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
Sedimentary rocks can provide information about the Earth paleoenvironment and are studied extensively to understand the causes and consequences of global climate changes in deep time. They facilitate long-time perspectives that constrain climate models and provide analogues for how Earth systems may respond to, and recover from, intervals of profound environmental change, including projected anthropogenic change. The Norwegian Svalbard archipelago offers an extensive Phanerozoic stratigraphic record that reflects the geological evolution of the northern flanks of continental assemblages that include Laurentia, Eurasia, and Pangea. Svalbard's Phanerozoic sedimentary and paleoclimatic archive is controlled largely by Svalbard's overall northward plate-tectonic motion from equatorial to high latitudes but also by regional to local formation of topography and basins in response to long-term plate reorganization, as well as the near- and far-field influence of large igneous province activity on the tectono-stratigraphic and paleoclimatic development. Various sedimentary and geochemical proxies, such as bentonite beds and carbon isotope excursions associated with the far-reaching environmental effects of the Siberian Traps, the High Arctic Large Igneous Province, and the North Atlantic Igneous Province, are present in Svalbard's near complete geological record. As such, Svalbard is unique in that these and numerous other global environmental perturbations are recorded within a relatively restricted study area, with most of the key events preserved and recorded in easily accessible drill cores and well-exposed outcrop sections. Here we review deep-time paleoenvironmental and paleoclimate research in Svalbard by summarizing 148 peer-reviewed scientific articles. The review builds on the well-established tectono-stratigraphic and lithostratigraphic framework, as well as state-of-the art environmental reconstructions, to provide insights into the Earth system during the Phanerozoic northward drift of Svalbard and the many major biotic crises in the geological past. We focus on globally significant events including (i) the expansion of Devonian vegetation, (ii) the Carboniferous–Permian response to icehouse conditions during the Late Paleozoic Ice Age (LPIA), (iii) the End-Permian Mass Extinction (EPME) and the subsequent Triassic recovery, the (iv) Carnian Pluvial Episode, (v) Jurassic–Early Cretaceous climate perturbations including the Volgian Isotopic Carbon Excursion (VOICE) and the Aptian Ocean Anoxic Event 1a (OAE1a), and (vi) the Paleocene–Eocene Thermal Maximum (PETM). We present and synthesize existing core and outcrop data that preserve biological and geochemical proxies and climate-sensitive sedimentary facies that reflect environmental change in terrestrial and marine settings. Finally, we discuss the Phanerozoic climate recorded in Svalbard and its role in providing high-latitude calibration points for several global paleoclimate events to provide a higher-latitude perspective to complement the dominance of mid- and low-latitude locations and datasets in the literature.
Continental breakup at the North Svalbard margin and the northern Barents Sea during the Paleogene led to the opening of the oceanic Eurasia Basin. However, the mechanisms behind this rift-to-drift evolution remain unclear. Here, we present seven crustal transects (CT1–7) integrating 2D forward modelling of potential field data and constrained by structural interpretation of multichannel seismic reflection profiles. These transects extend from the continental regions of North Svalbard to the oceanic domain in southwest Eurasia Basin. The Yermak Plateau comprises two juxtaposed tectono-magmatic blocks: the Northeast Yermak Plateau, linked to pre- or early Eurekan settings, and the Southwest Yermak Plateau, formed by shearing and oblique extension along the West Svalbard margin. Broadly, the North Svalbard margin is divided into three segments: (1) Northwest Spitsbergen-Southwest Yermak Plateau, (2) Northeast Spitsbergen-Northwest Kvitøya, and (3) Northeast Kvitøya-North Barents. Segmentation follows inherited north-northwest trending weak zones, guiding Paleogene multi-phase oblique rifting and formation of the Sophia Basin, underlain by thinned, high-density metamorphic crust. The results indicate a rift-shear breakup mode with exhumation of continental lower crust and/or serpentinized subcontinental mantle blocks within the continent-ocean transition (COT) that precedes seafloor spreading which started at ca. 53 Ma during magnetic chron C24. The continental breakup processes that led to margin segmentation reflect the interplay between inherited basement fabrics and plate opening directions of the Eurasia Basin region.
Geology is omnipresent in Svalbard, defining among other parameters the location of all major settlements. The SVALGEOL chapter provides an overview of the geology of Svalbard, and how it influences local and global society. We briefly describe the history of geological exploration and mapping of Svalbard, before outlining the various data sets geoscientists use in their work. We then focus on two key aspects of geology: the study of “deep-time” (i.e., rocks older than 2.58 million years; the pre-Quaternary period) and the study of “deep-Earth” (i.e., integration of data from Earth’s surface to the interior). By investigating the Earth System at the scale of millions to billions of years, geologists can decipher how the global climate has varied through time. Furthermore, studying different proxies allows us to investigate the processes linking the geosphere with the biosphere (e.g., evolution of life, recovery following mass extinctions). By using field and various geophysical data, geologists can understand the properties of the Earth from its surface to its core, and the processes causing them. Furthermore, by coupling deep, shallow and surface observations with a time component, geoscientists can characterise the underlying processes that also influence society (e.g., natural gas emissions, permafrost development, geothermal potential, earthquakes)
Gravity data provide constraints on lateral subsurface density variations and thus provide crucial insights into the geological evolution of the region. Previously, gravity data from the Norwegian Arctic archipelago of Svalbard comprised an onshore regional gravity database with coarse station spacing of 2–20 km, offshore gravity profiles acquired in some fjords, airborne gravity, and satellite altimetry. The sparse regional point-based onshore coverage hampered the direct integration of gravity data with seismic profiles acquired onshore Svalbard in the late 1980s and early 1990s. In April 2022, we acquired gravity data at 260 new stations along seven profiles from western to eastern Spitsbergen, with a cumulative length of 329 km. The profiles were acquired directly along selected seismic profiles and provide much closer station spacing (0.5–2 km) compared to the regional inland grid (2–20 km) acquired in the late 1980s (total number of onshore stations: 1,037). Having processed the data, we compared the first-order density trends of our new data with the legacy regional grid. The new gravity data are consistent with the regional data, imaging a gravity low in the western part of the area underlying a foreland basin and a gravity high in the northwestern part of the area likely associated with a basement high or denser basement. We compare the new and vintage gravity using maps and profiles, linked to the known major tectonic features such as major basinal axes and fault zones, as well as other geophysical data sets including seismics and magnetics
In a scientific context, a suitable color choice is more than simple decoration. Color handling, as part of scientific visualization, is a scientific methodology that is one of the most widely used, given the importance of figures and images in conveying results. Yet, an expert-level understanding and application of proper scientific coloring is rare. Here, a concise overview of important color tools is provided and complemented by ready-to-apply resources for using color in science research, publishing, communication, tool development, editing, and teaching. This overview offers a guide to spot problems, master the methodology, and support accessible and accurate use of color for science figures in both short and long terms.
