Controls on synrift turbidite deposition on the hanging wall of the South Viking Graben, North Sea rift system, offshore Norway

Abstract

Three-dimensional seismic, wireline-log, core, and biostratigraphic data from the South Viking Graben, North Sea rift system, are integrated to investigate the controls on the temporal and spatial development of an Upper Jurassic synrift turbidite system deposited on the hanging-wall dipslope of a salt-influenced half graben. Turbidite deposition was coeval with the initiation and upslope (paleo-landward) migration of activity across a gravity-driven normal fault array. Three main synrift stratal units are identified, and these are mapped using seismic and well data. The lowermost unit (upper Oxfordian) comprises thick amalgamated turbidites, which are restricted to the hanging wall of the earliest, most basinward, growth fault. The middle unit (Kimmeridgian) is more areally extensive than the underlying system, draping the now inactive basinward growth fault and extending upslope into the hanging wall of a newly activated landward growth fault. The uppermost unit (lower to middle Volgian) is more sheetlike and was deposited when activity across all growth faults had mostly ceased and slope topography had been almost fully healed. This study demonstrates that hanging-wall dipslopes within rifts can be characterized by volumetrically significant, sand-rich, gravity flow-dominated depositional systems, and that the reservoir architecture of such deposits can be strongly controlled by syndepositional growth faulting. In addition, this study provides insights into the response of turbidites to tectonically driven changes in bathymetry, which may be applicable in a range of basin settings.