82 SMITH : GEOLOGY OF MIKIR HILLS IN ASSAM, 



section is seen of nummulitic limestone, overlaid by coarse sand- 

 stone, resting, with a gentle northerly dip, apparently on the gneiss. 

 Up the Langhit river also three isolated patches of these rocks occur, 

 at an elevation of quite 500 feet above the level of the same 

 rocks a few miles to the south ; a fact presumably due to the up- 

 heaval of the gneissic area. Two patches of coarse white sandstone, 

 over 100 feet in thickness, occur near Dambu. The rock is fels- 

 pathic and shews much false bedding. The true bedding is not 

 visible. A third small patcjj is entirely composed of nummulitic lime- 

 stone, a massive grey shelly band, about 60 feet thick, dipping a 

 few degrees southwards. This rests directly on the gneiss, and its 

 relation to the sandstone is doubtful. 



Above the Jamuna Falls a few feet of nummulitic limestone 

 are seen, dipping gently northwards, and overlying the white rock 

 and mottled trap. Similar limestone is seen again in the Langhit 

 gorge, about 100 feet thick, with a gentle dip south-west, and resting 

 apparently on the gneiss. On the Borojan the limestone appears to 

 be overlaid by white, coarse sandstone and quartzite, the whole 

 dipping 3 south. A spring of tepid water, with a slight smell of 

 sulphuretted hydrogen, rises on the Borojan limestone. In the hills 

 round Miji the nummulitic limestone seems to be interbedded with 

 white and iron-stained sandstone, with a dip of 20 S. in the Jamuna 

 river. The beds reach a development of several hundred feet here. 



In the Jirilangso nala nummulitic limestone is overlaid by fine- 

 grained, iron-stained sandstone, which again is conformably over- 

 laid by grey clay-shales. 



On the Haria Jan the lower tertiary rocks are well exposed. A 

 continuous section of fine, grey clay-shales is 



Haria Jan. , . . . .',,,. , , 



seen, and their junction with the limestone below 

 is plainly visible. Massively bedded, nummulitic limestone is seen to 

 be overlaid with perfect conformity by the grey clay-shales, the whole 

 having a dip of 20 S.E. Below this limestone comes a band 

 of massive, unfossiliferous, soft, brown sandstone, which again 



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