Geochemical and Petrographic Characterization of the Lower Cretaceous Siliciclastic Malha Formation, Northern Galala Plateau, Egypt: Chemostratigraphy, Fractionation Trends, and Tectonic Setting

The Early Cretaceous Malha Formation of the Northern Galala Plateau, Egypt, is evaluated through an integrated petrographic, mineralogical, and geochemical investigation of a 222 m thick siliciclastic succession. Facies analysis identifies siliciclastic lithofacies, including five types (quartz arenite, calcareous ferruginous quartz arenite, litharenite, quartz graywacke, and kaolinitic sandstone), in addition to shale facies, reflecting alternating high-energy fluvial channels, low-energy floodplain deposits, episodic coastal influence, and marginal-marine conditions. X-ray diffraction analyses reveal a quartz–kaolinite–microcline mineral assemblage with variable iron-oxide components, indicating a compositionally mature sediment supply derived from deeply weathered felsic sources. Whole-rock geochemistry supports this interpretation, with SiO₂ frequently exceeding 75 wt.% and low Al₂O₃/SiO₂ ratios, together with elevated CIA and CIW values that reflect moderate to strong chemical weathering and significant sediment recycling. Provenance-sensitive trace-element ratios, such as Zr/Sc, Th/Sc, and Cr/Ni, consistently indicate derivation from felsic upper continental crust affected by repeated sedimentary reworking. Although only LREE were analyzed, their enrichment relative to UCC and PAAS further supports a mature felsic provenance. Four chemostratigraphic zones (CZ-1 to CZ-4) are identified, documenting an upward transition from kaolinitic, Fe-rich basal intervals to highly mature quartzose units. Collectively, the petrographic, mineralogical, and geochemical datasets indicate deposition within a fluvio–coastal to marginal-marine system developed along a tectonically stable passive continental margin.