Long term morphotectonic evolution in Sweden

Abstract

A morphotectonic interpretation of the relief of Sweden is presented based on an analysis of the gross forms of the topography. Computer-made topographic profiles covering 76,375 km have been examined together with contour maps. New maps of relief and layers of height have also been used. Three main aspects considered are: the relation between the surface of the Precambrian basement and its cover rocks; the erosional, new surfaces, developed in both Caledonian basement and reexposed Precambrian basement; and the evolution of the valley pattern. The analysis produced the following results: •The surface of the Precambrian basement is a mosaic of old, exhumed surfaces and new surfaces formed after erosion of the cover rocks. The exhumed surfaces include (1) a sub-Jotnian surface, mainly below cover rocks in downfaulted positions, (2) the sub-Cambrian peneplain, and (3) sub-Mesozoic etch-surfaces. Block-faulting was identified in relation to the different exhumed surfaces.•After the formation of the Caledonides, a post-Caledonian surface was cut across the Caledonian basement and the Precambrian basement with its cover. The subsequent evolution of the Swedish part of this surface has been traced through several new surfaces in stepped sequences and in relation to the exhumed surfaces.•Five main denudation intervals are distinguished that result in characteristic relief. They are preceded by intervals of orogeny, uplift, and faulting and followed by subsidence and/or deposition of sedimentary strata.•The valley patterns, the distribution of new and exhumed surfaces as well as remmants of cover rocks, give some fundamental clues to where and when uplift and subsidence occurred.Historical geomorphology has mainly been based on theories of erosion cycles. The relief of the cratons are difficult to fit exclusively into such a system. The importance of long lasting covers and of exhumed surfaces have not been considered enough, neither the movements of uplift and subsidence. Reconstruction of geomorphic events appears to be more important for understanding relief evolution than any model, as every phase is unique. The methods used in this study are worth testing within other cratons.