SUMMARY OF RESULTS. 145 



in general agreement with the long-established conclusions of the 

 Geological Survey of India. But the characters which indicate the 

 comparatively young age of this group are the result, according to 

 my observations, of their having been introduced as irruptive rocks 

 near or at the close of the great folding movements in Peninsular 

 India (see M The charnockite series," Mem., Geol. Surv., Ind. y Vol. 

 XXVIII, p. 2). 



The following are the principal groups of rocks now exposed in 

 the neighbourhood of Salem :— . 



(4) Post- Archaean eruptives. 

 (3) Pyroxene-granulites or charnockite series. 

 (2) Thinly foliated schists and leaf -gneisses. 

 (1) Older biotite-gneisses. 



The biotite-gneisses are much altered and in one place cor- 

 roded by fresh tongues of charnockite. They present an aspect 

 quite different to the great biotite-gneiss formation of the northern 

 taluks of Hosur and Krishnagiri which are also within the Salem 

 civil district, but whose geological relations to the charnockite 

 series have not yet been worked out. Pebbles of a gneiss similar to 

 the formation herein described in the immediate neighbourhood of 

 Salem town have been found in the Dharwar conglomerates of 

 Kolar (pp. 5—8), 



The schists of the Salem-Ahttir valley are very composite in 

 character, including highly crushed gneisses, hornblende-schists, 

 chloritic rocks and ferruginous quartzites. The last-mentioned 

 rocks are composed of quartz, grunerite, magnetite and hematite. 

 The two oxides of iron are apparently intergrown with one another 

 as well as found occurring in isolated crystals, and analyses showing the 

 relative proportions of ferrous and ferric oxides reveal the interesting 

 fact that many, perhaps most, of the Salem magnetic ores, contain 

 almost as much hematite as magnetite. In general composition these 

 schists recall the petrological characters of the Dharwar system, from 



( 43 ) 



