Trond Helge Torsvik

• Domeier, Mathew Michael; Gallo, Leandro C.; Marcilly, Chloé M. & Torsvik, Trond H. (2026). Quadrupolar sea level fluctuations reveal episodes of rapid polar wander. Science. ISSN 0036-8075. 394(6819), p. 87–90. doi: 10.1126/science.aec8423. Full text in Research Archive Show summary

  True polar wander (TPW) is presently occurring at a rate of ~10 centimeters per year, exceeding the mean rate of differential plate motion. Whether this rate is transient and negligible on geological timescales or whether Earth has experienced rapid TPW lasting millions of years is unclear. Paleomagnetic evidence has been used to propose fast episodes of TPW, but limitations of the paleomagnetic record have precluded definitive results. Rapid TPW will induce global sea level fluctuations associated with relative changes in centrifugal potential, offering an independent test. We evaluated this prediction using continental flooding reconstructions and identified multiple robust quadrupolar patterns since 320 million years ago, confirming that protracted rapid TPW has occurred on Earth and that couplings among Earth’s rotational dynamics, mantle processes, and surface environments can be strongly episodic.

• Pharaoh, Tim C.; Rushton, Jeremy; Condon, Dan; Chenery, Simon; Horstwood, Matt & Sahy, Diana [Show all 12 contributors for this article] (2026). The Wash Igneous Complex of eastern England: A candidate Avalonian source for Sandbian tephra in Baltoscandia and implications for closure of the Tornquist Sea. Geological Society of America Bulletin. ISSN 0016-7606. doi: 10.1130/b38831.1. Full text in Research Archive Show summary

  The Wash Igneous Complex (WIC) is a component of a Sandbian (Late Ordovician) calc-alkaline magmatic arc that extends from the Lake District in northern England to the Brabant Massif of Belgium, associated with fast subduction of Tornquist ocean crust separating Avalonia (upper plate) and Baltica (lower plate). Buried beneath the East Midlands and The Wash of eastern England, the WIC is likely to comprise an extensive nested caldera system, underlain by a granite batholith, inferred from geophysical data. New whole-rock geochemical data confirm the calc-alkaline character of the WIC and elucidate relationships with other calc-alkaline magmatic complexes in eastern England. Detailed petrographic and geophysical data indicate that the WIC had the capacity to generate super-eruptions. Evidence for ultraplinian volcanism comes from contemporary, regionally distributed and thick metabentonite tephra in Baltoscandia. New, high-precision U-Pb isotopic (chemical abrasion−isotope dilution−thermal ionization mass spectrometry; CA-ID-TIMS) ages of 454.45 ± 0.13/0.23/0.54 Ma and 454.40 ± 0.11/0.22/0.53 Ma (2σ, Sandbian, Late Ordovician) are reported for zircons from a heterolithic dacitic tuff-breccia and a subvolcanic microgranite respectively, recovered from two deep boreholes that intersect the WIC. These dates are identical, within their analytical uncertainties, with equivalently high-precision U-Pb zircon dates for the Kinnekulle Metabentonite (KKMB; Baltoscandia). A population of younger grains from the breccia yielding a CA-ID-TIMS age of 453.70 ± 0.17/0.26/0.55 Ma (2σ) may correlate with the Lower Grimstorp Metabentonite. The matching U-Pb dates and closely comparable apatite microphenocryst chemistry from WIC rocks and the Baltoscandian tephra suggest the WIC as a primary candidate for much of the composite KKMB.

• Marcilly, Chloe M. & Torsvik, Trond H. (2026). Palaeogeography and palaeoelevation through time: controls on weatherability and long-term CO2 evolution. Geological Society Special Publication. ISSN 0305-8719. 565(1). doi: 10.1144/gslspecpub2025-135. Full text in Research Archive Show summary

  Palaeogeography plays a fundamental control on Earth's long-term climate by regulating the efficiency of silicate weathering, the primary negative feedback stabilizing atmospheric CO 2 over geological timescales. Accurate reconstructions of past land distribution, topography and shelf geometry are therefore essential for quantifying weatherability and modelling deep-time climate–carbon cycle interactions. In this study, we present a new Paleozoic palaeogeographic and palaeoelevation model that can be extended for the whole Phanerozoic. Using updated plate tectonic models, fossil-constrained land–sea boundaries, climatically sensitive lithologies and physically informed elevation classes derived from modern Earth statistics, we produce global 10 Myr-interval maps that include seven topographic layers from deep shelves (−200 m) to high mountains (>4 km). Our approach improves estimates of exposed land area, shallow and deep continental shelves, and regions of high weatherability. We show that differences in land distribution within ±10° of the equator and within climatically defined high-weatherability zones, strongly affect CO 2 predictions in carbon-cycle models, particularly during the Early Paleozoic and the Devonian. The new reconstructions refine Paleozoic sea-level estimates and reveal how evolving continental elevations modulated silicate weathering intensity and contributed to transitions between greenhouse and icehouse states, including the initiation and termination of the Late Paleozoic Ice Age.

• Shephard, Grace; Abdelmalak, Mohamed Mansour; Faleide, Jan Inge; Clennett, Edward; Zahirovic, Sabin & Gac, Sebastien [Show all 9 contributors for this article] (2026). Multi-phase intra-plate rifting and deformable plate modelling of the Northeast Atlantic back to the Permian. Gondwana Research. ISSN 1342-937X. 149, p. 465–490. doi: 10.1016/j.gr.2025.09.002. Full text in Research Archive
• Zhang, Hongrui & Torsvik, Trond Helge (2025). The Maduo-Zaduo continental flood basalts in north-central Tibet: Implications for a large igneous province within the Paleo-Tethyan Ocean. Geological Society of America Bulletin. ISSN 0016-7606. 137(9-10), p. 3875–3888. doi: 10.1130/b38157.1. Full text in Research Archive Show summary

  Abstract Large igneous provinces (LIPs) are predominantly mafic volcanic provinces emplaced over a short time-period covering vast areas. They provide a direct link between the deep Earth and the atmosphere. Remnants of Early Permian LIP activity have been identified in Central Europe (Skagerrak in the North Sea) and many East Asian blocks (Tarim, Tethyan, and Zaduo). Here we demonstrate that ca. 280 Ma lavas from the Songpan-Ganzi Terrane (Maduo, north-central Tibet) have geochemical signatures of continental flood basalts resembling the similar-aged Zaduo LIP in North Qiangtang. These Tibetan blocks were geographically separated in the Early Permian, but the Maduo and Zaduo lavas together with ocean island basalt-type rocks preserved within the suture zone between the two blocks may have formed part of a single Early Permian LIP that we name the Maduo-Zaduo LIP. LIPs are episodically sourced by plumes from the lowermost mantle. Our plate reconstructions indicate that three Early Permian LIPs (Skagerrak, Tarim, and Tethyan) can be genetically linked to the African large low shear-wave velocity province (LLSVP) near the core-mantle boundary while the Maduo-Zaduo LIP was sourced from the Pacific LLSVP.

• Torsvik, Trond Helge; Cocks, L. Robin M.; Domeier, Mathew Michael; Marcilly, Chloe M. & Dowding, Elizabeth M. (2025). Devonian palaeogeography and environmental change: an incomplete chronicle. Zeitschrift der Deutschen Gesellschaft fur Geowissenschaften. ISSN 1860-1804. 176(2), p. 193–214. doi: 10.1127/zdgg/2025/0454. Full text in Research Archive Show summary

  Abstract: The 60-million-year-long Devonian Period witnessed a host of major environmental changes, encompassing the rise and global expansion of large land plants, the occurrence of several major biological turnovers (including the third largest mass-extinction), and significant fluctuations in atmospheric CO2 that may have, enigmatically, been decoupled from coeval trends in global temperature. Despite their importance, the origins and impacts of these environmental changes remain poorly understood. Palaeogeography undoubtedly played a key role in instigating and influencing these changes, but it too remains ill-resolved in Devonian time. Here we seek to both illuminate and promote the further consideration of the interplay between the evolving palaeogeography of the Devonian and its environmental transitions. We present a detailed dissection of the changing geography, palaeobiology and environment of the Devonian at the regional and global scale, together with a series of new palaeogeographic and palaeoenvironmental reconstructions. We also compare our new reconstructions with other widely used reconstructions from this time and discuss some key outstanding uncertainties whose resolution will be essential to further unravel the

• Jodder, Jaganmoy; Hofmann, Axel; Elburg, Marlina A.; Ngobeli, Rebeun & Torsvik, Trond Helge (2025). Reply to comment on “Debunking the myth of a single Iron Ore Group in the Singhbhum Craton, India”. Precambrian Research. ISSN 0301-9268. 427. doi: 10.1016/j.precamres.2025.107884. Full text in Research Archive
• Jodder, Jaganmoy; Hofmann, Axel; Elburg, Marlina A.; Ngobeli, Rebeun & Torsvik, Trond Helge (2025). Debunking the myth of a single Iron Ore Group in the Singhbhum Craton, India. Precambrian Research. ISSN 0301-9268. 423. doi: 10.1016/j.precamres.2025.107800. Full text in Research Archive Show summary

  Archaean cratonic cover successions with well-preserved banded iron-formations (BIF) and shales provide a crucial window into early Earth surface processes. Here, we report on the intra-cratonic volcano-sedimentary sequences of the Koira and Simlipal groups of the Singhbhum Craton of India, regarded by some to be equivalent of Palaeoarchaean BIF-bearing greenstone successions collectively referred to as Iron Ore Group. However, field relationships and precise LA-Q-ICP-MS U-Pb detrital zircon ages from basal siliciclastic units of the Koira Group, non-conformably overlying Palaeo- to Mesoarchaean granitoid-greenstone basement, record a maximum depositional age of ca. 2.86 Ga. Sandstone intercalated with shale and banded iron formation of the Koira Group yields a maximum depositional age of ca. 2.68 Ga, placing the deposition of the iron formation and correlative units firmly into the Neoarchaean. The data therefore call for separate BIF–bearing sequences of Palaeoarchaean and Neoarchaean age, thus debunking the persistent myth of a single Iron Ore Group in the Singhbhum Craton of India. It further underscores similarities in the evolution of the Kaapvaal, Pilbara and Singhbhum cratons, which emerged in Mesoarchaean times to accommodate shallow-marine strata and sub-aerial flood basalts in an intra-continental setting.

• Marcilly, Chloé Franca Margot; Torsvik, Trond Helge & Jones, Morgan Thomas (2025). Late Paleozoic climate transition from a long-term carbon cycle modeling perspective. Global and Planetary Change. ISSN 0921-8181. 253. doi: 10.1016/j.gloplacha.2025.104984. Full text in Research Archive Show summary

  The Late Paleozoic ice age (LPIA) is the longest-lived Phanerozoic icehouse climate and the only recorded greenhouse–icehouse–greenhouse cycle on a vegetated Earth. Sedimentary archives partially detail the glaciation events, but the reasons and timing of the LPIA's onset (∼330 Ma) and end (∼260 Ma) remain debated. In many models, the shift to icehouse conditions is linked to enhanced CO2 uptake through silicate weathering, but the causes of this increased carbon sink are unclear. Most carbon cycle models are limited by their non-dimensional nature, and spatially resolved models rely heavily on variables such as topography and bathymetry, which are difficult to constrain over time. This study investigates the influence of weatherability reconstructions in non-dimensional versus spatially resolved models in the context of the LPIA's onset and ending. We review constraints on simulated silicate weathering fluxes and test forcings affecting its rate. Our paleogeographic forcing review uses newly developed land-maps and reconstructed climatic belts to constrain weathering based on fossil paleo-indicators. Our findings suggest that increased land availability in the high weatherability zones (HWZ) led to enhanced weathering processes, likely contributing to the glaciation onset. However, when a high solid Earth degassing factor is included, the likelihood of an extensive glaciation diminishes, indicating the need for an intensified CO2 sink driven by higher erosion rates and associated chemical weathering tied to topographic elevation to instigate widespread glaciation. A reduction in available land for weathering in the HWZ appears to have a determining role in the LPIA's termination.

