Il6 HOLLAND: GEOLOGY OF THE NEIGHBOURHOOD OF SALBM. 



quantitative index of age. If, on the contrary, we assume that these 

 beds are merely altered outliers of the Dharwars, we must be pre- 

 pared for the conclusion that the break between what we distinguish 

 as Dharwars and what we class as Archaean has not been satisfact- 

 orily established for all South India ; it is the latter assumption that I 

 should feel inclined to favour. That some Dharwars are younger than 

 some gneisses has been locally established beyond question by 

 Mr. Foote ; but we are still in want of direct evidence as to the greater 

 antiquity of other very large formations of gneisses, notably the 

 charnockite series. 



(3) The Pyroxene-granulites, or Charnockite series. 



The most abundant rocks in the neighbourhood of Salem 

 present the characters of the peculiar group 



General characters. . 



known in Germany as " pyroxene-granulites, 

 and in France as "pyroxene gneisses." In South India we have 

 developed the habit of recognising these rocks under the name 

 " charnockite series," the reasons for which, together with a general 

 description of the whole group, are given in a separate paper, 

 Mem.y Geol. Surv t) Ind., Vol. XXVIII, part 2. These rocks occur in 

 much larger masses in South India than is usually the case with 

 their European equivalents ; in the present area, for instance, the 

 Shevaroy hills, forming a plateau of between 4,000 and 5,000 feet, 

 and covering an area of over 100 square miles, are composed entirely 

 of pyroxene-granulites. The lenticular habit of these rocks is very 

 well illustrated in the neighbourhood of Salem, where the lenses 

 vary in size from a few inches in length to small hillocks, rising 

 abruptly above the general level of the plains, and through larger 

 hills to mountain masses like the Shevaroys. 



These rocks which we now distinguish as the charnockite 

 series were referred to by Messrs. King and 



Previous classification. . ' c 



Foote as "syenitoid gneiss n on account ot 



1 Op, cit.y p. 269. 



( 14 ) 



