CHAPTER V. 



LoWEfe Gondwana. 



Talchir Group, 



The leading characteristics of the rocks which constitute the Tal- 

 chir group, and the theories which have from time to time heen put for- 

 ward to account for their origin, have been previously fully discussed in 

 reports upon areas in which these rocks are very much more extensively 

 developed than they are in the vicinity of the Rajmehal hills. For this 

 reason I shall not attempt to give any general account of the series, 

 but shall confine this account to a simple description of the lithological 

 and stratigraphieal characters which the Talchir beds exhibit at the 

 few isolated localities in our area where they crop out from beneath 

 rocks of younger age. 



Proceeding from south to north along the western margin of the 



Talchir boulder bed : kills, tbe firHfc localit y at which Talchir rocks are 

 Bramini section. met w f th i s at t h e base of the section of sedi- 



mentary rocks exposed in the Brahmini river. The boulder bed which 

 occurs there is probably truly referable to the lower series (Talchirs), 

 though no distinct break between it and the superimposed rocks (Bara- 

 kars) is discernible. Owing to the gradual passage upwards between all 

 the rocks seen, I was at first disinclined to adopt this view ; however, on 

 a second visit, having in the interim examined the northern part of 

 the area, I have accepted it as the only probable explanation of the 

 occurrence of a set of beds whose characters are quite distinct from those 

 of any rocks ordinarily met with in the Barakar group. The bed in con- 

 tact with the gneiss is perfectly vertical, but as we proceed higher in 

 the sequence, the dip falls to 35° and then to 20,° and finally within only 

 a few hundred feet the sandstones are nearly horizontal. The high incli- 

 nation of the bottom beds appears to be rather due to crushing, pro- 



( 175 ) 



