The Rannoch and Etive formations, a shallow-marine sandstone succession of the economically important Middle Jurassic Brent Group of the northern North Sea, has been re-examined in the Oseberg area, using twenty-six cored wells. An updated sedimentologic and sequence stratigraphic model for the two formations, and the lowest part of the overlying Ness Formation, is presented. The Rannoch and Etive formations were largely deposited within a wave-dominated, shore-zone setting. The orientation of the shoreline shifted gradually from a transverse (N-S) to an axial (E-W) orientation during a regression, under stable to slightly falling relative sea level. After a subsequent period of oblique aggradation involving a stable to slightly rising relative sea level, a more pronounced fall of relative sea level caused the development of a regional subaerial unconformity and an incised-channel complex in the Oseberg Gamma area.
A depositional and sequence stratigraphic model for the Rannoch and Etive formations, Oseberg Field, northern North Sea