Intraplate volcanism has occurred for the last 35 million years within Northeast Atlantic and Arctic margins, including the western Barents Sea, Svalbard, and northern Greenland. Earlier studies have suggested that some of this volcanism might be sourced from nearby mid-ocean ridges. However, legacy data does not reveal correlations between the sporadic volcanism, despite comparable setting, ages, and compositions of basalts across the area. Here, we utilize a compilation of geophysical data to document late Cenozoic intraplate volcanism affecting the northeastern Yermak Plateau and southwestern Eurasia Basin located north of Svalbard. The identified seabed and subsurface features include volcanic (Mound-A) and hydrothermal vent systems (Tayrona Vent) formed approximately 10 and 2.6 million years ago, respectively. These intraplate volcanic products are coincident in age and origin with observed hydrothermal systems on Svalbard and Northeast Atlantic. We propose that these magmatic features are the result of intraplate volcanism associated with seismic and thermal anomalies in the mantle beneath northern Svalbard.
Yin, Yue; Crameri, Fabio; Shephard, Grace & Heron, Philip J.
(2024).
Changing your perspective: the impact of different visualisation methods on seismic hazard maps.
Canadian journal of earth sciences (Print).
ISSN 0008-4077.
61(12),
p. 1264–1282.
doi: 10.1139/cjes-2023-0123.
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A number of widely used colour palettes applied to display critical scientific results not only distort data but are also inaccessible to a proportion of the population. An issue with the rainbow palette (and variants such as “jet”) is that the gradients between the colours are not even. The impact of an uneven colour gradient is that certain colours are highlighted over others, distorting the underlying data. Furthermore, an uneven colour palette like rainbow may be inaccessible for people with colour vision deficiencies or colour blindness. When communicating scientific results, data should always be presented without distortion and be universally accessible. This is particularly important when communicating public-facing and time-critical information such as hazards. Here, we show the impact of changing the visualisation profile of seismic hazard maps on the perception of risk, as well as qualifying the public accessibility of this information. Using Canadian seismic hazard as an example, our results reveal that an uneven colour map applied to seismic hazard data can exaggerate lower hazard values and reduce the perception of extremely high hazard values. Applying an even colour gradient to our sample data not only allows this essential public resource to be universally accessible but was found to lead to the greatest visual change in regions with the most populated cities. The choice of colour map and subsequent data interpretations also holds relevance for considerations such as insurance. We highlight potential next steps to promote inclusiveness in data visualisation and welcome discussion on science communication best practices.
Heron, Philip J.; Dannberg, Juliane; Gassmöller, Rene; Shephard, Grace; Hunen, Jeroen Van & Pysklywec, Russel N.
(2024).
The impact of Pangean subducted oceans on mantle dynamics: Passive piles and the positioning of deep mantle plumes.
Gondwana Research.
ISSN 1342-937X.
138,
p. 168–185.
doi: 10.1016/j.gr.2024.10.007.
Full text in Research ArchiveShow summary
Seismic imaging of the Earth’s interior reveals plumes originating from relatively hot regions of the lowermost mantle, surrounded by cooler material thought to be remnants of ancient subducted oceans. Currently, there is no clear consensus on the internal composition of the hot regions, with end-member conditions being that they are thermo-chemical in nature or purely thermal plume clusters. Previous modelling studies have shown a range of scenarios where deep chemical heterogenities or purely thermal anomalies are essential in developing appropriate present-day mantle dynamics. Here, we add to this discussion by quantifying the location of rising mantle plumes using numerical 3-D global mantle convection models constrained by 410 million years of palaeo-ocean evolution (encompassing the formation and breakup of supercontinent Pangea). Our study compares numerical simulations with purely thermal convection to those where a deep thermo-chemical anomaly is laterally mobile. The results show that models both with and without large-scale chemical heterogeneities can generate appropriate present-day plume dynamics, which illustrate the power of sinking ocean plates to stir mantle ow and control the thermal evolution of the mantle. Our models add to the discussion on bottom-up and top-down mantle dynamics, indicating the difficulty in unravelling the processes using numerical models alone.
Heyn, Björn Holger; Shephard, Grace & Conrad, Clinton Phillips
(2024).
