28 MALLET: COAL-FIELDS OF THE NAGA HILLS. 



In the Khasi region, too, the great mass of the distinctively nummulitic 

 strata is above the coal. Tn Upper Assam, on the contrary, there is a 

 closely transitional relation of the coal-measures with the great sandstones 

 of characteristic Sub-Himalayan type. Thus it would almost seem as 

 if this great coal formation may even be of middle tertiary age. 



Tipdm group. 



The junction of the coal-measures and Tipam beds, as seen in the 



Dihing and Disang, is fairly well defined. Some 

 Lithology. 



thick beds of sandstone of the Tipam type do 



occur amongst the lower strata near the top, but, in ascending the 



stream, a few yards above the last of the grey and brown shales with 



carbonaceous layers, &c., we come to thick-bedded sandstones in great 



force. These conform sensibly in dip and strike to the coal-measures, 



which they overlie at a high angle. 



Above the junction, fine sections are exposed in both rivers. Thick- 

 bedded and massive, frequently false -bedded, sandstones make up the 

 great bulk of the strata. They are rather soft, and graduate from a some- 

 what coarse to a fine-grained rock, and into earthy sandstone. The 

 usual colors are greyish-white speckled with black, speckled grey, and 

 yellowish. Under the lens, the constituents are generally found to be 

 quartz with some felspar, and dark specks like hornblende. Here and 

 there amongst the sandstones beds of clunch are interbanded, of various 

 colors — greenish-grey, green, purple and red, the last being often mottled 

 with yellowish white. The clunch beds are very subordinate to the 

 sandstones, although occasionally bands of some thickness are met with. 

 In the Disai and the (Janji) Tiru"^ the sandstones frequently pass into 

 grey sandy clays, which are sometimes mottled. 



Ferruginous bands are sometimes seen. South of Charaido and at 

 Dholbagan there are low hillocks covered with clay, through which, 



* There are two streams of this name ; one a tributary of the Janji, the other of the 

 Safffai. 



( 396 ) . 



