Two different regimes of Neogene sedimentation can be recognized along thr Red Sea coastal area:
1- The first regime comprises the Pre-Abu Dabbab Evaporite Miocene sediments.
The distribution of the facies is mainly governed by the main western Miocene NW fault bounding the edge of the Red Sea rift as well as the NW trending fault-blocks. Carbonates were mainly deposited on the highs and siliciclastics in the lows. The following facies are recognized:
a- Carbonate reefal and talus facies along the rift edge.
b- Siliciclastic-carbonate transitions where old NW grabens and NE shears open into the Miocene sea.
c- Restricted siliciclastic-evaporite-carbonate sequence in the down faulted grabens and half grabens between the NW fault blocks. Open marine carbonate-fine siliciclastic facies occur on the seaward side of the fault blocks.
2- The second regime comprises the post-abu Dabbab Evaporite Upper Miocene-Pliocene sediments. Their facies distribution was mainly governed by E to NE trending mild depressionss and highs resulting from the effect of rejuvinated transverse 40-60 faults cut by rejuvinated 120-140 faults. siliciclastic-carbonates transitions are also recognized on both the highs and lows but with relatively more biogenic carbonate on the highs and thicker siliciclastic sequence in the lows. Mild NW trending paleohighs due to synsedimentary faulting complicated the facies distribution. Occasionally these Nw Paleohighs acted as barriers against the siliciclastic influx,
The main differences between the two regimes lies in the more severe NW block faulting in Miocene times which led to the pronounced E-W facies variations , to the more differentiation of relatively pure and thick carbonates on the highs and siliciclastics in the lows and to local sealed structures due to the onlap of evaporites. In Pliocene times the E-W facies variations are more gradational and the carbonates are generally less pure.