Growth of normal faults in multilayer sequences: A 3D seismic case study from the Egersund Basin,Norwegian North Sea |
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| Affiliation: | 1. Centre for Integrated Petroleum Research, University of Bergen, Allégaten 41, 5007 Bergen, Norway;2. Department of Earth Science, University of Bergen, Allégaten 41, 5007 Bergen, Norway;3. Department of Earth Science & Engineering, Imperial College, London SW7 2BP, UK;1. Department of Earth Science, University of Bergen, Allégaten 41, 5007 Bergen, Norway;2. A/S Norkse Shell, Tankvegen 1, 4056 Tananger, Norway;1. School of Earth and Environmental Sciences, University of Manchester, Oxford Road, Manchester, M13 9PL, UK;2. The University of Texas at Austin, Bureau of Economic Geology, Jackson School of Geosciences, Austin, TX, USA;3. Basins Research Group (BRG), Department of Earth Science and Engineering, Imperial College London, South Bennington Campus, SW7 2BP, UK;1. Basins Research Group (BRG), Department of Earth Science and Engineering, Imperial College, London, SW7 2BP, UK;2. Department of Earth Science, University of Bergen, Allégaten 41, 5007 Bergen, Norway;3. Statoil ASA, Sandslihaugen 30, 5254 Sandsli, Norway |
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| Abstract: | We investigate the structural style and evolution of a salt-influenced, extensional fault array in the Egersund Basin (Norwegian North Sea) through analysis of 3D reflection seismic and well data. Analysis of fault geometry/morphology, throw distribution and syn-kinematic strata reveal an intricate but systematic style of displacement and growth, suggesting an evolution of (1) initial syn-sedimentary fault growth contemporaneous with salt mobilization initiated during the Late Triassic, (2) cessation of fault activity and burial of the stagnant fault tips, and (3) subsequent nucleation of new faults in the cover above contemporaneous salt re-mobilization initiated during the Late Cretaceous, with downward propagation and linkage with faults. Stage 3 was apparently largely controlled by salt mobilization in response to basin inversion, as reactivated faults are located where the underlying salt is thick, while the non-reactivated faults are found where salt is depleted. Based on the 3D-throw analyses, we conclude that a combination of basement faulting and salt (re-) mobilization is the driving mechanisms behind fault activation and reactivation. Even though the sub- and supra-salt faults are mainly geometrically decoupled through the salt, a kinematic coupling must have existed as sub-salt faults still affected nucleation and localization of the cover faults. |
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| Keywords: | Salt tectonics Fault reactivation Throw-length distribution Expansion index Fault linkage Vertical throw-distribution |
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