To the genesis of the purple and white sandstones
in the western part of the Gilf Kebir (Egypt/Libya)

Norbert Brügge, Germany


In the western part of the Gilf Kebir and its foothills at the Libyan side is observe widespread conspicuous red discolored areas on the satellite image. This area, beyond the Egyptian border, is an intensively influenced by hydro-volcanic activities during the Oligocene age (Gilf Kebir crater field, Regenfeld pipes, Libyan desert glass etc.). A striking feature is the "Red Spot". Here are the strata complete impregnated by iron-containing solutions. Locally it should be noted that these surfaces are covered with hardened ferruginous sandstone plates or detritus on alluvial plains.

In the profiles of the hills and mountains in this region is also to observe changes of normal stratiufied and colored sandstone to white (bleached) sandstone without visible stratification. Such changed white sandstone also contain clusters of red sandstone which break the original stratification.

This is a clear indication that the bleaching of the sandstones was done before the hydrovolcanic penetration of the iron-containing solutions.The possible chemical and mechanical processes are not explored.

IIt is striking that mostly the lower paleozoic sandstone parts, directly above the uplifted basement, in the western Gilf Kebir plateau are affected by the phenomenon of bleaching. Except the Abu Ras passage east of Jabal Asba, and also near Wadi Sura, in the lower parts of the Ordovician/Silurian sandstones, are changed white sandstone to observe. Often they are covered with very ferruginous sandstone.
Also upper parts of the plateau are affected by the phenomenon of bleaching (Wadi Abdel Malik). In principle, are the whole Gilf Kebir (inclusive the southern part) and also the Abu Ballas scarp-contour in the GKCF more or less affected by this phenomenon. Locally are to seen again and again white parts in the sandstones. To this belongs also the pushed zone of white erratic blocks in the northern foothills of the Gilf Kebir (by KLITZSCH called glaciogenic series).

Note: Another speciality are red clayey layers within Carboniferous strata in the Wadi Talh (western plateau along the Wadi Abdel Malik) and in the western foreland at the Libyan side, which are also partially exposed. These deposits are not formed secondarily. They document marine floodings in the Carboniferous period.

Photo documentation

Abu Ras passage
Photos: Ursula Steiner, Switzerland

 Inside Abu Ras passage

 Striking hydro-volcanic spot

 Northern Abu Ras exit

Western Gilf Kebir (Wadi Talh area)
Photos: Ursula Steiner, Switzerland

Western foreland of Gilf Kebir (Libyan side)

Wadi Sura area

Cliff of Gilf Kebir & Gilf Kebir Crater Field (GKCF)

Cliff of Gilf Kebir plateau

 GKCF (Abu Ballas area)