"The sedimentary rocks that lie unconformably over the Arabian-Nubian shield on the Red Sea rift margins between 20 degrees and 22 degrees 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."