The crust and mantle lithosphere in the Barents Sea/Kara Sea region

The focus of this study is the nature of a prominent, high-velocity (S-wave) anomaly in the upper mantle below the Barents Sea-Kara Sea region and its relation to the evolution of the sedimentary basins, in particular the Permo-Triassic East Barents Sea Basin. The high-velocity anomaly exhibits a thickness of 75-100 km below the central Barents Sea and thickens considerably below the East Barents Sea Basin (150 km). The thickest part of the high-velocity anomaly follows the outline of the East Barents Sea Basin which is bended around Pai-Khoi-Novaya Zemlya Fold Belt. Density modeling of the lithosphere along a 3200 km long transect from the Barents Sea to the West Siberian Basin was used to evaluate different models for the upper mantle structure. The best fit gravity model was achieved when either assuming a 1D, horizontally- layered mantle structure, or, a forward-modeled density structure using an average Proterozoic mantle composition. The first model requires a further, compensating excess mass below the (seismic) Moho in the East Barents Sea Basin region. The latter model exhibits a higher-density dome structure below the basin. Both models indicate probable old, continental lithosphere below the central part of the transect in eastern Barents Sea/Kara Sea region. Calculated temperatures of 400-1000 degrees C (60-200 km depth) further support this concept. Hence, the East Barents Sea Basin developed probably as an intra-continental basin within a non-extensional setting. Such basins exhibit generally crustal inhomogeneities which contributed considerably to their subsidence history. Likely structures below the East Barents Sea Basin are Pre-Permian rifts, accumulated melts derived by the Siberian mantle plume, and/or the Late Neoproterozoic Timanide Orogen. (C) 2008 Elsevier B.V. All rights reserved.