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North Atlantic and Arctic connections: Evolution, structure and landscapes

The North-Atlantic-Arctic realm hosts vast extended continental shelves bordering old land masses, two Large Igneous Provinces (LIPs), one of which is the largest known sub-marine LIP (Alpha-Mendeleev Ridge) and a complex ocean spreading systems, including the slowest mid-ocean spreading ridge (Gakkel Ridge) and several extinct ocean basins.
Over recent decades, increasing scientific interest has led to the acquisition of vast quantities of geological and geophysical data across the North Atlantic-Arctic realm, yet our understanding of the region has become, if anything, even more controversial than it was before. The geodynamic and geomorphological processes acting here (and globally) are key to the understanding of the structure, geodynamic and paleolandscape evolution, hazards and resources in the region.
This session provides a forum for discussions and reviews of a variety of problems linked to the North Atlanitc-Arctic geodynamics such as plate tectonic, geodynamic, compositional, thermal, structural and landscape models, configuration of sedimentary basin and to propose additional experiments that can test these models. We welcome contributions from all relevant disciplines, including, but not limited to, plate tectonics, geophysics, geodynamic modelling, igneous, metamorphic and structural geology, palaeomagnetism, sedimentology, geomorphology, geochronology, thermochronology, geochemistry and petrology.

Co-organized by GM4/GMPV11/TS6
Convener: Aleksandra Smyrak-Sikora | Co-conveners: Grace E. Shephard, Rebekka SteffenECSECS, Owen Anfinson
Presentations
| Thu, 26 May, 13:20–15:55 (CEST)
 
Room -2.47/48

Thu, 26 May, 13:20–14:50

Chairpersons: Aleksandra Smyrak-Sikora, Owen Anfinson, Rebekka Steffen

13:20–13:30
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EGU22-2379
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ECS
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solicited
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Highlight
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Virtual presentation
Valentin Zuchuat et al.

About 252 million years ago, near the end of the Permian, the Earth experienced its most dramatic mass extinction, caused by magmatic intrusions and volcanic eruptions associated with the Siberian Traps Large Igneous Province. This led to catastrophic global climatic changes, impacts of which lasted well into the Early Triassic.

Here, we summarise the results gathered from the study of sedimentary successions spread across the Barents Shelf that recorded the End Permian Mass Extinction (EPME) and its aftermaths across the Permian-Triassic boundary. Data and samples were collected from the Festningen section in western Spitsbergen; the DD-1 core and the associated river section in Deltadalen, central Spitsbergen; a core (7933/4-U-3) drilled by the Norwegian Petroleum Directorate offshore Kvitøya in northern Svalbard; and a core (7130/4-1; production licence 586) recovered from the Finnmark Platform in the Barents Sea. A series of state-of-the-art analyses were conducted on the collected material, including detailed facies analysis, organic and C-isotope geochemistry, mercury content, geochronology, high resolution XRF core scanning, petrography, ichnology, and palaeontology. Analyses were, where relevant, tied to the outcrops using digital outcrop models.

Traditionally, the Permian-Triassic boundary in Svalbard (and across the High Arctic regions) was placed at the marked and rapid facies change at the top of the siliceous mudstones and spiculites of the Kapp Starostin Formation, which are overlain by soft, non-siliceous mudstones and siltstones of the Vardebukta and Vikinghøgda formations. This abrupt facies change, which also marks the collapse of sponges, occurs across a few centimetres. Given that the non-siliceous mudstones were definitely of Early Triassic age, based on ammonoid biostratigraphy, this lithostratigraphic boundary was believed to represent a lacuna or a hiatus of several million years, with the uppermost Permian strata absent from the sedimentary record.

The base of the Triassic, however, is not defined by ammonoid biostratigraphy but by the conodont Hindeodus parvus, which was recently reported to occur a few meters above the lithostratigraphic boundary in the Deltadalen section. This means that the lithostratigraphic boundary is of Permian age. Additionally, our new data show that sedimentation was continuous across this lithostratigraphic boundary, corresponding to major environmental changes, potentially associated with a reorganisation of the basin(s) physiography.

Furthermore, the 6-8 ‰ δ13Corg negative excursion associated with the EPME falls between the lithostratigraphic and the Permian-Triassic boundary at all measured sections. These negative carbon isotope excursions occur in intervals with numerous tephra layers, the lowest of which has been dated at 252.13 ± 0.62 Ma, potentially connecting the recorded changes to the Siberian Traps. The EPME is also corroborated by the very abrupt decline of trace fossil abundance and diversity, as anoxia extended from proximal and shallow water to deeper settings. Geochemical and ichnological data support the existence of multiple anoxic pulses, separated by very brief periods of enhanced oxygen levels. It took ca. 150 Kyr for life to recover after the EPME, based on sedimentation rate calculations. Data also suggest that the hinterland of the basin experienced a shift towards more arid climatic conditions and increased eutrophication.

How to cite: Zuchuat, V., Augland, L. E., Jones, M. T., Sleveland, A. R. N., Twitchett, R., Rodríguez-Tovar, F. J., Hammer, Ø., Senger, K., Betlem, P., Turner, H. E., Midtkandal, I., Svensen, H. H., and Planke, S.: The Permian-Triassic boundary across the Barents Shelf: an intricate record of climate change, mass extinction, recovery, and basin reorganisation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2379, https://doi.org/10.5194/egusphere-egu22-2379, 2022.

