og king: nellore portion ov the carnatic. 



The difficulty indeed was at last to decide what we should consider 

 as quartzites of the one series or the other, for 

 ouisiiiiii;' these from the it was soon found out that along the outer edge 

 Cuddapa 1 c[uai ^ ^ transition rocks recognisable, Cuddapah 



strata are associated with the gneisses in a most obscure way, even to 

 their having apparently been wedged or let in as thin strips among 

 the gneisses. Mr. C. M. Oldham appears to have relied principally on 

 the micaceous constitution and the cleaved character of the beds in the 

 gneiss, though such characters are common enough among the mani- 

 festly detrital quartzites well into the interior of the Cuddapah area. I 

 myself was rather guided by the untoward positions of fairly rippled and 

 pebbly beds in my recognition of them as transition strata, and by the 

 continuance of strike with the gneiss for tolerable distances, or as- 

 sociation with hornblendic beds, as distinguishing features of the 

 gneiss quartzites ; though even with these guides I was continually 

 thrown out by the knowledge that the different quartzites could 

 be quite easily thrown together by faulting among the hornblendic 

 rocks, as in fact is often the case with them between Kaluvaya and 

 Paremkonda. 



The succession or changes in the subordinate quartzites may, however, 

 Lithology and distri- ^ e perhaps best shown by the following details 

 taken in the country westward of the town of 

 Nellore ; and the same style of beds is traceable to the north of the 

 Penner and in the Swarnamukhi region, though in this latter direction 

 they are much, and eventually completely, covered up by superficial 

 deposits. 



To the west of Nellore, in the rather picturesque ridges of Narasimha- 

 The Narashnuakonda konda ^ tnere is a strong development of thick beds 

 quartz-rock. f quartz-rock among schistose gneisses. Here the 



rock is a massive pale-brown or white, occasionally ferruginous, usually 

 very coarse granular crystalline aggregate of quartz, sometimes not at 

 all unlike a vein quartz. Still it is not so massive but that there 

 are small ragged and irregular crevices between the glassy and 

 semi-translucent particles of quartz which were once in part occupied 



( m ) 



