3.5.2. Quantifying the Uplift of Scandinavia in space and time

Development of the Norwegian passive margin was preceded by 280 My of intermittent rifting that culminated at the Paleocene-Eocene transition in crustal separation between Scandinavia and Greenland and the onset of sea-floor spreading (Ziegler, 1988). The present-day landscape of Scandinavia's Atlantic border is characterized by elevated margins with associated escarpments, and an overall topography that gradually diminishes towards the continental interior. In western Fennoscandia, a deeply incised topographic escarpment runs close to and parallel with parts of the Norwegian coast, separating the uplifted western Scandinavian landmass from deep offshore sedimentary basins. In south-central Norway, an uplifted sub-Cambrian peneplain is evident that reaches elevations of more than 1000 metres. To the east, in central Sweden and Finland, this sub-Cambrian peneplain lies very close to sea level, suggesting that very little vertical motion has occurred in these areas since the late Proterozoic. Thus, a flexural profile appears to characterize onshore Fennoscandia (Redfield et al., 2005). Offshore Mid-Norway, the extremely deep Møre and Vøring basins present megascale sags that developed in response to thermal subsidence and sedimentation after the Jurassic-Cretaceous rift phase that preceded crustal separation. In the hinge that developed between the uplifting landmass and the subsiding post-rift basins, inherited Paleozoic fault complexes appear to have been reactivated from the Late Cretaceous onwards, probably affecting the shape and distribution of topographic highs and lows. Offshore, the deep crustal geometry of the Møre and Vøring basins appear to be controlled by major extensional detachment faults that partly re-activate structures stemming from the late- and post-orogenic collapse of the Caledonides (Gabrielsen et al., 2005; Ebbing et al., 2006).

The topography of western Scandinavian borderlands is characterized by surfaces that reflect important stages in their uplift and erosion. The most clear is the so-called palaeic surface that occurs over large areas of southern Norway at elevations of 800-1000m. Topographically higher (and tentatively older) surfaces have been proposed. An intriguing challenge lies in understanding of mechanisms that controlled the development, uplift and incision of these surfaces that probably formed during the Late Mesozoic, Cenozoic and Quaternary (Lidmar-Bergstrom and Naslund, 2002). A critical component of this challenge is the exact dating of the development of these surfaces (Hendriks and Andriessen, 2002).

To unravel the dominant mechanisms responsible for the present-day Scandinavian topography and its past evolution, TOPO-EUROPE participants will examine the interaction between tectonics and landscape evolution, placing quantitative constraints on the timing of processes that control denudation and morphological development. To study these phenomena, new high-resolution data on denudation rates will be required. Local- versus regional-scale effects will be assessed and compared to the post-break-up landform evolution of the conjugate Norwegian and East Greenland (de)glaciated margins (Tsikalas et al., 2005). Available apatite fission track (AFT) data (Fig. 58) document a broad, regional-scale pattern of post-rift denudation and uplift (Rohrman et al., 1995; Cederbom, 2001; Hendriks and Andriessen, 2002; Rohrman et al., 2002; Huigen and Andriessen, 2004; Murrell and Andriessen, 2004; Redfield et al., 2004; Hendriks and Redfield, 2005). However, there is a lack of data on denudation rates at the finer resolution scale required for constraining numerical models for surface and deeper lithospheric or even asthenospheric processes. Therefore, TOPO-EUROPE will combine low temperature (<70ºC) apatite (U-Th)/He analyses with higher temperature (120-60ºC) AFT thermochronoloy to place as fine a resolution as possible on patterns and timing of denudation. Data will be collected along profiles that are carefully laid-out together with structural geologists to distinguish between tectonic juxtaposition and erosion-related denudation. The advantage of this approach is that a distinction can be made between regional- and local-scale exhumation patterns vs. regional or local scale patterns of post-rift tectonics (Redfield et al., 2005).

TOPO-EUROPE will thus focus on problems such as (a) quantification of timing and amount of uplift and denudation, (b) finer resolutions of denudation patterns stemming from syn-rift or post-rift structuring of the margin, and (c) comparing the post-break-up landform evolution of conjugate margins.