THE GEOLOGY OF THE MALAY PENINSULA. 247 
of radiolaria, the silica necessary for their growth being supplied 
by submarine volcanic emanations. Periodical slight changes in 
‘the sea level took place, which admitted detrital matter from the 
neighbouring land. These conditions produced the series of radio- 
larian cherts, interbedded with quartzites, sandstones, and grits, 
which cover a large area in Kedah, South Selangor, Negri Sembilan, 
and Pahang, in the Malay Peninsula, and in the island of Billiton. 
Radiolarian rocks probably of this period are common also in Bor- 
neo, Sumatra, Celebes, Timor, Rotti, and many other islands. In 
the Malay Peninsula the series, in some places, is built up of 
deposits of chert perhaps hundreds of feet in thickness, and thicker 
deposits of sandy beds, while in other places the series consists of 
alternating bands of chert and grit or quartzite, varving from 
several feet to only one inch in thickness. All the beds are con- 
torted into sharp folds, and the rocks, particularly the shales and 
shaley grits, have been metamorphosed by earth-movements. In 
Perak this series occurs only in the extreme north, where it is a 
continuation of the extensive development in Kedah. Further 
south it probably corresponds roughly with a series of shallow-water 
quartzites and shales, which covers the greater part of the area for 
thirty miles north of Taiping, and which disappears, west of the 
Semanggol range, under Recent alluvium. The Triassic fossil 
Estheriella was found in these shales at Semanggol. 
Certain boulder clavs in the Kinta Valley, which are older 
than the Mesozoic granite, have been provisionally allotted to the 
Permo-Triassic period. They are very interesting because they 
are the source of the greatest part of the tin deposits of the 
Kinta Valley. For a long time they were spoken of as alluvial 
deposits, until geological investigation showed that they are 
undoubtedly older than the eranite. It is possible that they have 
suffered considerable alteration since the granite was intruded, and 
one geologist holds that they were derived from quartzites and 
shales which had been mineralised by the Mesozoic granite. He 
says that the underlying rock, known in many cases to be limestone, 
has been partially dissolved by underground water, and that the 
quartzites and shales were let down into the resulting cavity, with 
a consequent destruction of the bedding. The result is a clay con- 
taining a large proportion of quartz sand with varying amounts of 
tin-ore. ‘That the clays are older than the granite is seen by the 
following facts. 
(1) Near the granite the clays are often rich in tourmaline 
streaks and patches, and in quartz, whereas further from 
the junction the tourmaline and quartz are less evident. 
(2) The clays near the granite are often richer in tin than 
those further away. 
The tourmaline patches and quartz are derived from veins of 
quartz and tourmaline which traversed the clays before they be- 
came jumbled up by the solution of the underlying lmestone. 
Rk. A. Soc., No. 86 1922, 