13:30–13:37
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EGU22-5989
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Highlight
Hans Thybo and Irina Artemieva

The whole North Atlantic region has highly anomalous topography and bathymetry. Observations show evidence for anomalously shallow bathymetry in the ocean as well as recent rapid topographic change with onshore uplift close to the Atlantic coast and simultaneous subsidence of basins on the continental shelves, most likely throughout the Mesozoic. We present a geophysical interpretation of the whole region with emphasis on data relevant for assessing hypsometric change

Most of the North Atlantic Ocean has anomalously shallow bathymetry by up-to 4 km compared to other oceans. Bathymetry is elevated by up-to 2 km and follows the square-root-of-age model, except for the region between Greenland Iceland Faroe Ridge (GIF) and the Jan Mayen Fracture Zone as well as in the Labrador Sea to Baffin Bay. Heat flow follows with large scatter the square-root-of-age model in parts of the ocean and is anomalously low on the Reykjanes and Mohns spreading ridges. Near-zero free-air gravity anomalies indicate that the oceanic areas are generally in isostatic equilibrium except along the mid-oceanic ridges, whereas anomalously low Bouguer anomalies in the oceanic areas indicate low density in the uppermost mantle. Anomalously thick crust is observed along GIF and extends into the Davies Strait. There is no correlation between bathymetry and heat flow, which indicates that the anomalous bathymetry mainly is caused by compositional variation and isostatic compensation of low density continental lithosphere within the oceanic regions. The location of major oceanic fracture zones and continental fragments appears to be controlled by onshore structures.

The onshore circum-Atlantic areas show rapid uplift close to the coast with rates of up-to 3 cm/yr. This is surprisingly mainly associated with strong positive free-air gravity anomalies, which would predict isostatic subsidence. Some parts of the high topography, however, appear supported by low-density anomalies below the seismic Moho. It is enigmatic that the presumed Archaean-Proterozoic continental Barents Sea region is submerged and includes deep sedimentary basins.

How to cite: Thybo, H. and Artemieva, I.: The anomalous North Atlantic region, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5989, https://doi.org/10.5194/egusphere-egu22-5989, 2022.

13:37–13:44
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EGU22-1122
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On-site presentation
David Schneider and Jeremy Powell

Geochronological studies illuminate our understanding of the tectono-stratigraphic evolution of the Arctic Ocean, submarine features, continental shelves and adjoining landmasses. The Franklinian and Sverdrup basins of the Canadian High Arctic preserve a near-continuous Phanerozoic succession detailing the geologic evolution of the northern Laurentian margin from the Neoproterozoic to Cenozoic. Whereas previous studies have documented the structural and stratigraphic record of several episodes of orogenesis and first-order depositional cycles related to Circum-Arctic evolution, supporting geochronological data are sparse because the logistical challenges associated with fieldwork at high latitudes resulting in poor temporal resolution on the magnitude and timing of: 1) accretion of the Pearya terrane to the Laurentian margin; 2) the Devonian to Carboniferous Ellesmerian orogeny; and 3) Paleogene Eurekan deformation. In an effort to constrain the age of these tectonic episodes, we applied 40Ar/39Ar and (U-Th)/He low-temperature geochronology to major polydeformed NE-SW trending strike-slip fault zones that bisect the Pearya terrane and Franklinian Basin of northern Ellesmere Island, Canada. Total fusion 40Ar/39Ar dating was conducted on 165 single muscovite grains from 22 samples. Age dispersion was sample dependent, with some samples exhibiting robust Paleozoic ages corresponding to the assembly and accretion of the Pearya terrane, and other samples yielding intra-sample date dispersion that spanned the late Paleozoic and Mesozoic, indicative of a previously unreported post-Ellesmerian and pre-Eurekan history. Zircon (U-Th)/He dates from 11 samples (n: 73) and apatite (U-Th)/He data from 6 samples (n: 21) are largely Eocene in age, with dominant populations of c. 48 Ma and c. 41 Ma, respectively. Inverse thermal history modelling of (U-Th)/He data indicates episodic Mesozoic burial and unroofing that coincide with changes in the regional stress regime from dominant N-S to WNW-ESE compression, and rapid cooling during the nascent (>53 Ma) and initial (53 Ma to 47 Ma) phases of Eurekan deformation. The improved geochronologic resolution of the eastern Canadian High Arctic will allow better correlation to offshore structural features and to deformation events on the Greenland plate and Svalbard archipelago.

How to cite: Schneider, D. and Powell, J.: Phanerozoic record of northern Ellesmere Island, Canadian High Arctic, resolved through 40Ar/39Ar and (U-Th)/He geochronology, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1122, https://doi.org/10.5194/egusphere-egu22-1122, 2022.

13:44–13:51
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EGU22-285
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ECS
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Virtual presentation
Megan Koch et al.

