Deep structure of the V ring Margin: the transition from a continental shield to a young oceanic lithosphere

The present-day lithospheric structure across the Norwegian Margin in the V ring region is presented. The V ring Margin is characterized by the presence of large volume of magmatic underplating, thick Mesozoic basins, and prominent crustal thinning. Results from recent deep seismic experiments in the V ring Basin and V ring Marginal High and 3-D gravity modelling have been implemented in a regional 2-D lithospheric transect that runs from the Norwegian Caledonian Belt to the oceanic domain, crossing the transition between the Precambrian Fennoscandian/ Baltic shield and the Cenozoic northern North Atlantic oceanic lithosphere. The modelling approach integrates elevation, gravity, geoid and heat flow data under the assumptions of thermal steady-state and local isostasy. The results confirm and refine the major trends of the crustal geometry which is characterized by a Moho depth varying from about 45 km beneath the Caledonian thrusts, to 30 km beneath the Tr ndelag Platform, to 20^14 km beneath the V ring Basin and to 13 km in the oceanic domain. The lithosphere thins from the Norwegian Caledonian Belt (190 km thick) to the oceanic domain (6 60 km) in a stepwise manner reflecting the progressive seawards migration of lithospheric deformation since the Paleozoic. Our lithospheric thickness results are different from those predicted by post-rift lithospheric cooling models. In the oceanic domain, observed residual bathymetry (V600 m) is interpreted as the remaining effect of a deep seated thermal perturbation during the upper Cretaceous which would also produce