• Thiagarajan, Nivedita; Lepland, Aivo; Ryb, Uri; Torsvik, Trond Helge; Ainsaar, Leho & Hints, Olle [Show all 7 contributors for this article] (2025). Reply to Grossman et al.: The case for a time-varying oxygen isotopic composition of seawater and cooler Ordovician oceans. Proceedings of the National Academy of Sciences of the United States of America (PNAS). ISSN 0027-8424. 122(12). doi: 10.1073/pnas.2426540122. Full text in Research Archive
• Thiagarajan, Nivedita; Lepland, Aivo; Ryb, Uri; Torsvik, Trond Helge; Ainsaar, Leho & Hints, Olle [Show all 7 contributors for this article] (2024). Reconstruction of Phanerozoic climate using carbonate clumped isotopes and implications for the oxygen isotopic composition of seawater. Proceedings of the National Academy of Sciences of the United States of America (PNAS). ISSN 0027-8424. 121(36). doi: 10.1073/pnas.2400434121. Full text in Research Archive
• Engbers, Y.A.; Thallner, D.; Bono, R.K.; Sprain, C.J.; Murray, M.J. & Bristol, K. [Show all 9 contributors for this article] (2024). A Global Paleosecular Variation Database for the Paleogene: Stationary Secular Variation Behavior Since the Triassic? Geochemistry Geophysics Geosystems. 25(6). doi: 10.1029/2023GC011203. Full text in Research Archive Show summary

  Paleosecular variation analysis is a primary tool for characterizing ancient geomagnetic behavior and its evolution through time. This study presents a new high-quality directional data set, paleosecular variation of the Paleogene (PSVP), with and without correction for serial correlation, compiled from 1,667 sites from 45 different localities from the Paleogene and late Cretaceous (84–23 Ma). The data set is used to study the variability, structure, and latitude dependence of the geomagnetic field during that period by varying selection criteria and PSV models. Modeled values for the equatorial virtual geomagnetic pole (VGP) dispersion have over-lapping uncertainty intervals within their uncertainty bounds between 8.3° and 18.6° for the past 250 Ma. We investigate the suitability of two descriptive models of PSV, Model G-style quadratic fits and covariant Giant Gaussian Process models, and find that both styles of model fail to satisfactorily reproduce the latitude dependent morphology of PSV, but suggest that estimates of the equatorial VGP dispersion may still robustly characterize aspects of Earth's long-term field morphology. During this time where the PSV behavior has not changed substantially, the reversal frequency has varied widely. The lack of a clear relationship between PSV behavior and reversal frequency is not trivially explained in the context of published findings regarding numerical geodynamo simulations.

• Torsvik, Trond Helge; Royer, Dana L.; Marcilly, Chloe M. & Werner, Stephanie C. (2024). User-friendly carbon-cycle modelling and aspects of Phanerozoic climate change. Applied Computing and Geosciences. 23. doi: 10.1016/j.acags.2024.100180. Full text in Research Archive Show summary

  Carbon-cycle modelling is essential for testing the main carbon sources and sinks as climate forcings, and we introduce and describe GEOCARB_NET, a graphical user interface for the geologic carbon and sulfur cycle model GEOCARBSULFvolc. The software system is menu-driven, user-friendly, and the user is never far removed from the basic input parameters from which atmospheric CO2 and O2 concentrations can be derived. GEOCARB_NET is supplied with several published models and the user can easily test and refine these models with different parametrizations. GEOCARB_NET also contains libraries of models and proxy data, which easily can be compared with each other. Our examples focus on how to use GEOCARB_NET in the context of Phanerozoic climate change and highlights how certain key input parameters can seriously affect reconstructed CO2 levels.

• Domeier, Mathew Michael; Robert, Boris; Meert, Joseph G.; Kulakov, Evgeniy; McCausland, Phil J.A. & Trindade, Ricardo I.F. [Show all 7 contributors for this article] (2023). The enduring Ediacaran paleomagnetic enigma. Earth-Science Reviews. ISSN 0012-8252. 242. doi: 10.1016/j.earscirev.2023.104444. Full text in Research Archive Show summary

  The Ediacaran Period was an interval of significant global transformation, marked by major changes in the biosphere, cryosphere, hydrosphere and atmosphere, and possibly the solid Earth. A better understanding of this interval is thus important to an understanding of the diversification of complex life, the history of long-term climatic change and the evolution of global geochemical cycles. Increasingly detailed temporal records are being acquired from Ediacaran rocks to investigate these changes in time, but we still lack a robust paleogeographic framework to study them in space. Paleomagnetic data—which are used to quantitatively determine the ancient position of continents—appear unusually complex and often contradictory throughout this period. The nature of these complex data remains elusive and four distinct hypotheses have been forwarded to explain them: 1) the tectonic plates were moving especially fast, 2) many of the paleomagnetic data have been corrupted in some as-yet unrecognized way, 3) the solid Earth underwent rapid bouts of true polar wander, or 4) the magnetic field was behaving abnormally. Each of these hypotheses have far-reaching implications. Hypotheses 1, 3 and 4 reflect processes which differ dramatically from their present-day counterparts and defy prevailing paradigms of secular change, whereas hypothesis 2 raises questions about the reliability of existing paleomagnetic interpretations and their paleogeographic derivatives. Significant advances will be garnered through resolution of this enigma, but its endurance reflects its intricacy, and any solution is going to require a collective effort. With the aim to stimulate additional community efforts toward solving it, we probe these multiple working hypotheses, elaborate how they may be further tested and discuss the implications of their possible validation.

• Giuliani, Andrea; Schmidt, Max W.; Torsvik, Trond Helge & Fedortchouk, Yana (2023). Genesis and evolution of kimberlites. Nature Reviews Earth & Environment. 4, p. 738–753. doi: 10.1038/s43017-023-00481-2. Full text in Research Archive
• Abdelmalak, Mohamed Mansour; Gac, Sebastien; Faleide, Jan Inge; Shephard, Grace; Tsikalas, Filippos & Polteau, Stephane [Show all 8 contributors for this article] (2022). Quantification and Restoration of the Pre-Drift Extension Across the NE Atlantic Conjugate Margins During the Mid-Permian-Early Cenozoic Multi-Rifting Phases. Tectonics. ISSN 0278-7407. 42(1). doi: 10.1029/2022TC007386. Full text in Research Archive Show summary

  The formation of the NE Atlantic conjugate margins is the result of multiple rifting phases spanning from the Late Paleozoic and culminating in the early Eocene when breakup was accompanied with intense magmatic activity. The pre-breakup configuration of the NE Atlantic continental margins is controlled by crustal extension, magmatism, and sub-lithospheric processes, all of which need to be quantified for the pre-breakup architecture to be restored. Key parameters that need to be extracted from the analysis of crustal structures and sediment record include stretching factors, timing of rifting phases, and nature of the deep crustal structures. The aim of this study is to quantify the pre-drift extension of the NE Atlantic conjugate margins using interpreted crustal structure and forward basin modeling. We use a set of eight 2D conjugate crustal transects and corresponding stratigraphic models, constrained from an integrated analysis of 2D and 3D seismic and well data. The geometry and thickness of the present-day crust is compared to a reference thickness which has experienced limited or no crustal extension since Permian time allowing the quantification of crustal stretching. Based on the eight conjugate crustal transects, the total pre-drift extension is estimated to range between 181 and 390 km with an average of 270–295 km. These estimates are supported by the results of forward basin modeling, which predict total extension between 173 and 325 km, averaging 264 km. The cumulative pre-drift extension estimates derived from basin modeling are in turn used to calculate the incremental crustal stretching factors at each of the three main rifting phases between the conjugate Greenland-Norwegian margins. The mid-Permian early Triassic rifting phase represents 32% of the total extension, while the equivalent values are 41% for the mid-Jurassic to mid-Cretaceous and 27% for the Late Cretaceous-Paleocene rifting phases. These values are used to establish and present at first, a full-fit palinspastic plate kinematic model for the NE Atlantic since the mid-Permian and will be the base for future work on more elaborated models in order to build accurate paleogeographic and tectonic maps.

• Zhang, Hongrui & Torsvik, Trond Helge (2022). Circum-Tethyan magmatic provinces, shifting continents and Permian climate change. Earth and Planetary Science Letters. ISSN 0012-821X. 584. doi: 10.1016/j.epsl.2022.117453. Full text in Research Archive
• Kulakov, Evgeniy & Torsvik, Trond Helge (2022). Comment on “Paleomagnetism of the Guanyang Devonian sedimentary successions in Guangxi province, South China” by Wu et al. Gondwana Research. ISSN 1342-937X. 107, p. 66–72. doi: 10.1016/j.gr.2022.03.002. Full text in Research Archive
• Marcilly, Chloe M.; Torsvik, Trond Helge & Conrad, Clinton Phillips (2022). Global Phanerozoic sea levels from paleogeographic flooding maps. Gondwana Research. ISSN 1342-937X. 110, p. 128–142. doi: 10.1016/j.gr.2022.05.011. Full text in Research Archive Show summary

  The validity of sea level estimates based on stratigraphic correlations has been debated since the 1990 s as relative sea level curves differ between sites due to local tectonics, different deposition rates and changes in dynamic topography. Here, we offer a new eustatic (global) sea level curve for the past 520 million years (Myrs) based on observations of global flooding. We use paleogeographic reconstructions to measure the area of today’s exposed land that was flooded in the past (modern-land flooding). We then apply the modern global hypsometric slope to reconstruct the sea level history. We find minimum sea levels (comparable to today’s level) towards the end of Pangea (210 Ma) and peak levels (∼280 m higher than today) at 80 Ma when Pangea was widely dispersed. A first-order “supercontinent” cycle of 250 million years (Myrs) is recognized but we also document a second-order cycle of 37 Myrs that was previously thought to be undetectable using the hypsometric method. The hypsometric slope is critical for reconstructing past sea levels, and steepening the hypsometric slope during Pangea assembly implies dramatically larger sea level fluctuations. Our new sea level curve shares strong similarities with stratigraphic constraints and correlates with seafloor production proxies throughout the Phanerozoic. Measurements of global flooding represent averages across great continental extents, making them less sensitive than stratigraphic analyses to regional-scale vertical land motion, such as from dynamic topography and hence more reliable for estimating eustatic sea level. This method can also help to identify local deviations caused by regional uplift or subsidence and serves to constrain geodynamic mechanisms for sea level change. Our new sea level reconstruction usefully tracks global variations in Phanerozoic eustatic sea level, but also opens opportunities to estimate such variations in deeper time.

• Marcilly, Chloe M.; Maffre, Pierre; Hir, Guillaume Le; Pohl, Alexandre; Fluteau, Frédéric & Godderis, Yves [Show all 9 contributors for this article] (2022). Understanding the early Paleozoic carbon cycle balance and climate change from modelling. Earth and Planetary Science Letters. ISSN 0012-821X. 594. doi: 10.1016/j.epsl.2022.117717. Full text in Research Archive Show summary

  The Ordovician global cooling trend observed by several temperature proxies, which coincides with one of the most significant evolutionary diversifications on Earth, is yet to be fully understood. This study presents new simulations of pCO2 and surface temperatures using a spatially resolved climate-carbon cycle Earth system model fed with refined continental reconstructions and new estimates of solid Earth degassing. First, in order to quantify the respective roles of paleogeography and degassing, the impact of continental drift alone is investigated. This is done by calculating its imprint on continental weathering rates throughout the Ordovician under a constant pCO2, and by testing different topography inputs. Secondly, the sensitivity of the Earth's climate to paleogeography and carbon degassing changes is investigated by coupling the climate and carbon cycles in the GEOCLIM model. Based on our experiments we show that, although Early Ordovician high temperatures can be replicated within error margins, our new constraints cannot explain the intense cooling over the Mid to Late Ordovician, even if a progressive enhancement in Earth surface weatherability is taken into account. By using GEOCLIM in an inverse modelling approach, we calculate that the theoretical degassing necessary to reach proxy-derived temperatures for the Early Ordovician is three-to-five times higher compared to modern values. Further, in order to simulate the following Ordovician cooling trend, the solid Earth degassing must be reduced to modern-day values in only 30 Myrs. We conclude that, if accepting the veracity of the high Early Ordovician temperatures, alternative sources but also sinks of carbon must be considered to explain the climatic shift over the period.