The Ordovician Kulutingwak Formation of Ellesmere Island, Nunavut, Canada is an enigmatic assemblage that occurs exclusively in fault-bounded panels in a critical 30 kilometer transect between the crystalline basement of the exotic Pearya terrane and clastic rocks on the Laurentian margin. The Pearya terrane is hypothesized to have accreted to the Laurentian margin during late Silurian to Devonian time. The Kulutingwak Formation includes metasedimentary, volcanic, and volcaniclastic rocks with local carbonate olistoliths and serpentinite-bearing lithologies that collectively represent a subduction-related assemblage formed in an accretionary prism. As such, this formation has been cited as evidence of an arc-continent collision, giving these rocks a significant role in shaping tectonic models for the accretion of the Pearya terrane, and subsequently, the assembly of the circum-Arctic region during the Paleozoic. Igneous and detrital zircon U-Pb and Lu-Hf data from 11 samples collected from the Kulutingwak and Silurian Danish River formations between the Petersen Bay fault zone (PBFZ) and the Emma Fiord fault zone (EFFZ) record a dynamic early Paleozoic tectonic setting at the northern Laurentian margin. Detrital zircon spectra from the Kulutingwak samples adjacent to the PBFZ show major age peaks at ca. 960 Ma that record affinity with the Pearya terrane basement, as well as peaks at ca. 1820 Ma and 2700 Ma that suggest a Laurentian margin source. Additionally, two samples record the presence of a 502–508 Ma source which is not well-documented in this region. Kulutingwak Formation volcaniclastic rocks further to the south in the EFFZ yield U-Pb zircon ages 456–465 Ma and εHf(t) signatures of -5 to +10, implying association with volcaniclastic rocks of the newly redefined Ordovician Fire Bay Formation, a dismembered arc fragment equivalent to Ordovician arc-related rocks connected with the Pearya terrane. The data demonstrate that there are at least two distinctive components within the currently defined Kulutingwak Formation: one that records combined provenance signatures from the Pearya terrane and the Laurentian margin in the Paleozoic and another that signals the presence of an Ordovician arc at ca. 455–470 Ma. U-Pb detrital zircon data collected from the Silurian Danish River Formation in this region demonstrate affinity with the Pearya terrane, with a major age peak at ca. 960 Ma. Composite signatures of ca. 960, 1820, and 2700 Ma in the Kulutingwak Formation suggest that the Pearya terrane had reached the Laurentian margin in Late Ordovician to Silurian time.

How to cite: Koch, M., McClelland, W. C., Gilotti, J. A., Kośmińska, K., Faehnrich, K., and Strauss, J. V.: A Paleozoic accretion history: Igneous and detrital zircon signatures of the Kulutingwak and Danish River formations in the Yelverton Inlet-Phillips Inlet region, Ellesmere Island, Nunavut, Canada, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-285, https://doi.org/10.5194/egusphere-egu22-285, 2022.

13:51–13:58
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EGU22-6068
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ECS
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On-site presentation
Mike Shotton et al.

Passive margins are commonly categorised into two end-member models based on the amount of magma produced during continental rifting and breakup, resulting in ‘magma-rich margins’, or ‘magma-poor margins’ as a generic classification. However, in recent years, substantial variability within these models, due to parameters such as rheology, structural inheritance, variations in magmatic budget, has been identified. Similarly, attempting to confidently interpret crustal architectures, particularly within the ocean-continent transition zone, is challenging and much uncertainty in geometries and crustal type exists across many rifted margins across the globe which require careful and robust interpretation to attempt to reduce this uncertainty.

This contribution focuses on the Eastern Seaboard of the United States; in which we show a suite of seismic interpretations (from seismic reflection data), together with validations from potential field data to produce a comprehensive map of the crustal types along the margin. Much recent work on the margin has investigated the segmentation along strike, indicating that the architecture of the Eastern Seaboard does not conform to any of the end-member models. Here we provide evidence of the segmentation and non-conforming nature of the margin, consistent with recent work on the US Eastern Seaboard which is at odds with typical models of rifted margin architectures. Furthermore, to accompany the new crustal architectures map, we propose a conceptual structural model of the development of the margin, constrained by our observations and accounting for the three-dimensional nature of the margin evolution.

How to cite: Shotton, M., Mortimer, E., Gouiza, M., and Green, C.: Evaluating the crustal architectures of the Eastern Seaboard of the United States: Insights from seismic reflection and potential field data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6068, https://doi.org/10.5194/egusphere-egu22-6068, 2022.

13:58–14:05
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EGU22-6077
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ECS
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Virtual presentation
Annabel Causer et al.

Cretaceous to earliest Oligocene plate motions between Greenland and North America are only modellable at high resolution from a short-lived (61-42 Ma) sequence of magnetic isochrons in the Labrador Sea. Understanding them at other times is hampered by interpretational conflicts and low resolution in geoscientific observations of the Labrador Sea, Davis Strait, Baffin Bay, and Eurekan Orogen. To better contextualize these observations, we build and manipulate models of North America-Eurasia and Eurasia-Greenland divergence in order to depict post-84 Ma North American-Greenland motions at quantified high resolution. Among our findings, we show that the North American-Eurasian plate boundary propagated northwards, leading the continental shelves in the Labrador Sea to separate by 74-72 Ma and in Baffin Bay later, at around 63 Ma, and that field evidence for the Eurekan Orogeny having occurred in two distinct phases is directly related to a 46 Ma change in Greenland-North American plate motion parameters.

How to cite: Causer, A., Eagles, G., Pérez-Díaz, L., and Adam, J.: Cenozoic relative movements of Greenland and North America by closure of the North Atlantic-Arctic plate circuit: The Labrador Sea, Davis Strait, Baffin Bay, and Eurekan Orogen, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6077, https://doi.org/10.5194/egusphere-egu22-6077, 2022.

14:05–14:12
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EGU22-11241
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ECS
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On-site presentation
Katrin Meier et al.

Eastern North Greenland is a key area for studying the reorganisation of the North Atlantic-Arctic Realm during the Cenozoic. Due to its crucial position at the intersection of Atlantic Ocean, Arctic Ocean, and the West Greenland Rift Basin this area was significantly involved in the Eureka Orogeny leading to intracontinental compression/transpression observed on the Svalbard-Barents margin and the Canadian Archipelago as well as Northern Greenland. In the Neogene the final breakup occurred in this area, leading to the deep-water connection of the Arctic and North Atlantic Oceans.

It is characterized by the Carboniferous-Paleogene deposits of the Wandel Sea Basin overlaying Mesoproterozoic to early Palaeozoic supracrustal rocks. They occur in a series of pull apart basins along a zone of NE-SW-oriented faults. These faults are part of the DeGeer Shear Zone, along which the lateral offset of Greenland and Spitsbergen occurred during the Eureka Orogeny. In accordance the deposits are deformed, but the timing and the structural context of the deformation is much debated. Also, some deposits show unusually high thermal maturities of which the origin and geodynamic context is unclear.

