Through examination of the scaling relations of faults and the use of seismic stratigraphic techniques, we demonstrate how the temporal and spatial evolution of the fault population in a half-graben basin can be accurately reconstructed. The basin bounded by the »62-km-long Strathspey-Brent-Statfjord fault array is located on the western flank of the Late Jurassic northern North Sea rift basin. Along-strike displacement variations, transverse fault-displacement folds and palaeo-fault tips abandoned in the hangingwall all provide evidence that the fault system comprises a hierarchy of linked palaeo-segments. The displacement variations developed while the fault was in a prelinkage, multisegment stage of its growth have not been equilibrated following fault linkage. Using the stratal architecture of synrift sediments, we date the main phase of segment linkage as latest Callovian - middle Oxfordian (10-14 Myr after rift initiation). A dense subpopulation of faults is mapped in the hangingwall to the Strathspey-Brent-Statfjord fault array. The majority of these faults are short, of low displacement and became inactive within 3-4 Myr of the beginning of the extensional event. Subsequently, only the segments of the proto-Strathspey-Brent-Statfjord fault and a conjugate array of antithetic faults located 3.5 km basinward continued to grow to define a graben-like basin geometry. Faults of the antithetic array became inactive ~11.5 Myr into the rift event, concentrating strain on the linked Strathspey-Brent-Statfjord fault; hence, the basin evolved into a half-graben. As the rift event progressed, strain was localized on a smaller number of active structures with increased rates of displacement. The results of this study suggest that a simple model for the linkage of 2-3 fault segments may not be applicable to a complex multisegment array.
|Number of pages||22|
|Publication status||Published - Sept 2000|