Notices of Memoirs — The Oilfields of Egypt. 319 



retarded. Moreover, valuable information may be, and often is, lost. 

 Wherever Governments grant facilities for exploration by deep bores 

 they should see that accurate records are kept and made public after 

 a reasonable lapse of time. 



The two outstanding features which sharply differentiate the oil- 

 field region from the plateau regions of Sinai and Egypt are the 

 presence (1) of a thick series of Miocene rocks belonging to the 

 Mediterranean area, and (2) of sharp folding due to tangential 

 pressure. We repeat the question that we put in reviewing 

 Dr. Ball's memoir on West Central Sinai. Did the Miocene sea 

 advance over a planed down surface of the older rocks? It was 

 at one time supposed that some at least of the faulting in the region 

 between Suez and Cairo was of post-Eocene and pre-Miocene date, 

 and that Miocene rocks had been deposited against " horsts " of 

 Eocene limestone. That view was disproved by Barron, 1 who showed 

 that they were superposed upon, not apposed against, the Eocene 

 strata, and that no evidence of pre-Miocene faulting was to be found 

 in that district. Now Dr. Hume comes forward with evidence that 

 the Miocene rocks of the oilfield region were formed over the 

 denuded arch of the great post-Eocene fold whose axis coincided 

 approximately with what is now the Gulf of Suez. Although we 

 are not able to define with precision the boundaries of this southward 

 extension of the Miocene sea there is some evidence to show that it 

 did not extend far beyond the faults which bound the sunken tract 

 on the east and on the west, and, therefore, as Dr. Hume points out, 

 that it found a gulf agreeing approximately in position and direction 

 with this tract and its continuation in the Red Sea trough. But in 

 any case there must have been a considerable geocratic movement 

 in post-Miocene times, for Dr. Ball has shown that Miocene rocks 

 occur at a height of 642 metres on Sarbut el GamaP in West Central 

 Sinai, and has estimated the throw of the post-Miocene faults in 

 that region at about 2,000 metres. Even allowing for the possibility 

 that this may be an over-estimate, there seems no escape from the 

 conclusion that the oilfield region owes its position largely to 

 subsidence along faults of later date than the Miocene rocks of the 

 district. But we must await the more precise determination of the 

 pakeontological horizons before attempting to correlate the physical 

 history of the oilfield region with that of the Mediterranean area to 

 which it belonged until it was invaded by the Erythraean fauna in 

 comparatively recent times. 



It is interesting to compare the views of Suess as to the structure 

 of the district with those set forth in this memoir and in other 

 publications of the Egyptian Geological Survey. In his chapter on 

 the Great Desert Plateau Suess shows that flat-bedding in the 

 Cretaceous and Tertiary rocks is the characteristic feature of large 

 portions of North Africa south of the Atlas range, of the Sinai 

 peninsula, of North and South Arabia, of Palestine and Syria, and 

 that the same feature probably extends as far east as the Persian 



1 The' Topography and Geology of the District between Cairo and Stiez, 

 Cairo, 1907, p. 55. 



2 See Geol. Mag., February, 1917, p. 83. 



