusive porphyritic bodies and not in the main calc-alkaline Eocene volcanic succession as previously thought. The Tafresh adakitic porphyritic bodies have an age of 15.7 ± 0.1 Ma (n = 183, 2σ SE), which fits well with a regional younging of the adakites towards the southeast of Iran. The Tafresh adakitic rocks are classified as the high-silica variety, and show trace element signatures and isotopic values that are consistent with melting of the lower continental crust. We hypothesise that progressive slab break-off provided a mechanism for the formation of high-silica adakitic rocks along the former Neotethys arc.

• Honarmand, Maryam; Boon, Annique van der; Neubauer, Franz; Heberer, Bianca; Li, Qiuli & Kuiper, Klaudia F. [Show all 8 contributors for this article] (2023). Geochemical constraints on the geodynamic setting of Alborz-Azerbaijan Cenozoic magmatism. Chemical Geology. ISSN 0009-2541. 645. doi: 10.1016/j.chemgeo.2023.121889. Full text in Research Archive

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• Boon, Annique van der; Boer, Rosa de; Groot, Bertwin de; Nakrem, Hans Arne; Nogueira, Liebert Parreiras & Ruggiu, Lisa Krämer [Show all 8 contributors for this article] (2026). A promising novel recorder of Earth’s ancient magnetic field: fossil micrometeorites as paleomagnetic archives. doi: https:/royalsociety.org/science-events-and-lectures/2026/09/unravelling-magnetic-histories/. Full text in Research Archive Show summary

  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. I will introduce a novel, unexplored recorder of Earth’s magnetic field: fossil micrometeorites. Micrometeorites (MM) are small cosmic particles (50 μm-2mm) that make up a substantial part of the ~40,000 tons of extraterrestrial material delivered to Earth each year. Many MMs melt during atmospheric entry at altitudes of 80-90 km, transforming into cosmic spherules (CS). During this process, particles oxidise and form new minerals, particularly wüstite and magnetite, which record thermoremanent magnetisations upon subsequent cooling. CS are strongly magnetic and can be extracted from sedimentary rocks. Diagnostic features such as metal beads and vesicles inside some CS allow the reconstruction of their flight trajectory, which can be combined with their magnetisations to reconstruct the polarity of Earth’s magnetic field. While modern CS from Antarctica are already known to be robust recorders of the geomagnetic field, their deep-time counterparts remain almost entirely unexplored. I will present the first results of a paleomagnetic study of anthropogenic magnetite spherules that resemble iron-type (I-type) CS, as well as several Paleozoic I-type CS. These 50-300 μm spherules are measurable with standard paleomagnetic tools and, together with flight trajectories obtained using NanoCT scanning, are capable of opening a new window on the ancient geomagnetic field.

• Ryen, Sofie Hildegard; Domeier, Mathew Michael; Augland, Lars Eivind & Boon, Annique van der (2026). Investigating anomalous behaviour of Earth’s magnetic field in the mid- Palaeozoic – preliminary palaeomagnetic results from Silurian Ringerike sandstone of the Oslo Region, Norway. Full text in Research Archive
• Chiara, Anita Di; Paterson, Greig; Thallner, Daniele; Milanese, Florencia; Boon, Annique van der & Bonilla-Alba, Raquel [Show all 10 contributors for this article] (2026). Virtual Frontiers in Earth Magnetism: The legacy of MagNetZ webinar series . doi: 10.5194/egusphere-egu26-10349. Full text in Research Archive Show summary

  The MagNetZ (Magnetic Network on Zoom) webinar series stands as a cornerstone for geomagnetism research, hosting online seminars since the early 2020. Launched amid COVID-19 constraints, MagNetZ are convened by a team of scientists to give visibility to scientific work of both leading scientists and early career researchers, to foster virtual collaboration, overcoming geographical limits for students and professionals alike. It promotes open science sharing, with broad appeal evidenced by international viewership and institutional ties. The presentations typically began with a short talk, followed by interactive Q&A space, which are both recorded, post-edited and published on YouTube (https://www.youtube.com/@MagNetZ) in a continuously growing archive of recorded content. These webinars are also uploaded to the EarthRef.org Digital Archive (ERDA), development and maintained by the EarthRef.org Database Team and can be cited. Thus far, more than 80 webinars are available for viewing. MagNetZ also supports for national meetings, such as the UK-based annual Magnetic Interactions meeting, offering them the platform to view the recordings of three meetings so far. The webinars provide in-depth discussions on paleo- and rock-magnetism and geomagnetic modeling, with topics spanning from geo- and planetary magnetic field dynamics to mineral properties studies for paleoclimatic reconstructions, from paleomagnetic data for geodynamic applications to archaeomagnetism, and more. The core features of MagNetZ are to ensure accessibility for all genders, all career stages and geographical distributions, enhancing community networks, and serving as an educational hub for magnetic data in tectonics and climate studies. Its YouTube platform ensures enduring access, sparking collaborations and awareness.

