Dr. W. F. Hmne — Geology of Emtet-ii Sinai. 201 



valleys, these beiug often over twenty metres liigb, the gravels being 

 characterized by the fact that they contain fragments of all shapes 

 and sizes derived from tlie surrounding hills, largely embedded in 

 a sandy matrix consisting of materials of the same derivation, their 

 source being thus strictly local. While found in almost all the 

 principal valleys and many of the side tributaries, they are often 

 particularly well developed at points where longitudinal and transvei'se 

 depressions cross one another. Their probable age can be but 

 determined on the coast of the Gulf of Akaba, where they are found 

 to overlie raised coral-reefs containing such typical Pleistocene or 

 recent forms as Laganum depressum and Heterocentrotns mammillatus. 

 The gravels are therefore not earlier than the Pleistocene, thus 

 agreeing with the conclusion arrived at by Mr. Barron for those 

 on the west coast of the Red Sea. 



One of the most striking features connected with these gravel 

 plateaux is the perfectly flat nature of their upper surfaces, even 

 in the upland wadis, a character which appears inconsistent with 

 their having been produced by rushing torrents, but in accordance 

 with the hypothesis of their formation in lakes or marine fjords. 

 Unfortunately, no shells having been obtained in these beds, their 

 mode of origin still remains doubtful. 



Attention is also called to several special varieties of these 

 gravels, the most notable being : — 



(a) The Manganiferous Pebble Gravels of Sherm, in which the 

 cementing material of the conglomerate consists of the hydrous 

 black oxide of manganese, psiloinelane, the beds being in places 

 as much as four metres thick, while underneath are strata coloured 

 red by ferruginous ochre. These gravels are closely connected with 

 a core of red granite, ending abruptly where the latter is no longer 

 exposed at the surface, and only overlying it along the edge where 

 it faces the sea. It is of interest to note that the S.S. " Pola " 

 expedition found manganiferous deposits forming on the floor of 

 the Gulf of Akaba, a fact which also suggests the marine origin 

 of the Sherm Gravels. 



(fo) Oolitic Valley Deposits. — An oolitic rock is described from the 

 neighbourhood of Ras Muhammed, whose components closely agree 

 in their characters with oolitic grains found by Professor Walther 

 at the mouth of Wadi Dehese, near Suez, and whicli he believed to 

 be a marine deposit in statu naticendi, mineral fragments being 

 enclosed by successive calcareous layers. 



In Wadi Hashubi, where these beds are best developed,, they are 

 composed of grains of quartz and orthoclase, cemented by carbonate 

 of lime, which frequently surrounds them in a series of concentric 

 coats, while the strata themselves also show traces of ripple-marking 

 and very fine sun-cracks. In the lower part of the valley they are 

 often strongly current-bedded, and contain lenticular masses of 

 pebbles, while in its upper part they give rise to striking ravines, 

 bounded on both sides by vertical walls of the light-coloured sand- 

 rock. An interesting feature, too, is the height at which these beds 

 are met with, a typical example being still present at 696 metres 



