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SUMMARY The northern Barents–Kara Sea continental margin is a poorly investigated area because of a permanent ice cover hampering seismic exploration. The available geological and geophysical data show that the magma‐poor margin developed in response to early Cenozoic break‐up and subsequent opening of the Arctic Eurasia Basin. In this study, a series of crustal‐scale geotransects illustrating the architecture of the continental margin are constructed using sparse seismic reflection profiles and a gravity inversion method incorporating a thermal model of rifting. The continental side of the northern Barents Sea margin is underlain by Palaeozoic–Early Mesozoic deep sedimentary basins separated from the oceanic side by the marginal uplift. A bathymetry analysis complements low‐resolution seismic data to predict the sedimentary depocenters beyond the shelf break. These depocenters are associated with troughs, perpendicular to the shelf edge. The depocenter in front of the St. Anna Trough may contain a sedimentary section more than 4 km thick. The gravity correction for the effect of sedimentary cover was added to the inversion. This correction used an exponential density–depth function. The inversion supports a narrow and steep continent–ocean transition (COT; ca. 100 km). The conjugate Lomonosov Ridge margin is modelled using the same technique. Palaeoreconstructions were made to predict the break‐up setting. The northern Barents Sea–Lomonosov Ridge rift system can be described as an initially narrow symmetric rift. A transitional zone of extreme thinning is assumed between the oldest spreading magnetic anomaly and the stretched continental crust. The free‐air gravity anomaly in the western part of the margin can be predicted by the upwelling divergent flow model implying the exhumation of the lower crust and the continental upper mantle within the COT. It is suggested that an episode of shear or oblique extension before breakup is required to explain the observed narrow symmetric conjugate margins in the Eurasia Basin.

We perform an integrated analysis of magnetic anomalies, multichannel seismic and wide-angle seismic data across an Early Cretaceous continental large igneous province in the northern Barents Sea region. Our data show that the high-frequency and high-amplitude magnetic anomalies in this region are spatially correlated with dykes and sills observed onshore. The dykes are grouped into two conjugate swarms striking oblique to the northern Barents Sea passive margin in the regions of eastern Svalbard and Franz Josef Land, respectively. The multichannel seismic data east of Svalbard and south of Franz Josef Land indicate the presence of sills at different stratigraphic levels. The most abundant population of sills is observed in the Triassic successions of the East Barents Sea Basin. We observe near-vertical seismic column-like anomalies that cut across the entire sedimentary cover. We interpret these structures as magmatic feeder channels or dykes. In addition, the compressional seismic velocity model locally indicates near-vertical, positive fingershaped velocity anomalies (10-15 km wide) that extend to mid-crustal depths (15-20 km) and possibly deeper. The crustal structure does not include magmatic underplating and shows no regional crustal thinning, suggesting a localized (dyking, channelized flow) rather than a pervasive mode of magma emplacement. We suggest that most of the crustal extension was taken up by brittle-plastic dilatation in shear bands. We interpret the geometry of dykes in the horizontal plane in terms of the palaeo-stress regime using a model of a thick elastoplastic plate containing a circular hole (at the plume location) and subject to combined pure shear and pressure loads. The geometry of dykes in the northern Barents Sea and Arctic Canada can be predicted by the pattern of dilatant plastic shear bands obtained in our numerical experiments assuming boundary conditions consistent with a combination of extension in the Amerasia Basin sub-parallel to the northern Barents Sea margin and a mild compression nearly orthogonal to the margin. The approach has implications for palaeo-stress analysis using the geometry of dyke swarms. Supplementary material: Details on traveltime tomography model: Resolution tests, traveltime information and ray coverage are available at

The employed method of 3D gravity modeling is based on calculation of the gravity effects of the main density boundaries of the lithosphere, subtraction of these effects from the observed gravity field, and the subsequent conversion of the residual gravity anomalies first to the Moho depth and then to the total thickness of the Earth’s crust and the thickness of its consolidated part. On the modeling, we also took into account the gravity effects due to an increase in the sediment density with increasing sediment depth and a rise of the top of the asthenosphere beneath the mid-ocean Gakkel Ridge. The resulting 3D models of the Moho topography and crustal thickness are well consistent with the data of deep seismic investigations. They confirm the significant differences in crustal structure between the Eurasian and Amerasian Basins and give an idea of the regional variations in crustal thickness beneath the major ridges and basins of the Arctic Ocean.

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