﻿part 3] STANNIFEROUS DEPOSITS OF KINTA DISTRICT. 187 



less gritty ... It is, in every respect, a characteristic till ... In places 

 the beds become highly siliceous and very close in grain, probably owing to 

 the introduction of silica- charged waters, which have given rise to much 

 quartz-veining at some points.' Again : ' When the till is of an earthy, or 

 non-siliceous, nature, it frets away rapidly by weathering - , and sometimes 

 forms cavernous shelters in the faces of cliffs. Under such circumstances, 

 with a friable and freshly-exfoliated surface, its resemblance to the Pleistocene 

 Boulder- Clay of Europe is very striking.' 1 



It is then pointed out that, in the case of the Kinta Valley 

 clays, the deposits have for a long time been exposed to agencies 

 possessed of great power to dissolve quartz, and that there seems to be 

 no need to postulate a great sinking movement over the limestone 

 in order to account for the recent appearance of the clays, but 

 that they may have been largely silicified at one time, the hardening 

 silica having been since removed by ground- water. 



That silicified beds can become desilicified in the tropics is 

 abundantly proved in numerous cases in Malaya and elsewhere. 

 But silicification is not the only effect of metamorphism that 

 one would expect to have taken place in clays older than the 

 granite, situated in a narrow valley bounded by granite-ranges 

 of immense mass, intruded into by numerous granitic veins, and 

 inter bedded between rocks which themselves have been highly 

 metamorphosed. 



The Australian deposits described by the Eev. W. Howchin 

 cannot be considered a parallel case, for the latter are not situated 

 in a metamorphosed area, no igneous rock being shown in any of 

 the sections illustrating that paper, although three of them extend 

 over 15, 30, and 60 miles respectively. 3 



At the junction of the clays with the underlying limestone signs 

 of metamorphism might reasonably be expected, both being sup- 

 posed to be older than the granite ; but, as Mr. Scrivenor remarks, 

 'the limestone is generally separated from them by ironstone.' 3 

 In places, the junction between the so-called 'glacial' clays and 

 the limestone is remarkably free from any signs of interaction. 



V. Mode of Faulting of the Clays. 



The presence of faults in the ' clays ' is advanced as evidence 

 of their greater antiquity than the granite, and the impossibility 

 that they could be recent deposits. 4 Two faults are mentioned : 

 one at Rotan Dahan, in which the clays showed distinct slicken- 

 siding, and one at Tekka, where a ' remarkable fault-breccia 

 occurred.' The bed-rock at both these places is limestone. 



Now, this bed-rock of metamorphosed limestone in the Kinta 

 Valley has been attacked by ground water to an extraordinary- 

 degree, and big ' cups ' and ' troughs ' separated by ' pinnacles ' are- 



1 Q. J. Gr. S. vol. lxiv (1908) p. 239. 



2 Ibid. pp. 236, 256, 257. 



3 'The Geology & Mining Industry of the Kinta District' 1913, p. 31. 



4 Ibid. p. 37. 