Prolonged Multi-Phase Magmatism Due To Plume-Lithosphere Interaction as Applied to the High Arctic Large Igneous Province.
Geochemistry Geophysics Geosystems.
25(6).
doi: 10.1029/2023GC011380.
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The widespread High Arctic Large Igneous Province (HALIP) exhibits prolonged melting over more than 50 Myr, an observation that is difficult to reconcile with the classic view that large igneous provinces (LIPs) originate from melting in plume heads. Hence, the suggested plume-related origin and classification of HALIP as a LIP have been questioned. Here, we use numerical models that include melting and melt migration to investigate a rising plume interacting with lithosphere of variable thickness, that is, a basin-to-craton setting applicable to the Arctic. Models reveal that melt migration introduces significant spatial and temporal variations in melt volumes and pulses of melt production, including protracted melting for at least about 30–40 Myr, because of the dynamic feedback between migrating melt and local lithosphere thinning. For HALIP, plume material deflected from underneath the Greenland craton can re-activate melting zones below the previously plume-influenced Sverdrup Basin after a melt-free period of about 10–15 Myr, even though the plume is already ∼500 km away. Hence, actively melting zones do not necessarily represent the location of the deeper plume stem at a given time, especially for secondary pulses. Additional processes such as (minor) plume flux variations or local lithospheric extension may alter the timing and volume of HALIP pulses, but are to first order not required to reproduce the long-lived and multi-pulse magmatism of HALIP. Since melting zones are always plume-fed, we would expect HALIP magmatism to exhibit plume-related trace element signatures throughout time, potentially shifting from mostly tholeiitic toward more alkalic compositions.
Large igneous provinces (LIPs) have been linked to both surface and deep mantle processes. During the formation, tenure and break-up of the supercontinent Pangaea, there is an increase in emplacement events for both continental and oceanic LIPs. There is currently no clear consensus on the origin of LIPs, but a hypothesis relates their formation to crustal emplacement of hot plume material originating in the deep mantle. The interaction of subducted slabs with the lowermost mantle thermal boundary and subsequent return flow is a key control on such plume generation. This mechanism has been explored for LIPs below the interior of a supercontinent (i.e. continental LIPs). However, a number of LIPs formed exterior to Pangaea (e.g. Ontong Java Plateau), with no consensus on their formation mechanism. Here, we consider the dynamics of supercontinent processes as predicted by numerical models of mantle convection and analyse whether circum-supercontinent subduction could generate both interior (continental) and exterior (oceanic) deep mantle plumes. Our numerical models show that subduction related to the supercontinent cycle can reproduce the location and timing of the Ontong Java Plateau, Caribbean LIP and potentially the Shatsky Rise by linking the origin of these LIPs to the return flow that generated deep mantle exterior plumes.
Geologically, the Arctic is one of the least-explored regions of Earth. Obtaining data in the high Arctic is logistically, economically, and environmentally expensive, but the township of Longyearbyen (population of 2617 as of 2024) at 78° N represents a relatively easily accessible gateway to Arctic geology and is home to The University Centre in Svalbard (UNIS). These unique factors provide a foundation from which to teach and explore Arctic geology via the classroom, the laboratory, and the field. UNIS was founded in 1993 as the Norwegian “field university”, offering field-based courses in Arctic geology, geophysics, biology, and technology to students from Norway and abroad. In this contribution, we present one of the educational components of the international collaboration project NOR-R-AM (a Norwegian-Russian-North American collaboration in Arctic research and collaboration, titled Changes at the Top of the World through Volcanism and Plate Tectonics) which ran from 2017 to 2024. One of the key deliverables of NOR-R-AM was a new graduate (Master's and PhD-level) course called Arctic Tectonics and Volcanism that we have established and taught annually at UNIS since 2018 and detail herein. The course's main objective is to teach the complex geological evolution of the Arctic from the Devonian period (∼ 420 million years ago, Ma) to the present day through integrating multi-scale datasets and a broad range of geoscientific disciplines. We outline the course itself before presenting student perspectives based on both an anonymous questionnaire (n=27) and in-depth perceptions of four selected students. The course, with an annual intake of up to 20 MSc and PhD students, is held over a 6-week period, typically in spring or autumn. The course comprises modules on field and polar safety, Svalbard/Barents Sea geology, wider Arctic geology, plate tectonics, mantle dynamics, geo- and thermochronology, and geochemistry of igneous systems. A field component, which in some years included an overnight expedition, provides an opportunity to appreciate Arctic geology and gather field observations and data. Digital outcrop models, photospheres, and tectonic plate reconstructions provide complementary state-of-the-art data visualization tools in the classroom and facilitate efficient fieldwork through pre-fieldwork preparation and post-fieldwork quantitative analyses. The course assessment is centred around an individual research project that is presented orally and in a short and impactful Geology journal-style article. Considering the complex subject and the diversity of students' backgrounds and level of geological knowledge before the course, the student experiences during this course demonstrate that the multi-disciplinary, multi-lecturer field-and-classroom teaching is efficient and increases their motivation to explore Arctic science.
Detailed student perspectives on their involvement in prison education are limited in published literature, yet such contributions are invaluable to education practitioners wanting to create inclusive learning environments. This article focuses on the student experience of taking part in a science outreach programme teaching science in prison in England, which was designed to build confidence in students who face challenges in accessing education pathways. Here, former students share their experiences of the programme, as well as other education courses in prison, and offer guidance on best practices for those engaging in outreach or research with the prison population. In particular, their reflections highlight that by creating and maintaining an environment that is accessible, inclusive and relatable, students from all backgrounds are able to engage in course content, and overcome hidden barriers to accessing education. Furthermore, based on their lived experience, the students offer practical advice with regard to improving future access to education in prison. The aim of this article is to give a voice to students in prison about their education experience, highlighting which aspects of this outreach programme (and other education courses) were impactful for them.
