Evolution of topography of post-Devonian Scandinavia: effects and rates of erosion

Abstract:

The mechanisms and timing of mountain growth in Scandinavia remain enigmatic given that the region has not been involved in active orogenesis since the Devonian and in any large-scale tectonic activities after the NE Atlantic breakup during the early Cenozoic. In this study we combine analysis of the vertical motions of the region caused by (dominantly) glacial erosion during the Quaternary with Apatite Fission Track (AFT) analysis of rocks from the area. Using numerical models, we first quantify how fluvial and glacial erosion carved out the fjords and valleys to a depth of 2 km below the paleosurfaces. This erosional episode represents a major local weight loss and results in up to a 0.8-km uplift of rocks and up to a 0.5-km rise of local topography. These estimates only marginally depend on the effective elastic thickness of the lithosphere and thus are robust. We show then that no correlation exists between sample altitude and published AFT data, but that a correlation does exist between AFT age and the depth below our constructed pre-glacial summit surface. This correlation demonstrates the robustness of the numerical erosional model, quantifies average erosion rates during Carboniferous–Cretaceous at < 10 m/My, and outlines the regions of western Scandinavia (Lofoten and Bergen areas and Møre-Trøndelag fault complex) with atypical Mesozoic–Cenozoic evolution, probably related to regional tectonic activities.