The lithology of the Quseir Formation (Middle Campanian) has an important effect on soils of Dakhla Oasis. The clay mineralogy of Quseir Formation reveals four clay associations for Mut Member as saponite-kaolinite; mixed layer-kaolinite; saponite-mixed layer and sepiolite, and seven clay associations for El Hindaw Member as montmorillonite-kaolinite; illite-palygorskite; montmorillonite-saponite; kaolinite-chlorite; kaolinite-sepiolite, stevensite-sepiolite and quartz-illite beside one sand facies.
The Mut Member associations indicate slightly alkaline to weakly acidic pH environment whereas El Hindaw Member associations reveal three cycles of environmental conditions beginning with slightly alkaline to slightly acidic that are changed to slightly acidic to slightly basic environment at the top of the three cycles.
From the geochemical studies, the variation in each major oxide and trace elements discussed revealing the kind of clay mineral associations and other minor components present. The highest value of Fe2O3 are due to the presence of iron oxides whereas the anomalous FeO are attributed to the presence of glauconite. The highest P205 and CaO values reflect the presence of phosphate mineral whereas the high CaO value did not support by the presence of phosphate mineral are due to the presence of gypsum and/or anhydrite. The LIL elements (K, Rb, Ba, Ca and Sr) are controlled by the dominance of mixed layer clays whereas the Ni, Co, V and Cr are controlled by magnesian ones. The HFS elements Y and Zr are mainly controlled by the presence of elastic material from the surrounding environments.
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