IV.—The Pahang Volcanic Series

By far the greater part of the volcanic rocks of Malaya consists of fragmental deposits, which at first sight seem to be andesite-tuffs and andesite-breccias, for most of them contain abundant fragments of andesitic lava. However, the majority also contain numerous fragments of quartz, some of which occur as isolated angular grains in the cement, others embedded in a very fine-grained siliceous rock, and sometimes showing rounded outlines and even bays, invaded by the siliceous aggregate. Tuffs which occur in certain localities, e.g. at Kuala Tekal, Tembeling, and Sibah near Kuala Lipis on the Pahang railway, contain the usual fragments of andesite-lava, with numerous fragments of quartz like those just described, and in addition fragments of rhyolite-lava or quartz-porphyry. It is probable that the great majority of the Pahang Volcanic Series of tuffs are formed of an admixture of andesitic, rhyolitic, and sedimentary material.