• Kulakov, Evgeniy; Slagstad, Trond; Ganerød, Morgan & Torsvik, Trond Helge (2022). Paleomagnetism and ⁴⁰Ar/³⁹Ar geochronology of Meso-Neoproterozoic rocks from southwest Norway. Implications for magnetic remanence ages and the paleogeography of Baltica in a Rodinia supercontinent context. Precambrian Research. ISSN 0301-9268. 379. doi: 10.1016/j.precamres.2022.106786. Full text in Research Archive Show summary

  Here we present new 40Ar/39Ar geochronology, rock magnetic, and paleomagnetic data obtained from rocks from three distinct domains of the Precambrian Sveconorwegian orogen (Southern Norway) that record progressively younger orogenic events from east to west. The first locality is in the Bamble lithotectonic unit and the other two areas are located within the Telemark and Rogaland–Vest Agder sectors in the central and southwestern parts of the Telemark lithotectonic unit, respectively. New and existing geochronology data on metamorphism and cooling, combined with detailed rock magnetic analyses indicate that studied rocks cooled and blocked (acquired) the natural remanent magnetization at ∼ 1090 Ma (Bamble Lithotectonic unit), 1000 Ma (Central Telemark), and at around 900 Ma in the westernmost part of the Telemark Lithotectonic Unit. Accordingly, the new paleomagnetic poles for the Bamble (Plat = -6.6°N, Plong = 218.4°E, N = 38, A95 = 6.1°, K = 15.6), central Telemark (Plat = -17.4° N, Plong = 229.8° E, N = 23. A95 = 6.5 °, K = 22.6), and western Telemark Lithotetonic Unit (Plat = -46.2° N, Plong = 209.4° E, N = 9, A95 = 12.0, K = 19.4) were assigned 1090 Ma, 1000 Ma, and 900 Ma ages, respectively. The new Bamble paleomagnetic pole reconstructs Baltica at ∼ 1090 Ma with noticeable latitudinal gap from the eastern Laurentian margin and thus does not support classical Baltica-Laurentia configuration within the Rodinia supercontinent. The other two younger poles, when used together with the coeval paleomagnetic data from Laurentia do not support the traditionally envisaged Meso- to Neoproterozoic Baltica-Laurentia relationship either. Overall, the new data do not lend any support to the close connection between the two continents during the proposed Rodinia tenure but instead emphasize the problems with the traditional paleogeographic reconstructions of Rodinia. The new data appear more in line with the geological record within the Sveconorwegian orogen, which indicates that the orogeny developed at or behind active continental margins. While Baltica and Laurentia may have resided at broadly similar latitudes between 1000 and 900 Ma, there is no geologic and paleomagnetic evidence for placing them next to each other.

• Marcilly, Chloe M.; Torsvik, Trond Helge; Domeier, Mathew Michael & Royer, Dana L. (2021). New paleogeographic and degassing parameters for long-term carbon cycle models. Gondwana Research. ISSN 1342-937X. 97, p. 176–203. doi: 10.1016/j.gr.2021.05.016. Full text in Research Archive Show summary

  Long-term carbon cycle models are critical for understanding the levels and underlying controls of atmospheric CO2 over geological time-scales. We have refined the implementation of two important boundary conditions in carbon cycle models, namely consumption by silicate weathering and carbon degassing. Through the construction of continental flooding maps for the past 520 million years (Myrs), we have estimated exposed land area relative to the present-day (fA), and the fraction of exposed land area undergoing silicate weathering (fAW-fA). The latter is based on the amount of exposed land within the tropics (±10°) plus the northern/southern wet belts (40-50°N/S) relative to today, which are the prime regions for silicate weathering. We also evaluated climate gradients and potential weatherability by examining the distribution of climate-sensitive indicators. This is particularly important during and after Pangea formation, when we reduce fAW-fA during times when arid equatorial regions were present. We also estimated carbon degassing for the past 410 Myrs using subduction flux from full-plate models as a proxy. We then, for the first time, used the subduction flux to scale and normalize the arc-related zircon age distribution (arc-activity), which allows us to estimate carbon degassing in much deeper time. The effect of these refined modelling parameters for weathering and degassing was then tested in the GEOCARBSULF model, and the results are compared to other climate models and CO2 proxies. The use of arc-activity as a proxy for carbon degassing brings Mesozoic model estimates closer to CO2 proxy values but our models are highly sensitive to the definition of fAW-fA. Considering the land availability to weathering to only variations in tropical latitudes (corrected for arid regions) combined with our new degassing estimates leads to notably higher CO2 levels in the Mesozoic and a better fit with the CO2 proxies.

• Domeier, Mathew Michael; Font, Eric; Youbi, Nasrrddine; Davies, Joshua H.F.L.; Nemkin, Samantha & Voo, Rob Van der [Show all 10 contributors for this article] (2021). On the Early Permian shape of Pangea from paleomagnetism at its core. Gondwana Research. ISSN 1342-937X. 90, p. 171–198. doi: 10.1016/j.gr.2020.11.005. Full text in Research Archive Show summary

  Although central to an understanding of Earth's paleogeography and the myriad processes that it affects, the geometry of Pangea during the early phase of its lifetime has remained a topic of contention since the plate tectonic revolution. Despite decades of analysis and discussion, the crux of this debate still largely hinges on sparse, legacy paleomagnetic data derived from early Permian rocks of the Moroccan Meseta. In this work, we present the results of a study designed to revisit, update and expand on those key data, with the provision of new geochronologic and paleomagnetic results from six Permo-Carboniferous basins in central Morocco. New U-Pb zircon ages from volcanic rocks substantiate and refine existing geochronological data and reveal that volcanism among the studied basins spanned approximately 30 Ma, from at least 305 to 277 Ma, but was possibly punctuated by a more intense pulse in the mid-early Permian (~285 Ma). These new U-Pb data furthermore suggest that the age estimates previously assigned to the key poles from the Moroccan Meseta are probably too young, by some ~10 Ma. New paleomagnetic results from six basins yielded a common, well-defined remanent magnetization from 20 sites that is demonstrated to be pre-middle Permian in age. However, it remains unclear whether this magnetization (which is directionally similar to the previous paleomagnetic data from the same basins) is a primary magnetization acquired at ~285 Ma, or a syn-folding remagnetization that was acquired shortly thereafter, at ~275 Ma. In adopting both interpretations as alternative hypotheses, we examine the corresponding paleogeographic implications of both. Through exhaustive comparisons with reference apparent polar wander paths and the direct reconstruction of Gondwana using these new paleomagnetic results, we demonstrate that in either case (i.e. whether the remanent magnetization is primary or was acquired soon after during folding) the data is compatible with a Pangea A geometry during the early Permian. We close with a topical discussion of some persisting arguments used to defend Pangea B and why we consider them to be flawed.

• Kulakov, Evgeniy; Torsvik, Trond Helge; Doubrovine, Pavel V.; Slagstad, Trond; Ganerød, Morgan & Silkoset, Petter [Show all 7 contributors for this article] (2021). Jurassic fast polar shift rejected by a new high-quality paleomagnetic pole from southwest Greenland. Gondwana Research. ISSN 1342-937X. 97, p. 240–262. doi: 10.1016/j.gr.2021.05.021. Full text in Research Archive Show summary

  A selective compilation of paleomagnetic data from North America indicates that a vast amount of rapid polar motion occurred in Late Jurassic time. The over 30° polar shift that accumulated during a relatively short time interval (~160–145 Ma) suggests an episode of fast true polar wander (TPW) and was referred to as the Jurassic “monster polar shift” by some workers. However, this rapid TPW event is not supported by paleomagnetic data on a global scale. Here, we scrutinize the Jurassic apparent polar wander path (APWP) by virtue of a new paleomagnetic and 40Ar/39Ar geochronology study of Mesozoic coast-parallel dykes exposed in southwest Greenland. Combined with existing geochronological data, our results show that the dykes were emplaced during a prolonged period centered at 147.6 ± 3.4 Ma (2σ). A primary nature of the characteristic remanent magnetization is supported by multiple positive baked contact tests and a reversal test. The paleomagnetic pole calculated from 40 site-mean paleomagnetic directions is located at Plat = 69.3°S, Plong = 5.0°E (A95 = 4.6°), or at Plat = 73.9°S and Plong = 0.4°E when reconstructed to North America. Our new high-quality paleomagnetic pole and an updated global APWP do not support the fast Jurassic polar shift but instead indicate steady polar motion with moderate rates of about 0.7°/Myr. The new pole effectively reduces the mismatch between the APWPs for Laurentia and Europe. Our critical reassessment of the monster polar shift indicates that it may be an artifact of paleomagnetic and geochronological data that were previously used to argue for its existence.

• Torsvik, Trond Helge; Svensen, Henrik; Steinberger, Bernhard; Royer, Dana L.; Jerram, Dougal Alexander & Jones, Morgan Thomas [Show all 7 contributors for this article] (2021). Connecting the Deep Earth and the Atmosphere. Geophysical Monograph Series. ISSN 0065-8448. 263, p. 413–453. doi: 10.1002/9781119528609.ch16. Full text in Research Archive
• Cocks, L. Robin M. & Torsvik, Trond Helge (2020). Ordovician palaeogeography and climate change. Gondwana Research. ISSN 1342-937X. doi: 10.1016/j.gr.2020.09.008. Full text in Research Archive Show summary

  New palaeogeographical reconstructions for the earlier Ordovician (480 Ma), and later Ordovician (450 Ma) integrate revised longitude-calibrated palaeomagnetic reconstructions and the inclusion of synthetic plate margins within the now-vanished oceanic areas. There are substantial published differences from the previous placing of some of the continents and terranes in Asia; for example, Siberia and Gondwana have previously been placed at varied distances and relative positions in relation to the Kazakh terranes, South and North China, and Tarim. But there are only minor changes for most of the world, particularly in the North American and European areas. The global distributions of benthic trilobites and brachiopods within faunal provinces and their changes through the Ordovician are plotted, including the new term Cathay-Tasman Province for some pan-equatorial brachiopod faunas from China and Australia, and key sites and provinces are shown on the revised maps. The 30 Myrs from 470 to 440 Ma (mid Ordovician to early Silurian) saw some of the most varied and changeable climates of the whole Phanerozoic culminating in the ‘Hirnantian’ ice age. Those changes in turn much affected the rates of evolution of many benthic and pelagic animal groups which were driven by both biological and environmental causes. Global cooling during the Ordovician was a prime factor by reducing sea surface temperatures which challenged life to evolve faster and more substantially than before. That cooling was driven by decreasing atmospheric CO2, for reasons that are not fully resolved, but probably included reduced sourcing (reduced continental arc activity) combined with increased silicate weathering due to the advent of land plants and perhaps the progressive exhumation of low-latitude collisional arcs. Since long-term CO2 sinks are largely controlled by palaeogeography, the general increase in the concentration of continents in the tropics during the Ordovician increased the overall global weathering.