We took samples across the Tolle-Land-Fault-Zone from the coast in the NE into the Caledonian basement in SW and applied apatite fission tack analysis and (U-Th-Sm)/He thermochronology to reconstruct the thermal history of the respective segments of the fault zone and their thermal evolution in respect to the deformation and opening of the northern Atlantic. Preliminary results will be presented and the exhumation history and timing of deformation and thermal anomalies in eastern North Greenland and influence of the breakup will be discussed.

How to cite: Meier, K., O'Sullivan, P., Monien, P., Piepjohn, K., Lisker, F., and Spiegel, C.: The Eurekan in eastern North Greenland: insights from thermochronology, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11241, https://doi.org/10.5194/egusphere-egu22-11241, 2022.

14:12–14:19
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EGU22-4322
Anatoly Nikishin et al.

We present an interpretation of the regional seismic lines for the Amerasia Basin, and new data from analyses of rocks from the Alpha-Mendeleev Rise. This report is based primarily on interpretation of 2D seismic lines and analysis of magnetic and gravity field anomalies, from data acquired through the Russian Arktika-2011, Arktika-2012, Arktika -2014, and Arktika-2020 projects. We use also open Canadian seismic data (Shimeld et al., 2021) and published data. We propose that the Alpha-Mendeleev Rise is a Eurasian aborted double-sided volcanic passive continental margin with stretched and hyper-extended continental crust intruded by basalts. This rise has a number of SDR-like seismic units. The age of volcanism is ~125-100 Ma. The Podvodnikov, Toll, Mendeleev, Nautilus, Stefansson basins have SDR-like seismic units. The top of SDR-like units has a similar age in all basins. The Alpha-Mendeleev Rise has an axis of symmetry. The East North Chukchi, Toll, Mendeleev, Nautilus, Stefansson basins are coeval basins with very stretched continental crust. They are connected by a long united axial line of hyperextension, subsidence and volcanism.  The Makarov, Podvodnikov, West North Chukchi basins are coeval basins with very stretched continental crust. They are connected by a long united axial line of hyperextension, subsidence and volcanism.  The Alpha-Mendeleev Rise and all mentioned basins originated simultaneously in the same geodynamic environment during the HALIP magmatic epoch at nearly 125-100 Ma. This study was supported by the Russian Science Foundation (Grant 22-27-00160).

How to cite: Nikishin, A., Petrov, E., Rodina, E., Startseva, K., Chernykh, A., Cloetingh, S., Foulger, G., and Posamentier, H.: Amerasia Basin: new data and new geological model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4322, https://doi.org/10.5194/egusphere-egu22-4322, 2022.

14:19–14:26
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EGU22-4415
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ECS
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Virtual presentation
Elizaveta Rodina et al.

Study area includes Alpha-Mendeleev Rise and contiguous deep-water basins – Toll, Mendeleev, Nautilus and Stefansson Basins near the eastern slope and Podvodnikov and Makarov Basins near the western slope. The western boundary is Lomonosov Ridge; the eastern boundary is Chukchi Plateau and part of the Canada Basin. There are Chukchi and East Siberian Seas on the continental shelf.

Within the study area, we studied and interpreted seismic 2D profiles from the Russian Arktika-2011, Arktika-2012, Arktika -2014, and Arktika-2020 expeditions. We also worked with open Canadian seismic data (Shimeld et al., 2021) and published data (e.g., Ilhan, Coakley, 2018). A unified seismostratigraphic correlation was carried out for the entire region.

Many half-grabens locate on the edges of deep-sea basins. Bright-amplitude reflectors with wedge-shaped architecture fill half-grabens. These reflectors are similar to SDR and they represent by interbedding of basaltic lavas and sedimentary rocks. They are typical for the synrift complex within the study area. The top of the synrift complex (or top of SDRs like units) is a bright boundary with age ~100 Ma.  Sometimes the top of the synrift complex contains conical edifices with a chaotic internal structure. Their height is 400-800 m. This is possible underwater volcanoes. The base of the synrift complex (or base of SDRs like units) is unclear and corresponds to the top of the acoustic basement. This age is near 125 Ma. We assume that SDRs like units and volcanos were formed during the HALIP epoch (~125-80 Ma).

 We found a regularity in the distribution of half-graben and SDRs like units. They are all located at the edges of the basins near the slopes of the uplifts. Two axes can be distinguished as the centers where SDRs like units and half-grabens converge. The western axis goes through Podvodnikov Basin and corresponds with the central uplift of the Podvodnikov basin. Reflectors dip from the western slope of the Mendeleev Rise from one side and from the Lomonosov Ridge from another. They converge near the central uplift. The eastern axis goes through Toll, Mendeleev, Nautilus and Stefansson Basins. In Toll and Mendeleev Basins reflectors and half-grabens dip from east slope of Mendeleev Rise from one side and from Chukchi Plateau from another. The Stefansson Basin looks similar to the Podvodnikov Basin. The central uplift is located in the center of the Stefansson Basin. Reflectors and half-grabens dip from Alpha Rise from one side and from Sever Spur from another. We have compiled a map of the distribution of SDR’s like units, volcanoes and half-grabens based on the map of the acoustic basement.

This study was supported by the Russian Science Foundation (Grant 22-27-00160).

How to cite: Rodina, E., Nikishin, A., and Startseva, K.: SDR (Seaward Dipping Reflectors) mapping in the Amerasia Basin, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4415, https://doi.org/10.5194/egusphere-egu22-4415, 2022.

