Structure of the Scandes lithosphere from surface to depth

In this review we give an overview of geophysical data and models available for the Scandinavian mountains and adjacent areas, as they are of relevance to the debate about the existence and cause of Neogene uplift. Emphasis is given to potential field and petrophysical data of which the earth science communities of Norway and Sweden have a long tradition of acquisition and interpretation. This is reflected in the wealth and dense coverage of data available. The topography of the Scandes mountain chain correlates to a large degree with a Bouguer gravity low, which suggests isostatic compensation. But comparison with magnetic and petrophysical data shows that the gravity low is partly influenced by the Trans-Scandinavian Igneous Belt. Signals due to the effects of surface geology can be further eliminated by considering the near-surface density distribution as provided by petrophysical sampling. To illuminate the entire lithospheric structure, active and passive seismic and magnetotelluric data can be used. Recent and ongoing experiments are aimed at improving the existing models of the lithosphere. Integration of these different geophysical data sets allows the structure of the lithosphere of the Scandes and its surroundings to be addressed. Seismic models show no pronounced crustal root below the Scandes which could provide isostatic compensation, but instead an increase of crustal thickness towards the central Fennoscandian Shield. From the integrated model, isostatic compensation is inferred to be largely controlled by the density distribution of the crust and that a high-density lower crust to the east of the Scandes is necessary to achieve isostatic equilibrium on a regional scale. We demonstrate the typical crustal structure with profiles crossing from the Scandes into the shield, and a combined onshore–offshore basement map. ► Description of regional geophysical data base over the Scandes. ► Near-surface gravity effect vs. deep lithospheric sources. ► Discussion of seismic crustal thickness compilations. ► Isostatic model that explains the absence of a crustal root beneath the Scandes. ► Thickness of high-density lower crust beneath Scandinavia.