A series of 34 shallow-penetration seismic-reflection profiles made across the Red Sea show that it developed in two main stages. Initially, an early or pre-Miocene uplift and lateral extension resulted in crustal thinning and eventual formation of the main Red Sea Basin. During Miocene time, the Red Sea was isolated from the Indian Ocean but possibly connected with the Mediterranean Sea, which, like the Red Sea, was an evaporite basin at that time. A distinct acoustic reflector (reflector S) in the Red Sea marks the top of the Miocene evaporite sequence and is correlative with reflector M in the Mediterranean, which is similarly identified with termination of evaporite conditions.
In Pliocene time, connection with the Indian Ocean was re-established, the opening to the Mediterranean was closed, and normal marine conditions were resumed in the Red Sea. Sea-floor spreading first started in Pliocene-Pleistocene time, and resulted in the formation of the axial zone of the Red Sea.