The structural geology of the Southern Norwegian Caledonides in the Oslo Graben and Sparagmite region

In order to construct the most continuous balanced cross-section from undeformed foreland to higher thrust sheets in the southern Caledonides of Norway, selected areas of Cambro-Silurian rocks were mapped in the Oslo Graben. Undeformed rocks are only present in the southern part of the Oslo Graben and palinspastic reconstructions of the Oslo Graben restore the traditional thrust front in southern Mjosa 135km NNW of its current position. Therefore it is proposed that the thrust front now be recognised in the southern Oslo Graben. The traditional thrust front is interpreted here as the most southerly of a series of ramps in the Osen-Roa Thrust as it cuts. up section towards the SSE. After ramping through the Hedmark Group (Eocambrian) the Osen-Ro Thrust forms the bed-parallel detachment in the Alum Shales (Middle Cambrian) of the Oslo Graben. Therefore, it is proposed that the Osen-Roa Thrust Sheet continues into the Oslo Graben