• Franke, Wolfgang; Cocks, Leonard Robert Morrison & Torsvik, Trond Helge (2020). Detrital zircons and the interpretation of palaeogeography, with the Variscan Orogeny as an example. Geological Magazine. ISSN 0016-7568. 157(4), p. 690–694. doi: 10.1017/S0016756819000943. Full text in Research Archive
• Hinsbergen, Douwe Van; Torsvik, Trond Helge; Schmid, Stefan M.; Matenco, Liviu; Maffione, Marco & Vissers, Reinoud L.M. [Show all 8 contributors for this article] (2019). Orogenic architecture of the Mediterranean region and kinematic reconstruction of its tectonic evolution since the Triassic. Gondwana Research. ISSN 1342-937X. 81, p. 79–229. doi: 10.1016/j.gr.2019.07.009. Full text in Research Archive
• Torsvik, Trond Helge; Steinberger, Bernhard; Shephard, Grace; Doubrovine, Pavel; Gaina, Carmen & Domeier, Mathew [Show all 8 contributors for this article] (2019). Pacific‐Panthalassic reconstructions: Overview, errata and the way forward. Geochemistry Geophysics Geosystems. 20(7), p. 3659–3689. doi: 10.1029/2019GC008402. Full text in Research Archive Show summary

  We have devised a new absolute Late Jurassic‐Cretaceous Pacific plate model using a fixed hot spot approach coupled with paleomagnetic data from Pacific large igneous provinces (LIPs) while simultaneously minimizing plate velocity and net lithosphere rotation (NR). This study was motivated because published Pacific plate models for the 83.5‐ to 150‐Ma time interval are variably flawed, and their use affects modeling of the entire Pacific‐Panthalassic Ocean and interpretation of its margin evolution. These flaws could be corrected, but the revised models would imply unrealistically high plate velocities and NR. We have developed three new Pacific realm models with varying degrees of complexity, but we focus on the one that we consider most realistic. This model reproduces many of the Pacific volcanic paths, modeled paleomagnetic latitudes fit well with direct observations, plate velocities and NR resulting from the model are low, and all reconstructed Pacific LIPs align along the surface‐projected margin of the Pacific large low shear wave velocity province. The emplacement of the Shatsky Rise LIP at ~144 Ma probably caused a major plate boundary reorganization as indicated by a major jump of the Pacific‐Izanagi‐Farallon triple junction and a noteworthy change of the Pacific‐Izanagi seafloor spreading direction at around chron M20 time.

• Owen-Smith, T.M.; Ganerød, Morgan; Hinsbergen, Douwe J J van; Gaina, Carmen; Ashwal, Lewis D. & Torsvik, Trond Helge (2019). Testing Early Cretaceous Africa - South America fits with new palaeomagnetic data from the Etendeka Magmatic Province (Namibia). Tectonophysics. ISSN 0040-1951. 760, p. 23–35. doi: 10.1016/j.tecto.2017.11.010. Full text in Research Archive Show summary

  We provide an independent test for the proposed pre-breakup fits between the South American and African continental margins based on new palaeomagnetic data. In the course of modelling the opening of the South Atlantic Ocean, several reconstructions have been proposed, which correspond to different estimates of the amount of pre-drift extension in the South American and African continental margins, and amounts of displacement along intracontinental accommodation zones. The Paraná–Etendeka Large Igneous Province erupted during a brief time interval between ~ 136 and ~ 131 Ma, just prior to opening of the South Atlantic, and has magmatic products on both the African (Etendeka lavas) and South American (Paraná lavas) plates. Here we provide new palaeomagnetic constraints on the Etendeka volcanic rocks. These yield a declination of D ± ∆ Dx = 314.4 ± 7.0° and inclination of I ± ∆ Ix = − 42.7 ± 8.3° (Plat = 47.5, PLon = 88.9, K = 26.1, A95 = 6.3, n = 21). When our results are combined with another recently published dataset, we obtain an Etendeka palaeopole at 49.1° S, 87.6° E (D ± ∆ Dx = 315.9 ± 3.8°, I ± ∆ Ix = − 43.9 ± 4.4°, K = 23.4, A95 = 3.5, n = 75). We compare three recent models for South Atlantic Ocean opening, discuss which of the models best fits the palaeomagnetic data, and present a revised reconstruction for West Gondwana during the Early Cretaceous.

• Torsvik, Trond Helge & Cocks, L. Robin M. (2019). The integration of palaeomagnetism, the geological record and mantle tomography in the location of ancient continents. Geological Magazine. ISSN 0016-7568. 156(2), p. 242–260. doi: 10.1017/S001675681700098X. Full text in Research Archive
• Domeier, Mathew & Torsvik, Trond Helge (2019). Full-plate modelling in pre-Jurassic time. Geological Magazine. ISSN 0016-7568. 156(2), p. 261–280. doi: 10.1017/S0016756817001005. Full text in Research Archive
• Steinberger, Bernhard; Bredow, Eva; Lebedev, Sergei; Schaeffer, Andrew & Torsvik, Trond Helge (2019). Widespread volcanism in the Greenland–North Atlantic region explained by the Iceland plume. Nature Geoscience. ISSN 1752-0894. 12(1), p. 61–68. doi: 10.1038/s41561-018-0251-0. Full text in Research Archive Show summary

  In the classical concept, a hotspot track is a line of volcanics formed as a plate moves over a stationary mantle plume. Defying this concept, intraplate volcanism in Greenland and the North Atlantic region occurred simultaneously over a wide area, particularly around 60 million years ago, showing no resemblance to a hotspot track. Here, we show that most of this volcanism can nonetheless be explained solely by the Iceland plume interacting with seafloor spreading ridges, global mantle flow and a lithosphere (the outermost rigid layer of the Earth) with strongly variable thickness. An east–west corridor of thinned lithosphere across central Greenland, as inferred from new, highly resolved tomographic images, could have formed as Greenland moved westward over the Iceland plume between 90 and 60 million years ago. Our numerical geodynamic model demonstrates how plume material may have accumulated in this corridor and in areas east and west of Greenland. Simultaneous plume-related volcanic activities starting about 62 million years ago on either side of Greenland could occur where and when the lithosphere was thin enough due to continental rifting and seafloor spreading, possibly long after the plume reached the base of the lithosphere.

• Tegner, Christian; Andersen, Torgeir Bjørge; Kjøll, Hans Jørgen; Brown, Eric L.; Hagen-Peter, Graham & Corfu, Fernando [Show all 8 contributors for this article] (2019). A mantle plume origin for the Scandinavian Dyke Complex: a "piercing point" for 615 Ma plate reconstruction of Baltica? Geochemistry Geophysics Geosystems. 20(2), p. 1075–1094. doi: 10.1029/2018GC007941. Full text in Research Archive Show summary

  Abstract The origin of Large Igneous Provinces (LIPs) associated with continental breakup and the reconstruction of continents older than c. 320 million years (pre-Pangea) are contentious research problems. Here we study the petrology of a 615 - 590 Myr dolerite dyke complex that intruded rift-basins of the magma-rich margin of Baltica and now is exposed in the Scandinavian Caledonides. These dykes are part of the Central Iapetus Magmatic Province (CIMP), a LIP emplaced in Baltica and Laurentia during opening of the Caledonian Wilson Cycle. The >1000 km long dyke complex displays lateral geochemical zonation from enriched to depleted basaltic compositions from south to north. Geochemical modelling of major and trace elements shows these compositions are best explained by melting hot mantle 75-250°C above ambient mantle. Although the trace element modelling solutions are non- unique, the best explanation involves melting a laterally zoned mantle plume with enriched and depleted peridotite lithologies, similar to present-day Iceland and to the North Atlantic Igneous Province. The origin of CIMP appears to have involved several mantle plumes. This is best explained if rifting and breakup magmatism coincided with plume generation zones at the margins of a Large Low Shear-wave Velocity Province (LLSVP) at the core mantle boundary. If the LLSVPs are quasi-stationary back in time as suggested in recent geodynamic models, the CIMP provides a guide for reconstructing the paleogeography of Baltica and Laurentia 615 million years ago to the LLSVP now positioned under the Pacific Ocean. Our results provide a stimulus for using LIPs as piercing points for plate reconstructions.

• Berndt, Christian; Planke, Sverre; Teagle, Damon; Huismans, Ritske; Torsvik, Trond Helge & Frieling, Joost [Show all 12 contributors for this article] (2019). Northeast Atlantic breakup volcanism and consequences for Paleogene climate change – MagellanPlus Workshop report. Scientific Drilling. ISSN 1816-8957. 26, p. 69–85. doi: 10.5194/sd-26-69-2019. Full text in Research Archive Show summary

  The northeast Atlantic encompasses archetypal examples of volcanic rifted margins. Twenty-five years after the last ODP (Ocean Drilling Program) leg on these volcanic margins, the reasons for excess melting are still disputed with at least three competing hypotheses being discussed. We are proposing a new drilling campaign that will constrain the timing, rates of volcanism, and vertical movements of rifted margins. This will allow us to parameterise geodynamic models that can distinguish between the hypotheses. Furthermore, the drilling-derived data will help us to understand the role of breakup magmatism as a potential driver for the Palaeocene–Eocene thermal maximum (PETM) and its influence on the oceanographic circulation in the earliest phase of the northeast Atlantic Ocean formation. Tackling these questions with a new drilling campaign in the northeast Atlantic region will advance our understanding of the long-term interactions between tectonics, volcanism, oceanography, and climate and the functioning of subpolar northern ecosystems and climate during intervals of extreme warmth.

• Domeier, Mathew; Magni, Valentina; Hounslow, Mark W. & Torsvik, Trond Helge (2018). Episodic zircon age spectra mimic fluctuations in subduction. Scientific Reports. 8. doi: 10.1038/s41598-018-35040-z. Full text in Research Archive Show summary

  Decades of geochronological work have shown the temporal distribution of zircon ages to be episodic on billion-year timescales and seemingly coincident with the lifecycle of supercontinents, but the physical processes behind this episodicity remain contentious. The dominant, end-member models of fluctuating magmatic productivity versus selective preservation of zircon during times of continental assembly have important and very different implications for long-term, global-scale phenomena, including the history of crustal growth, the initiation and evolution of plate tectonics, and the tempo of mantle outgassing over billions of years. Consideration of this episodicity has largely focused on the Precambrian, but here we analyze a large collection of Phanerozoic zircon ages in the context of global, full-plate tectonic models that extend back to the mid-Paleozoic. We scrutinize two long-lived and relatively simple active margins, and show that along both, a relationship between the regional subduction flux and zircon age distribution is evident. In both cases, zircon age peaks correspond to intervals of high subduction flux with a ~10–30 Ma time lag (zircons trailing subduction), illuminating a possibly intrinsic delay in the subduction-related magmatic system. We also show that subduction fluxes provide a stronger correlation to zircon age distributions than subduction lengths do, implying that convergence rates play a significant role in regulating the volume of melting in subduction-related magmatic systems, and thus crustal growth.

