50 PASCOE : GEOLOGICAL NOTES OX MESOPOTAMIA. 



lowest horizons of this zone. Between the Kurah Chai and Kifri no 

 distinction between zones " a " and " b" can be recognized. 



Zone "b" is characterised by many thick massive sandstone 

 bands, which, if they do not actually preponderate in bulk over the 

 inter-bedded clays, are of more importance than they are elsewhere. 

 The sandstone or sand-rock is soft, moderately friable, light-coloured, 

 frequently current-bedded, and sometimes full of root-like concre- 

 tions ; it is coarser and less argillaceous than that in zone " a." The 

 bands increase in thickness towards the middle of the zone ; towards 

 the top the separating clays become thicker and thicker, and assume 

 the light brown colour so typical of the next zone, while the sand- 

 stones become pebbly and contain thin inter-bedded layers of conglo- 

 merate. This zone forms a belt of high-lying country between the 

 two lower-lying belts of " a " and " c " ; it produces rugged topo- 

 graphy consisting of ridge after ridge rapidly alternating with deep, 

 narrow, straight, simple valleys. 



Zone " c " consists of very light brown clay with very few sand- 

 stone bands. The latter increase towards the base as the zone passes 

 down into " b." The sandstones usually contain strings of pebbles, 

 and thin inconstant conglomerates are seen in them and separating 

 the clays. This zone forms a comparatively low belt between the 

 sandstone ridges of " b " and the round-featured range of zone " d." 

 "Where the dip is low, open, gently-sloped country is produced, 

 but where the dip is steep, as on the Aq Su, there results a bewil- 

 dering assemblage, of steep conical hills, which are almost as difficult 

 to traverse as the sandstone ridges of " b." The colour of the clay — 

 an extremely pale brown — is very characteristic and differs from the 

 red of the zone " a " clays. 



Zone " d " is typified especially by a thick somewhat loose conglo- 

 merate, which caps a long, regular, level, uninterrupted range of 

 hills, low or high according to the thickness of the conglomerate, its 

 dip and other factors. The conglomerate usually contains sandy 

 partings, and overlies light brown clay over which it has spilled its. 

 pebbles, producing intricately dissected topography of which all the 

 details aie so rounded off and deprived of sharp angles, that the zone 

 can usually be identified from a long distance. Streams of good 

 water originate from it and the slopes of the range are typically 

 more grassy than others. Other conglomerates occur in the zone, 

 sandstone is poorly represented, and light brown clay predominates 

 in actual bulk. As will be seen, this zone is strikingly developed 



