The northern Arabo-Nubian craton witnessed a major Late Cretaceous-early Tertiary marine transgression that culminated in the deposition of widespread shelf-sea carbonates during Early Eocene (Ypresian) time. In Egypt, these Early Eocene strata (the Thebes Limestone and its equivalents) crop out over more than 100,000 km² (38,610 mi²), and reveal a mosaic of carbonate facies consistent with the general model of "epeiric clear water sedimentation" proposed by Irwin in 1965.

"Outer shelf" facies characterize exposures in central Egypt (Assiut, Luxor, Kharga), and are composed primarily of rhythmically interbedded chalk and micritic limestone with minor intercalated marine hardgrounds. To the south (Kurkur-Dungul), these fine-grained lithologies give way to "inner shelf" foraminiferal wackestones and grainstones, typical Tethyan "Nummulitic" facies. Missing in southern Egypt is the restricted dolomitic evaporitic facies predicted by the Irwin model and observed in the lower Eocene of the Sirte basin to the west and the Arabian Platform to the east. The absence of this marginal marine evaporite belt in Egypt is presumably the result of post-Ypresian uplift and removal.

Comparing the areal distribution of these lower Eocene carbonates to coeval facies developed across the remainder of northern Africa and Arabia reveals the presence of a broad marine embayment which extended through central and eastern Egypt into northern Sudan during Ypresian time. The widespread subsidence that resulted in the development of this feature may have been an effect of regional crustal attenuation preceding the rifting of the Red Sea.

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Concomitant with this regional subsidence were localized uplift and extensional block faulting in the vicinity of the incipient Red Sea rift (the Safaga-Quseir coastal plain). Here, lower Eocene carbonate facies are indicative of shallow water platforms developed on horst blocks, and deeper water, turbidite-fed basins in intervening grabens.

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