Federated Malay States. 



451 



the quartz-porphyry is seen to be traversed by numerous good 

 joint planes which are much more strongly developed than, for 

 instance, is the case in granite, and their distribution at rather 

 irregular intervals causes the rock to separate into angular blocks 

 of very different sizes. Here is seen what is sometimes noticed in 

 granite, namely, that the transition from unweathered hard rock 

 to soil is very abrupt and that there is no partially decomposed 

 rock. At first sight it would appear that the freshness of the 

 rock as seen on the Kuala Lumpur— Benton g * road is against 

 its being older than the Mesozoic granite, but there are signs that it 

 has been brecciated and subjected to strong shearing, and any 

 secondary minerals that were formed before those movements may 

 have been reconstituted. Some specimens from Jeram Gading* 

 contain epidote in abundance, and the presence of this mineral, which 

 is characteristic of the igneous rocks older than the granite, is an 

 indication that the quartz-porphyry belongs to the Pahang Yolcanic 

 Series, and the numerous boulders of volcanic tuff and breccia, also 

 containing epidote, which can be seen in the stream show that rocks 

 of the series occur in the neighbourhood. In addition, pebbles and 

 boulders of hornblende-augite-schist were seen in the Bivers Seli * 

 and Klang*, and one specimen when examined under the microscope 

 revealed that the schist was originally a porphyritic igneous rock. 

 Similar schists and gneisses in situ bordering the alluvial plain of 

 Kuala Lumpur* are penetrated and altered by the Main Range 

 granite, and the field evidence goes to show that the schistose 

 structure was induced by the earth-movement which took place when 

 the granite was intruded, so it is probable that they were originally 

 rocks of the Pahang Yolcanic Series. A single boulder of the 

 quartz-porphyry was found lying on weathered granite at the eighth 

 mile from Kuala Lumpur* on the Rawang road*, and one boulder of 

 the pyroxene-granite-porphyry was found at the foot of Bukit 

 Lanjan*, near Kepong, in Lower Selangor, so it appears that there 

 was a widespread occurrence of the Pahang Yolcanic Series in 

 Selangor, but that a great part of it has been denuded since the 

 intrusion of the Main Range granite. 



The different types of rocks belonging to the Pahang Yolcanic 

 Series are indicated in the following table : — 



