GEOLOGICAL OCCURRENCE OF COAL IN INDIA. 
7 
inconstant, but small workable areas occur near Kalabagh. Coal of 
the same age is said to occur in the Kohat district of the North- 
West Frontier Province, and in the Doab Valley, Afghanistan. 
(iii). The Cretaceous Coalfields. 
Coalfields of Cretaceous age are found in the Khasia and Garo 
hills in Assam. The fields of the former hills 
HifL''*^'* usually occur as small basins of original deposi- 
tion, lying on rocks of Purana age, and on 
Archaean gneiss. The rocks of these basins vary in thickness from 
about 600 to 2,000 feet, but thin out on the edges of the basins. 
They appear to be mainly composed of coarse sandstones, 
conglomeratic towards the base, and with occasionally an inter- 
mediate zone of fine, glauconitic sandstones. The coal-seams occur 
near the top of the series and the latter is in places capped by 
Lower Tertiary deposits. 
(iv). The Tertiary Coalfields. 
Coal of Tertiary age is found in the foothills throughout almost 
the whole of extra-peninsular India, from Baluchistan on_^ the north- 
west to Assam on the north-east. It also occurs in Sind, Rajpu- 
tana, Burma and in the Andamans and Nicobars. The majority 
of the seams are lignite. They occur in eocene rocks, and are 
almost invariably associated with characteristic beds of nummulitic 
limestone. In Upper Assam, however, important deposits of true 
coal are found, which are considered to be of middle Tertiary, 
probably miocene, age. 
The characteristics of the coals of the extra-peninsidar areas are 
so variable that they must be described under their separate head- 
ings below. Generally speaking, the Tertiary coakj are bright, 
jetty and non-laminated, and they contain a larger proportion of 
volatile matter than the coal of the peninsular fields ; many of 
them are extremely friable and susceptible to disintegration under 
exposure ; they do not cake as a rule and the proportion of ash is 
usually small. 
