STRATIGRAPHY. 1 5 



has been specifically separated as the porcellanite stage owing to the 

 marked prevalence of the harder beds. 



When well developed and well exposed the outcrop of this 

 stage forms a band of low hills, covered with a forest of sal at trees 

 (Boswellia thurifera) and the surface in detail is also very character- 

 istic, owing to the interbedding of soft shales with the hard beds, 

 which are traversed by numerous joint planes running through the 

 bed at right angles to the bedding, most of them not continuing 

 into the beds above and below. 



The distribution of the rocks of this stage is peculiar. Near the 

 western limit of the Rewah State they attain, 

 as has been mentioned, a thickness of not less 

 than 800 feet, and here the coarse-grained beds, containing an 

 abundance of felspar and quartz, are largely developed. Passing 

 eastwards the thickness diminishes somewhat and the porphyritic- 

 looking beds gradually disappear, being seldom seen east of 8i° 30' 

 Long. From here on to the Gopat the outcrop is still easily traced 

 though the beds are thinning, and beyond the Gopat the thinning 

 is very marked. The last good exposure near Pari shows only fine- 

 grained beds associated with shales and not more than about 200 feet 

 in total thickness. A small exposure is seen on the south bank 

 of the Son east of Gangi, but the outcrop of the rocks of this stage 

 south of Hurma is hidden by the Son. 



East of Khattai exposures of rock are few and far between ; 

 some beds of a porcellanite rock are seen and the porcellanites 

 are represented by some very rare angular fragments in the subrecent 

 river gravels. At Gurdah the porcellanites are not seen, being 

 apparently cut out by a strike fault, but a short distance to the east 

 they reappear and can be traced to and beyond the limits of the 

 map. In this direction, too, they thicken out and at the same time 

 the coarser-grained reappear, and east of Kon, beyond the limit 

 of the map attached to this memoir, there is evidently a develop- 

 ment of these beds comparable to that on the western border of 

 Rewah. 



( '5 ) 



