The sedimentary rocks that lie unconformably over the Arabian-Nubian shield on the Red Sea rift margins between 20° and 22° N. Lat. range from Late Cretaceous to Recent in age. Unconformities mark three main regressions, probably in the late Eocene to Oligocene, in the late (?) Miocene to early-middle (?) Pliocene, and in the late Pleistocene.

Each regression was followed by active deposition of clastics, reflecting major periods of rift-border uplift. The Pliocene to early Pleistocene uplift was probably the most intense. Carbonate deposition was subordinate; it was quantitatively important only during the Maestrichtian (Hejaz coast), the early to middle Miocene (Sudan coast), and the Pleistocene to Recent. Carbonate depositional environments were shallow neritic and littoral, much like those of the present coastal shelf. The shoreline was no more than 20-30 km. inland from the present coast. The outcropping Cenozoic strata of the Sudan coast consist of a clastic to carbonate and evaporitic sequence in the lower part, most of which is of Miocene age, and a partly Pliocene (?) and Pleistocene clastic group in the upper part The Miocene sequence includes, in ascending order, the Maghersum, Khor Eit, Abu Imana, and Dongunab Formations. The Miocene sequence of Sudan is very similar to that of Egypt (Gulf of Suez and Quseir) and Eritrea. Cenozoic faulting has left a deep imprint on the topography; the main trends, on land and on the coastal shelf floor, are north-south, east-west, north-northwest, and northeast-southwest. Many faults cut the entire sedimentary sequence, including the Pleistocene alluvial deposits.