Nubia sandstone strata of southwestern Egypt were deposited mainly on vast alluvial plains with a northward slope and range in age from Jurassic to latest Cretaceous. The unique aspects of the Nubia as compared to most published fluvial models are that: (1) the sequence is composed almost entirely of medium to coarse-grained sand through a thickness of 1,000 to 2,000 m, (2) the stream channels were relatively straight, commonly only 2 to 4 m deep, and occupied by sandwave bed forms, and (3) the overbank deposits were thin, sandy, and contain fine kaolin clay plates introduced by infiltration of muddy flood waters.

The typical Nubia fluvial cycle is simple and of two parts. The lower part, commonly 2 to 4 m of porous clay-free sandstone, is composed of tabular sets of cross strata 20 to 100 cm thick, with consistent north dips. The upper part, only 1 to 2 m thick, is also sandstone but contains abundant kaolin platelets 1 to 2 µ in size. These clayey sandstones have numerous root traces and commonly lack primary lamination, although remnants of tabular sets are rarely partly preserved. The contact between upper and lower parts is transitional, with downward decreasing root-trace abundance. The basal contact of each cycle is an erosional surface with slight relief, and commonly eroded clayey sandstone clasts are reworked into the overlying sandstone.

Environmental reconstruction suggests that alluvial plains sloped northward from northern Sudan for hundreds of kilometers toward the Mediterranean. The climate was warm and humid or semihumid, judging from the flora. Streams crossing the plain were mostly fairly small, shallow, straight, but not braided. Interchannel areas were densely vegetated by plants typical of the Jurassic and Cretaceous. The sandstone is nearly pure quartz, although the source area is largely crystalline basement. This mineralogic maturity testifies to rigorous weathering and a long time span for fluvial recycling. Three alluvial plain sequences, each several hundred meters thick, are separated by thin marine or marginal marine muddy sediments deposited during extensive southward transgressions into Egypt.

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