COUNTRY NORTH OF THE SON AND WEST, ETC. 153 



It seems to die out shortly, or is not at any rate traceable 

 further. 



Zone VIII. — These are the well-laminated argillaceous shales 

 Characterised by shales that immediately underlie the Rohtas lime- 



with calcareous ^concre- 

 tions, stone. 



These shales have characteristic calcareous concretions developed 

 in them, and have also frequent beds of limestone intercalated in them 

 and are besides almost free from arenaceous beds, points which dis- 

 tinguish the shales of Zone VIII hum those of any of the underlying 

 zones of the Kheinjua stage. 



As for the calcareous concretions, although they certainly charac- 

 terize the argillaceous sholes of Zone VIII, occurring more or less 

 through the entire thickness of it, they are not confined to this zone 

 alone but are found also, and in some abundance too, in some parts of 

 the Rohtas limestone, as for instance, near Marwar (south-east of 

 Mankaihri), Deori (west by south of Gursari), etc., and those that occur 

 in the Rohtas are quite indistinguishable from those of the Kheinjua 

 beds. 



Crystals of quartz often of good size and beauty occur in places 

 Occurrence of quartz in fair abundance in the shales of this zone. 

 crystals. From the state of exposure of the beds it is 



not possible to say if they are confined to any particular set or sets 

 of beds. On the left bank of the Son, north-west by west of 

 Bardi, for instance, is a good exposure of these shales with the 

 quartz crystals. 



IV.— Rohtas Stage. 



The stage is made up entirely of limestone. 



This is the limestone that comes in immediately underneath the 



Kaimur sandstones and shales of the Kaimur 



Rohtas Stage. ■ 



scarp and forms the youngest of the four 

 stages constituting the lower Vindhyans, 



This stage comprises Nos. 9, 10 and 11 of Mr. Mallet's sub- 

 Comprises Mallet's sub- divisions. The shales of No. 10 have not been 

 divisions Nos. 9, io&n. observed in the area under notice; while the 



( 153 ) 



