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Turner (1974a) proposed the Ringerike Group to embrace all red bed units earlier assigned to stage 10. The group comprises an approximately 1,250 m thick sequence of red siltstones and sandstones in its type area in the Ringerike district. Turner also defined the Sundvollen (lower 500 m) and Stubdal (upper 750 m) Formations within the Ringerike Group in its type area. The type section of the Sundvollen Formation on the western slopes of Kroksund (NM7259) consists mostly of red siltstones and sandstones arranged in fluvial upwards fining sequences. Interbedded marine mudstones and limestones of tidal inlet origin suggest coastal plain to estuarine environments.