14:26–14:33
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EGU22-12316
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ECS
Ivan Sobolev et al.

Collisional igneous units of the Carboniferous and Permian age in the Polar Urals are poorly studied. This is due to the fact that most of them are probably hidden under the Mesozoic-Cenozoic cover of the West Siberian Plate. Thin bodies of gabbroids, lamprophyres, monzonitoids, and granitoids are known (Musyur, Yarkeu, Yayu, and Pogurej complexes), which are usually attributed to the collisional stage of the Uralian orogeny. Their age, in most cases, is based on geological data and methodologically outdated K-Ar ages (Shishikin et al., 2007; Pryamonosov et al., 2001).

We have studied one of the largest intrusions in the Polar Urals attributed (Shishkin et al., 2007) to the Late Carboniferous Yarkeu complex of the West Ural megazone and considered to be collisional. The pluton is located 13 km north of Kharp township, making up most of Mount Yarkeu. The intrusion is predominantly composed of monzogabbro, monzodiorite, and monzonite which form a «ring» structure among the Neoproterozoic plagiogranitoids of the Kharbey-Sob' complex, with which they have indistinct (gradual) contacts. K-Ar dating of K-feldspar and plagioclase mix from quartz monzonite (Pryamonosov et al., 2001) yielded the age of 310±10 Ma.

To clarify the time of monzonitoids formation, we carried out additional isotope-geochronological studies using modern methods (U-Pb and Ar-Ar). From the monzodiorite sample, 48 zircon grains were dated according to the method (Nikishin et al., 2020). Discordance in all cases did not exceed 2%. The individual 206Pb-238U ages of dated grains are in the range from 650–707 Ma, and the average concordant age is 680±2 Ma (95% confidence interval, MSWD=0.35).

The 40Ar-39Ar dating of the primary magmatic amphibole from monzodiorite was carried out by the method of stepwise heating according to the standard method (Travin et al., 2009). In the high-temperature part of the age spectrum, a six-step plateau was distinguished, characterized by 83.5% of the released 39Ar and a value of 669±8 Ma (MSWD=0.62).

The new U-Pb and Ar-Ar Neoproterozoic ages are similar and correspond to the time of formation of monzodiorites in the considered pluton. The younger Carboniferous K-Ar age (310±10 Ma) obtained from feldspars (Pryamonosov et al., 2001) is probably rejuvenated. The disturbance of the K-Ar isotope system in feldspars can be explained by the significant saussuritization of plagioclase as well as the lower closing temperature of the K-Ar isotope system in plagioclase and K-feldspar compared to magmatic amphibole. Thus, the Late Carboniferous age of feldspars does not correspond to the time of formation of monzonitoids but to the dynamo-thermal events associated with the collisional stage of the Uralian orogeny (Puchkov, 2010), which occurred at the end of the assembly of the Pangea (Kuznetsov, Romanyuk, 2014).

The obtained Neoproterozoic age of monzodiorite is close to the zircon ages 671±4 Ma and 662±6 Ma from the host subduction-related diorites and plagiogranitoids of the Kharbey-Sob complex (Dushin et al., 2014). The monzonitoids of Mount Yarkeu complement the evolutionary trend of the Late Precambrian subduction-related magmatism attributed to the Neoproterozoic Kharbey-Sob' complex.

This work was supported by RFBR grant 19-55-26009.

How to cite: Sobolev, I., Vikentiev, I., Sheshukov, V., Dubenskii, A., Travin, A., and Novikova, A.: The age of monzonitoids of the Mount Yarkeu, Polar Urals: first U-Pb (LA-ICP-MS) and 40Ar-39Ar ages, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12316, https://doi.org/10.5194/egusphere-egu22-12316, 2022.

14:33–14:40
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EGU22-4449
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ECS
Ksenia Startseva et al.

On the seismic lines acquired in 2011-2020 for the North-Chukchi Sea and East Siberian Sea basins plenty of low-amplitude normal faults is identified. Maximal apparent throw of the faults is 100-200 ms, and occasionally reaches up to 300-400 ms. Dip angles of the faults are often directed towards each other, the resulting flower structure is related to strike-slip tension. For individual faults it is possible to ascertain strike azimuth – near 350° for the North Chukchi basin and near 340° in East Siberian basin. By the seismic data, the faults are distributed within an area of ~1.500 km long- and ~350 km wide.

According to interpretation, the faults activation occurred from 45 Ma to 34 Ma. This time corresponds to a regional tectonic rebuilding, that is observed across all the region. For example, a sharp slowdown of the Eurasian Basin spreading had place then. Formation of the North-Chukchi and East Siberian basins is related to Aptian-Albian (~125 Ma) rifting, that manifested itself on the De Long Islands and the Mendeleev Rise. Isometric form of the basins could indicate the conditions of pull-apart tension. Data of gravity and magnetic anomalies support this assumption – a long linear anomaly of ~285° strike is identified to the North of the Wrangel Island (in Chukchi, the last is called Umkilir – “White Bear Island”). The anomaly is interpreted as regional strike-slip that was formed ~125 Ma. The angle between the strike-sleep and the multiple low-amplitude Eocene faults is about 55-65°. It is possible to relate the low-amplitude faults to the reactivation of the great strike-slip.

This study was supported by the Russian Science Foundation (Grant 22-27-00160).

How to cite: Startseva, K., Nikishin, A., and Rodina, E.: The great Arctic Eocene strike-slip zone Umky, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4449, https://doi.org/10.5194/egusphere-egu22-4449, 2022.

14:40–14:47
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EGU22-12218
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Virtual presentation
Viacheslav Bogoliubskii et al.

