A post-Pliocene transgressive phase, characterized by its own fossil suite and its field appearance, has been recognized along the nothern part of the Nile Valley. The sediments of this transgressive phase was usually mistakenly lumped with a pre-existing and closely similar phase of Pliocene age, the sediments of the latter are named the Kom el Shellul Formation. The recognition and delineation of the sediments of this transgressive phase has been achieved through field study, sampling of numerous outcrops from the area between Cairo and Sakkara (Fig. 1) and also a critical review of the previous numerous studies dealing with the Pliocene and post-Pliocene geology of the Nile Valley and of the Cairo region in particular.