Vol. 65.] NUBIAN SANDSTONE, ETC. SOUTH OF KHA.RGA OASIS. 51 



dip from the north, and south sides into a narrow trough, forming a 

 syncline with angles up to 45°. Both Eocene and Cretaceous strata 

 are again involved, though the former, owing to their crystalline and 

 crushed nature, are not so obvious as in the fold J just described, 

 18 kilometres farther west. Drawn-out and distorted nummulites 

 are, however, quite common in some of the upper beds. 



The importance of these hills of highly disturbed strata lies in 

 the fact, that if connected with the intrusion of the granites — which 

 from their position appears almost certainly is the case, — the date 

 of the latter would be later than the Lower Eocene. 



Similarity of Crystalline Rocks in the Western and 

 Eastern Deserts. 



The crystalline rocks forming the bosses just described do not 

 appear to differ essentially from those of the Cataracts and the 

 Eastern Desert. As already mentioned, they form two parallel 

 ridges trending east and west ; and as they are situated on almost 

 the same latitude, the natural inference is that both they and the 

 rocks of the First Cataract at Aswan are of the same age, repre- 

 senting different portions of the same great underground ridge, the 

 latter being exposed on the comparatively low ground of the Nile 

 Valley and on the floor of the Oasis, but hidden by the immense 

 thickness of the sedimentary formations forming the intervening 

 plateau-massif. 



This view, however, at once brings us face to face with the 

 difficulty that, whereas in the Oasis the granite appears to have 

 intruded into the sedimentaries, at the Cataracts and in the 

 Eastern Desert they are, according to the authors who have dealt 

 with the subject, unquestionably of far greater age than the Nubian 

 Sandstone. 



The general conclusions at which I have arrived are that there 

 seems reason to believe that the crystalline rocks of Egypt are of 

 many different ages, and that at various periods there have been 

 upward movemeuts and intrusions from the underlying magma, 

 with a tendency for successive consolidations to assume somewhat 

 marked similarities. The Nubian Sandstone appears to have been 

 unconformably deposited, partly on pre-existing sedimentary forma- 

 tions, and partly on the planed-down surfaces of still older crystalline 

 and metamorphic rocks. Subsequently, at one or more periods, 

 they and the sedimentary and crystalline rocks on which they lie, 

 were in some regions invaded by outbursts from the underlying 

 magma, the intrusions being probably connected with the elevation 

 of the mountainous regions on the east side of the Nile. 



EXPLANATION OF PLATE II. 

 Geological map of the Libyan Desert south of the Oasis of Kharga, showing 



iles tc 

 e2 