Tjörnes transform zone (TFZ) is complicated fracture zone in North Iceland connecting Kolbeinsey ridge and Northern rift zone of Iceland. It includes several different structures such as segmented oblique rift, amagmatic rifts and oblique slip fault zones. They developed consequently since ca. 9 Ma. The aim of this work is to determine current geodynamic activity and ratio of tectonic and magmatic activity of each structure and adjacent structures of Mid-Atlantic ridge (MAR) basing on normal faults morphometric parameters and to reconstruct evolution of TFZ by physical modelling. Morphometric analysis is based on multibeam bathymetry data of Marine and Freshwater Research Institute in Iceland and ArcticDEM digital elevation model. There were collected data on more than 900 normal faults on five parameters: heave, thrust, length, distance between faults and maximum profile curvature. They reflect recent rate of horizontal and vertical deformations and morphological age of the normal fault. Heave and distance ratio shows the relative intensity of tectonic and magmatic activity. The results show that structures have different level of recent tectonic activity and therefore, are on different stages of their evolution. In addition, they have various tectono-magmatic ratio that proceeds from their development stage, width of faulting zone and mantle structure. Physical modeling is based extending setting with mineral oil that have numerical resemblance with oceanic crust in density, shear modulus and thickness. Two-layered model have elastic bottom layer, brittle top one and local heating source corresponding to Icelandic plume impulses. Initial configuration reflects two spreading segments of MAR that develop transform zone in conditions of crust thinning in direction out of Icelandic plume center. In result of their interaction is generation of overlapping spreading centers. One of them became extinct and another one develops into transtensive transform zone, which corresponds to Husavik-Flatey oblique slip fracture zone (HFFZ) and adjacent amagmatic rift. Activation of local heating source rejuvenates extinct branch of the overlap and generates subparallel to extension direction rifting fractures reconstructing Grímsey oblique rift with high magmatic activity. HFFZ activity abruptly declines. In conclusion, consequent development, activation and decline of structures correctly correlate with results of morphometric analysis and reflect the development stages of each structure. The specific current structure of TFZ is determined by initial development of overlapping spreading centers and their control by Icelandic plume magmatic impulses.

How to cite: Bogoliubskii, V., Dubinin, E., and Grokholsky, A.: Current geodynamics and evolution of Tjörnes transform zone, North Iceland, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12218, https://doi.org/10.5194/egusphere-egu22-12218, 2022.

Thu, 26 May, 15:10–16:40

Chairpersons: Rebekka Steffen, Aleksandra Smyrak-Sikora, Grace E. Shephard

15:10–15:20
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EGU22-10387
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solicited
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Highlight
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On-site presentation
Sergei Medvedev and Ebbe Hartz

Extensive surface erosion may cause sizable lithospheric deformations. The effects are even more remarkable in regions subjected to glacial erosion. The isostatic response shielded by flexurally strong lithosphere is usually wider than localized glacial erosion and causes non-linear local effects. We use erosion backward in time (EBT) to model this process. In our experiments, we numerically fill the eroded voids with crustal material and calculate isostatic response to this added surface load. We assume that these calculations approximate amplitudes of erosion-related processes occurred in nature. Our studies started with considering enigmatic marine Mesozoic sediments stored at the elevation of 1.2 km in central east Greenland, the area free from recent compressional tectonic processes. The location is surrounded by the world’s biggest fjord system, Scoresby Sund. Application of the EBT allows us to estimate the unloading by the glacial fjord carving and conclude about a km-scale regional uplift explaining elevated marine sediments. Similar study on the development of the Europe’s biggest plateau, Hardangervidda in the southern Norway, demonstrated that glacial erosion caused up to 40% uplift of the plateau. Analyzing the Quaternary evolution of the North Sea, we found that on-shore erosion and off-shore sediment accumulation results in differential vertical motion of the lithosphere of up to 1 km across the sea. Applied to a particular petroleum system, the Troll field, this tilting explains significant oil spilling during the Quaternary.

How to cite: Medvedev, S. and Hartz, E.: Lithosphere response to erosion: Model and case studies, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10387, https://doi.org/10.5194/egusphere-egu22-10387, 2022.

15:20–15:27
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EGU22-6201
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On-site presentation
Owen Anfinson et al.

During the Devonian, the Svalbard Archipelago lay near the equator, occupying an important paleogeographic position at the intersection of Caledonian and Ellesmerian orogens. We provide new sediment provenance constraints, including detrital zircon U-Pb ages, from the Devonian Andrée Land Basin, Svalbard, to understand the tectonic history of the archipelago at that time. Sedimentary provenance analysis of Devonian aged strata can help reconstruct the sediment sources and paleogeography to understand the assembly of the domains that make up Svalbard, that are presently separated by Devonian sedimentary basins and(or) faults with syn- to post Devonian displacement. The studied Andrée Land Group strata in Dicksonland, 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 data are dominated by ages sourced from Svalbard’s Northwestern and Southwestern Basement provinces. In Middle and Upper Devonian strata, paleocurrents and detrital zircon ages suggest a shift to a predominantly eastern-northeastern provenance, likely sourced from the uplifting Ny-Friesland block along the Billefjorden Fault Zone. The addition of significant late Ediacaran-early Cambrian detrital zircons in a sample from the uppermost Planteryggen Formation (Frasnian) indicate sources associated with the Timanian orogen and provide a useful palaeogeographic indicator when compared to other regional detrital zircon data sets. Detrital zircon ages and provenance data suggest Svalbard may have already been assembled, similar to the block we see today, with the Andrée Land Basin 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 Lower, Middle, and Upper Devonian strata provides further insight on Svalbard’s paleogeographic position in the Devonian.

