THE GEOLOGY OF THE MALAY PENINSULA. 245 
most places, all traces of organism have been destroyed by the re- 
ervstallisation of the limestone, and specimens of homotaxial value 
have been found only in Pahang, east of the Main Range, and in 
Patalung, Siam. The Pahang fossils vield types ranging from 
lower Carboniferous to Permilan, whereas the Siamese fossils have 
been deseribed by one author as lower Carboniferous and by another 
as Permo-Ciarboniferous. South of a lime drawn east and west 
through Kajang in South Selangor, the limestones and shales seem 
to pass into an unfossiliferous’ shaley series. devoid of sandy beds, 
and non-calcareous, excent for calcareous shales and shaley lime- 
stones occurring in the Muar Valley. 
In Sumatra Carboniferous limestones occur, forming mount- 
ains nearly 2000 feet high, crvstalline and contaming black nodular 
chert. There are also other Palaeozoic limestones with very scanty 
fossils whose age has not yet been determined. Probably they too 
are Carbonifercus to Permian. 
In the Malay Peninsula and Archipelago the Carboniferous 
and Permo-Carboniferous limestones just described are the oldest 
rocks known, with the following exceptions, (1) a granite im Am- 
boyna ils said to be Palaeozoic, and the granite fragments in volcanic 
ash near Singapore may be of the same age, Gin a series of shales 
and fine-grained quartzites underlying limestone in the Langkawi 
Islands. perhaps corresponding with the Mergui series of shales and 
arenaceous rocks in Burma, underlying the Moulmein Limestone. 
The Oudeschiefer formation of the Archipelago is believed to be. 
of Permian to Jurassic age, in snite of the fact that many geologists 
™m the past have considered it to be Palaeozoic or even pre- 
Cambrian. 
Folding movements, which took place towards the close of the 
period of formation of this verv widespread series of limestones, 
were heralded and accompanied by a big show of volcanic activity, 
not, however, displayed in all parts of the area. It is evident in 
Western Yunnan, where the greater part of the ’ermo-Carbonifer- 
ous series is often made up of tuff and ash beds, intercalated with 
thick andesitic, doleritic, and basaltic lava flows; in Eastern Yun- 
nan, where basic lavas are found interbedded with the upper part 
of the middle Carboniferous limestone; in the Malay Peninsula, 
particularly in Pahang, east of the Main Range, where it is 
represented by acid, intermediate, and occasionally basic, lavas, 
dykes, and tuffs; near Singapore; in South Sumatra, where a series 
similar to that in the Malay Peninsula occurs; and in Borneo. 
In Pahang, volcanic activity began probably in the Carbonifer- 
ous period and continued intermittently through the greater part 
of the Triassic, although, as land conditions followed the deposition 
of the limestone, a good deal of the series has been denuded away. 
Evidence of the persistence of volcanic activity, during the shallow- 
water and land conditions, is furnished by a remarkable deposit of 
boulders of voleanic rocks, dyke rocks lavas and tuffs, embedded 
R. A. Soe., No. 86 1922 
