I 



34 mallet: coal-fields of the nIga hills. 



in the other j to faulting* ; or to inversion in the Makum field (the Jaipur 

 beds being clearly in their normal order) : and judging from the evidence 

 then available, he was inclined to the last view. The much more detailed 

 examination I have had the opportunity of making of the various coal- 

 fields has led me to a different conclusion. At Jaipur the coal-measures 

 are so obscured that little is visible save the coal-seam itself (p. 49) 

 with a few beds of shale, and the over-lying Sub-Himalayan sandstones, the 

 measures being those at the very top of the group. The Tirap coal I 

 believe to belong to a lower part of the group, the sandstone overlying it 

 being a portion of the measures themselves, and lying in normal (non- 

 inverted) position. I have not found any trace of the synclinal structure, 

 implied in the supposition of inversion, along the inner zone of coal- 

 measures, nor will the facts now known allow of this interpretation. 



There is some direct evidence of great faulting along this inner 

 zone. In the Saffrai, for a mile or so below the junction between 

 the Sub-Himalayan and coal rocks, conglomeritic sandstones containing 

 rolled pieces of coal, &c., are visible at intervals, with a rather steady 

 dip a little south of east at about 15°. Then, as we ascend the stream, 

 we come suddenly on the coal rocks with an average dip of 60° or 70°. 

 At the head waters of the Tiru, again, the Tipam strata at the junction, 

 which is clearly defined, dip at a markedly lower angle than the coal mea- 

 sures, or 20° to 25°, while the latter are inclined at 70° or 80°. In the 

 Dikhu the actual junction is not seen, but in the Sanga jan and the Janji, 

 except near the junction of the two streams where there is a small develop- 

 ment of coal rocks, the Tipam and Disang groups are again in contact. 



To the south of the coal-measures in the Dikhu Valley, we find (as 

 noticed above) the Tipam beds again. The river here flows through a narrow 

 rocky gorge in which they are finely seen, consisting of rather hard and 

 sometimes coarse sandstone very thickly bedded, and showing false bed- 

 ding in places. Many of the strata are over 20 feet thick. Towards the 

 base there is some shale with thin carbonaceous layers interbanded. The 

 bold way in which these rocks weather led me at first to question their 

 ( 302 ) 



