10 PASCOE: GEOLOGICAL NOTES ON MESOPOTAMIA. 



in many cases is represented only by a loose gravel strewn over the 

 tops of the hills ; in the latter case it is only its altitude which dis- 

 tinguishes it from the recent gravel of the Mesopotamian Alluvium. 

 Its pebbles consist of the same siliceous rocks as those forming the 

 Tertiary conglomerates already described, and frequently attain 

 9 — 10 inches across, though the average size is nearer 2 — 3 inches. 

 This conglomerate, derived from the conglomerates of the Kurd 

 series, is evidently a gravel deposit of the Pleistocene ancestor of 

 the present Tigris, which must have flowed over a large part of 

 the continuation of the Jabal Khanuqah overlooking the Hurar Plain. 



Recent. — The Mesopotamian Alluvium has been referred to in 

 an earlier report. It has interbedded pockets of gravel, which are to 

 be seen on both banks of the river at Fathah, at the north-western 

 corner of the Humr Plain and elsewhere. Its pebbles, derived from 

 the Pleistocene and Tertiary conglomerates, consist of the same 

 siliceous sandstone, chert, quartz, igneous greenstone and rarer 

 pieces of grey limestone : in addition fragments of a blue-black 

 pumice were observed between Fathah and Nukhailah. The 

 Mesopotamian Alluvium covers nearly all the Kurd series, which 

 is not always clearly exposed in consequence ; the very broken 

 ground between the Jabal Makhul and the hills above Humr, for 

 instance, really forms part of an alluvial plain through which some 

 of the sandstones may have occasionally projected in the form of 

 low mounds. Near the Fars this deposit contains water-worn 

 blocks of white gypsum. One occasionally gets an impression of 

 slight dip in the alluvium. The boundary mapped is a purely 

 arbitrary one, being the approximate limit of Tertiary exposures. 



The New Alluvium fringing the river calls for no remarks. 



Structure. 



As already stated the Hamrin and Makhul ranges coincide 

 with a remarkably long and persistent, simple anticline. A second 

 anticline commences east of the Humr Plain and continues north-north- 

 westwards in the Jabal Khanuqah. The distance between the two 

 anticlinal axes, which are not quite parallel, varies from 2>\ to 5|- 

 miles, the syncline between being occupied by the Kurd series. 



The Hamrin-Makhul anticline is slightly asymmetric, the south- 

 western limb being a little steeper than the north-eastern (see 



sections on pi. 1). As the folding movement, in all probability, 



l 



