48 ball: geology of aurunga and hutar coal fields. 



much more marked unconformity between the Mahadevas and the 

 underlying Panchets than there is between the other groups respect- 

 ively. 



The absence_, in the eastern fields^ of clearly marked unconformable 

 Scarcity of coUateral Junctions showing disturbance is no doubt a diffi- 

 evidence of disturbance. eulty in Connection with this theory^ as some evi- 

 dence of the kind might reasonably be expected ; but if it be remembered 

 that the disturbance need not have been very marked along the central 

 axis of the subsided rocks*^ and that the scour of the supposed river could 

 not be very great, as the average gradient throughout the 240 miles can 

 scarcely have exceeded three feet per mile", the difficulty is considerably 

 lessened. 



Moreover, it may be that the absence of the normal sequence of beds 

 between the Barakars and Mahadevas in the west 



Possible denudation • 



of groups to west of may really be due to denudation. Thus to the west 



of Latiahar in the Aurunga field, and in the Hutar 

 and Tatapani fields, the Mahadevas rest directly on the Barakars with- 

 out the intervention of representatives of the groups found to the 

 east. 



The maximum thickness of these beds is probably not less than 800 

 feet, and may be nearer to 1,000. In the detailed 

 accounts below I give measurements. With Mr. 

 Hughes' estimate of the thickness of these rocks in the Karanpura field 

 I cannot agree. " Three or, perhaps, two hundred feet,''' he writes, " would 

 probably be its maximum development/' But in some of the scarps 

 wholly formed of these rocks in the Karanpura field, a thickness of 500 

 feet is frequently exposed, and in the Maudih hill the total thickness 

 must be several hundred feet more. 



^ On the margins of tbe fields in those cases where there are no main bounding faults, 

 there are often evidences in the tilted beds of great lateral crushing and pressiu-e. 



'' The Balumath watershed (■yj^^e p. 13) was very possibly formed after the deposition 

 of the Mahadevas. If it existed before, the beds in the Karanpura and Aurunga fields, 

 although the scarps are so similar, could not have been continuous. 



( 48 ) 