• Torsvik, Trond Helge (2018). Earth history: A journey in time and space from base to top. Tectonophysics. ISSN 0040-1951. doi: 10.1016/j.tecto.2018.09.009. Full text in Research Archive
• Svensen, Henrik; Torsvik, Trond Helge; Callegaro, Sara; Augland, Lars Eivind; Heimdal, Thea Hatlen & Jerram, Dougal Alexander [Show all 8 contributors for this article] (2018). Gondwana large igneous provinces: plate reconstructions, volcanic basins and sill volumes. In: Large Igneous Provinces from Gondwana and Adjacent Regions. Geological Society Special Publication. ISSN 0305-8719. 463, p. 17–40. doi: 10.1144/SP463.7. Full text in Research Archive
• Tappe, Sebastian; Smart, Katie; Torsvik, Trond Helge; Massuyeau, Malcolm & Wit, Mike de (2018). Geodynamics of kimberlites on a cooling Earth: Clues to plate tectonic evolution and deep volatile cycles. Earth and Planetary Science Letters. ISSN 0012-821X. 484, p. 1–14. doi: 10.1016/j.epsl.2017.12.013. Full text in Research Archive
• Jerram, Dougal Alexander; Sharp, Ian; Torsvik, Trond Helge; Poulsen, Ragnar; Watton, Timothy J. & Freitag, Ulrike [Show all 15 contributors for this article] (2018). Volcanic constraints on the unzipping of Africa from South America: Insights from new geochronological controls along the Angola margin. Tectonophysics. ISSN 0040-1951. doi: 10.1016/j.tecto.2018.07.027. Full text in Research Archive
• Franke, Wolfgang; Cocks, L. Robin M. & Torsvik, Trond Helge (2017). The Palaeozoic Variscan oceans revisited. Gondwana Research. ISSN 1342-937X. 48, p. 257–284. doi: 10.1016/j.gr.2017.03.005. Full text in Research Archive
• Ashwal, Lewis D.; Wiedenbeck, Michael & Torsvik, Trond Helge (2017). Archaean zircons in Miocene oceanic hotspot rocks establish ancient continental crust beneath Mauritius. Nature Communications. 8. doi: 10.1038/ncomms14086. Full text in Research Archive Show summary

  A fragment of continental crust has been postulated to underlie the young plume-related lavas of the Indian Ocean island of Mauritius based on the recovery of Proterozoic zircons from basaltic beach sands. Here we document the first U–Pb zircon ages recovered directly from 5.7 Ma Mauritian trachytic rocks. We identified concordant Archaean xenocrystic zircons ranging in age between 2.5 and 3.0 Ga within a trachyte plug that crosscuts Older Series plume-related basalts of Mauritius. Our results demonstrate the existence of ancient continental crust beneath Mauritius; based on the entire spectrum of U–Pb ages for old Mauritian zircons, we demonstrate that this ancient crust is of central-east Madagascar affinity, which is presently located ∼700 km west of Mauritius. This makes possible a detailed reconstruction of Mauritius and other Mauritian continental fragments, which once formed part of the ancient nucleus of Madagascar and southern India.

• Tappe, Sebastian; Romer, Rolf L.; Stracke, Andreas; Steenfelt, Agnete; Smart, Katie A. & Muehlenbachs, Karlis [Show all 7 contributors for this article] (2017). Sources and mobility of carbonate melts beneath cratons, with implications for deep carbon cycling, metasomatism and rift initiation. Earth and Planetary Science Letters. ISSN 0012-821X. 466, p. 152–167. doi: 10.1016/j.epsl.2017.03.011. Full text in Research Archive
• Domeier, Mathew; Shephard, Grace; Jakob, Johannes; Gaina, Carmen; Doubrovine, Pavel & Torsvik, Trond Helge (2017). Intraoceanic subduction spanned the Pacific in the Late Cretaceous–Paleocene. Science Advances. 3(11). doi: 10.1126/sciadv.aao2303. Full text in Research Archive Show summary

  The notorious ~60° bend separating the Hawaiian and Emperor chains marked a prominent change in the motion of the Pacific plate at ~47 Ma (million years ago), but the origin of that change remains an outstanding controversy that bears on the nature of major plate reorganizations. Lesser known but equally significant is a conundrum posed by the pre-bend (~80 to 47 Ma) motion of the Pacific plate, which, according to conventional plate models, was directed toward a fast-spreading ridge, in contradiction to tectonic forcing expectations. Using constraints provided by seismic tomography, paleomagnetism, and continental margin geology, we demonstrate that two intraoceanic subduction zones spanned the width of the North Pacific Ocean in Late Cretaceous through Paleocene time, and we present a simple plate tectonic model that explains how those intraoceanic subduction zones shaped the ~80 to 47 Ma kinematic history of the Pacific realm and drove a major plate reorganization.

• Torsvik, Trond Helge; Doubrovine, Pavel; Steinberger, Bernhard; Gaina, Carmen; Spakman, Wim & Domeier, Mathew (2017). Pacific plate motion change caused the Hawaiian-Emperor Bend. Nature Communications. 8. doi: 10.1038/ncomms15660. Full text in Research Archive Show summary

  A conspicuous 60° bend of the Hawaiian-Emperor Chain in the north-western Pacific Ocean has variously been interpreted as the result of an abrupt Pacific plate motion change in the Eocene (∼47 Ma), a rapid southward drift of the Hawaiian hotspot before the formation of the bend, or a combination of these two causes. Palaeomagnetic data from the Emperor Seamounts prove ambiguous for constraining the Hawaiian hotspot drift, but mantle flow modelling suggests that the hotspot drifted 4–9° south between 80 and 47 Ma. Here we demonstrate that southward hotspot drift cannot be a sole or dominant mechanism for formation of the Hawaiian-Emperor Bend (HEB). While southward hotspot drift has resulted in more northerly positions of the Emperor Seamounts as they are observed today, formation of the HEB cannot be explained without invoking a prominent change in the direction of Pacific plate motion around 47 Ma.

• Steinberger, Bernhard; Seidel, Miriam-Lisanne & Torsvik, Trond Helge (2017). Limited true polar wander as evidence that Earth's nonhydrostatic shape is persistently triaxial. Geophysical Research Letters. ISSN 0094-8276. 44(2), p. 827–834. doi: 10.1002/2016GL071937. Full text in Research Archive Show summary

  Earth’s spin axis follows the maximum moment of inertia axis of mantle convection, with some delay due to adjustment of the rotational bulge. Here we compute this axis for geodynamic models based on subduction history, assuming constant slab sinking speed, with another contribution due to thermochemical piles. For a wide range of parameters, a large shift of ≈90∘ is predicted around 80–90 Ma. It can be largely attributed to a change in circum-Pacific subduction from predominantly in the North and South toward East and West. Actual amounts of true polar wander are much smaller, pointing toward additional inertia tensor contributions, possibly due to slabs in the lowermost mantle below both polar regions. These slabs would have been subducted before ≈150 Ma, when plate motions in the Panthalassa basin are largely unknown. Matching predicted and observed true polar wander can serve at constraining such plate motions. This research was originally published in Geophysical Research Letters. © 2017 American Geophysical Union

• Jerram, Dougal Alexander; Widdowson, Mike; Wignall, Paul B.; Sun, Yadong; Lai, Xulong & Bond, David P.G. [Show all 7 contributors for this article] (2016). Submarine palaeoenvironments during Emeishan flood basalt volcanism, SW China: Implications for plume-lithosphere interaction during the Capitanian, Middle Permian ('end Guadalupian') extinction event. Palaeogeography, Palaeoclimatology, Palaeoecology. ISSN 0031-0182. 441, p. 65–73. doi: 10.1016/j.palaeo.2015.06.009. Full text in Research Archive
• Ashwal, Lewis; Torsvik, Trond Helge; Horvath, P.; Harris, C; Webb, S. & Werner, Stephanie C. [Show all 7 contributors for this article] (2016). A Mantle-derived Origin for Mauritian Trachytes. Journal of Petrology. ISSN 0022-3530. 57(9), p. 1645–1675. doi: 10.1093/petrology/egw052. Full text in Research Archive
• Doubrovine, Pavel; Steinberger, Bernhard & Torsvik, Trond Helge (2016). A failure to reject: Testing the correlation between large igneous provinces and deep mantle structures with EDF statistics. Geochemistry Geophysics Geosystems. 17(3), p. 1130–1163. doi: 10.1002/2015GC006044. Full text in Research Archive Show summary

  Absolute reconstructions of large igneous provinces (LIPs) for the past 300 Ma reveal a remarkable spatial pattern suggesting that almost all LIPs have erupted over the margins of the two large‐scale structures in the Earth's lower mantle commonly referred to as the Large Low Shear‐wave Velocity Provinces (LLSVPs). This correlation suggests that mantle plumes that have triggered LIP eruptions rose from the margins of LLSVPs, implying long‐term stability of these structures and suggesting that they may be chemically distinct from the bulk of the mantle. Yet, some researchers consider the LLSVPs to be purely thermal upwellings, arguing that the observed distribution of LIPs can be explained by plumes randomly forming over the entire areas of LLSVPs. Here we examine the correlation between the LIPs and LLSVPs using nonparametric statistical tests, updated plate reconstructions, and a large number of alternative definitions of LLSVPs based on seismic tomography. We show that probability models assuming plume sources originating at the margins of LLSVPs adequately explain the observed distribution of reconstructed LIPs. In contrast, we find strong evidence against the models seeking to link LIPs with plumes randomly forming over the entire LLSVP areas. However, the hypothesis proposing that the correlation can be explained by plumes randomly forming over a larger area of slower‐than‐average shear wave velocities in the lowermost mantle cannot be ruled out formally. Our analysis suggests that there is no statistically sound reason for questioning the hypothesis that the LIPs correlate with the margins of LLSVP globally. This research was originally published in Geochemistry, Geophysics, Geosystems. © 2016 American Geophysical Union

• Domeier, Mathew; Doubrovine, Pavel; Torsvik, Trond Helge; Spakman, Wim & Bull, Abigail (2016). Global correlation of lower mantle structure and past subduction. Geophysical Research Letters. ISSN 0094-8276. 43(10), p. 4945–4953. doi: 10.1002/2016GL068827. Full text in Research Archive
• Gassmöller, René; Dannberg, Juliane; Bredow, Eva; Steinberger, Bernhard & Torsvik, Trond Helge (2016). Major influence of plume-ridge interaction, lithosphere thickness variations, and global mantle flow on hotspot volcanism - The example of Tristan. Geochemistry Geophysics Geosystems. 17(4), p. 1454–1479. doi: 10.1002/2015GC006177. Full text in Research Archive Show summary

  Hotspot tracks are thought to originate when mantle plumes impinge moving plates. However, many observed cases close to mid‐ocean ridges do not form a single age‐progressive line, but vary in width, are separated into several volcanic chains, or are distributed over different plates. Here we study plume‐ridge interaction at the example of the Tristan plume, which features all of these complexities. Additionally, the South Atlantic formed close to where plume volcanism began, opening from the south and progressing northward with a notable decrease in magmatism across the Florianopolis Fracture Zone. We study the full evolution of the Tristan plume in a series of three‐dimensional regional models created with the convection code ASPECT. We then compute crustal thickness maps and compare them to seismic profiles and the topography of the South Atlantic. We find that the separation of volcanism into the Tristan and Gough chain can be explained by the position of the plume relative to the ridge and the influence of the global flow field. Plume material below the off‐ridge track can flow toward the ridge and regions of thinner lithosphere, where decompression melting leads to the development of a second volcanic chain resembling the Tristan and Gough hotspot tracks. Agreement with the observations is best for a small plume buoyancy flux of 500 kg/s or a low excess temperature of 150 K. The model explains the distribution of syn‐rift magmatism by hot plume material that flows into the rift and increases melt generation. This research was originally published in Geochemistry, Geophysics, Geosystems. © 2016 American Geophysical Union

• Midtkandal, Ivar; Svensen, Henrik; Planke, Sverre; Corfu, Fernando; Polteau, Stephane & Torsvik, Trond Helge [Show all 11 contributors for this article] (2016). The Aptian (Early Cretaceous) oceanic anoxic event (OAE1a) in Svalbard, Barents Sea, and the absolute age of the Barremian-Aptian boundary. Palaeogeography, Palaeoclimatology, Palaeoecology. ISSN 0031-0182. 463, p. 126–135. doi: 10.1016/j.palaeo.2016.09.023. Full text in Research Archive Show summary

  The age of the Cretaceous Barremian-Aptian boundary has been a long-standing problem in the geological timescale. Age suggestions range between 126 Ma and 117 Ma, making causal links between environmental crises and large-scale processes such as large igneous provinces (LIPs) problematic. New stratigraphic and radiometric data from three drillcores in Svalbard show that Barremian shelf siltstones and sandstones are overlain by Aptian shallow-marine mudstones. The organic carbon content in the mudstones is higher than 1.0 wt%, with values ranging up to 70 wt% in coal-dominated intervals. Carbon isotope measurements of the TOC show a negative δ13C excursion of 4.5‰ followed by a positive excursion of 6.7‰ within a 20-m interval, identified as the early Aptian Oceanic Anoxic Event 1a (OAE1a). This isotopic pattern of the excursion is in perfect agreement with excursions from lower latitude sections of the same age. A ~ 10-cm-thick zircon-bearing bentonite was discovered in the lower part of the Barremian, about 40 m below the OAE1a interval. U-Pb TIMS zircon analyses of two equivalent bentonites in adjacent boreholes gave a robust age of 123.1 ± 0.3 Ma. Based on the Barremian depositional systems, we estimate that a time interval of 1–2 Myr separates the bentonite and the OAE1a, providing an age of about 121–122 Ma for the Barremian-Aptian boundary. Our results stress that the geological timescale needs revision, and provide a benchmark test for the correlation between the OAE1a and LIPs in general.

