J. B. Scricenor — Igneous Rocks of Singapore. 17 



V. — Note on the Igneous Rocks of Singapore, with special 



REFERENCE TO THE GrANITE AND ASSOCIATED lloCKS CARRYING 



Rhombic PrRoxENE. 



By J. B. ScRiYENOK, F.G.S., Geologist to the Federated Malay States Government, 

 and fornierly of H. M. Geological Survey of Great Britain. 



IN a former paper ' the writer endeavoured to show the connection 

 between the sedimentary rocks of Singapore and certain rocks in 

 Pahang. On the occasions when opportunities for geological work in 

 Singapore have iH'esented themselves numerous specimens of igneous 

 rocks have been collected, and it is the purpose of the present paper 

 to describe briefly the observations recorded. It is hoped that this 

 will give some further idea of the geology of the island of Singapore ; 

 but apart from a general description the pyroxene - bearing rocks 

 associated with the granite appear to the writer to require a note as 

 being of exceptional petrological interest. 



The island of Singapore is composed, as far as is known at present, 

 of a series of estuarine rocks, which are a continuation of the Tembeling 

 Series in Pahang, granite, with associated rocks to be described later, 

 and some other igneous rocks, most of which are referred to an 

 extensive series of volcanic rocks in Pahang associated with Permo- 

 Carboniferous beds. The estuarine series may be referred to the 

 Upper Gondwana on the one hand, while on the other it is probably 

 represented by some of the West Borneo Beds described by Mr. Wing 

 Easton. 



The granite is certainly later than the sedimentary rocks, which 

 are, in some parts of the island, highly disturbed ; therefore it may be 

 assumed that the granite is at any rate post-Triassic, perhaps post- 

 Inferior Oolite. In tbe peninsula the writer's observations have led 

 him to believe that there are two types of granite which may be of 

 different age, a porphyritic and a non-porphyritic type. As pointed 

 out before, however, "against a difference in age may be urged the 

 fact that both facies are connected with deposits of tin-ore, and also 

 that beyond areas of gneiss, produced apparently by movements in the 

 partially solidified magma, no evidence has been found of disturbances 

 on a large scale affecting either." The Singapore granite belongs to 

 the non-porphyritic facies. 



Mr. R. B. Newton- gives a list of the early literature dealing with 

 Singapore in his "Notes on Literature bearing on the Geology of the 

 Malay Peninsula, etc.", Logan ^ says that in Bukit Timah "solid 

 greenish granite and syenite, passing in some places into compact 

 laminated felspar", are seen, while on Pulau TJbin are " various forms 

 of granite and syenite (often approaching and sometimes passing into 

 greenstone)", and hornblende occurs, both on Pulau TJbin and 

 elsewhere. 



Hocks of the Pahang Volcanic Series. — None of these rocks have 



' Geol. Mag., 1908, pp. 289-91. The map with this paper -Aill serve to show 

 the position of Pulau Ubin in Changi. 



* Geol. Mag., 1901, pp. 128-34. 



^ J. R. Logan, "Notices of the Geology of the Straits of Singapore" (with 

 geological map) : Q.J.G.S., I80I, vol. vii, p. 310. 



IJECADE V. — VOL. VI. NO. I. - 