• Test, Claudio Robustelli; Chiara, Anita Di; Paterson, Greig; Milanese, Florencia; Boon, Annique van der & Bonilla-Alba, Raquel [Show all 8 contributors for this article] (2026). The inclusivity of online seminars. doi: 10.5194/egusphere-egu26-19333. Full text in Research Archive Show summary

  The online seminars, or webinars, provide a virtual space for in-depth discussions on a variety of scientific- and academic-related topics.Several webinar series were launched amid COVID-19 constraints, providing the opportunity to keep the scientific community united during the challenging times of the global pandemic. Webinars have proven their advantage in overcoming geographical limitations and funding issues for in-person or online conference attendance. Virtual approaches are a powerful tool for promoting open science sharing, improving community networks and fostering virtual collaboration, with broad appeal evidenced by international viewership and institutional ties.We recommend offering a flexible format, which may include an initial talk followed by interactive Q&A space. Scientific talks can be recorded and published on online platforms that provide a DOI and on YouTube, giving visibility and credits to both early career researchers and leading scientists, as well as providing potential teaching material for undergraduate and postgraduate courses. Good practice is to create an unrecorded space for informal meetings, where a relaxed environment is fostered that encourages questions, free discussion, and facilitates mentoring.With a view to making webinars inclusive, we encourage a balanced selection of speakers, considering gender, career stage and country of origin, to promote the inclusion of minorities. Conveners are also recommended to ensure the correct pronunciation of the names and pronouns of the speakers before the beginning of the webinar. The live session, however, is as inclusive as the time zones in which the webinar is hosted. Hence, geographical inclusion of live attendance can be achieved by shifting time zones from the eastern and western hemisphere during the year.Finally, webinar using online platforms with close captions and careful post-production editing with subtitles integration allows for a more accessible material for both non-native English speakers and underrepresented minorities such as hard of hearing and deaf peoples.Although these options tend not to be used, it is important to open up dialogue on how to make webinars more inclusive and oriented as an educational hub for Earth science studies.

• Boon, Annique van der; Boer, Rosa de; Groot, Bertwin de; Nakrem, Hans Arne; Ruggiu, Lisa Krämer & Goderis, Steven [Show all 7 contributors for this article] (2026). A promising novel recorder of Earth's ancient magnetic field: fossil micrometeorites as paleomagnetic archives. doi: 10.5194/egusphere-egu26-18433. Full text in Research Archive Show summary

  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).

• Jakobsen, Renate & Boon, Annique van der (2025). A PALEOMAGNETIC STUDY OF THE DEVONIAN OLD RED SANDSTONE FROM WOODFJORDEN, SVALBARD. Geological Society of America Abstracts with Programs. doi: 10.1130/abs/2025NE-407489. Full text in Research Archive
• Boon, Annique van der (2024). The Earth’s magnetic field and Planetary Habitability. Full text in Research Archive
• Boon, Annique van der (2024). PANDA - A 100 Myr PAleozoic paleomagNetic Data gAp & CHANGE: Characterizing Anomalous Geomagnetic Fields in Earth’s Deep Past. Full text in Research Archive
• Boon, Annique van der (2024). The end of the Neotethys - reconstructing the closure of an ocean. Full text in Research Archive
• Boon, Annique van der & Werner, Stephanie (2024). Lonely exoPlanet – Din guide med anbefalinger for både populære og mindre kjente planeter. geoforskning.no. Full text in Research Archive
• Boon, Annique van der; Niknam, Ali; Rezaeian, Mahnaz; Kaymakci, Nuretdin & Langereis, Cor (2024). Block rotations in NW Iran in response to the Arabia-Eurasia collision constrained by paleomagnetism. Full text in Research Archive
• Jakobsen, Renate & Boon, Annique van der (2024). Paleomagnetism of Devonian Old Red Sandstone from Woodfjorden, Svalbard. Full text in Research Archive
• Ryen, Sofie Hildegard; Boon, Annique van der & Domeier, Mathew Michael (2024). The anomalous behaviour of Earth’s magnetic field in the middle Palaeozoic – investigating a 100 million year mystery. Full text in Research Archive
• Ryen, Sofie Hildegard (2024). Universets mysterier: Hva gjør en planet beboelig? - Jordas magnetfelt. Full text in Research Archive
• Ryen, Sofie Hildegard; Boon, Annique van der & Domeier, Mathew Michael (2024). The anomalous behaviour of Earth’s magnetic field in the middle Palaeozoic – investigating a 100 million year mystery. Full text in Research Archive
• Boon, Annique van der (2023). The quest for the Devonian magnetic field: an update. Full text in Research Archive
• Boon, Annique van der (2023). A 100 Myr Paleozoic paleomagnetic data gap: Investigating anomalous behaviour of Earth’s magnetic field in the middle Paleozoic. Full text in Research Archive
• Lloyd, Simon; Biggin, Andy; Boon, Annique van der; Domeier, Mathew Michael & Lundmark, Anders Mattias (2023). Recent Attempts to Measure the Paleointensity in Key Intervals within the Paleozoic. Full text in Research Archive
• Ryen, Sofie Hildegard & Boon, Annique van der (2023). Earth’s magnetic field in the middle Palaeozoic: Investigating a 100 million year mystery. Full text in Research Archive

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