*54 GEOLOGY OF THE SON VALLEY, ETC. 



limestone of sub-division No. 9 is so like that of No. m that it is 

 impossible to separate one from the other. Thus all the limestone 

 has been classed as forming one stage, the Rohtas. 



The rock is a pure grey limestone, somewhat pinkish or salmon- 

 Reck thin-bedded and colored in places in the upper part and generally 

 Baggy, very thin-bedded. This flagginess obtains 



throughout the thickness of the stage, thick beds being rare. 



The limestone towards the base of the stage exhibits a tendency 

 r, , L . towards concretionary character, circular to 



Calcareous concretions. J ' 



oval concretions of carbonate of lime, often of 

 great regularity and beauty, being in places abundantly developed. 

 ~ . , Crystals of quartz have in some places 



Quartz crystals, J * " 



been developed in drusy cavities in the 

 limestone. 



The sudden and extreme bending and contortion, also equally 



Local bending and shared by the upper beds of the Kheinjua 



contortion of the rock. gtagej wh j ch the Rohtas hag ^^ undergQnej 



forming a remarkable and conspicuous feature in these beds, has been 



noticed by Mr. Mallet. 1 The topmost beds — those by the junction 



with the Kaimurs — show, however, no evidence of such disturbance. 



The limestone being of a uniform character from the top to the 



base, the stage is not susceptible of any 



The stage not divisible. . , 



further sub-division. 



As already stated, sub-divisions No. 9 (limestone), No. 10 (shales) 



and No. n (limestone) of Mr. Mallet's are corn- 

 Mr. Mallet's Sub-divi- 

 sion No. 10 not observ- prised in our Rohtas stage. But nowhere in the 



able here. 



area under examination could 1 come upon the 

 shales that form sub-division No. io. 2 Though fairly good exposures 

 are available in the western parts of the area, no shales were there 

 observable in the limestone except here and there to the thickness of 

 6 to 9 inches or so. As regards the eastern parts of the area under 

 notice, though alluvium prevails here to a very considerable extent 



1 Mem., Geol. Surv. Ind., Vol. VII., p. 43. 



3 Mem., Geol. Suiv. Ind., Vol. VII., pp. 28, 42. 



( '54 ) 



