Combined petrographic and geochemical methods are utilized to investigate the provenance, tectonic setting, palaeo-weathering and climatic conditions of the Cambrian Araba clastic sediments of NE Egypt. The ~ 60 m thick Araba Formation consists predominantly of sandstone and mudstone interbedded with conglomerate. Petrographically the Araba sandstones are mostly sub-mature and classified as subarkoses with an average framework composition of Q80F14L6. The framework components are dominated by monocrystalline quartz with subordinate K-feldspar, together with volcanic and granitic rock fragments. XRD analysis demonstrated that clay minerals comprise mixed-layer illite/smectite (I/S), illite and smectite, with minor kaolinite. Diagenetic features of the sandstone include mechanical infiltration of clay, mechanical and chemical compaction, cementation, dissolution and replacement of feldspars by carbonate cements and clays. The modal composition and geochemical parameters (e.g. Cr/V, Y/Ni, Th/Co and Cr/Th ratios) of the sandstones and mudstones indicate that they were derived from felsic source rocks, probably from the crystalline basement of the northern fringe of the Arabian–Nubian Shield. The study reveals a collisional tectonic setting for the sediments of the Araba Formation. Palaeo-weathering indices such as the chemical index of alteration (CIA), chemical index of weathering (CIW) and plagioclase index of alteration (PIA) of the clastic sediments suggest that the source area was moderately chemically weathered. On the northern margin of Gondwana, early Palaeozoic weathering occurred under fluctuating climatic conditions.

The petrographic and geochemical compositions of the Lower Miocene Moghra siliciclastic sediments in the Qattara Depression, north Western Desert, were investigated to infer their provenance, tectonic setting, palaeoweathering conditions, and diagenetic history. The Moghra Formation (~200 m thick) is dominated by sandstones intercalated with mudstone and carbonates. X‐ray diffraction analysis revealed that smectite, kaolinite, and illite are the dominant clay minerals found in mudstones. The sandstones are mainly subarkose, sublitharenite, and quartzarenite types with an average modal composition of Q89F6L5. The sandstones possess various diagenetic overprints including mechanical infiltration of clay, compaction, cementation, dissolution, and replacement. Major and trace element concentrations suggested that the parent rocks are intermediate to felsic in composition derived from the Neoproterozoic Arabian Nubian Shield. The weathering indices such as the chemical index of alteration and the plagioclase index of alteration implied that the intensity of chemical weathering in the source area was moderate under semi‐arid climatic conditions. On the other hand, the index of chemical variability indicates a low compositional maturity. The tectonic discrimination diagrams demonstrated a collision setting for the Arabian Nubian Shield, which represents the main supplier of sediments to the study area. Statistical parameters, sedimentary structures, and ichnofossil contents suggested that the Moghra sediments were deposited in a tidally‐influenced fluvial environment.

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We examine the evolution of the northwestern Red Sea, Egypt, by study of the Quseir-Umm Gheig subbasin. The subbasin records two main tectonic events. The fi rst event is related to development of Late Cretaceous synclinal basins due to sinistral movement along the reactivated Najd fault system. Evidence for this includes: (1) the Cretaceous basins are concentrated mainly in the central Eastern Desert, which represents the main infl uence zone of the Najd fault system, (2) folds are not everywhere parallel to the faults and their axes are curvilinear, (3) the faults dislocated the axial plane of the synclines, (4) the Cretaceous basins occur in an en-echelon arrangement, (5) there is a difference of 20° between the orientation of the sinistral strike-slip shear zones and the associated en-echelon synclinal folds, (6) principal stress directions are delineated by subhorizontal σ 1 and σ 3 and subvertical σ 2 , (7) sheared conglomerate is detected in the Nubia Formation, (8) minor overturned folds and minor NE-vergent thrusts occur in the Duwi and Dakhla Formations, and (9) there is a predominance of NE-SW normal faults in Cretaceous-Eocene sequences. The second event is related to the sinistral movement along the NNE-SSW Aqaba-Dead Sea transform and dextral movement along Queih and Hamrawin shear zones. This movement was synchronous with northeast extension of the Red Sea. The structures developed during this movement include: (1) NW-trending extensional faults, (2) extensional fault-related folds in Miocene-Pliocene deposits, and (3) buckle folds in Pliocene and post-Pliocene sequences. Buckle folds were developed during NW compression associated with sinistral movement along NNE-SSW strike-slip faults. Gypsiferous shale-rich beds in Miocene-Pliocene rocks played the main role in development of fault-related folds and buckle folds in the Quseir-Umm Gheig subbasin.