Tectono-stratigraphic analysis of Late Oligocene-Early Miocene Nakheil and Ranga Formations, based on outcrop data from Hamadat and Zug El Bohar half-graben basins, south Quseir, indicates that the evolution of normal fault segments was an important control on syn-rift depositional patterns and sequence stratigraphic development. Sedimentological and stratigraphic analysis of the Nakheil Formation indicates that it was deposited in a series of folds-controlled depocentres of early-formed propagating fault segments during the low subsidence rift initiation phase. The Nakheil Formation is composed of deltaic-lacustrine deposits that arranged in several stacked TST-HST cycles having a wedge-shaped geometry near the fault-bounded areas, reflecting the continuous creation of accommodation in the immediate hangingwall to the fault zone. In the hangingwall dip-slope ramp where low accommodation space occurred, these deposits are dominated by HST cycles of broad, sheet-like fan deltas with clear evidence of relative lake-level fall in the form of incised channels and forced regression. The overlying Ranga Formation was deposited during the high subsidence rift-climax phase, and is composed of shallow marine sand bodies, stacking aggradational and progradational HST of Gilbert-type fan deltas, along the border fault. Towards the hangingwall dip-slope margin dominant progradational conglomerates were deposited and extending southeastwards and laterally parallel to the Hamadat and Zug El Bohar fault blocks.
Three main stages in the evolution of the border fault zone are recorded in the syn-rift
stratigraphy. These are: following initiation of rifting isolated, steeply dipping normal fault
segments that propagated upwards resulting in the development of distinct local depocentres in their hanging wall synclines that controlled the architecture and distribution of the lower unit of Nakheil Formation. 2-The isolated fault segments had linked alongstrike producing long through-going fault segments, at that time with increasing displacement, generated a more typical half-graben basins, a structural configuration that exerted the influence on the architecture and distribution of the upper unit of Nakheil Formation and the lower unit of Ranga Formation. 3- In the later stage the fault segments linked forming a single, continuous fault trace, that controlled the development of the longitudinal deltas of the upper unit of Ranga Formation which is proposed to be a function of its location adjacent to an evolving of Hamadat and Zug El Bohar fault blocks rotation and plunging.
This evolving structural style from growth synclines and surface–breaking faults, as well as along-strike displacement variation, fault linkage and associated block rotation and plunging had a major impact on the stratal geometry, sediment transport pathways and facies stacking patterns of coeval syn-rift sediments.