Extensional fault-related folding in the northwestern Red Sea, Egypt: segmented fault growth, fault linkages, corner folds and basin evolution

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Abstract Segmented, planar, domino-style extensional fault arrays and their associated hanging wall fault-related folds form complex linked basins along the onshore margin of the northwestern Red Sea, Egypt. The extensional fault systems form half-graben basins with kilometre-scale, asymmetrical, doubly plunging longitudinal synclines and narrow, plunging transverse anticlines and synclines. The axial traces of the hanging wall longitudinal folds are curvilinear, sub-parallel to the half-graben Border faults, and bend or are offset at relay ramps and at fault linkage points. Transverse corner fold systems occur at the fault linkage points and fault jogs. The fold geometries, variations in fault displacement, and fault slip indicators indicate that the fold and fault systems are kinematically related and formed during the Late Oligocene–Miocene rifting of the northern Red Sea. The folds were controlled by vertical and lateral fault propagation and by the mechanical anisotropy of the pre-rift strata. The proposed model for these extensional folds is the initial formation of monoclinal flexures above reactivated blind basement faults. Increased displacement, propagation and segment linkage formed hanging wall longitudinal folds and transverse corner folds. The longitudinal folds grew progressively at the expense of the transverse folds and merged along-strike into long hanging wall synclinal basins.