The Late Oligocene- Middle Miocene rift sediments in Wadi Wizr-Wadi Assal area south of Quseir could be subdivided into four lithofacies: Facies A : Dominantly alluvial, coarse clastic, fans (Lower part of Ranga Formation). Facies B: Fluviatile coarse and fine siliciclastics, with marine evaporites near the top (upper part of Ranga Formation). Facies C: Open marine, mixed coralgal carbonate-siliciclastic sediments (Lower part of Um Mahara Formation) . Facies D: Restricted marine, algal laminated carbonate and siliciclastic sediments (upper part of Um Mahara Fm.).
Synsedimentary tectonics have played a great role in the distribution of these facies in the studied area. Thus by late Oligocene time, the intersection of NW and SE faults created two structural depressions trending NW and W separated by a NW trending high. Facies A was deposited on the lows. No sedimentation took place on the high. By Early Miocene time, Facies B was deposited on both the highs and lows but thicker and coarser siliciclastics in the lows. By Middle Miocene time rejuvination along NW trending faults resulting in the formation of NW fault blocks, thus giving rise to new highs and lows with NW orientation influencing the deposition of Facies C and D.