Derived Soils
Nubian sandstone exposures in sub-humid, semi-arid, and arid conditions produce soil that is red-sandy but very different in other aspects. Only in sub-humid zones do these soils contain a moderately developed profile, including a textural B horizon lacking soluble salts and carbonates. In semi-arid and arid zones, profile differentiation is either weak or does not exist. In arid zones soils are shallow and contain carbonates, and soluble salts, including gypsum. The sole clay common to all Nubian sandstone parent materials is Kaolinite, which is the major clay mineral in sub-humid zone soil. In semi-arid soils smectite is a second major clay component. In arid zones small amounts of smectite and palygorskite accompany kaolinite. It is likely that smectite and palygorskite are products of pedogenic neoformation. Aeolian material was probably introduced into the silt and fine sand fractions from semi-arid and arid soils. It is also possible that some contamination of clay fractions occurred.
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