246 THE GEOLOGY OF THE MALAY PENINSULA. 
in voleanic tuff. It is supposed to be a beach deposit formed of 
boulders of volcanic rocks which were exposed along the shore line, 
and cemented by volcanic ashes which were all the time being ejected 
by neighbouring volcanoes. Tuffs and lavas are interbedded with 
the succeeding shallow-water series of quartzites, shales, and schists, 
of Triassic age, both in Pahang, and, on the western flanks of the 
Main Range, in South Selangor. 
In Central Borneo volcanic rocks of an andesitic type are 
interbedded with rocks which are probably of Jurassic age, and 
certain amphibolites there are variously held to be pre-Cambrian 
crystalline slates, or eruptive rocks, belonging to this Jurassic 
period, which have been uralitised and altered by mountain-pressure. 
Permo-Carboniferous and Mesozoic voleanic rocks, including 
serpentine and andesite, with corresponding tuffs and breccias, 
and occasionally dolerites, are very widespread throughout the 
smaller islands of the Archipelago, though only in a few of the 
places, such as at Letti, where volcanic breccias are overlain by 
fossiliferous Permian limestone, is it possible to be sure whether 
they are pre-Permian or Mesozoic. In Java there are volcanic 
rocks known to be pre-Eocene, but nothing more definite can be 
stated as to their age. 
Triassic and Rhaetic. 
Towards the middle of the Permian period the emergence of 
the land from the sea began in Eastern Yunnan, and the Permo- 
Carboniferous limestone masses were attacked by denudation, so 
much so, that, in some places, they were completely removed. The 
shore line retreated back far to the south and west. The thick Red 
Beds of upper Permian and perhaps lower Triassic age, were then 
deposited in Yunnan, the lower part of the series in Hast Yunnan 
consisting of conglomerates, and passing up into sandstones and 
shales, often containing salt and gypsum. Widespread basaltic 
and andesitic eruptions occurred at the close of the Permian. 
Triassic beds are preserved in East Yunnan only where they were 
faulted down, and so preserved from the severe erosion to which 
the country was subjected at the close of the Plhocene period. 
The beds are alternations of marine and land deposits, passing into 
deep-sea deposits at the top. After the deposition of the Red beds, 
no more marine sediments were formed, and Yunnan has been a 
land surface from the upper Triassic period to the present day. 
The Shan States were dry land during the greater part of the 
Permian and the whole of the Triassic period, and no deposition 
took place, except for beach deposits derived from the denudation 
of the Plateau limestone and the underlying rocks. In the Malay 
Peninsula there was probably a land-period after the formation of 
the Permo-Carboniferous limestone, followed by shallow-water con- 
ditions, during which the sea was dotted with lagoons, probably 
formed by coral-reefs, enclosing clear water suitable for the growth 
Jour. Straits Branch 