Abstract Our understanding of Earth's paleogeography relies heavily on paleomagnetic apparent polar wander paths (APWPs), which represent the time‐dependent position of Earth's spin axis relative to a given block of lithosphere. However, conventional approaches to APWP construction have significant limitations. First, the paleomagnetic record contains substantial noise that is not integrated into APWPs. Second, parametric assumptions are adopted to represent spatial and temporal uncertainties even where the underlying data do not conform to the assumed distributions. The consequences of these limitations remain largely unknown. Here, we address these challenges with a bottom‐up Monte Carlo uncertainty propagation scheme that operates on site‐level paleomagnetic data. To demonstrate our methodology, we present an extensive compilation of site‐level Cenozoic paleomagnetic data from North America, which we use to generate a high‐resolution APWP. Our results demonstrate that even in the presence of substantial noise, polar wandering can be assessed with unprecedented temporal and spatial resolution.
During the Devonian, the Svalbard Archipelago lay at low latitudes, occupying a paleogeographic position at the intersection of Caledonian and Ellesmerian orogens. Provenance analysis, including detrital zircon U-Pb age studies, of Devonian (ca. 420–360 Ma) strata from the Andrée Land Basin, Svalbard, help reconstruct sediment sources to understand the assembly of the three basement provinces that make up Svalbard, which are presently separated by Devonian sedimentary basins and(or) faults with syn-to post-Devonian displacement. The studied Andrée Land Group strata, which are part of the North Atlantic's Old Red Sandstone, consist of the Early Devonian Wood Bay Formation and Middle to Late Devonian Mimerdalen subgroup. Paleocurrent indicators from Lower to lower-Middle Devonian strata record north-directed sediment transport. Detrital zircon U-Pb ages indicate a prominent “Caledonian” signal and include sources from Svalbard's Northwestern and(or) Southwestern basement provinces. In Middle and Upper Devonian strata, paleocurrents and detrital zircon ages record a shift to a predominantly eastern-northeastern provenance, likely from the uplifting Ny-Friesland block along the Billefjorden Fault Zone. Late Ediacaran-early Cambrian detrital zircons in the uppermost Planteryggen Formation (Frasnian) indicate extrabasinal sources possibly associated with the Timanian orogen of Northern Baltica. The combined provenance data suggest Svalbard may have already been assembled, similar to the modern block, with the Andrée Land Basin located between modern exposures of the Southwestern/Northwestern and the Northeastern basement provinces. Comparison of detrital zircon ages from Andrée Land Group strata with those from other circum Arctic Devonian strata provides constraints on Svalbard's paleogeographic position in the Devonian.
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 ArchiveShow 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.
Shephard, Grace; Houser, Christine; Hernlund, John W; Valencia-Cardona, Juan J.; Trønnes, Reidar G & Wentzcovitch, RM
(2021).
Seismological expression of the iron spin crossover in ferropericlase in the Earth’s lower mantle.
Nature Communications.
12.
doi: 10.1038/s41467-021-26115-z.
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Abstract The two most abundant minerals in the Earth’s lower mantle are bridgmanite and ferropericlase. The bulk modulus of ferropericlase (Fp) softens as iron d-electrons transition from a high-spin to low-spin state, affecting the seismic compressional velocity but not the shear velocity. Here, we identify a seismological expression of the iron spin crossover in fast regions associated with cold Fp-rich subducted oceanic lithosphere: the relative abundance of fast velocities in P- and S-wave tomography models diverges in the ~1,400-2,000 km depth range. This is consistent with a reduced temperature sensitivity of P-waves throughout the iron spin crossover. A similar signal is also found in seismically slow regions below ~1,800 km, consistent with broadening and deepening of the crossover at higher temperatures. The corresponding inflection in P-wave velocity is not yet observed in 1-D seismic profiles, suggesting that the lower mantle is composed of non-uniformly distributed thermochemical heterogeneities which dampen the global signature of the Fp spin crossover.
Gac, Sebastien; Minakov, Alexander; Shephard, Grace; Faleide, Jan Inge & Planke, Sverre
(2020).
Deformation analysis in the Barents Sea in relation to paleogene transpression along the Greenland-Eurasia plate boundary.
Tectonics.
ISSN 0278-7407.
39(10).
doi: 10.1029/2020TC006172.
Full text in Research ArchiveShow summary
Late Cretaceous‐Cenozoic contractional structures are widespread in the Barents Sea. While the exact dating of the deformation is unclear, it can only be inferred that the contraction is younger than the early Cretaceous. One likely contractional mechanism is related to Greenland Plate kinematics at Paleogene times. We use a thin sheet finite element modeling approach to compute deformation within the Barents Sea in response to the Greenland‐Eurasia relative motions during the Paleogene. The analytical solution for the 3‐D folding of sediments above basement faults is used to assess possibilities for folding. Two existing Greenland Plate kinematic models, differing slightly in the timing, magnitude, and direction of motion, are tested. Results show that the Greenland Plate's general northward motion promotes growing anticlines in the entire Barents Sea shelf. Our numerical models suggest that the fan‐shaped pattern of cylindrical anticlines in the Barents Sea can be associated with the Eurekan deformation concurrent to the initial rifting and early seafloor spreading in the northeast Atlantic. The main contraction phase in the SW Barents Sea coincides with the timing of continental breakup, whereas the peak of deformation predicted for the NW Barents Sea occurred at later times. Svalbard has experienced a prolonged period of compressional deformation. We conclude that Paleogene Greenland Plate kinematics are a likely candidate to explain contractional structures in the Barents Sea
Abstract The accurate representation of data is essential in science communication. However, colour maps that visually distort data through uneven colour gradients or are unreadable to those with colour-vision deficiency remain prevalent in science. These include, but are not limited to, rainbow-like and red–green colour maps. Here, we present a simple guide for the scientific use of colour. We show how scientifically derived colour maps report true data variations, reduce complexity, and are accessible for people with colour-vision deficiencies. We highlight ways for the scientific community to identify and prevent the misuse of colour in science, and call for a proactive step away from colour misuse among the community, publishers, and the press.
