46 BLANFORD : GEOLOGY OF WESTERN SIND. 



a considerable thickness of pale-green gypseous clays is exposed, with a 

 few bands of impure dark limestone and calcareous shale. No Foramini- 

 fera have been found in these clays, although Nummulites abound in the 

 limestone immediately overlying ; several species of mollusca occur, but 

 none are characteristic, and it is far from clear whether the green clays 

 and their associates are merely thick bands intercalated in the limestone, 

 or whether they belong to a lower group. Probably these argilla- 

 ceous beds of the Rohri hills represent some of the marls, shales, and 

 clays forming the lower portion of the upper Khirthar group on the 

 Gaj river. 



The nummulitic limestone of the Rohri hills is softer and whiter 

 than that of the Khirthar range, a difference doubtless due to the much 

 smaller amount of disturbance that the rocks have undergone in the former 

 instance. A somewhat similar, but greater, difference has been shown to 

 exist between the Nummulitic limestone of the Salt Range and that 

 of the Himalayas in the Punjab. 



In some places west of Kotri, a band of argillaceous and ferruginous 



rock is found close to the base of the Khirthar group. This rock 



weathers into laterite ; it is mainly' composed of brown haematite, and 



appears to be found over a considerable area near 

 Laterite band. . . . 



Kotri and Jhirak. It is impossible to avoid 



suggesting its identity with the ferruginous lateritic bed found in a simi- 

 lar position in Guzerat, Cutch, the Salt Range, and the Sub- Himalayan 

 region. 



It has already been mentioned that in the Laki range the nummu- 

 litic limestone rests unconformably on the Ranikot group. The Khir- 

 thar group here cannot be much more than 500 or 600 feet thick, and 

 consists entirely of limestone. To the south-east, towards Kotri and 

 Tatta, there is no unconformity between the Ranikot and Khirthar groups, 

 _ , .. , but on the contrary there is an almost complete 



Relations between J x 



Khirtbar and Ranikot passage between the two, and the limestone of the 



groups. i'ii 



latter becomes much split up and intercalated 



with shales and sandy beds. This is even more the case further to the 



( ^ ) 



