The Buried Grand Canyon in Egypt: Structural controls on the Neogene River Nile

The origin and intricate history of the River Nile are still widely disputed. Some studies have claimed that the present course of the Nile has formed at ~7-5 Ma, while others have suggested a much longer evolution. We proposed earlier that the southern and central segments of the River Nile in Egypt have originally evolved along a NW trending short-lived rift that was formed by NE-SW extension at ~25-23 Ma, and abandoned at an early stage. Here we focus on the development of the northern segment of the river, which we interpret as having both a relatively young age (~7-6 Ma) and different tectonic evolution. Gravity models and 3D seismic and well data show the presence of a deeply buried canyon west of the northern modern River Nile, 120 km southwest of Cairo, and approximately parallel to its present-day valley with a predominant NNE-NE course. The U-shaped canyon is up to 13 km wide and attains a maximum depth of around 1,900 meters, about as deep as the Grand Canyon of the Colorado River in Arizona, USA. The canyon was cut into a rising plateau along deep-seated NNE to NE-striking faults that formed at ~90-80 Ma as secondary shears to the main structures of the WNW oriented Cretaceous Beni-Suef rift and possibly have been reactivated at ~14 Ma with the origin of the Gulf of Aqaba-Dead Sea NNE sinistral transform plate boundary. The deeply incised canyon formed as a result of severe erosion due to significant sea level drop and desiccation of the Mediterranean in late Miocene time (Messinian Crisis ~7-6 Ma), which was accompanied by continued progressive uplift of the north-eastern Egyptian terrain[KJ1] . [2] The ancestral river excavated and widened a vast braided channel[3]  that cut deeply into Turonian-Campanian sediments in the Beni-Suef basin. The canyon attained its maximum depth by ~5 Ma, and subsequently it was filled by six successive clastic-dominated units of different fluvial facies.[4]