2 
BALL AND SIMPSON: COALFIELDS OF INDIA. 
deposited in fresh water and probably by rivers. As a rule tbey 
are found occupying basin-shaped depressions in the older forma- 
tions, and such depressions frequently coincide with the existing 
river valleys. On the west these areas appear to be basins of 
original deposition, but on the east abrupt faulting on the 
southern margin of the fields points to the probability that these 
areas, in part at least, owe their preservation from denudation 
to the fact of their having been sunk by earth movements to a 
level lower than neighbouring portions of the same deposits. From 
the following table^ the geological sequence of the coal-bearing 
portion of the Gondwana rocks can be understood : — 
Panchet 
Lower Gondwana / Damuda 
Talchir 
Panchet 
r Raniganj 
\ Ironstone 
j shales. 
Barakar. 
j* Karharbari. 
X Talchir. 
Almod ? 
or Bijori 
Motur. 
or Kamthi. 
Talchirs. 
The names of most of the groups are taken from the names of 
their representatives in the Bengal fields, which were first examined ; 
the best sequence of the beds, however, is seen in the fields 
of the Narbada valley. The alternative names are those given by 
the early observers in the fields of the Narbada and Godavari valleys 
before correlation with the Bengal fields was attempted. 
Commencing with the lowest member of the system, the Talchir 
beds consist in general of fine, silty shales and 
fine, soft sandstones. The shales are usually 
greenish-grey or olive in colour, and are traversed by innumerable 
joints. The sandstones are fine, even-grained and vary in colour from 
olive to pale-pink. They are composed chiefly of quartz and un- 
decomposed pink felspar. A thin coal-seam occurs amongst the 
Talchir beds in the Jhilmilli coalfield in Sarguja, but, as a rule, 
these beds do not contain coal-seams. Towards the base of the 
group the frequent occurrence of a remarkable boulder-bed contain- 
ing striated pebbles points to the existence of glacial conditions 
in early Gondwana times. It may be remarked that the occurrence 
of a similar bed (Dwyka conglomerate) in an analogous position in 
Manual of t/ie Geology of India, 2nd edition, p. l'>6, 
