Deep structure of the Scandinavian Caledonides and the Baltic Shield – a review with new integrated gravity-isostatic and thermal modelling

The Scandinavian Mountains span approximately 1,500 km and broadly follow the trace of the Scandinavian Caledonides, formed during the collision between Baltica and Laurentia. While the formation of this orogen is well established, the origin and timing of the present-day topography remain debated. This study investigates the structure and evolution of the deep-seated masses supporting the present-day topography. A comprehensive review of geological and geophysical data facilitates new integrated gravity-isostatic and thermal modelling, enabling a quantitative understanding of the interplay between the crust-Moho system (CMS) and the lithosphere-asthenosphere system (LAS). Crustal thickening from the Norwegian coast toward the Baltic Shield initially raises topography, while further inland a thicker lithosphere subdues topography despite a thick crust. Offshore, crustal thinning persisted from the late Mesozoic through the Paleogene. However, inland areas show no evidence of significant post-Permian crustal thinning or magmatism. These observations indicate that the underlying isostatic structure was primarily established during and in the aftermath of the Caledonian orogeny, with the modern topography representing a long-lived remnant sculpted by slow erosion and passive isostatic rebound.