CORRELATION OF THE MIKIR ROCKS. 9* 



It is interesting to see how the younger tertiaries of the Mikir 

 hills correspond with the rocks of the Naga hills across the 

 Dhansiri valley. The fullest report, up to date, on these rocks will 

 be found in Mallett's Memoir 1 on the "Coal Fields of the Naga 

 Hills." 



I am inclined to think that Mallett, following the example of 

 Medlicott, assigns too great an age to beds of doubtful position in 

 these hills. Doubtful beds, especially coal-bearing ones, were fre- 

 quently classed as cretaceous. Now the nummulitic band is seen 

 to be continuously developed from far west of Cherra Poonjee, in an 

 easterly and northerly direction, for 250 miles, as far as the Haria 

 Jan in the Mikir hills. In the North Cachar hills, it underlies some 

 thousands of feet of shales and sandstones. It is highly probable, 

 then, that it occupies a similar position in the Naga hills, which 

 seem to be a direct continuationi stratigraphically as well as 

 orographically, of the North Cachar hills. If this be so, the great 

 thickness of shales and sandstones of the Naga hills, overlying a 

 presumable nummulitic band, would be entirely post-eocene. 



These Naga hill rocks, described by Mallett under the names 

 of Disang, Coal-measures, Tipam and Dihing groups, corre- 

 spond very fairly closely with the post-eocene rocks of the Mikir 

 hills. 



The shale-series of the Mikir hills, probably oligocene and 

 miocene, seems to represent Mallett's ' Disang ' and ' Coal-measure ' 

 groups. 



The Disang grey-shales, with some sandstone, and nodules of 

 calcareous sandstone towards the base, corresponds with the 

 Haria Jan section. The ' Coal-measures ' of alternating shales, 

 sandstone and coal represent the upper beds of the Mikir shale 

 series, passing into the sandstone series, and containing a few 

 bands of coal. The massive ' Tipam ' false-bedded sandstone seems 



I Mem. Geol. Sur. f Ind., Vol. XII, Pt. 2, pp. 17—35. 



( 91 ) 



