NJG74-1-01
1994
The amplitude and decay of the glacial forebulge in Fennoscandia
74
1
pp. 2-8

Forebulge is upward movement of the surface peripheral to glaciated areas above its equilibrium position. The amplitude and decay history of the forebulge will differ for different models of the viscosity of the mantle and rigidity of the lithosphere. For a low-viscosity asthenosphere situated between the rigid lithosphere and mantle mesosphere, the forebulge could be significant. The other extreme, a uniform mantle viscosity, would give no forebulge at all. Tilting of palaeo-shorelines in peripheral areas and the pattern of present uplift and subsidence is best modelled using the following parameters: ( 1) a lithosphere of flexural rigidity 1023 Nm; (2) a mantle of viscosity of 1.0 x 1021 Pa s; and (3) asthenosphere of viscosity 1.3 x 1019 Pa s. This model is used to study the amplitude and decay history of the Scandinavian forebulge. It is shown that the latest Fennoscandian glaciation produces a forebulge of 60 m at 15,000 BP, collapsing smoothly without any migration. The zero uplift isoline in Fennoscandia is relatively stationary over time in late- and post-glacial time, dose to the maximum extent of the glacier. The minimum sea levet at 15,000 BP is modelled to be 125 m below the present sea levet, located 1 00 km from the former ice front.

0029-196X