Vol. 65.] NUBIAN SANDSTONE, ETC. SOUTH OF KHARGA OASIS. 41 



3. The Relations of the Nubian Sandstone and the Crystalline 

 Bocks south of the Oasis of Kharga (Egtpt). By H. J. 

 Llewellyn Beadnell, Assoc.Inst.M.M., F.G.S., F.B.G.S., late 

 of the Geological Survey of Egypt. (Bead November 4th, 

 1908.) 



[Plate II— Map.] 



In the geological study of a country there is nothing of more 

 importance than the mutual relations of the different rock-groups 

 of which it is made up, and yet in Egypt it is perhaps more 

 especially in regard to those relationships that our views have had 

 from time to time to be materially altered. In particular, I may 

 instance the relationships of the Eocene and Cretaceous Systems in 

 different parts of the country, notably at Abu Boash,in the Eastern 

 Desert, and in the Oases. The object of the present paper is to 

 raise the question of the relation of the granites and associated 

 crystalline rocks to the overlying sedimentary formations, a relation- 

 ship of fundamental importance, and to put on record some obser- 

 vations bearing on the subject made during a brief examination of 

 the country to the south of the Oasis of Kharga, undertaken with 

 the primary object of eliciting certain information regarding the 

 water-supply of that oasis. These observations appear to me to 

 afford strong evidence that in this district the granites, in their 

 present position at least, are younger than the overlying members 

 of the Cretaceous Series. 



The Crystalline Rocks south of the Oasis of Kharga. 



That a solitary exposure of igneous rock exists at Jebel Abu 

 Bay an, in the Libyan Desert south of the Oasis of Kharga, has long 

 been known. Capt. Lyons, with reference to this locality, wrote 1 : 



' The rock is a coarse-grained hornblendic granite, with large crystals of 

 pink orthoclase, and is apparently identical with that described by Prof. 

 Bonney.- The hill also contains dykes of a fine-grained granitic rock, and 

 some of a diorite, as well as one of a fine-grained basalt.' 



The relations to the surrounding sedimentaries are not touched 

 upon. 



That other granitic bosses occurred in this desert, I have long sus- 

 pected, from reports of Bedawin tribesmen who traverse this country 

 on their way to and from El Atrim (Bir-el-Sultan). Indeed, this 

 was partly confirmed by a prospector whom I sent in 1906 to 



1 ' On the Stratigraphy & Physiography of the Libyan Desert of Egypt' 

 Quart. Journ. Geol. Soc. vol. 1 (1894) p. 532. 



2 ' Note on the Microscopic Structure of some Eocks from the Neighbour- 

 hood of Assouan, collected by Sir J. W. Dawson ' Geol. Mag. dec. 3, vol. iii 

 (1886) pp. 103-107. 