• Torsvik, Trond Helge; Steinberger, Bernhard; Ashwal, Lewis D.; Doubrovine, Pavel & Trønnes, Reidar G (2016). Earth evolution and dynamics—a tribute to Kevin Burke. Canadian journal of earth sciences (Print). ISSN 0008-4077. 53(11), p. 1073–1087. doi: 10.1139/cjes-2015-0228. Full text in Research Archive Show summary

  Kevin Burke’s original and thought-provoking contributions have been published steadily for the past 60 years, and more than a decade ago he set out to resolve how plate tectonics and mantle plumes interact by proposing a simple conceptual model, which we will refer to as the Burkian Earth. On the Burkian Earth, mantle plumes take us from the deepest mantle to sub-lithospheric depths, where partial melting occurs, and to the surface, where hotspot lavas erupt today, and where large igneous provinces and kimberlites have erupted episodically in the past. The arrival of a plume head contributes to continental break-up and punctuates plate tectonics by creating and modifying plate boundaries. Conversely, plate tectonics makes an essential contribution to the mantle through subduction. Slabs restore mass to the lowermost mantle and are the triggering mechanism for plumes that rise from the margins of the two large-scale low shear-wave velocity structures in the lowermost mantle, which Burke christened TUZO and JASON. Situated just above the core–mantle boundary, beneath Africa and the Pacific, these are stable and antipodal thermochemical piles, which Burke reasons represent the immediate after-effect of the moon-forming event and the final magma ocean crystallization. This research has been accepted and published in the Canadian Journal of Earth Sciences. © 2016 NRC Research Press

• Steinberger, Bernhard; Spakman, Wim; Japsen, Peter & Torsvik, Trond Helge (2015). The key role of global solid-Earth processes in preconditioning Greenland’s glaciation since the Pliocene. Terra Nova. ISSN 0954-4879. 27(1), p. 1–8. doi: 10.1111/ter.12133. Full text in Research Archive Show summary

  After >500 Ma of absence, major Northern Hemisphere glaciations appeared during the Plio-Pleistocene, with Greenland leading other northern areas. Here, we propose that three major solid-Earth processes underpinned build-up of the Greenland ice-sheet. First, a mantle-plume pulse, responsible for the North Atlantic Igneous Province at ~60 Ma, regionally thinned the lithosphere. Younger plume pulses led to uplift, which accelerated at ~5 Ma, lifting the parts of the East Greenland margin closest to Iceland to elevations of more than 3 km above sea level. Second, plate-tectonic reconstruction shows a ~6° northward component of Greenland motion relative to the mantle since ~60 Ma. Third, a concurrent northward rotation of the entire mantle and crust towards the pole, dubbed True Polar Wander (TPW), contributed an additional ~12° change in latitude. These global geodynamic processes preconditioned Greenland to sustain long-term glaciation, emphasizing the role of solid-Earth processes in driving long-term global climatic transitions.

• Voo, Rob Van der; Hinsbergen, D.J.J van; Domeier, Mathew; Spakman, Wim & Torsvik, Trond Helge (2015). Latest Jurassic-earliest Cretaceous closure of the Mongol-Okhotsk Ocean: A paleomagnetic and seismological-tomographic analysis. Geological Society of America, Special Paper. ISSN 0072-1077. 513, p. 589–606. doi: 10.1130/2015.2513(19. Full text in Research Archive
• Torsvik, Trond Helge & Burke, Kevin (2015). Large igneous province locations and their Connections With the core-mantle boundary. In Schmidt, Anja; Fristad, Kirsten & Elkins-Tanton, Linda T. (Ed.), Volcanism and global environmental change. Cambridge University Press. ISSN 9781107058378. p. 30–46. doi: 10.1017/cbo9781107415683.005. Full text in Research Archive

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• Torsvik, Trond Helge & Cocks, Robin (2017). Earth History and Palaeogeography. Cambridge University Press. ISBN 9781107105324. 317 p. Full text in Research Archive

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• Torsvik, Trond Helge (2026). Apparent polar wander paths and their errors. Full text in Research Archive
• Straume, Eivind Olavson; Torsvik, Trond Helge & Domeier, Mathew Michael (2026). Paleogeography linking mantle processes, climate, and biotic evolution. Full text in Research Archive
• Torsvik, Trond Helge (2025). Planetary Habitability. Full text in Research Archive Show summary

  The idea that worlds around other stars could develop and maintain environments hospitable to life ― in a way like our planet ― has captivated scientists for centuries. Yet, to investigate this question, we must recognize and characterize the key conditions that make a planet habitable. This endeavour is the prime objective for the Centre for Planetary Habitability (PHAB). The only planet on which life is known to have originated (Earth) appears unique in many ways, including the presence of abundant surface water, a large moon, a long-lived magnetic field, and plate tectonics. Yet, which of these and other characteristics are essential for its long-term habitability? Equally, how have Earth’s physical and chemical attributes, and thus our planet’s proclivity for life, evolved? How can we recognize distant worlds around other stars that have been or could be habitable? These questions, and a new understanding of planetary habitability unfolding from them, are especially important as we now embark on an unprecedented era of exploration and discovery of extra-solar planetary systems.

• Torsvik, Trond Helge (2025). Planetær beboelighet og fortidens klimautvikling. Full text in Research Archive Show summary

  Torsdag 30. oktober er det fagleg-pedagogisk dag ved Universitetet i Oslo. Denne dagen tilbyr lærarar fagleg påfyll i undervisningsfaga sine. Institutt for geofag og NHM deltar i år med fire foredrag i fagløp geofag. Velkommen til alle interesserte!

• Torsvik, Trond Helge (2025). Darwin Day 2025: Astrobiology and the origin of life - CEES - Centre for Ecological and Evolutionary Synthesis. Full text in Research Archive Show summary

  Open lectures on the prerequisites for life, the origin and evolution of life, and the possibilities of life elsewhere in the universe by Trond H. Torsvik, Sarah Johnson, Liv Hornekær, and Tue Hassenkam. The event will be held in English.

• Torsvik, Trond Helge (2025). Den store oksygenhendelsen: Jordens viktigste vippepunkt - Universitetsbiblioteket. Full text in Research Archive Show summary

  Er du nysgjerrig på å vite mer om den store oksygenhendelsen? Den definerer et av de viktigste positive vippepunktene i jordens historie når det gjelder planeters beboelighet og banet vei for komplekse livsformer. Kom på GeoOnsdag med foredrag av professor Trond Helge Torsvik fra Institutt for Geofag. 

• Shephard, Grace; Abdelmalak, Mohamed Mansour; Faleide, Jan Inge; Clennett, Edward; Gac, Sebastien & Zahirovic, Sabin [Show all 9 contributors for this article] (2025). A basin-to-plate deformable plate framework to capture the multi-phase rifting of the Northeast Atlantic. Full text in Research Archive
• Setså, Ronny & Torsvik, Trond Helge (2024). Får høyeste utmerkelse i London. [Internet]. geoforskning.no. Full text in Research Archive
• Torsvik, Trond Helge (2024). The fourth revolution – Plumes, plates, and climate. Geoscientist. 34, p. 22–23. Full text in Research Archive
• Marcilly, Chloe M.; Torsvik, Trond Helge & Conrad, Clinton Phillips (2024). Corrigendum to “Global Phanerozoic sea levels from paleogeographic flooding maps” [Gondwana Res. 110 (2022) 128–142, (S1342937X22001563), (10.1016/j.gr.2022.05.011)]. Gondwana Research. ISSN 1342-937X. 129, p. 367–368. doi: 10.1016/j.gr.2024.01.006. Full text in Research Archive
• Torsvik, Trond Helge (2024). Early Earth and the Boring Billion. Full text in Research Archive
• Torsvik, Trond Helge (2024). Linking Surface and Deep Processes. Full text in Research Archive
• Tegner, Christian; Andersen, Torgeir Bjørge; Kjøll, Hans Jørgen; Brown, Eric L.; Graham-Hagen, Peter & Corfu, Fernando [Show all 8 contributors for this article] (2024). Dyke Complexes of the Scandinavian Caledonides. Full text in Research Archive Show summary

  Dyke Complexes of the Scandinavian Caledonides Christian Tegnera, Torgeir B. Andersenb, Hans Jørgen Kjøllb, Eric L. Browna, Graham Hagen-Peterc, Fernando Corfub, Sverre Plankeb, and Trond H. Torsvikb aDepartment of Geoscience, Aarhus University, Denmark, christian.tegner@geo.au.dk; bDepartment of Geosciences, University of Oslo, Norway; cEarth Sciences, Vrije Universiteit Amsterdam, Netherlands Dyke complexes (c. 615 – 560 Ma) exposed in the Scandinavian Caledonides are part of the Central Iapetus Magmatic Province, a large igneous province related to the opening of the Iapetus Ocean and an earlier phase of the North Atlantic Wilson Cycle. These include a >1000 km long dyke complex preserved in the Särv, Seve and Corrovarre nappes (Andréasson et al., 1998; Hollocher et al., 2007; Tegner et al., 2019) and dykes of the Seiland Igneous Province preserved in the Kalak nappe (Robins and Takla, 1979; Reginiussen et al., 1995). The compositions of the >1000 km long dyke complex is mainly tholeiitic and displays lateral geochemical zonation from enriched to depleted basaltic compositions from south to north. In addition, the central part of this dyke complex (in Trøndelag, Norway and Jämtland, Sweden) displays alkali basalt compositions. In contrast, the dykes of the Seiland Igneous Province are entirely composed of alkali basalts including ankaramite, picrite and lamprophyres. In this talk we will review the geochemical details of the basaltic magmas in the Scandinavian dyke complexes and discuss their origin from heterogenous and most likely multiple mantle plumes, and from enriched subcontinental lithospheric mantle. References Andréasson, P.G., Svenningsen, O.M., Albrecht, L. (1998). Dawn of Phanerozoic orogeny in the North Atlantic tract; Evidence from the Seve-Kalak Superterrane, Scandinavian Caledonides. Journal of the Geological Society of Sweden GFF 120, 159–172. doi:10.1080/11035899801202159 Hollocher, K., Robinson, P., Walsh, E., Terry, M.P. (2007). The Neoproterozoic Ottfjället dike swarm of the Middle Allochthon, traced geochemically into the Scandian Hinterland, Western Gneiss Region, Norway. American Journal of Science 307, 901–953. doi:10.2475/06.2007.02 Reginiussen, H., Ravna, E.J.K., Berglund, K. (1995). Mafic Dykes from Øksfjord, Seiland Igneous Province, northern Norway: geochemistry and palaeotectonic significance. Geological Magazine 132, 667–681. Robins, B., Takla, M.H. (1979). Geology and geochemistry of a metamorphosed picrite-ankaramite dyke suite from the Seiland province, northern Norway. Norsk Geologisk Tidsskrift 59, 67-95. Tegner, C., Andersen, T.B., Kjøll, H.J., Brown, E.L., Hagen-Peter, G., Corfu, F., Planke, S., and Torsvik, T.H. (2019). A mantle plume origin for the Scandinavian Dyke Complex: a “piercing point” for 615 Ma plate reconstruction of Baltica? Geochemistry, Geophysics, Geosystems 20, 1075-1094. doi:10.1029/2018GC007941

