254 THE GEOLOGY OF THE MALAY PENINSULA. 
sandy clays were first encountered, followed by running sands with 
traces of coal from 125 feet to 205 feet below the surface. 
The coal at Enggor and at Perlis is similar in composition to that 
at Rantau Panjang, and is probably of the same age. 
There are still considerable areas in the Peninsula, east of the 
Main Range, as vet unexplored, an it is possible that in these areas 
there may be extensive tracts of country covered with marine 
and fresh-water beds, equivalent to those of the Irrawaddy plains. 
Such tracts provide the only possibility of mineral oil being found 
in payable quantities in the Malay Peninsula. Unfortunately there 
is no evidence that any such beds exist. 
Tertiary of Sumatra. 
In Sumatra there is a considerable area of Tertiary beds, both 
near the coast and in subsided areas inland. Near the east coast 
they are concealed by Pleistocene deposits. There 1s very little 
fossil evidence to go by, but the percentage of water in the inter- 
bedded brown coals gives information as to the age of the beds. 
The Ombilin coal field near Padang, which has been worked by the 
Government for many years, is of Eocene age, judging by the low 
percentage of moisture, and more Eocene coals occur at Gunong 
Tusam in North Sumatra. The younger Tertiaries in North 
Sumatra usually contain no coal at all, but the commonest coal occur- 
rences in the south are in the upper Miocene beds (veanger Tertia- 
ry), as at Palembang. In the Boekit Asam Field, where the estimat- 
ed amount of workable coal is forty million tons, the seams are 6 to 
7, 3 to 6, and 5 to 6 metres thick. ‘This upper Miocene series with 
coal seams is recognised’ also in Djambi though the seams are dimi- 
nishing in number and thickness, so it appears that the Djambi Pro- 
vince forms a transition from Palembang to Deli and Atjeh in the 
north.* 
No unconformity has been found im the coastal regions affect- 
ing the later Tertiaries, except that between Tertiary and very 
voung Pleistocene strata. In the Andaman Islands, on the other 
hand, the Eocene is highly folded, and the Miocene, unconformable 
on the Eocene, is only slightly folded, showing that the main young- 
er folding was pre-Miocene. A similar unconformity exists between 
the Eocene and Miocene inland in Sumatra. No information about 
this system of folding can be obtained from the small exposures of 
Tertiary (Miocene) rocks i in the Malay Peninsula, except that the 
small dips indicate that no imtense folding has occurred after 
Miocene times. In the Mesozoic granite there are sheared areas 
which are probably the result of Tertiary movements. 
In the Tertiarv-Quaternary period in Sumatra, there was con- 
siderable volcanic activity, generally of an andesitic type, accom- 
panied by subordinate intrusions of quartz-porphyry, porphyrite, 
gabbro, picrite, basalt and diorite. The upper Miocene lignite beds 
of Palembang have been subjected to the heat developed by the 
intrusion of such rocks, and their economic value has thereby been 
increased. 
Jour. Straits Branch 