How to cite: Anfinson, O., Odlum, M., Piepjohn, K., Poulaki, E., Shephard, G., Stockli, D., Levang, D., and Jensen, M.: Provenance Analysis of the Andrée Land Basin and the Paleogeography of Svalbard in the Devonian, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6201, https://doi.org/10.5194/egusphere-egu22-6201, 2022.

15:27–15:34
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EGU22-5930
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On-site presentation
Paul Béguelin et al.

The Azores Plateau in the North Atlantic is a classic example of near-ridge oceanic plateau (600 km) associated with the upwelling of the Azores mantle plume. The radiogenic isotope signatures of Azores lavas show systematic inter-island variations, which are often interpreted in terms of sampling several distinct, chemically enriched reservoirs from the Azores plume [1].

Here we discuss new radiogenic cerium isotope data on Azores lavas in the context of recent isotope data on olivine-hosted melt inclusions [2]. Olivine-hosted melt inclusions have very high neodymium isotope ratios (up to εNd = 18.1), suggesting that variably depleted mantle is the dominant component of the Azores mantle source [2]. Radiogenic Ce isotopes reflect the time-integrated La/Ce ratio of the mantle source. La/Ce approaches zero values in incompatible element depleted mantle, while the Sm/Nd and Lu/Hf ratios retain higher, more variable values. Melts from variably depleted mantle therefore develop distinct signatures in Ce–Nd–Hf space [3].

The new Ce isotope values for 36 whole-rock lava samples covering the whole Azores Plateau reveal a number of parallel, vertically stacked trends in Ce–Nd and Ce–Hf isotope space, pointing to variably incompatible depleted end-members, that are not discernible in Sr–Nd–Pb–Hf isotope space. The observed isotope trends in Ce–Nd–Hf space are readily explained by variable contribution of melts from volumetrically dominant, but variably depleted mantle and similar, but inherently heterogeneous enriched local plume components. Hence, although not directly reflected in the erupted basalts on a whole-rock scale [1, 2], variable contribution of melts from a variably, in part highly depleted mantle control the isotope composition of Azores lavas.

These results indicate the North Atlantic mantle below the Azores is variably depleted and contains highly depleted domains. The lavas closest to the proposed plume center [4] do not correspond to either extreme in terms of mantle depletion, suggesting mantle depletion in Azores is inherently complex and not a simple mixing product between plume and ridge mantle.

 

[1] Béguelin et al. (2017) Geochimica et Cosmochimica Acta, 218, 132-152.

[2] Stracke et al. (2019) Nature Geoscience, 12(10), 851-855.

[3] Willig et al. (2020) Geochimica et Cosmochimica Acta, 272, 36-53.

[4] Bourdon et al. (2005) Earth and Planetary Science Letters, 239, 42-56.

How to cite: Béguelin, P., Stracke, A., Genske, F., Bizimis, M., Beier, C., and Willig, M.: Variably depleted mantle in the source of Azores lavas, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5930, https://doi.org/10.5194/egusphere-egu22-5930, 2022.

15:34–15:41
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EGU22-7053
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ECS
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On-site presentation
Åse Hestnes et al.

We here present the first U-Pb geochronology from calcites precipitated on fracture and fault surfaces from the passive continental margin of Western Norway. The evolution of passive continental rifted margins is reflected in complex fracture and fault networks which have been activated and reactivated through time. Constraining the timing of fault activity and fracturing can assist in revealing the interaction between tectonic processes and the topographic response onshore. Recently, U-Pb calcite dating has proven to be a useful tool to complement other geochronological methods and to produce more complete records of brittle deformation in different geological settings. In this study, we collected 35 calcite samples from different fault and fracture planes in Western Norway, 14 of which gave reliable U-Pb dates. The onshore field area is located at the junction of the NE-SW trending Norwegian Sea and the N-S trending North Sea. 1) The oldest calcites measured are from the Dalsfjord fault, a complex brittle fault related to the Nordfjord-Sogn Detachment Zone. The ages obtained from a green cataclasite indicate fluid flow and calcite precipitation around 208 ± 25 Ma and 205 ± 6 Ma, whereas a reddish cataclasite and fault gouge zone were dated 142 ± 15 Ma. 2) Two calcite samples from the northern part of the study area were collected along fractures parallel to the Møre-Trøndelag Fault Complex and yield dates of 89 ± 4 Ma and 79 ± 3 Ma. 3) Five samples from variously oriented fractures and faults spread over the field area gave dates of 69 ± 2 Ma, 67 ±15 Ma, 65 ± 2 Ma, 64 ± 2 Ma and 59 ± 2 Ma. These ages can be linked to the base Tertiary unconformity in the offshore stratigraphic record of the northern North Sea interpreted to be caused by onshore uplift. Several processes have been proposed to cause a possible uplift during this time span; a) regional influence of the Icelandic mantle plume, b) rift footwall uplift, c) climatically controlled topographic changes. 4) Five samples from across the field area yield dates of 49 ± 3 Ma, 35 ± 1 Ma, 21 ± 1 Ma, 5.5 ± 4.5 Ma and 0.8 ± 0.1 Ma. All these calcites precipitated on faults and fractures striking NE-SW, and its formation may be related to relaxation along the passive margin. The dated calcites from this study provide Cenozoic brittle deformation ages much younger than previously obtained by other geochronological methods, possibly allowing to decipher the youngest brittle tectonic evolution of the margin in unprecedented detail.

How to cite: Hestnes, Å., Drost, K., Gasser, D., Jacobs, J., Scheiber, T., Sømme, T., and Chew, D.: New insights into the brittle evolution along the passive continental margin of Western Norway from U-Pb calcite dating , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7053, https://doi.org/10.5194/egusphere-egu22-7053, 2022.