Subduction zones are pivotal for the recycling of Earth’s outer layer into its interior. However, the conditions under which new subduction zones initiate are enigmatic. Here, we constructed a transdisciplinary database featuring detailed analysis of more than a dozen documented subduction zone initiation events from the last hundred million years. Our initial findings reveal that horizontally forced subduction zone initiation is dominant over the last 100 Ma, and that most initiation events are proximal to pre-existing subduction zones. The SZI Database is expandable to facilitate access to the most current understanding of subduction zone initiation as research progresses, providing a community platform that establishes a common language to sharpen discussion across the Earth Science community.
Plate tectonics is the root concept underpinning our current knowledge of how Earth's internal dynamics are linked to geologic deformation at the surface. Since the discovery of plate tectonics in the 1960s, geoscientists have developed a first-order understanding of a plate system in which the Earth's surface is broken into about a dozen mostly rigid tectonic plates that move relative to each other at speeds of a few centimeter per year. The boundaries of these plates accommodate diverging, converging, and lateral motions, and are associated with surface features such as rift zones, mountain belts, faults, earthquakes, and volcanoes. The motions of the plates can be detected geodetically, described kinematically, and reconstructed back in time. This descriptive understanding of Earth's surface deformation is now recognized as the surface expression of a larger, dynamic framework of mantle convection. Gravity acting on density variations within Earth's interior generates broad-scale flow of the mantle, which mainly drives, but can also resist, the horizontal plate motions at the surface. Within this system, oceanic plates originate from and are recycled back into the mantle, forming a dynamic cycle captured by the recently described “ocean-plate tectonics” concept. This intimate relationship between surface and internal dynamics appears to be unique to the Earth, as it is clearly different from the modes of mantle convection inferred for other rocky planetary bodies within our solar system. Earth's unique interplay between its interior and surface shapes our planet's morphology and recycles its volatiles to produce the lively and life-bearing planet that Earth has become. How ocean-plate tectonics started, how it has repeatedly opened and closed ocean basins, assembled and dispersed supercontinents, and initiated and terminated fault systems, and how it continues to operate today are still major open questions. New techniques for studying Earth's interior dynamics, new possibilities for comparing Earth to other freshly understood or recently detected planetary bodies, and new unifying concepts like ocean-plate tectonics bode well for future resolution of the remaining mysteries surrounding plate tectonics today.
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.
The deep-time Cenozoic history (the last 60 Myr) of the Barents Sea shows complex interplay between tectonics, climatics and surface processes. What did the actual paleotopography look like back then? How did the climate perturbation control the sediment transfer from the source area to the sink? We use a coupled model of GPlates tectonic reconstruction software and Badlands – basin and landscape open-source codes to untangle these intricate processes. The model is calibrated using available seismic and well datasets, including biostratigraphy data. The outcome of this study is important to understand the impact of climate and how our Earth responded in the past, e.g. PETM (Paleocene–Eocene Thermal Maximum). The basin-landscape configuration along the Barents Seaway is also crucial for analysing the ocean circulation between the Atlantic and Arctic oceans during the Cenozoic, which is key for ocean/climate modelling and has also global climatic implications.
Landscapes preserve Earth’s history, yet much of that record is missing. Erosion removes material from the surface, while sedimentation preserves parts of that history elsewhere. The same principles shaped the world’s northernmost mountain belt, the Eurekan Orogeny. The eroded fragments have contemporaneously filled kilometre-deep oceanic basins alongside the development of Earth’s slowest seafloor spreading (Gakkel Ridge). Moreover, the opening of the Fram Strait remains debated in terms of the timing, nature, and evolution. How effectively does erosion shape the Arctic topography? What role do different sedimentary processes play in transporting and distributing Earth’s archive into the evolving oceanic basins? Here, we use coupling Badlands codes and GPlates to simulate the sedimentary source-to-sink system and basin filling during the tectonic plate separation between the Lomonosov Ridge and the northern Barents Shelf. I will present numerical modelling results as part of the framework of the BRAVO (Barents Sea Evolution) project, a Marie Skłodowska-Curie Global Fellowship between the University of Sydney and the University of Oslo.
Lasabuda, Amando; Salles, Tristan; Zahirovic, Sabin; Shephard, Grace; Faleide, Jan Inge & Muller, Dietmar
(2025).
Sedimentary source-to-sink of the northern Barents Shelf and its implication for the opening of the Nansen Basin.
doi: https:/zenodo.org/records/16810950.
