Vol. 6S.'] THE GOPEI^G BEDS OP KINTA. 157' 



resemblance which the Gopeng "Beds bear to drift, stratified and 

 unstratified, is genuine, and that they are in fact glacial clays and 

 boulder-clays which we may compare with the Talchir Beds of Orissa, 

 and with their correlatives in Africa and Australia ; and we can, 

 moreover, regard the Gopeng Beds as the base of an extension of 

 the Gondwana System in the Malay Peninsula. 



(10) Economic Aspect of the Recognition of the Nature 

 of the Gopeng Beds. 



Interesting as the Gopeng Beds are to a student of the earth's 

 history, there is no doubt that in the Federated Malay States their 

 economic possibilities claim the greatest attention. The field and 

 petrological evidence show that the material of which they are 

 composed was derived from a tin-bearing granite mass and the 

 altered rocks on its margin. This granite mass was probably 

 situated somewhere to the west of the position of the Gopeng Beds, 

 and was part of Gondwanaland. Although much older than the 

 Mesozoic granite that forms the granite hills of to-day, it may be 

 still within reach as undiscovered outcrops, or under younger 

 rocks; and the extent of the tin-bearing glacial detritus under 

 younger rocks, or in unprospected parts of the country, calls for 

 immediate investigation. 



A digression may perhaps be made here, to notice a point raised 

 in my paper on the rocks of Pulai Ubin and Pulau Nanas (Q. J. G. S. 

 vol. Ixvi, 1910, p. 430), where it was shown that there was at least 

 a strong probability of the fragments of granite in the tuff of Pulau 

 JN'anas belonging to the same period of irruption as the granite of 

 Amboyna, which Dr. Yerbeek stated could not be younger than the 

 Permian. It may prove, then, in the course of further work in the 

 Peninsula and the Archipelago, that the parent granite of the original 

 tin-ore in the Gopeng Beds, the granite of Amboyna, and the granite 

 fragments in the tuff of Pulau ISTanas, all belong to the same period 

 of irruption. It is interesting also to recall the mention of the 

 small pebbles of schorl-rock in the Tembeling conglomerate, and 

 especially the following sentence : — 



' These pebbles may have come from the pre-Oarboniferous granite ; but, as 

 tourmaline in a granite mass always suggests the possibility of finding tin-ore 

 also, I must add that hitherto I have found no detrital tin-ore in rocks older 

 than the tin-bearing [Mesozoic] granite.' (0/>. cit. p. 428.) 



This admission is no longer necessary. 



(11) Relation of the Corundum Boulders to the Tourmaline- 

 Corundum Rocks of Kinta. 



Three striking points about the geology of the Kinta Yalley, so 

 far as it is known at present, are that on the east side boulders of 

 pure corundum are found, on the west boulders of the tourmaline- 

 corundum rocks, and that the two have never been found together : 



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