15:41–15:48
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EGU22-9399
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Highlight
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Virtual presentation
Carmen Gaina et al.

Most of the Arctic region is contained within the territory of Norway, Russia, USA, Canada and Denmark/Greenland, yet the natural boundaries and processes do not conform to these political borders. This remote region requires special logistics, equipment and substantial financial support. The last decade has seen an increase in knowledge about the northern polar region for economic and political reasons, such as the extended continental shelf claims under UNCLOS and Arctic Council activities.

It is crucial that scientific research, activities and their outcome are visible to the broader scientific community and communicated to the wider public. In recent years considerable effort has been invested by several groups and institutions to make various data and results available online and to use it for education and outreach. Examples include: the Arctic Observing Viewer which is a web mapping application in support of U.S. SEARCH, AON, SIOS, and other Arctic Observing networks (https://arcticobservingviewer.org/); Arctic Research Mapping Application (https://armap.org/) and the NSF Arctic Data Center (https://arctic data.io) for locating projects and data supported by US funding agencies; Svalbox (www.svalbox.no), a database for digital outcrop models from Svalbard, the comprehensive PANGAEA database  (https://www.pangaea.de), a data publisher for Earth and Environmental sciences; and GeoMapApp (http://www.geomapapp.org/), a map-based application for browsing, visualizing and analyzing a diverse suite of curated global and regional geoscience data sets.

While a wealth of data can be located and viewed in these databases and data repositories, the scientific community and geoscience educators may benefit from a collection of geological and geophysical data that can be easily visualized, analyzed and used for a quick assessment of present-day geodynamic setting and further for paleogeographic reconstructions  in the circum-Arctic region.

Consequently, a group of scientists from four Arctic countries and their collaborators are aiming to consolidate and further develop the Arctic-related common scientific basis and educational programmes under the auspices of the Norwegian Research Council programme INTPART (International Partnerships for Excellent Education, Research and Innovation).

The project NOR-R-AM (https://norramarctic.wordpress.com/), established in 2017, focused on assessing the openly available information accumulated at participating institutes. During the first phase of this project, we have gathered and interpreted data in various sub-regions, especially in Svalbard and in Russia. The second phase of the NOR-R-AM project aims to complete and launch the digital Circum-Arctic geodynamics platform. This web-based platform will incorporate geological and geophysical data and models, tomographic and kinematic models and paleogeography and paleoclimate indicators. The digital Circum-Arctic geological repository,  to be hosted by our project webpage https://norramarctic.wordpress.com/, assembles the data in openly accessible formats that are compatible with GPlates, GeomapApp and Google Earth. These data are consistently formatted to simplify exchange and completely open to the scientific community.

How to cite: Gaina, C., Shephard, G., Minakov, A., Anfinson, O., Ershova, V., Schaeffer, A., Senger, K., Stockli, D., Coakley, B., Augland, L. E., Audet, P., Midtkandal, I., and Jones, M.: A digital Circum-Arctic geological repository from the NORRAM project, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9399, https://doi.org/10.5194/egusphere-egu22-9399, 2022.

15:48–15:55
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EGU22-6253
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Highlight
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Virtual presentation
Gillian Foulger et al.

The disintegration of Pangea north of the Charlie Gibbs fracture zone led to the formation of the NE Atlantic and Arctic Oceans. Both these oceans are exceptionally complex in terms of diversity of the structures they contain and the sequence of events leading to their formation. Recent, extensive work by cross-disciplinary international groups has cast a great deal of new light on the structure and evolution of both oceans. Both have experienced fan-shaped oceanic-type spreading and ridge growth by linear propagation. Both contain shallow, linear bathymetric highs which comprise substantially or almost wholly, continental crust. There are also regions of continental crust, some hyper-extended, capped with lavas. Much of the NE Atlantic Ocean is floored by oceanic crust produced by classical, albeit piecemeal, oceanic spreading. The spreading rate is low and dwindles to ultra-low on the Gakkel Ridge in the Eurasia Basin of the Arctic Ocean. The Gakkel Ridge is flanked by linear, oceanic-like magnetic anomalies although it is not entirely clear whether these represent fully oceanic crust formation or whether some residual stretched continental crust remains beneath this region. The same may be true of the extinct Canada Basin spreading axis in the Amerasia Basin. Likewise, the nature and location of the continent-ocean transition in the NE Atlantic is currently under discussion and it has recently been proposed that the oldest linear magnetic anomalies, closest to the continental edges, characterize some form of magma-injected continental crust. A similar structure has been recently proposed for the Greenland-Iceland-Faroe Ridge  and the Alpha-Mendeleev Rise. What is currently unclear is the extents, in both oceans, of the three kinds of crust – true continental crust including microcontinents, magma-injected continental crust, and fully oceanic crust. There is furthermore likely a structural and geological continuum between these types. Classical linear magnetic anomalies are discontinuous between sections of the spreading ridge, raising the question of whether continuous fully oceanic crust connects these sections. In our presentation we will summarize what is known geologically and tectonically about both oceans, compare and contrast them, and outline their evolution. We will discuss the extents of the three types of crust and explore the implications for the history and mechanisms of ocean formation and the origins and extents of flood basalts. Of particular interest also is the control of pre-existing structure on the style of breakup.

How to cite: Foulger, G., Nikishin, A., Rodina, E., Startseva, K., Gernigon, L., Geoffroy, L., Phethean, J., and Chernykh, A.: The Arctic and NE Atlantic Realms: A comparison, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6253, https://doi.org/10.5194/egusphere-egu22-6253, 2022.