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Reconstructing Cenozoic sedimentary source-to-sink in the greater Barents Sea is highly uncertain due to heavily eroded Cenozoic strata during the Quaternary glaciations. This uncertainty led to diverging models of the Barents Shelf paleo-landscape in the Cenozoic, ultimately affecting the accuracy of climate, oceanographic and sediment source-to-sink simulations. The ratio between off-shelf Cenozoic pre-glacial and glacial sediments is relatively higher in the Barents Sea northern continental margin than the western margin. This observation and other studies point to a hypothesis of an elevated terrain of the paleo-northern Barents Sea in the Paleogene-Neogene. However, it is not clear when and how this paleo-topographic high was formed, and how it evolved throughout the Cenozoic. The spatio-temporal pattern of the catchment area supplying sediments to the evolving ultra-slow seafloor spreading of the Nansen Basin remains enigmatic. Moreover, the impact of rift-flank uplift on the sediment routing from the source to the sink area is also unclear, considering a relatively sharp boundary between the continental and oceanic plates in the study area. Here we used Badlands forward modelling coupled with GPlates tectonic reconstructions to simulate the basin-filled stratigraphy in the Nansen Basin and the landscape evolution of the northern Barents Sea. We compared the numerical outcomes with the seismic data from and across the continental margin. Our simulations shed light on constraining the opening configuration of the Nansen Basin, reflecting interactions between tectonic (deeper mantle processes, isostasy), climatic and surface processes (sediment erosion, transport and deposition).
Sartell, Anna Marie Rose; Söderlund, Ulf; Beier, Christoph; Senger, Kim; Shephard, Grace & Mosociova, Tereza
[Show all 8 contributors for this article](2025).
Geochemistry and Emplacement Geometries of the Wallenbergfjellet Intrusions, Svalbard: Insights into the High Arctic Large Igneous Province.
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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.
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Shephard, Grace
(2025).
Comparing and contrasting multiple phases of Arctic Ocean development; insights on tectonics and magmatism from recent numerical modelling approaches including the surface and mantle.
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Shephard, Grace
(2025).
Eksklusive øydestinasjoner som du garantert aldri har sett før.
geoforskning.no.
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Shephard, Grace
(2025).
Over the rainbow: making better colour bar choices for your scientific figures.
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Sartell, Anna Marie Rose; Beier, Christoph Patrick; Senger, Kim; Shephard, Grace; Mosociova, Tereza & Mäkinen, Kristofer
[Show all 7 contributors for this article](2025).
Geochemistry of the Wallenbergfjellet intrusions, a case study of the High Arctic Large Igneous Province on Svalbard.
10th International Conference on Arctic Margins (ICAM-X) - Abstract Volume.
2025,
p. 53–53.Full text in Research ArchiveShow summary
The High Arctic Large Igneous Province (HALIP) encompasses large-scale volcanism and magmatism emplaced in the circum-Arctic during the Early Cretaceous. In the Svalbard archipelago, the HALIP is formally classified as the Diabasodden Suite, and here the magma was mainly emplaced as sills and dikes. Wallenbergfjellet, a mountain in central Spitsbergen, was investigated in detail during two weeks in July 2022. The site offers a laterally continuous intrusion (for at least 5 km) with variable geometries, including a 50 m
thick main sill and various transgressive segments feeding shallower sills. This study site was chosen to test how large the compositional variation within a HALIP outcrop locality is, specifically to see how many samples are needed to get a representative dataset for an intrusion of this size (ca. 5 x 5 km). On Svalbard, boat-based summer campaigns are most common and because of constraining factors, e.g. weather, wildlife, and limited time, usually only a handful of samples can be collected at each site. At Wallenbergfjellet, over 100 samples were systematically collected, with good coverage both laterally and over the full thickness of the main sill. These samples are used for whole-rock geochemical analysis, to examine in detail the geochemical variability. In addition to traditional geological fieldwork, this igneous complex was documented through the acquisition of high-resolution UAV images to create digital outcrop models (DOMs). The DOMs allow for the geochemical dataset to be visualized three-dimensionally to see where each data point originates from and for a thorough interpretation of the structures within the intrusion. Here we present the whole-rock geochemical data and DOMs from Wallenbergfjellet, and discuss the compositional variability found within these intrusions.
Lasabuda, Amando P. E.; Salles, Tristan; Shephard, Grace; Zahirovic, Sabin; Faleide, Jan Inge & Muller, Dietmar
(2024).
Impact of landscape evolution on the ocean circulation and glaciation: A forward modelling of basin and landscape dynamics, northern Barents Sea, Norwegian Arctic.
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Basin and landscape dynamics play a key role in oceanographic and climate evolution, such as connecting two major oceans and establishing a paleotopographic high at the onset of large-scale glaciations. The Barents Sea is an underexplored ocean gateway (also known as the Barents Seaway) connecting the Atlantic and Arctic oceans. However, unlike the Fram Strait Gateway, its formation over the past 66 Myr in the Cenozoic remains unclear. Several studies suggest that a paleo-topographic high was formed in the northern Barents Sea as early as the Miocene (c. 23 Ma), preconditioning an ice cap formation that led to the development of large-scale glaciation in the Northern Hemisphere (c. 2.7 Ma). However, the exact timing of this mountainous terrain remains uncertain. Here we used badlands, an open-source basin and landscape forward modelling framework to simulate the evolution of basin and landscape in the northern Barents Sea in the Cenozoic. To constrain the geometry of the oceanic basin for the sediment filling to the Nansen Basin we take advantage of GPlates. We then test different scenarios of catchment models and their associated sediment transport and accumulation in a source-to-sink context. Paleo-precipitations, sea-level fluctuations and tectonic/flexural response are used to understand the controlling parameters. The numerical results are then compared with seismic profiles and available well and core data. This study contributes to constraining the spatio-temporal pattern of the northern Barents Shelf landscape morphology, which can be applied in other formerly glaciated areas.
