A revised stratigraphy for the Ringerike Group (Upper Silurian, Oslo Region)

The Ringerike Group is a terrigenous succession of Upper Silurian sediments that outcrops in a number of areas within the Oslo Region of southern Norway. Despite being the focus of a number of studies in the past, the stratigraphic relationships between different outcrop areas are still poorly understood. This paper compiles sedimentological and stratigraphic evidence from all the outcrop areas and a revised stratigraphy for the Ringerike Group is presented. The revised stratigraphy comprises four formations - the Sundvollen Formation, the Stubdal Formation, the Store Aroya Formation (new), and the Holmestrand Formation. These formations vary according to whether they lie north or south of Oslo. The base of the Ringerike Group is diachronous, being younger to the south, reflecting the fact that its siliciclastic depositional systems were advancing southwards from the Caleclonides to the north of the Oslo Region.