The Pliocene consists of interbeded red brown clay, Paleonile (Madamoud Formation), which acts as an aquiclude
for the overlying Quaternary aquifers.
The small capacity to store excess water in the clay-rich sediments, together with low hydraulic conductivity, suggests that an increase in the capture of rainfall by zero-tillage cropping without greater water use (and productivity) could result in either an increase in deep drainage and the rate of discharge into shallow aquifers, or near-surface saturation and waterlogging should the clays behave as an aquiclude
Hydraulic testing has identified a 450 m thick aquiclude
having remarkable underpressuring, possibly due to Cenozoic erosion and glaciation, and ultra-low permeability with horizontal K measurements on the order of 10-14 m/s (i.
The terms aquifer, aquiclude
, and aquitard are relative in a carbonate sequence because of variability in bedding, jointing, and fracturing.
A thick or extensive aquiclude
can and does exclude further penetration of salt water under such circumstances.
The underlying Esna shale is considered as the aquiclude
, which separates the Eocene beds from the underlying aquifer (Nubia).
9m depth acts as an aquiclude
, restricting water movement to a deeper subsurface water.