Basement Inhomogeneities and Crustal Setting in the Barents Sea from a Combined 3-D Gravity and Magnetic Model

Laura Marello

We present a new 3D geophysical model for the Barents Sea that highlights the basement properties and crustal setting. The model results from the modelling of gravity and magnetic field anomalies and is based on a large number of seismic and petrophysical data. The set up consists of: a water layer, sedimentary units that incorporate density variations associated with depth and time of deposition (Cretaceous-Cenozoic, Triassic-Jurassic, Late Palaeozoic and deeply buried sediments), upper and lower basement, and an upper mantle. The upper crust is considered as the major source of the magnetic anomalies and has been divided into a number of units characterised by constant densities and magnetisation, which show a good correlation with the main structural elements of the Barents Sea. The Southwest Barents Sea crust is an aggregation of allochthonous Caledonian terranes and autochthonous Archaean and Palaeoproterozoic complexes. We interpret the different crustal blocks in terms of distinctive lower, middle, upper and uppermost allochthonous terranes that can be linked with the major nappes onshore. The largest part of the North Barents Sea is distinguished from the rest of the shelf by its low-magnetic properties and its large crustal thickness. These differences are compatible with a geodynamic scenario in which an independent crustal block (Barentsia, not corresponding entirely to the island of Svalbard) was located between Baltica and Laurentia and became attached to the shelf during the Caledonian orogeny. To the east, the basement underlying the large mega-sag East Barents Basin, is an assemblage of Precambrian rocks deformed during the Timanian and Uralian orogenies. The basement is characterised by an alternation of high-magnetic and low-magnetic units that mimic the arcuate shape of Novaya Zemlya. In the Southeast Barents Sea, the crustal units are linked to the onshore geology of the Timan-Pechora region and are mostly the result of Timanian orogenesis.

AAPG Search and Discovery Article #90177©3P Arctic, Polar Petroleum Potential Conference & Exhibition, Stavanger, Norway, October 15-18, 2013