]6 K1Nc ; : NJiLLOilE PORTION OF THE CARNATIC. 



So fai;, the distribution and succession of the different rock groups 

 a are clear: but there are other irregular distdbu- 



Less regularly arranged . 



series. tions of doubtful strata, the most important ot 



which have really so long delayed the publishing of this memoir, as 



Dr. Oldham was never quite satisfied whether in these we had not either 



a newer group among the gneisses or whether they were really only 



more highly altered Cuddapahs. These strata are still quartzites like 



those of the Cuddapah beds, but they have, as shown in the map, a 



somewhat irregular diagonal lie across the gneiss field, and are involved 



amoug schistose gneisses. Hence it was surmised that these schistose 



o-ueisses themselves might be after all only altered Cuddapahs. 



Of much less importance is a series of patches of ferruginous or 

 lateritic conglomerates and breccias scattered at wide intervals all over 

 the field, and forming a skin on the laterite and sandstone belt of 

 Nellore. These belong to Mr. Foote's comprehensive group of 'Lateritic 

 deposits/ 1 



A well-defined belt of subaerial rocks lies immediately along the 

 eastern base of the Veligondas, forming a series of great heaps of talus 

 debris derived from the destruction of the strata forming the mountain 

 wall. Manifestly much of this band of angular and sub-angular debris 

 must be as recent as any deposits in the field for its formation is still 

 going on ; but in many places it must be considered as coeval with the 

 lateritic deposits or ferruginous conglomerate and breccia patches men- 

 tioned in the last paragraph. So much as is seen of it must be essen- 

 tially recent, ranging at any rate from the lateritic deposits up to the 

 present time; but it would be an interesting problem to decide for 

 the whole length, breadth, and thickness of this talus, whether it may 

 not be to a great extent a beach deposit which was even in process of 

 formation during much of the mesozoic period. 



» Mem. Gcol. Surv. of India, Vol. X, pt. 1 ; Vol. XII, pt. 1 ; Vol. XVI, pt. 1. 



( 12* ) 



