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The coastal ranges of the NW Egyptian Red Sea are composed of Precambrian basement rocks bordered by Tertiary and Quaternary formations, the latter including river alluvium, fanglomerates, reef, and beach deposits. The modern morphology is a result of 3 dynamic agents: Quaternary climatic oscillations, changes in sea level and tectonic adjustments.

Two different types, i.e. internal and external piedmonts, characterize this area. Internal piedmonts are extensive, gently sloping plains, separated from the sea by a coastal range of Pliocene formations. Relatively narrow valleys which cut across coastal hills were the only outlets for Quaternary rivers and fanglomeratic cones as they are for modern wadis. In external piedmonts,extensive alluvial cones extend down to the immediate vicinity of the sea where they pass into modern sabkha and Quaternary beach and fringing reef deposits. Alluvial deposits comprise: 1) river deposits and tufaceous limestones. Which fill linear incisions, 10 to 20 m deep, 200 to 300 m wide; 2) fanglomerates formed by an association of debris flow and sheet flood deposits, leaving surficial, braided microchannel deposits. This alternation of contrasting runoff regimes is an effect of climatic oscillations, river deposits corresponding to ’’humid’’ episodes and fanglomerates to subarid / arid conditions. Sedimentary and diagenetic carbonates occurred during ’’humid’ episodes.

Neotectonic effects are indicated both by synsedimentary and postsedimentary faults, flexures and hydroplastic deformations in Quaternary sediments. Moreover, recent, seaward block tilting is indicated by discrepancies in the distribution of the slopes of Quaternary terraces, fanglomerates and associated rocky pediments. An interpretation of the events in terms of climatic episodes suggests a stratigraphical succession which includes at least 3 glacial stages. The available radiocarbon ages (on littoral reefs) support this interpretation.