472 Reviews — Topograplty aiid Geology of Northern Sinai. 



To note the many other interesting features of this memoir is 

 impossible ; only one or two will be referred to. The history of the 

 discovery of Jurassic and Lower Cretaceous rocks in Northern 

 Sinai in which Barthoux, Fourtau, and Douville have each played 

 important parts, together with some account of the later researches 

 recorded in this memoir, have been given by Dr. Hume in the paper 

 already cited and need not be summarized here. The Jurassics 

 resting on sandstones of " Nubian " type range from Bajocian to 

 Callovian and the Lower Cretaceous from Barremian (according 

 to Douville) to Albian. All the subdivisions established by Douville 

 have been recognized by Sadek and Moon, with the possible exception 

 of Barremian. The scale of the map and the time at their disposal 

 did not allow them to trace out these various subdivisions, but they 

 describe their lithological characters and give lists of the fossils 

 which they collected from each horizon. 



The Nubian sandstone question is discussed at some length and 

 Douville's view (1916) that the term should be restricted to pre- 

 Bajocian sandstone is repeated. The authors point out that the so- 

 called Nubian sandstones of Egypt and Sinai are now known to be 

 of different ages in different places — and suggest that the use of the 

 term should be dropped whenever the age of the sandstone can be 

 determined. No traces of marine Jurassic or Lower Cretaceous 

 rocks have as yet been recognized in Egypt or Sinai south of the 

 latitude of the Maghara area. In this connexion it is interesting to 

 note that in Central Sinai, about 100 miles south of Maghara, the 

 long period of time which elapsed between the deposition of the 

 Carboniferous limestone and the Cenomanian is represented by 

 650 metres of sandstones of Nubian type, conformable to the rocks 

 below and the rocks above, in which no break can be detected.^ 

 What will be found in that 100 miles of unexplored territory '? It is 

 to be hoped that before long the Geological Survey of Egypt will be 

 able to answer this question. 



Igneous intrusions play a very subordinate part in the geological 

 history of the district. They are represented only by two or three 

 basalt dykes and sills, presumably of Miocene age. 



In discussing the oil prospects of the area the authors speak very 

 guardedly. No actual seepage of free oil has been observed either in 

 the Miocene rocks near the coast or in the Eocene, Cretaceous and 

 Jurassic rocks which lie east of the north-south fault, but oil-stained, 

 oil-impregnated, and oil-smelling rocks are noted as occurring 

 in many localities, and " the structure (consisting of long anti- 

 clines on whose crests domes of considerable size are situated) is 

 in several instances very favourable ". Oil impregnation was noted 

 at several places in the Chalk (Campanian) and in the Cenomanian, 

 which is referred to as a possible oil horizon. The authors j)oint out 



^ See Ball on the Geography and Geology of West Central Sinai. Cairo : 

 Government Press, 1916. Reviewed in Geol. Mag., 1917, p. 80. 



