The Proto-rift Late Oligocene?-Lower Miocene sediments in the initiation grabens exhibit mixed siliciclastic, carboate and evaporite transitions.

     Distribution and rapid lateral and vertical facies changes exhibited by these sediments led to recognition of three modes of deposition: (i) continental (lacustrine and alluvial fans) sediments (Mode 1), (ii) continental (talus, channels and alluvial fans) and restricted marine (evaporite) sediments (Mode 2) and (iii) continental  (flood plain and alluvial fans), restricted and open marine sediments (Mode 3).

    Mode 1 is located in Mohamed Rabah graben which occurs  along the axis of a synclinal drag folds, while Modes 2 and 3 are located in Assal and Sharm Luli-Abu Ghusun grabens. related to downfaulted blocks trending N120 and 140.

     It is believed that the most important factors which affected the diversity of Late Oligocene?-Lower Miocene sedimentary sequences and their environments of deposition in the study areas are: climate, relief of hinterland, types of terrigenous supply and the morphotectonic framework.