Is there evidence for magmatic underplating beneath the Oslo Rift?

We challenge some of the long-standing beliefs related to the Permian Oslo Rift structure, often referred to as a case example/type locality for continental rifting. The crustal structure of the Oslo Rift was long presumed to be thinned Proterozoic crust overlying a Permian high-density layer, interpreted as magmatic underplating. New data support an alternative view of the crustal structure in the Oslo Rift region. The Bouguer gravity high in the region shows a strong asymmetry: a steep, westward-facing gradient to the west of the rift, and a much gentler eastern gradient. We present a 3D density model based on petrophysical and seismic information, which accounts for the Bouguer gravity high using an eastward extension of old Precambrian structures, without invoking a prominent magmatic underplated structure. Reactivation of old pre-rift structures appears to be an important feature, affecting the evolution and location of the Permo-Carboniferous Oslo Rift.