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.