• Shephard, Grace; Faleide, Jan Inge; Gaina, Carmen; Abdelmalak, Mohamed Mansour; Gac, Sebastien & Torsvik, Trond Helge (2022). Building deformable plate models for the Northeast Atlantic. Full text in Research Archive
• Marcilly, Chloe M.; Torsvik, Trond Helge; Domeier, Mathew Michael & Royer, Dana L. (2021). Refining key parameters for long-term carbon cycle models. Full text in Research Archive
• Marcilly, Chloe M.; Torsvik, Trond Helge; Domeier, Mathew Michael & Royer, Dana L. (2021). Revising key parameters for long-term carbon cycle models. Full text in Research Archive
• Tegner, Christian; Andersen, Torgeir Bjørge; Kjøll, Hans Jørgen; Brown, Eric L.; Hagen-Peter, Graham & Corfu, Fernando [Show all 8 contributors for this article] (2021). A mantle plume origin for the Scandinavian Dyke Complex: a “piercing point” for 615 Ma plate reconstruction of Baltica? Full text in Research Archive Show summary

  The origin of Large Igneous Provinces (LIPs) associated with continental breakup and the reconstruction of continents older than c. 320 million years (pre-Pangea) are contentious research problems. Here we study the petrology of a 615 - 590 Myr dolerite dyke complex that intruded rift-basins of the magma-rich margin of Baltica and now is exposed in the Scandinavian Caledonides. These dykes are part of the Central Iapetus Magmatic Province (CIMP), a LIP emplaced in Baltica and Laurentia during opening of the Caledonian Wilson Cycle. The >1000 km long dyke complex displays lateral geochemical zonation from enriched to depleted basaltic compositions from south to north. Geochemical modelling of major and trace elements shows these compositions are best explained by melting hot mantle 75-250°C above ambient mantle. Although the trace element modelling solutions are non-unique, the best explanation involves melting a laterally zoned mantle plume with enriched and depleted peridotite lithologies, similar to present-day Iceland and to the North Atlantic Igneous Province. The origin of CIMP appears to have involved several mantle plumes. This is best explained if rifting and breakup magmatism coincided with plume generation zones at the margins of a Large Low Shear-wave Velocity Province (LLSVP) at the core mantle boundary. If the LLSVPs are quasi-stationary back in time as suggested in recent geodynamic models, the CIMP provides a guide for reconstructing the paleogeography of Baltica and Laurentia 615 million years ago to the LLSVP now positioned under the Pacific Ocean. Our results provide a stimulus for using LIPs as piercing points for plate reconstructions.

• Torsvik, Trond Helge; Svensen, Henrik; Steinberger, Bernhard; Royer, Dana L.; Jerram, Dougal Alexander & Jones, Morgan Thomas [Show all 7 contributors for this article] (2020). Connecting the Deep Earth and the Atmosphere. Full text in Research Archive
• Shephard, Grace; Abdelmalak, Mohamed Mansour; Gaina, Carmen; Faleide, Jan Inge; Torsvik, Trond Helge & Jackson, Ruth [Show all 9 contributors for this article] (2019). A Greenland centered puzzle: Updated plate reconstructions of the North Atlantic and Arctic. Full text in Research Archive
• Shephard, Grace; Gaina, Carmen; Torsvik, Trond Helge & Faleide, Jan Inge (2019). Plate tectonics and mantle structure of the Arctic, North Atlantic, and Panthalassa: recent updates. Full text in Research Archive
• Domeier, Mathew; Torsvik, Trond Helge; Conrad, Clinton Phillips; Steinberger, Bernhard; Doubrovine, Pavel & Trønnes, Reidar G [Show all 9 contributors for this article] (2019). On the stability of Earth’s degree 2 mantle structures. Full text in Research Archive
• Domeier, Mathew; Torsvik, Trond Helge; Conrad, Clinton Phillips; Steinberger, Bernhard; Doubrovine, Pavel V. & Trønnes, Reidar G [Show all 9 contributors for this article] (2019). On the stability of Earth’s degree 2 mantle structure. European Geosci. Union, Gen. Assembly, Geophys. Res. Abstr.. Full text in Research Archive
• Andersen, Torgeir Bjørge; Jakob, Johannes; Kjøll, Hans Jørgen; Quintela, Orlando; Corfu, Fernando & Torsvik, Trond Helge [Show all 9 contributors for this article] (2019). Hyperextension in magma-poor and magma-rich domains along the pre-Caledonian passive margin of Baltica. Full text in Research Archive Show summary

  Hyperextension in magma-poor and magma-rich domains along the pre-Caledonian passive margin of Baltica Torgeir B. Andersen, Johannes Jakob, Hans-Jørgen Kjøll, Orlando Quintela, Fernando Corfu, Trond H. Torsvik, 1)Christian Tegner, 2)Loic Labrousse and 3)Geoffroy Mohn CEED, Univ. Oslo; 1)Århus Univ.; 2)Sorbonne Univ, ISTeP-Paris; 3)Univ. Cergy-Pontoise Email: t.b.andersen@geo.uio.no The pre-Caledonian Baltican rifted margin has been outlined as a tapering wedge with increasing magmatism towards the ocean-continent transition (OCT), and with a mostly similar structure along its length. It is, however, well-known that passive margins can be complex, with different and diachronous segment-evolutions along and across strike. The Baltican nappes in the Scandes preserve a complexity akin to modern margins, including an OCT, a micro-continent and continental slivers, hyperextended-to-embryonic oceanic basins as well as a major magma-rich segment. The margin was several hundred-, probably up to 1500 km wide, before its distal parts were affected by convergence between ~480 and 450 Ma. Its vestiges, overprinted by Scandian and earlier fabrics as well as the late/post-orogenic extension, now occur at low to middle structural levels in the mountain belt. Proximal parts comprise continental to marine rift-basins with syn- to post-rift deposits of Late Cryogenian, Ediacaran and Lower Palaeozoic age. Its vestiges also comprise continental slivers, coarse- to fine-grained sediments as well as deep-marine deposits. A major change in the nappe-structure occurs across a NW-SE transverse zone parallel to a fundamental basement structure within Baltica, the Sveconorwegian front. The most prominent changes across this lineament are: 1) the coincidence with the NE-termination of the Jotun-Lindås-Dalsfjord nappe complex, interpreted as the Jotun- Lindås-Dalsfjord microcontinent (JMC) and 2) the transition from the magma-rich segment in the NE to the hyperextended, magma-poor segment in the SW. The latter has numerous (>100) solitary meta-peridotites and detrital serpentinites (some fossiliferous). The mantle-fragments w/ophicalcite breccias were emplaced tectonically and are covered mostly by deep-basin sediments and local breccias and conglomerates. This ‘mixed’ (mélange) unit was locally affected by pre-Caledonian metasomatism and intruded by gabbros and granitoids (at ~487±1 to 471±2 Ma); this magmatism is also reflected by clastic zircons (>468 Ma) present in the sediments. Other important features are Baltican basement slivers (up to 40 x 1.5 km). The magma-poor SW segment is overlain by a huge basement/cover nappe complex, which after rifting, but prior to Scandian collision, was positioned outboard the hyperextended domain as the Jotun-Lindås-Dalsfjord Microcontinent (JMC). JMC´s distal parts at Atløy, have mafic dykes and lavas in the Høyvik Gp, and were affected by early-Caledonian event(s). The SW margin segment was ~400 km long, hyperextended- and magma-poor, and received sediments as late as the Middle Ordovician (and perhaps until the onset of the mid-Silurian Scandian orogeny?). The NE magma-rich segment also has mantle peridotites and detrital serpentinites (locally w/fossils), but its most prominent characteristic is the Scandinavian Dyke Complex (SDC) forming parts of a ~615-595 Ma Large Igneous Province that probably assisted opening of the Iapetus Ocean. In the SW segment there is so far no evidence of Late Proterozoic magmatism, but Baltican basement was locally truncated by mafic dykes at ~850 to 830Ma and 615 Ma. The magma-poor SW segment, inboard the JMC, formed a transitional-crust basin opening to an ocean basin, similar to the present North Atlantic rift system between Ireland and the Hatton-Rockall ribbons. The margin of Baltica probably has its best modern analogue in the North-Atlantic and Norwegian-Greenland Sea margins.

• Andersen, Torgeir Bjørge; Jakob, Johannes; Kjøll, Hans Jørgen; Corfu, Fernando; Torsvik, Trond Helge & Tegner, Christian [Show all 8 contributors for this article] (2018). Architecture and Palaeography of the per-Caldonian Margin of Baltica. Full text in Research Archive
• Andersen, Torgeir Bjørge; Jakob, Johannes; Kjøll, Hans Jørgen; Corfu, Fernando; Planke, Sverre & Torsvik, Trond Helge [Show all 9 contributors for this article] (2018). The Pre-Caledonian Margin of Baltica: overview and research in progress. Full text in Research Archive Show summary

  The Caledonian margin of Baltica formed by continental break-up of Rodinia in the Late Proterozoic to Ediacaran. With exception of the dike-swarm near Egersund in SW Norway, the Fennoscandian basement including the autochthonous basement windows along the axis of the mountain belt were little affected by the magmatism associated with the break-up. The distal parts, however, were strongly attenuated, hyper-extended and a 1000 km long segment, intensively intruded by a Large Igneous Province (LIP), the Pre-Caledonian LIP (PC-LIP). Here, we provide glimpses of our work in progress from the vestiges of the margin. More details on several aspects of the margin evolution are presented by co-authors. Here we present a regional model for the pre-Caledonian margin suggesting it was highly complex and included micro-continental sliver(s) and both a hyperextended, magma-poor domain with transition(s) to attenuated embryonic oceanic and magma-rich margin domains. The break-up related PC-LIP magmatism lasted from approximately 615 to 570 Ma, but the most intense activity appears to have been at ~600 Ma. Our ongoing work suggests that the impingement of a mantle plume on the Ediacaran continental lithosphere was associated with a temperature anomaly of ~100oC, causing widespread melting of the asthenosphere and dyke-intrusion of the continental crust and sediments of the margin. We suggest that the pre-Caledonian margin of the Iapetus preserved in the Scandes comprise most of the elements of passive continental margins, and that it probably represents one of the best exposed field analogue for the deeper and least known parts of passive margins.

• Tegner, Christian; Andersen, Torgeir Bjørge; Kjøll, Hans Jørgen; Brown, Eric L.; Hagen-Peter, Graham & Corfu, Fernando [Show all 8 contributors for this article] (2018). The pre-Caledonian Scandinavian Dyke Complex and 600 Ma plate reconstructions of Baltica. Full text in Research Archive Show summary

  A spectacular dyke complex is surprisingly well preserved along c. 1000 km in the Caledonian nappes of central and northern Scandinavia. This dyke complex was originally emplaced into continental sedimentary basins along the rifted margin of Baltica, it is part of the Central Iapetus Magmatic Province (CIMP), and it has U-Pb ages of 615-590 Ma. To constrain its origin and to potentially guide plate reconstructions of Baltica we: (1) re-visited the dyke complexes of the Ottfjället, Sarek, Kebnekaise, Tornetrask and Indre Troms mountains of Sweden and Norway; (2) produced new and compiled published geochemical data; (3) modeled mantle sources and melting dynamics; and (4) extended reconstructions of the paleo-position of Baltica back to 600 Ma. The compiled dataset includes c. 600 analyses that forms a coherent suite dominated by tholeiitic ferrobasalt, but including alkali basalts in the central portion. The tholeiitic dykes display lateral variations in geochemical enrichment (e.g. delta-Nb, La/Sm(N) and Sr isotopes) in the southern and central portions, grading to more depleted compositions in the north. Our petrological modeling suggests melting of asthenospheric mantle involving at least two source compositions at temperatures elevated about 100 °C above ambient mantle, consistent with melting of a zoned mantle plume originating from a plume generation zone at the core-mantle boundary. If the position of the present plume generation zone in the Pacific can be viewed as stationary back to 600 Ma, we entertain the idea that the Scandinavian Dyke Complex may be used to guide plate reconstructions.

