Younger Dryas transgression in western Norway: a modelling approach

Fennoscandia has experienced major uplift since late-glacial time. However, in the Younger Dryas (similar to 12,700-11,500 calibrated years before present) 10 metres of transgression occurred at the Norwegian west coast. This transgression was most significant in the area around Bergen; both to the north and to the south of this area the relative sea level fell during the Younger Dryas. Thus, in the area of transgression the shorelines are twisted; the 60 m Younger Dryas isobase crosses the 60 m Allerod isobase. The same section of the coast that was transgressed during the Younger Dryas also experienced a major ice-sheet readvance. In part of this area the ice sheet readvanced by at least 40 km. It seems likely that there is a causal connection between the ice readvance and the shoreline transgression. In this paper we report modelling of the isostatic and eustatic response of a readvancing Younger Dryas ice sheet. It is found that a halt in the glacial isostatic rebound is the major cause for the observed transgression. This, however, presupposes an Earth rheology with a low-viscosity asthenosphere and a weak effective elastic lithosphere.