| Summary: | 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 age 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 pre-linkage, multi-segment stage of its
growth have not been equilibrated following fault linkage. Using the stratal architecture of syn-rift
sediments, we date the main phase of segment linkage as latest Callovian - Middle Oxfordian (10-14
M.yr. after rift initiation). A dense sub-population 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 M.yr. 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 de fine a graben-like basin geometry. Faults of the antithetic
array became inactive approximately 11.5 M.yr. 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 localised 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 multi-segment array.
|
|---|