Isostatic and dynamic support of high topography on a North Atlantic passive margin

- We quantify crustal isostasy and dynamic topography in southwestern Scandinavia.
- Significant isostatic compensation suggests old Caledonian age for most topography.
- We infer dynamic rejuvenation of existing topography locally over the last 10 Myr.
- We reject the existence of an uplifted, dissected peneplain in Scandinavia.
- Recent peneplain uplift is incompatible with significant isostatic compensation.

Substantial controversy surrounds the origin of high topography along passive continental margins. Here we focus on the well-documented elevated passive margin in southwestern Scandinavia, and quantify the relative contributions of crustal isostasy and dynamic topography in controlling the present topography. We find that majority of the topography is compensated by the crustal structure, suggesting a topographic age that is in accord with the 400 Myr old Caledonian orogenesis. In addition, we propose that dynamic uplift of ∼300 m has rejuvenated existing topography locally in the coastal region over the last 10 Myr. Such uplift, combined with a general sea level fall, can help explain a variety of observations that have traditionally been interpreted in favor of a peneplain uplift model. We conclude that high topography along the Scandinavian margin cannot represent remnants of a peneplain uplifted within the last 20 Myr. The topography must have been high since the Caledonian orogeny.