JABAL HAMRJX AND JABAL MAKHUL. 7 



weathers in the peculiar way often seen in the case of a homogeneous 

 limestone, the surface becoming scoured by numerous curved channels 

 like those produced by a cheese-scoop. Although such a compara- 

 tively soluble mineral, it resists weathering more than the associated 

 beds of clay ; in fact its resistance to erosion is somewhat surprising. 

 More than half of the Hamrin range consists of this deposit which, 

 there is every reason to conclude, is a sedimentary one. Associated 

 with it are thin bands of limestone which may be comparatively 

 solid and crammed with obscure shells, especially of a small 

 pelecypod, or may consist of a cellular rock identical in appearance 

 with Mr. Cunningham Craig's " detrital limestone " of the Maidan- 

 i-naftun oilfield of Persia, The latter rock presents the appearance 

 of having been formed of comminuted shell fragments which have 

 lost their original organic ornamentation and outline, but which are 

 still separated by the original but modified interstices which divid- 

 ed them at the time they were strewn along the bed of the sea ; 

 this is the actual oil-bearing rock in the Maidan-i-naftun field, the 

 interstices being filled with oil. In both banks of the river and in 

 some of the small water-courses around Fathah, limestones of this 

 nature are found seeping tarry oil and bitumen. Occasionally re- 

 cognisable specimens of Pecten and Ostrcva are observable in it. 

 East of Fathah there is probably not more than a total of 50 feet of 

 limestone in separate bands exposed ; but in the Jabal Makhul a 

 distinct increase in the amount and a corresponding increase in 

 the steepness and ruggedness of the cliffs are discernible. The Fars 

 beds exposed in this and other localities are identical in character 

 with the lower stage of Dr. Pilgrim's Fars series. 



Alternating with the gypsum and limestone bands are beds of 

 sandy clay, sometimes gypseous and marly, frequently permeated 

 with thin laminae of translucent selenite derived from the gypsum, 

 This clay is typically of a light greenish or brownish pink colour 

 and is sometimes— as for instance half-way between Fathah and 

 Ain Nukhailah— stained a conspicuous red with oxide of iron. 

 Both gypsum and gypseous clay in the neighbourhood of oil see- 

 pages contain yellow sulphur, and give forth a strong odour of 

 hydrogen sulphide. It is a matter for consideration whether the 

 sulphur and hydrogen sulphide have not originated by the reduction 

 of sulphates by crude oil, one of the results being tar or bitumen 

 {see p. 70). Small pockets of red oxide of iron are sometimes to 

 be seen in the gypseous clays. 



