Eonile Canyon, Ancestor of the Nile River, Geology and Structural Implications

By

Sherif El-Bishlawy¹, Srecko Leustek¹, Hossam El-Kayal¹, Adel Sehim²

(1) Ina-Naftaplin (Egypt Branch), Cairo, Egypt (2) Cairo University, Cairo, Egypt

 The Eonile Canyon represents the Upper Miocene Nile River ancestor through which clastics were transported to Mediterranean where several gas fields are discovered. This work provides a detailed mapping of the upstream onshore river system utilizing subsurface data which shows structural control of canyon entrenchment during Tortonian low-stand.

South of Cairo, cliffs of 200-500 m high of Eocene carbonate plateaus face narrow Eonile-path which runs along-strike of a major flexure-zone that shows 1600-1900 m drop for Eocene sequences. This flexure represents a Post-Eocene drape over a blind-inherited fault-zone of basement-suture.

North of Cairo, this suture and the Eonile pathfinder cross ENE-trending belts of Upper Cretaceous wrench-flowers and culminations with entrenchment into the Cretaceous to Jurassic sediments. Further north, several NW-trending gorges of tributaries flux into the main Canyon with slope-gradient of 1:30 where large volume of Middle-Miocene to Eocene rocks excavated and transported to the main Eonile-Canyon.

The calculated depth of entrenchment reaches 1400 m south of Cairo and sunk to 2400 m in the north with 1:185 slope-gradient. This reflects steep gradient relative to 1: 4000 gradient of the Nile River, indicating powerful hydraulic system that was able to cascade the Mid-Delta hinge and transport huge amounts of coarse-reservoir clastics to Mediterranean in Upper Miocene. In Early-Pliocene high-stand, the Mediterranean transgressed the Eonile Canyon depositing thick prism of source rock shale. Upward in the sequence, ripple marked and burrowed shallow-marine carbonates exist and partially scoured and caped by channel deposits of Late Pliocene to Holocene.