Fault-propagation folding in extensional settings: Examples of structural style and synrift sedimentary response from the Suez rift, Sinai, Egypt

Field data from the Oligocene-Miocene Gulf of Suez rift demonstrate that co eval growth faults, folds, and transfer zones exerted a major control on sy nrift stratigraphic sequence development. Growth folds in the Suez rift are related to steeply dipping normal faults that propagated upward, resulting in broad, upward-widening monoclines in overlying strata, Folding during f ault propagation was accommodated by layer-parallel slip and detachment alo ng mudstone horizons as well as by normal and rare reverse secondary faults that propagated away from the master fault. The eventual propagation of th e master fault through to the surface left the steep limb of the monocline and most of the secondary faults in the hanging wall. This evolving structural style exerted a marked control on the geometry and stacking patterns of coeval synrift sediments. Synrift sediments display o nlap and intraformational unconformities toward the growth monoclines and b uried faults, whereas they diverge into broadly synclinal expanded sections away from the growth monocline. Continued movement across buried faults re sulted in the progressive rotation of the monoclinal limb and associated sy nrift sediments, each successively younger sequence dipping basinward at a shallower angle than the previous one. The resulting synrift geometries dif fer significantly from stratal geometries normally anticipated adjacent to normal faults. Along-strike variations in facies stacking patterns are also commonly associated with decreasing displacement across faults and associa ted folds toward low-relief transfer zones. Data from other rift basins ind icate that fault-propagation folds are not unique to the Gulf of Suez.