86 



SMITH : GEOLOGY OF MIKIR HILLS IN ASSAM. 



Other localities. 



The coal can be traced for 50 yards to the south-west, where it 

 appears again, in a small nala, giving the same section, but quite 

 horizontal, which seems to be the normal condition of the beds 

 around. 



Grey shales are seen lying horizontally over most of the Lum- 

 ding plain. Thin bands of conglomerate occur 

 in it on the Dyung river, and concretionary slabs 

 of blue sandy limestone, 1 to 2 feet thick, are seen in it east of Lum- 

 ping. 



In the Katabaiong nala, on the northern flanks of Inlong Giri, 

 similar hard calcareous bands are frequently seen in the shales, which 

 are somewhat disturbed but usually horizontal. A shell bed is asso- 

 ciated with one of these bands, giving the following section in de- 

 scending order : — 



Ft. In. 

 Fine grey clay-shales . • 

 Shelly clay«limestone • 

 Grey clay-shales, without shells 

 Shelly-clay-limestone . . 

 Grey clay-shales, without shells 

 Hard blue limestone, without shells 

 Hard blue limestone, full of shells 

 Soft blue clay shales, full of shells 

 Fine grey clay-shales 



The broken bivalve shells seen in these bands give no further 

 evidence than that of a probable tertiary age. 



Round Lokpo and Dawk hard calcareous and arenaceous bands 

 are common in the fine grey shale, which is sometimes micaceous or 

 sandy. The hard bands vary from 6 inches to 2 and 3 feet in thick- 

 ness, and from grey limestone to very hard, yellow, micaceous, 

 calcareous sandstone in composition. The rocks are horizontal. 



The low hills covering most of the Dhansiri valley are composed 



of alluvial sands, gravels and clays; but in 



nearly all the larger nalas and in the Dhansiri 



itself the horizontal grey clay-shale appears. Up the Haria Jan, a 



( 86 ) 



Dhansiri valley. 