Lasabuda, Amando P. E.; Shephard, Grace; Zahirovic, Sabin & Salles, Tristan
(2024).
Recent advances in stratigraphic forward modelling, scientific colour maps and diamond open-access journals.
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Lasabuda, Amando; Tristan, Salles; Zahirovic, Sabin; Shephard, Grace; Faleide, Jan Inge & Muller, Dietmar
(2024).
Cenozoic Sediment Multi-source-to-sink in the Barents Sea: Insights from Stratigraphic Forwad Modelling.
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Heyn, Björn Holger; Shephard, Grace & Conrad, Clinton Phillips
(2024).
Prolonged multi-phase volcanism in the Arctic induced by plume-lithosphere interaction.
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Shephard, Grace
(2024).
Geodynamics of the Arctic and North Atlantic - Modelling mantle plume-lithosphere interactions, and deformable tectonic plates.
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Shephard, Grace & Heyn, Björn Holger
(2024).
New insights into the protracted and widespread nature of the High Arctic LIP and mantle plume.
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Jaah, Ilyas; Kiraly, Agnes; Shephard, Grace; Conrad, Clinton Phillips & Domeier, Mathew Michael
(2024).
On the Role of Anisotropic Viscosity on the Motion of the Pacific Plate.
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Shephard, Grace
(2024).
Not Just for Plate Tectonics: A GPlates Software Crash Course in Displaying Diverse Geoscientific Datasets.
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Schneider, Anna; Schuberth, Bernhard; Koelemeijer, Paula; Shephard, Grace & Al-Attar, David
(2024).
Exploring the potential of normal mode seismology for the assessment of geodynamic hypotheses.
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Distlebrink, Amber; Shephard, Grace; Koehl, Jean-Baptiste P.; Bergh, Steffen Gunnar & Beniest, Anouk
(2024).
Insights into the tectonic evolution of the northern Norwegian passive margin: Integrating field observations and plate modeling over 200 million years.
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Straume, Eivind Olavson; Shephard, Grace & Crameri, Fabio
(2024).
Building and establishing the open collection of geoscience graphics.
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Shephard, Grace
(2024).
False islands of the Arctic: the enigmatic and enduring Arctic landmass Crockerland.
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Lasabuda, Amando P. E.; Shephard, Grace; Faleide, Jan Inge; Salles, Tristan & Muller, Dietmar
(2023).
RECONSTRUCTING THE BARENTS SEAWAY IN THE CENOZOIC – THE BRAVO PROJECT.
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The Barents Seaway represents an important marine connection between the Atlantic and Arctic oceans. However, how and when precisely the Barents Seaway formed are not very well understood being overshadowed by its neighbor, the Fram Strait Gateway. The Bravo (Barents Sea Evolution) project will address this issue and aims at reconstructing the Barents Seaway paleobathymetry in the Cenozoic. The key challenge is to quantify the spatial distribution and temporal evolution of km-scale vertical movement of Cenozoic uplift and erosion due to glaciations and pre-glacial tectonism. BRAVO approach requires a comprehensive analysis of off-shelf sediment estimation, lithospheric strength, and other mantle-related processes in order to produce a reliable model. BRAVO will use extensive seismic and well data, and utilize numerical modelling technique using pyGPlates software. BRAVO will also test the paleobathymetry reconstructions by simulating the corresponding sediment source-to-sink in the Cenozoic using pyBadlands, an open-source codes for sediment transport, erosion and depositional processes. BRAVO is a Marie Skłodowska-Curie Actions (MSCA) project funded by the European Union’s Horizon Europe and the Research Council of Norway (2023-2026).
Shephard, Grace; Heyn, Björn Holger & Conrad, Clinton Phillips
(2023).
Prolonged multi-phase magmatism due to plume-lithosphere interaction as applied to the High Arctic Large Igneous Province.
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Heyn, Björn Holger; Shephard, Grace & Conrad, Clinton Phillips
(2023).
Locally amplified plume-lithosphere interaction and multiple melting events for 2-phase flow models.
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Shephard, Grace
(2023).
Dont pat the polar bear” – and other life lessons from a decade in Norway.
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Shephard, Grace; Crameri, Fabio & Heron, Philip J.
(2023).
End the rainbow! Choose scientific colours for science.
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Heyn, Björn Holger; Conrad, Clinton Phillips & Shephard, Grace
(2023).
Plume-lithosphere interaction and continental plume tracks.
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Heyn, Björn Holger; Shephard, Grace & Conrad, Clinton Phillips
(2023).
Amplification of sub-lithospheric dynamics by melt migration during plume-lithosphere interaction.
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Shephard, Grace
(2023).
Scaling across fields of knowledge: A perspective from the Solid Earth Sciences.
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Shephard, Grace; Heyn, Björn Holger & Conrad, Clinton Phillips
(2023).
Large-scale volcanism at the top of the world; plume and melt modelling of the High Arctic Large Igneous Province (HALIP).
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Shephard, Grace; Crameri, Fabio & Straume, Eivind Olavson
(2023).
Ongoing experiences in establishing and building a grass-roots science outreach initiative; the s-Ink.org graphics repository.
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Shephard, Grace; Crameri, Fabio & Straume, Eivind Olavson
(2023).
Open graphics for open science; the s-Ink.org graphics repository.
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Shephard, Grace
(2022).
Introducing the POLARIS project – uncovering deep-to-surface connections.
