﻿188 



DR. W. R. JONES ON THE SECONDARY 



[vol. lxxii, 



found practically over the floor of the Avhole valley. The ' cups ' 

 are sometimes very deep, one at Siputeh exceeding over 130 feet 

 in depth, and into these cups the clays have sunk. 



That the limestone -floor of the valley was in places exposed by 

 denudation and then partly covered by recent alluvium is con- 

 clusively proved by the fact that occasionally it still forms the 

 surface-rock, and that in other localities the limestone has, resting 

 directly upon it, clays, sands with rounded pebbles, and beds of 

 lignite, partly carbonized wood, and leaves. These beds also contain 

 rounded grains of cassiterite — as at Tronoh South, Lahat, etc. The 

 limestone, even when covered by these beds, is still being dissolved 

 away, and this accounts very simply for the fact that beds of 

 undoubted alluvial origin show clear evidence of faulting down 

 into the enlarged limestone cups directly underneath. Indeed, in 

 the Serendah Valley, in Ulu Selangor, I was able to foretell 

 the presence of a big limestone cup in one mine by the presence of 

 small faults (having a throw of a few feet only) in the exposed 

 face of the overlying alluvium. 



But a more striking example was seen at Penkalan Mine in the 

 Kinta Valley, about two years ago. A circular patch of the 

 surface had suddenly subsided from 3 to 4 feet, and further work 

 on the mine showed that directly underneath was a limestone cup. 

 Another such subsidence on a bigger scale occurred recently on the 

 Government road at Lahat, and was supposed, for good reasons, to 

 be due to the presence directly underneath of a limestone cup 

 out of which the water had drained into the deep workings of 

 the Lahat Mine. 



In that mine a very interesting case of faulted alluvium was 

 seen recently. That the deposit was alluvium was shown by its 

 sandy nature, and the presence of partby decayed wood and occa- 

 sional lumps of vegetable gum in the faulted beds. The bed-rock 

 has proved to be limestone, and it is probable that a limestone 

 cup will be found underneath. The top of a limestone ' pinnacle ' 

 has already been exposed here. 



At Ranching, in Ulu Selangor, alluvium containing very well- 

 rounded pebbles of granite, aplite, and pegmatite was seen to be 

 faulted, and limestone cups are known to be numerous here. I 

 was fortunate in coming across another clear case of faulting in 

 alluvium at Ranching, when in Mr. Scrivenor's company. 



VI. Absence of Glacial Characters. 



There is no other case on record, so far as I have been able to 

 ascertain, where deposits known to be of glacial origin have not 

 yielded some polished and striated boulders. In the 'clays and 

 boulder-clavs ' of the Rinta Valley, however, Mr. Scrivenor states 

 that 



' No clear evidence has been seen on the boulder or on the limestone bed- 

 rock of ice-action, such as the polishing and striations frequently seen in 

 glaciated regions.' (' The Geology & Mining Industry of the Kinta District ' 

 1913, p. 39.) 



