Structural style and stratigraphic response to normal fault growth in extensional basins

The early growth of normal faults is typically associated with the development of at-surface monoclinal folds and the deposition of wedge shaped syn-rift deposits that typically thin and onlap towards these growth structures. This is especially true in salt-influenced rift basins, where the presence of mechanically-weak, evaporite rich units within the pre-rift succession may serve to decouple folded supra-salt strata from faulted sub-salt strata, resulting in the formation of extensional forced folds in the overburden. However, uncertainties still exist with respect to; (i) the controls of the structural style and kinematics of normal fault growth in salt-influenced rifts; (ii) the syn-rift stratigraphic response to faulting and folding; and (iii) the along-strike variability of these linked structural and stratigraphic relationships in both salt-influenced and non-salt influenced extensional settings. To address these outstanding research issues, an integrated dataset of three-dimensional seismic reflection and borehole data from the Stavanger Fault System (SFS), Egersund Basin, North Sea and field data from the Hadahid Fault System (HFS), Suez Rift, Egypt is used. The results demonstrate that; (i) the structural style of fault growth in salt-influenced basins is primary controlled by the pre-rift salt distribution and thickness, and that the sub- and supra-salt fault populations initiate and grow as brittle elements of a single, geometrically and kinematically coherent structure; (ii) the stratal architecture of and facies variations in early syn-rift deposits are controlled by the growth of normal faults and extensional forced folding, and changes in base-level; and (iii) the along-strike variability in the stratal architecture of and facies variations in early syn-rift deposits are influenced by growth folding and faulting, which may vary markedly in time and space at both the fault-segment and fault-system scales.Open Acces