>06 HOLLAND: GEOLOGY OF THE NEIGHBOURHOOD OF SALEM. 



recognised on the geological map of France, is in agreement with 

 the classification which has been so long recognised in India. But, 

 apart from the internal evidence of composition and structure of the 

 rocks themselves, some of the observations recently made as to the 

 relations which these pyroxene-granulites present to their gneissose 

 neighbours, can only be explained, so far as I can see, by assuming 

 for them an igneous origin and an intrusive habit. 1 In a highly 

 crushed country it is only natural to expect that the rocks which are 

 old enough to show the general foliation of the area will have had 

 most of their original structures mutilated if not totally destroyed. 

 But the south of India offers an unusual number of chances for the 

 preservation of the primary structures in our old rocks, for the 

 reason that no crumpling, and practically no crust disturbances of 

 any serious sort, have taken place in the peninsula of India since 

 lower palaeozoic times. In consequence of this circumstance many 

 of the original structures in our oldest formations, and even in 

 rocks like the pyroxene-granulites which we cannot remove from 

 the Archaean group, are still preserved with little or no signs of 

 secondary change. One is so surprised on discovering positive 

 evidences of intrusion amongst the members of an old Archaean 

 terrain (whose constituents are generally highly altered by the 

 many disturbances which follow as a result of their great age), that 

 it is only natural to regard these observations with some suspicion. 

 But in the present instance there seems to be no other conclusion 

 which satisfies the facts of the case, and, after all, when we consider 

 the remarkable quiet which South India has enjoyed for such long 

 ages, it ought not to be surprising to meet with phenomena in these 

 rocks for which European experience would not prepare us. 



During the course of this work I was fortunate in obtaining 

 the advice of Mr. R. Bruce Foote, F.G.S., whose experience and 

 knowledge of the older rocks in South India are unique. 



i For a detailed account of the pyroxene-granulites of South India, under the name 

 " charnockite series," see Mem., G. S- L, Vol. XXVIII, pt. 2. 



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