LITHOSPHERE-SCALE 3D-DENSITY AND THERMAL MODELS FOR THE BARENTS SEA AND KARA SEA REGION

The Barents Sea and Kara Sea as part of the Northern European Arctic amalgamated during three major orogenies from latest Precambrian to late Paleozoic times. Subsequent subsidence phases were driven by locally different basin forming mechanisms as indicated by the present-day geometry of the sedimentary cover, the crystalline crust and the deeper lithosphere. We investigate the present-day density and temperature distributions of the entire lithosphere. In particular, we assess how compositional heterogeneities in the subsedimentary crust (tracing back e.g. to terrane amalgamations) control the distribution of thermal properties and consequently temperature anomalies.

To perform 3D-gravity modelling, we make use of a recently introduced lithosphere-scale 3D-structural model which resolves the thicknesses of five sedimentary units, the subsedimentary crust as well as the lithospheric mantle for the greater Barents Sea and Kara Sea region. The geometries of this 3D-structural model are consistent with interpreted seismic refraction and reflection data, geological maps and previously published 3D-models. The density distribution of the sedimentary units is constrained by their lithologies, porosity data and the known effects of post-depositional erosion and glaciation. Density anomalies within the continental lithospheric mantle are derived from a recently published velocity-density model [Levshin, A.L., Schweitzer, J., Weidle, C., Shapiro, N.M., Ritzwoller, M.H., 2007. Surface wave tomography of the Barents Sea and surrounding regions. Geophys. J. Int. 170, 441–459]. Starting with this initial 3D-model, the density distribution is stepwise modified to reproduce the observed gravity field to further investigate the composition of the crystalline crust and in particular, to define the extent of possible high-density bodies.

The obtained density distribution within the lithosphere provides further constraints on regional variations in thermal properties, which we use to calculate the conductive thermal field. The modelled 3D‑thermal field is validated with measured borehole temperatures and surface heat flow data to assess the major controlling factors of the latter.