OLDER TERTIARY — NUMMULITIC. Si 



Older Tertiary — nummuliiic. 



A fairly strong band of nummulitic strata occurs constantly at the 

 base of the tertiary rocks. It consists of highly nummuliferous* 

 earthy limestones, generally nodular in appearance, associated with 

 siliceous, unfossiliferous sandstones and grit. 



The section varies very considerably both in thickness and com- 

 position. Some of the upper sandstones are of doubtful age, and 

 may be post-eocene. But as they always occur closely associated 

 with the limestone, probability and convenience unite in grouping 

 them with the nummulitics. 



I have never met with any trace of eocene coal either in the 

 limestone or sandstone. 



The isolated band of nummulitic limestone on Longloi hill has 

 been already referred to. No other exposure 



South Mikir hills. . ..,:■., , . , . „f lf 



is to be found connected with it. From Silbatta 

 nummulitic rocks can be traced southwards, down the Meyongdisa 

 river, as far as the Dogaon hill, 3 miles east of Longloi. No rocks of 

 eocene age are seen south of this, until they reappear near the Kopili 

 Hot-springs, in the North Cachar hills. At the Jamuna Falls 

 nodular, earthy, nummulitic limestone is seen, somewhat massively 

 bedded, with a gentle dip 7 N.W. The hills immediately to the 

 south are composed of similar limestone, but rather more compact. 

 The total thickness is about 200 feet. 



A fair section is seen in the nala running from Megik into 

 the Meyongdisa. Hard, nummulitic limestone is overlaid by coarse 

 Purple sandstone, interbedded with hard, white, quartzitic sandstone 

 with a general dip 3 N.W. On the Dogaon hill massive, coarse, white 

 sandstone overlies • the nummulitic limestone. On the southern 

 face of the hill, both are seen dipping 30 to 40 S.VV. 



From Silbatta the nummulitic band can be traced cotinu- 

 M , . ously north-eastwards, alongr the eastern flanks 



North Mikir hills. J . 



of the north Mikir hills, to the Boro Neoria. 

 Two outlying exposures also occur. On the Disobai nala a broken 

 s . ( 81 ) 



