The Rocks of Pulau Ubin and Pulau Nanas (Singapore)

Abstract

I. I ntroduction . I n the January number of the ‘Geological Magazine’ for 1909 a short note of mine appeared on the igneous rocks of Singapore, giving the results of observations made on occasional visits to Singapore from the Malay States during the years 1904 to 1908. Not many weeks after the paper had been despatched, a further opportunity presented itself of visiting some of the localities mentioned; and, as perhaps has happened to others, I found that the fresh information available in the quarries was so extensive and so significant that my remarks in the note mentioned appeared very meagre. It proved too late, however, to withdraw the paper, and therefore the following remarks must be considered in some sense supplementary to those in the earlier paper; but, at the same time, they embody other new information that will, I think, be found to be of considerable interest to those who have studied the geology of the East Indies. My object in the present paper is to describe the granite of Pulau Ubin, veins of rhombic pyroxene-bearing rocks traversing this granite, as well as ‘basic masses’ in the granite of the same island; also to describe fragments of granite in tuffs on Pulau Nanas, and to show that these are derived from a granite mass distinct from and much older than that forming Pulau Ubin, and therefore also older than the tin-bearing granite that now forms the backbone of the Peninsula. Further, the mutual relations of the granite, the veins, and