Br. W. F. Hume — Oilfield Region of Egypt. 5 



II. — Some Notes on the Post-Eocene and Post-Miocene Move- 

 ments in the Oilfield Region of Egypt. 



By William Fraser Hume, D.Sc, A.E.S.M., F.G.S., Director of the 

 Geological Survey' of Egypt. 



[T may interest readers of the Geological Magazine to have 

 a summarized account of the new data ohtained regarding the 

 Post-Eocene and Post-Miocene movements in the Gulf of Suez area, 

 and notably in its southern portion, the oilfield region of Egypt (see 

 Map, Fig. 1). 



To understand the subsequent remarks it is necessary to have one 

 or two fundamental conceptions, obtained from previous studies, well 

 established in our minds. The first is the nature of the strata which 

 were present in the region before folding began. Owing to the 

 great depression of Cretaceous times a mass of limestones, clays, and 

 sandstones were laid down on the old solid continental foundation of 

 granites and metamorphic rocks. These soft sedimentary beds may 

 have attained a thickness of at least 2,000 feet. 



In the second place, folding at the close of the Cretaceous period 

 (the nature of which is masked by subsequent events) led to the 

 redistribution of much of the upper highly calcareous material, and 

 no doubt supplied the carbonate of lime necessary for the shell- 

 deposits, nummulitic beds, etc., of the Egyptian Eocene. These 

 gave an additional 2,000 feet or more of strata, and it is thus possible 

 that in the basin portions of the Post-Cretaceous fold the sedi- 

 mentaries may be fully 4,000 feet thick as an average. When 

 examining the total thickness of the Eocene and Cretaceous beds in 

 Egypt for the "Explanatory Notes to accompany the Geological Map 

 of Egypt " I found a maximum of 6,000 feet. 



The great primary Egyptian fold is, however, undoubtedly the one 

 which closed the Eocene Period. A glance at the geological map of 

 Egypt exhibits to us the broad shallow synclinal basin of Central 

 Egypt with N.W.-S.E. axis, and it needs but little imagination 

 mentally to picture the corresponding anticline, the central axis of 

 which would lie in the Gulf of Suez and Red Sea. We have thus 

 a region of compression in Egypt proper, but one of tension where 

 the Red Sea now is. In that of tension there would be tendency for 

 the formation of a series of fractures parallel to and including one at 

 the axis. It seems to me that the underlying harder granite- 

 metamorphic complex will break more readily than the more plastic 

 materials overlying it, the result being that spaces will be left 

 beneath the sedimentaries into which these would naturally tend to 

 sink. But in the rising anticline there will also be maximum erosion 

 towards the central axis, so that the Eocene-Cretaceous sedimentaries 

 will be greatly reduced or wholly disappear. The facts are clear 

 enough. 



Nearest the centre of the anticlinal axis, on Shadwan Island, for 

 example, the Miocene beds rest directly against the granite, there 

 being no sign of more ancient sedimentaries. In Gebel Zeit, slightly 

 to the west of the probable axis, all the Eocene and uppermost 

 Cretaceous beds have disappeared (being only shown to have existed 



