STRATIGRAPHY. 21 



From this it would seem that, though a rock similar to the hard 

 pale-coloured siliceous rock of the west is to be found east of Bardij 

 it does not show the same constancy of horizon and cannot be 

 safely correlated with that which for a distance of some 80 miles is 

 found separating the Kaimur sandstones from the limestones of the 

 Rohtas stage. 



The thickness of the beds attributed to this stage varies largely, 

 _, . notwithstanding the statement in Mr. Mallet's 



Variation in thickness. 



memoir 1 to the contrary. It must be re- 

 membered that these statements were based on a survey of the 

 country east of the map accompanying this memoir and of the 

 country west of Rewah, the intermediate country being practically 

 unknown, and as regards these areas the statement is substantially 

 correct. 



The greatest thickness is attained near the western limit of 

 Rewah territory. Here there cannot be less than 1,000 feet of beds 

 belonging to this stage, while the actual thickness is probably over 

 1,500 feet. In an easterly direction the stage maintains a consider- 

 able thickness, and though there is a narrowing of the outcrop as 

 mapped, no great importance can be attached to this on account of 

 the impossibility of determining the exact position of its southern 

 boundary. 



At Hurma, where the lower boundary can once more be seen, it 

 has fallen much in thickness, but east of this the Kaimur boundary 

 recedes northwards, away from the southern limit of the lower 

 Vindhyans, and the Rohtas outcrop widens once more, probably in 

 unison with an increase of thickness. 



Near Gurdah there is not more than 150 feet of the limestones 

 actually seen, though the total thickness' may be more, and near 

 Markundi the thickness reaches its minimum. In the Ghagar not 

 more than 50 feet of bedded limestones separate the Kaimur sand- 

 stone from the shales with calcareous concretions, and this thick- 

 ness only increases to not much over 100 feet about Rudauli. There 

 1 Mem., Geol. Surv. Ind., Vol. VII., p. 47. 



< 21 ) 



