Structure and evolution of the northern Barents-Kara Sea continental margin from integrated analysis of potential fields, bathymetry and sparse seismic data

Abstract

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 breakup and subsequent opening of the Arctic Eurasia Basin. In this study, a series of crustalscale 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 ofthemargincanbepredicted bytheupwelling divergentflowmodel implying theexhumation of the lower crust and the continental upper mantle within the COT. It is suggested that an episodeofshearorobliqueextensionbeforebreakupisrequiredtoexplaintheobservednarrow symmetric conjugate margins in the Eurasia Basin.