Implications of Controlling Fault Geometry on the Structural and Sedimentary Development of Extensional Systems: Zeta-Snorre Fault System, Northern North Sea, Norway

Douglas A. Paton¹ and John R. Underhill^2
1 Grant Institute of Earth Sciences, Edinburgh EH9 3JW United Kingdom, Potsdam, Germany
² School of GeoSciences, University of Edinburgh, Edinburgh, United Kingdom

Two commonly cited end-members for normal fault geometries are steeply dipping planes in a domino-fault block configuration, and shallow dipping planes with associated rollover geometries. We document the presence of both of these end-members in a single basin (Tampen Spur, North Viking Graben, Norway) and demonstrate the profound impact that fault geometry has on the basin's structural and sedimentological evolution.

The south of the basin comprises the Snorre-Zeta fault hangingwall in the west and the Visund footwall in the east. Both faults have a steep dip (~ 45°) with little internal deformation between them, therefore conforming to a domino-fault block model. In contrast, the north comprises the shallower dipping Zeta fault (~30°) with no eastern bounding fault. Deformation in the northern intra-basin setting is significantly greater with arrays of synthetic and antithetic faults similar to that associated with listric fault rollover geometries.

This variation in structural style has a profound affect on sedimentation and depocentre configuration. The south has a single depocentre adjacent to the bounding fault that forms early in the syn-rift phase with a deep water depositional environment during the late rift phase. In contrast, the rollover geometry in the north results in the establishment of a number of fault arrays and smaller depocentres that are conduits for sediment dispersal and associated footwall flanks that act as local sources of sediment. These faults develop in accordance to established fault growth models with gradual localisation of strain towards the east onto a smaller population of larger displacement, longer faults.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005