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Shephard, Grace; Faleide, Jan Inge; Gaina, Carmen; Abdelmalak, Mohamed Mansour; Gac, Sebastien & Torsvik, Trond Helge
(2022).
Building deformable plate models for the Northeast Atlantic.
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Shephard, Grace
(2022).
The seafloor is not a rainbow, implementing better colour choices in science.
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Wentzcovitch, Renata; Shephard, Grace; Houser, Christine; Hernlund, John; Trønnes, Reidar G & Valencia, Juan
(2022).
Seismological expression of the iron spin crossover in ferropericlase in the Earth’s lower mantle.
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Kästle, Emanuel; Shephard, Grace & Paul, Anne
(2022).
Vote maps of the Alpine upper mantle.
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Shephard, Grace; Crameri, Fabio & Straume, Eivind Olavson
(2022).
Introducing s-Ink.org; a community portal for sharing quality science graphics.
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A suspended globe with visitors walking towards it from both directions. This composition gives an impression that the museum visitors are meeting at the Planet Earth. Photo taken at Miraikan – the National Museum of Emerging Science and Innovation in Tokyo, Japan. At the moment the photo was taken the projection shows a satellite image of the Earth – just upside down – or an antipodean pun of “Down Under On Top.” There are many tesselated tiles – electroluminescent panels – that make up the projection, utilizing over 10 million pixels. The background of image turned black-and-white but globe remains coloured.
Shephard, Grace; Houser, Christine; Hernlund, John W; Valencia-Cardona, JJ; Trønnes, Reidar G & Wentzcovitch, RM
(2021).
Detecting the spin crossover in ferropericlase. Am. Geophys. Union Fall Mtg. DI14A-01.
Am. Geophys. Union Fall Meeting Abstr..
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Trønnes, Reidar G & Shephard, Grace
(2021).
Elektronisk spinn-overgang i ferroperiklas i Jordas dype indre.
Forskning.no.
ISSN 1891-635X.Full text in Research Archive
Shephard, Grace Elizabeth; Crameri, Fabio & Heron, Philip J.
(2020).
At the end of the rainbow – Scientific Colour Maps for science and society.
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Shephard, Grace Elizabeth; Hernlund, John; Houser, Christine; Trønnes, Reidar G; Crameri, Fabio & Wentzcovitch, Renata
(2020).
Mapping out the lower mantle - the iron spin crossover and the ambient mantle.
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Shephard, Grace Elizabeth; Houser, Christine; Hernlund, John; Trønnes, Reidar G; Valencia-Cardona, Juan J. & Wentzcovitch, Renata
(2020).
Detection of the spin crossover in ferropericlase in the Earth’s lower mantle; an interdisciplinary approach. Full text in Research Archive
Shephard, Grace Elizabeth
(2020).
Mapping the mantle from multiple seismic tomography models – visualisation and applications.
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Shephard, Grace; Hernlund, John W; Houser, Christine; Trønnes, Reidar G & Crameri, Fabio
(2020).
Ambient lower mantle structure and composition inferred from seismic tomography, convection models and geochemistry.
European Geosci. Union, Gen. Assembly, Geophys. Res. Abstr..
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Shephard, Grace Elizabeth & Crameri, Fabio
(2020).
How many transdisciplinary researchers does it take to find out how an ocean sinks?
EGU Blogs.
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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.
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Shephard, Grace & Gaina, Carmen
(2019).
The Arctic in deep time and space: a Earth Scientist's perspective.
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Shephard, Grace; Houser, Christine; Hernlund, John; Trønnes, Reidar G & Wentzcovitch, Renata
(2019).
Detection of the lower mantle iron spin transition in ferropericlase through vote maps of seismic tomography.
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Shephard, Grace; Crameri, Fabio & Gaina, Carmen
(2019).
Shifting around, digging up, and colouring in oceans.
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Shephard, Grace; Houser, Christine; Hernlund, John; Trønnes, Reidar G; Wentzcovitch, Renata & Valencia, Juan
(2019).
Seismic detection of iron spin pairing in ferropericlase and the structure of the lower mantle.
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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.
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Hernlund, John W; Shephard, Grace; Houser, Christine; Wentzcovitch, RM & Trønnes, Reidar G
(2019).
Detection of an Iron Spin Transition in Ferro-periclase in the Lower Mantle.
AGU Fall Meeting Abstr..
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Shephard, Grace; Houser, Christine; Hernlund, John W; Wentzcovitch, RM & Trønnes, Reidar G
(2019).
Seismic detection of iron spin pairing in ferropericlase and the structure of the lower mantle.
Ada Lovelace Workshop on Modelling Mantle and Lithosphere Dynamics. Abstr..
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The CAGE22-6 cruise on-board R/V Helmer Hanssen hosted UiT´s Arctic Marine Geology and Geophysics (GEO-8144 and GEO-3144) field course for PhD and Master students, and was carried out in collaboration with NPD – the Norwegian Petroleum Directorate and the INTPART project HOTMUD based at Centre for Earth Evolution and Dynamics (CEED) the University of Oslo. The cruise was also a part of the UNESCO Training Through Research program (formerly, The Floating University) and in the framework of this project is also coded as TTR22.<p> <p>The main scientific objectives of the cruise were to investigate: geological controls on fluid-flow dynamics on an uplifted, repeatedly glaciated, and eroded Northern Norwegian Barents Sea shelf and, the fate of the released hydrocarbons in the water column, on the sea surface, and in the atmosphere.<p> <p>The cruise may be known as: CAGE22_6
