Dr. W. F. Hume — Oilfield Region of Egypt. 7 



by a flint conglomerate), but we find the Lower Cretaceous strata 

 and Nubian Sandstone between the Miocene and the granite, whereas 

 in Gebel Esh, 1 some 20 kilometres west of Gebel Zeit, the missing 

 Eocene and Cretaceous beds are represented. 



The broad space between the Red Sea Hills and Sinai Mountains 

 would, on this view, have originated as the result of a combination 

 of anticlinal fracture and erosion, acting on two media, the lower one 

 of which was, in the main, hard and brittle, the upper one plastic 

 and pliable. The above-mentioned ranges are themselves connected 

 with dislocation-lines of the most pronounced type, the faulted 

 borders in each case being on the sides towards the Gulf of Suez. 

 At the close of the Lower Miocene period there appears to have been 

 a general sinking, as a result of which the waters of the Mediterranean 

 were enabled to invade the above-mentioned groove. The breadth of 

 this greater Gulf of Suez appears to be at its maximum about 

 70 kilometres, and in it were laid down deeper- water strata, such as 

 Globigerina Oozes, and also others in which various characteristic 

 Miocene Pecten species predominate, whilst later these were overlain 

 by a vast series of calcareous gypsum and salt deposits, which in 

 places appear to attain thicknesses of at least 3,000 feet ! (a thickness 

 of 6,000 feet is suggested north of lat. 28° N., but the country has 

 not been studied in detail). 



The shore-lines of this Miocene arm are well defined by the 

 presence of coral reefs and flint conglomerate beds, the latter repre- 

 senting the erosion of Eocene or Upper Cretaceous beds previously 

 existing. 



With the close of Miocene times this triple complex of Miocene 

 beds, older sedimentaries preserved from erosion, and granite- 

 metamorphic rock core, became subject to new compression by 

 which the whole region was thrown into a series of IST.W.-S.E. 

 trending folds, in which the anticlines, asymmetrical in character, 

 had their most steeply inclined sides directed towards the Gulf of 

 Suez. Each of these anticlines has determined a well-marked 

 physical feature, the Esh-Mellaha, Zeit, and Araba (in Sinai) Hills 

 respectively. In the simplest case the relation of slope on the two 

 flanks is about 1 to 3 or 4, the general dip on the less inclined limb 

 being 8° to 10°, and on the more inclined one 25° to 35°. As already 

 stated, the resistant centre of the fold system must be along the Gulf 

 of Suez, as the steeper wave-fronts are toward it both to eastward 

 and westward. The effects of the folding are greatly exaggerated 

 where granite forms the lowest known member of the fold. In 

 such instances the granite behaves as though it had been a solid 

 wedge driven through the underlying softer strata ; the beds near 

 the granitic apex of the anticline are greatly reduced in thickness, 

 and on the steeper side of the arch in extreme cases are pinched out, 

 or otherwise violently dislocated. 



The structure in Gebel Zeit is of interest as an example. In the 

 typical cross-section the central axis of the anticline is formed by 

 the granitic massif, on the western flank of which the immediately 



1 Gebel means ' hill ' in Arabic. 



