Fault-controlled alpine topography in Norway

Abstract

Alpine topography in Norway is largely fault-controlled. Linear and asymmetric ranges developed in the footwalls of normal faults that were reactivated after the main phase of Mesozoic rifting, but prior to the Late Cenozoic glaciations. Stark geomorphological contrasts developed across the faults, reflecting differential glacial exploitation of the pre-glacial drainage pattern. Alpine topography developed preferentially in the footwalls. Triangular facets mark the traces of the most recently active faults. At the base of deeply incised, alpine range-front escarpments, the best-exposed faults display metres-thick fault-rock successions and record multiple phases of fault movement. Juxtaposition of Precambrian and Caledonian basement rocks with Jurassic or Cretaceous sedimentary rocks provides evidence for fault activity in or after the Mesozoic for some of the faults. Late Cretaceous or younger reactivation is indicated by jumps in apatite fission-track apparent ages across the faults, and interferometric synthetic aperture radar and earthquake data attest to normal faulting at the present day. Two of the areas described host anomalous clusters of rockslides that may relate to tectonic activity. The most distinct landscape-forming faults in western Scandinavia were probably active in the Cenozoic, and imposed asymmetric landscape patterns from the scale of single mountain ranges to the whole of Scandinavia.

On Palaeozoic–Mesozoic brittle normal faults along the SW Barents Sea margin: fault processes and implications for basement permeability and margin evolution

“…Instead, Mesozoic fault activity took place offshore, along the Troms-Finnmark Fault Complex (Gabrielsen et al 1990), further north in Finnmark (Roberts & Lippard 2005 ;Torgersen et al 2013) and to the south in Vesterålen and Andøya (Dalland 1981;Fürsich & Thomsen 2005;Eig 2008;Hansen 2009;Hendriks et al 2010;Osmundsen et al 2010;Davids et al 2013). The onshore faults in Troms are therefore believed to have been abandoned after the Late Permian-Early Triassic rifting phase and thus reflect conditions of early stages of rifting (Davids et al 2013;Indrevaer et al 2013).…”

Gravitational slope deformation, not neotectonics: Revisiting the Nordmannvikdalen feature of northern Norway

“…Furthermore, it is located in a region where a variety of observations point strongly towards Cenozoic, and probably Quaternary, tectonic activity ( Fig. 1; see Osmundsen et al, 2009Osmundsen et al, , 2010. Because earthquakes in onshore Norway tend to be normal to normal-oblique Keiding et al, 2015), repeat intervals for medium-large (M w ≥ 6.0) events are uncertain in Scandinavia (e.g., Bungum et al, 2005), and such tremors are known to cause landsliding (see Keefer, 1984), its importance to Norwegian geology becomes that much the greater.…”

Elevated, passive continental margins: Not rift shoulders, but expressions of episodic, post-rift burial and exhumation

“…Our observations and our conceptual model suggest that the heights of EPCMs are large compared to massifs within cratons, and that this additional height may be due to processes operating where lateral contrasts in thickness of the crust or lithosphere make the margins of the cratons unstable (e.g. Praeg et al, 2005;Japsen et al, 2006;Osmundsen et al, 2010). Whether a passive margin is low-lying or elevated will consequently depend on the geometry of the edge of the crust or lithosphere and on the stress exerted on it in the immediate geological past (typically, within the Neogene).…”

“…Osmundsen et al (2010), for example, documented major, normal faulting that affected the continental crust of western Scandinavia after rifting and breakup, and prior to late Cenozoic glaciations, and argued that these faults were important during the post-rift uplift of Scandinavia. Osmundsen et al (2010) considered the Scandinavian topography to be a rejuvenated rift flank, but did not recognise that the AFT ages younger than 100 Ma that they reported from near Jurassic rift basins along the coast of north Norway (69°N), mean that these basins and their margins must have been exhumed from below a kilometre-thick cover.…”