Home – Home – Jornals – Russian Geology and Geophysics 2005 number 7

The 16-20 km deep Barents basin is among world deepest sedimentary basins. Its eastern part occupied by the East Barents subbasin develops upon very thin consolidated crust with high P velocities. It is often interpreted as oceanic crust, though the thickness of sediments (up to 10-12 km) accumulated after the subsidence of oceanic crust would have completed far exceeds the amount necessary to fill an oceanic basin. The Moho is underlain by an ~20 km thick layer of heavy mafic rocks with crustal chemical signatures and P velocities typical of garnet granulite and eclogite, intermediate between crustal and mantle velocities. Thus, the total thickness of consolidated rocks, including those above and below the Moho, amounts to 35-40 km and indicates its continental origin. A lithospheric extension of 10-15% can be hypothesized but cannot be verified because the available penetration of seismic profiling is limited to 12-14 km. Most of subsidence in the East Barents basin was caused by phase-change consolidation of the lower crust anyway.
A granitic layer is present in the thin crust over the greatest part of the Barents basin. Its large-scale subsidence is commonly explained by strong lithospheric extension but this explanation contradicts the seismogeological evidence that extension was weak almost throughout the basin. It can allow for only 5 % of subsidence which was to the greatest extent caused by phase change in the lower crust. Rapid subsidence at the Early/Middle Permian boundary and in the Late Jurassic produced relatively deep seas providing a favorable environment for the formation of the Barents petroleum province.