• Tegner, Christian; Andersen, Torgeir Bjørge; Brown, Eric L.; Corfu, Fernando; Planke, Sverre & Kjøll, Hans Jørgen [Show all 7 contributors for this article] (2017). The pre-Caledonian Scandinavian Dyke Complex and 600 Ma plate reconstructions of Baltica. Full text in Research Archive Show summary

  Magmatism of the first known rifting phase of the North Atlantic Wilson cycle is surprisingly well preserved in the Cale- donian nappes of central and northern Scandinavia. Along c. 1000 km the Särv and Seve Nappes are characterised by spectacular dyke complexes and other intrusive forms origi- nally emplaced into continental sedimentary basins along the rifted margin of Iapetus. We refer to this as the magma-rich segment of the pre-Caledonian margin of Baltica, in contrast to the hyper-extended and magma-poor segment exposed in southern Norway (Andersen et al., Jakob et al., this meeting). In the larger picture the Scandinavian Dyke Complex is part of the Central Iapetus Magmatic Province ( ). The intensity, volume and structure of the Scandinavian Dyke Complex is comparable to that of the present passive margins of the North Atlantic large igneous province (Kjøll et al., this meeting) and U-Pb ages suggest magmatism was short-lived at 610-590 Ma. To constrain the origin of the Scandinavian Dyke Complex and to potentially guide plate reconstructions of Baltica we: (1) re-visited the dyke complexes of the Särv, Sarek, Kebnekaise, Tornetrask and Indre Troms mountains of Sweden and Norway; (2) compiled new and published geochemical data for the entire dyke complex; (3) modeled mantle sources and melting dy- namics; and (4) extended reconstructions of the paleo-position of Baltica back to 600 Ma. Although the appearance of the dykes ranges from garnet amphibolite gneiss to pristine mag- matic intrusions, all bulk rock compositions largely reflect the original magmatic rock. The compiled dataset includes c. 600 analyses that essentially forms a coherent suite dominated by tholeiitic ferrobasalt akin to the North Atlantic large igneous province, but including alkali basalts in the central portion where meta-carbonatite is also reported. A few samples (<30) are significantly contaminated with crust, but most are largely uncontaminated. The tholeiitic dykes display systematic lateral variations over c. 1000 km in trace element compositions suggesting geochem- ical enrichment (e.g. delta-Nb and La/Sm(N) relative to mid- ocean ridge basalt) in the southern and central portions, grad- ing to more depleted compositions in the north. The most enriched tholeiites occur in the central portion that also in- cludes alkali basalts. The lateral geochemical zoning is com- parable to e.g. the North Atlantic large igneous province and around Iceland today. Our petrological modeling suggests melting of asthenospheric mantle involving at least two source compositions at temperatures elevated above ambiant mantle. We therefore speculate that the Scandinavian Dyke Complex formed by melting of a zoned mantle plume originating from a plume generation zone (margins of large low shear-wave velocity provinces) at the core-mantle boundary. If the posi- tion of the present plume generation zone in the Pacific can be viewed as stationary back to 600 Ma, we entertain the idea that the Scandinavian Dyke Complex may be used to guide plate reconstructions.

• Faleide, Jan Inge; Abdelmalak, Mohamed Mansour; Shephard, Grace; Torsvik, Trond Helge; Gaina, Carmen & Tsikalas, Filippos [Show all 9 contributors for this article] (2017). Quantification and restoration of pre-drift extension across NE Atlantic conjugate margins. Full text in Research Archive
• Torsvik, Trond Helge & Domeier, Mathew (2017). Correspondence: Numerical modelling of the PERM anomaly and the Emeishan large igneous province. Nature Communications. 8:821, p. 1–3. doi: 10.1038/s41467-017-00125-2. Full text in Research Archive
• Andersen, Torgeir Bjørge; Jakob, Johannes; Kjøll, Hans Jørgen; Corfu, Fernando; Planke, Sverre & Torsvik, Trond Helge [Show all 8 contributors for this article] (2017). The Pre-Caledonian Margin of Baltica. Full text in Research Archive Show summary

  The pre-Caledonian margin of Baltica formed by the rifting and eventual continental break-up of Rodinia in the Late Proterozoic to Ediacaran. With exception of the ca. 615 Ma dolerite dike-swarm near Egersund in SW Norway, the Fennoscandian basement including the mostly autochthonous basement windows in western Scandinavia (Lofoten, Western Gneiss Region, etc.) were surprisingly little affected by the rifting and the subsequent magmatism associated with the break-up. The distal parts of the margin, however, were strongly attenuated, hyper-extended and in a more than 1000 km long segment, intensively intruded by a break-up related Large-Igneous Province (LIP), here referred to as the Pre-Caledonian LIP (PC-LIP). In this presentation, we provide glimpses of new results and observations as well as work in progress from a large part of the nappe-stack of Scandinavian Caledonides containing the vestiges of the pre-Caledonian margin. More details on several aspects of the Pre-Caledonian margin evolution are presented by co-workers during this meeting. Based on our recent and some previous work, we propose a regional paleogeography model for the pre-Caledonian passive margin as it evolved from the Ediacaran into the late-Cambrian to the early-Ordovician, when the Iapetus Ocean started closing. We suggest that the distal margin architecture was highly complex and included micro-continental sliver(s) and a hyperextended, magma-poor domain with transition(s) to highly attenuated embryonic oceanic and magma-rich passive margin domains. The break-up related PC-LIP magmatism lasted from approximately 615 to 570 Ma, but the most intense dyke-emplacement appears to have been around 600 Ma. Our ongoing structural and metamorphic petrology studies, combined with geochronology, geochemical analyses and petrological modelling suggest that the impingement of a mantle plume on the Ediacaran continental lithosphere may have been associated with a temperature anomaly of up to 100oC, causing widespread melting of the asthenosphere as well as partial melt-generation in highly attenuated and intensely dike-intruded parts of the continental crust and sediments of the margin. It is our opinion that the pre-Caledonian distal margin rocks of the Iapetus as preserved in nappes of Scandinavian Caledonides preserve most of the elements of wide passive margins, and that it probably represents one of the best exposed field analogue for the deeper and least known parts of passive margins.

• Tegner, Christian; Andersen, Torgeir Bjørge; Brown, Eric L.; Corfu, Fernando; Planke, Sverre & Kjøll, Hans Jørgen [Show all 7 contributors for this article] (2017). The pre-Caledonian Scandinavian Dyke Complex and 600 Ma plate reconstructions of Baltica. Full text in Research Archive
• Doubrovine, Pavel; Torsvik, Trond Helge & Domeier, Mathew (2017). Paleomagnetism and paleosecular variation from the late Miocene to recent lavas of Mauritius. Full text in Research Archive Show summary

  We present new paleomagnetic data from the late Miocene to recent lavas of the island of Mauritius in the southwestern Indian Ocean (20.3°S, 57.6°E). The island is a shield volcano that has formed over the Reunion hotspot and is composed of three temporally-distinct series of basaltic lavas: the Older Series (4.7-8.9 Ma), the Intermediate Series (1.7-3.5 Ma) and the Younger Series (0-1 Ma). Oriented core specimens were collected from 36 sampling sites covering all three lava series. Rock magnetic analyses indicate that the remanence carriers in these basalts are pseudo-single-domain titanomagnetites with variable degrees of high-temperature oxidation. Nearly half of the sites showed pervasive magnetic overprints imparted by lightning strikes. Nonetheless, in almost all cases (35 sites), we were able to isolate the characteristic (primary) remanence directions through detailed thermal and alternating field demagnetization experiments, using the principal component analysis of demagnetization data and the analysis of remagnetization circles. Both normal and reverse polarity directions were observed, with the mean direction of the reversely-magnetized lavas (15 sites, D = 189.2°, I = 44°, a95 = 5.3°) being steeper than and ca. 9° of antiparallel from the mean direction of the normal-polarity flows (20 sites, D = 1.1°, I = -37.3°, a95 = 6.9°). The mean normal and reverse directions yield a negative reversal test that is just significant at the 5% probability level (P = 4.5%). However, when our new data set is combined with previously published paleomagnetic results from Mauritius, the difference between the normal mean direction and the antipode of the reverse mean is not significant at the 5% level, yielding a positive reversal test. The paleomagnetic pole corresponding to the combined polarity data set excluding transitional directions (86.7°N, 186.2°E, A95 = 3.5°, n = 32) is slightly far-sided, but the difference between its position and the geographic pole is not statistically significant. The estimates of paleosecular variation (PSV) and inclination anomaly (Sb = 11°, DI = -2°) are in good agreement with the results of PSV studies of recent lavas erupted at low latitudes. The implications of our new results for the structure of time-averaged geomagnetic field and the latitude dependence of PSV will be discussed.

• Tegner, Christian; Andersen, Torgeir Bjørge; Corfu, Fernando; Planke, Sverre; Kjøll, Hans Jørgen & Torsvik, Trond Helge (2016). The pre-Caledonian Large Igneous Province and the North Atlantic Wilson Cycle. Full text in Research Archive
• Torsvik, Trond Helge & Trønnes, Reidar G (2016). VPRO Television Netherlands, 9.-13. mai, Tilrettelegging og instruksjon for filmproduksjon på Island i serien „The mind of the universe. A journey along the frontiers of knowledge“. Serien er open access under: www.vpro.nl/motu www.themindoftheuniverse.nl/ og Trond H. Torsvik (founding CEED-director) er hovedperson i dette programmet. Full text in Research Archive
• Midtkandal, Ivar; Faleide, Jan Inge; Planke, Sverre; Myrsini, Dimitriou; Dahlberg, Maria E. & Myklebust, Reidun [Show all 8 contributors for this article] (2015). Source-to-sink Dynamics in the Early Cretaceous Boreal Basin; Progradational Lobes from a Missing Source. Full text in Research Archive
• Trønnes, Reidar G & Torsvik, Trond Helge (2015). Dispersion of a continental crust component by the Iceland plume. Goldschmidt2015, Abstracts, 3175. Full text in Research Archive
• Torsvik, Trond Helge & Trønnes, Reidar G (2015). Deeply buried continental crust under Iceland. Forskning-no www.forskning.no/blogg/forskningsetikken/deeply-buried-continental-crust-under-iceland. Forskning.no. ISSN 1891-635X. Full text in Research Archive
• Torsvik, Trond Helge & Trønnes, Reidar G (2015). Deeply buried continental crust under Iceland. ScienceNordic http://sciencenordic.com/content/deeply-buried-continental-crust-under-iceland. ScienceNordic.com. Full text in Research Archive
• Torsvik, Trond Helge (2015). Paleomagnetism and Plate Tectonics. Full text in Research Archive
• Bull, Abigail Louise; Torsvik, Trond Helge & Shephard, Grace (2015). Past Plate Motions and The Evolution of Earth’s Lower Mantle: Relating LLSVPs and Plume Distribution. Full text in Research Archive
• Torsvik, Trond Helge (2015). Past Plate Motions and The Evolution of Earth’s Lower Mantle: Relating LLSVPs and Plume Distribution. Full text in Research Archive
• Domeier, Mathew & Torsvik, Trond Helge (2015). An explicit kinematic scenario for the Iapetus and Rheic Oceans. Full text in Research Archive
• Buiter, Susanne; Tetreault, Joya L. & Torsvik, Trond Helge (2015). Geodynamic models of the Wilson Cycle: From rifts to mountains to rifts. Full text in Research Archive

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