GEOLOGICAL STRUCTURE. 



Should miners, however, be required over and above the local supply,^ 

 the district of Chota-Ndgpur, with its Koles and Miindas, would 

 always be a good recruiting ground. 



Before entering upon a special description of the rock formations 

 Geological composifcion o^ this field, it will be expedient to present a 



of Damu da valley. . 1.10,1 i • i . . n 



concise sketch 01 the geological composition of 



the Damiida valley. Commencing near Raniganj, where the rocks are 



first seen to crop up from under the alluvium of Lower Bengal, we 



find that three distinct series of sedimentary beds occur, resting upon 



a floor of metamorphic strata. Each series is separable on the ground 



of at least apparent unconformity, and is more or less perfectly divisible 



on palaeontologieal evidence. As we proceed further up the valley of 



the Damuda, we find a repetition of the geological structure of the 



Raniganj area; no new series aj^pears, and the stratigraphical relations 



are but slightly modified. 



The lowest of these three series is the Talchir; overlying it, is the 

 Damiida, and above this is the Panchet. The Talchir is subordinate 

 in thickness to either of the other series ; but it is more constant in the 

 character of its strata. Its characteristic rocks are fine-grained sand- 

 stones, silty shales, and conglomerate beds. 



The Damiida comprises argillaceous and silicious sandstones, shales, 

 and numerous seams of coal. Its greatest development is in the Damiida 

 valley, where it is divisible into three distinct groups. Towards the west, 

 the sub-divisions are not so marked, and, in the wide spread area of 

 the Sirgiija and Central Provinces^ coal-fields, only one group is re- 

 cognisable. 



The Panchet is a very extensive formation in the valley. The- 



most prominent hills within the limits of the various basins, are made 



up of the rocks of this series. It has been divided into two groups ; 



each differing very much in the character of its strata. The lowei' 



b ( 293 ) 



