32 MIDDLEMISS: PHYSICAL GEOLOGY OF SUB-HIMALAYA. 



towards older rocks is a normal one in the Sub-Himalayan zone, 

 as all students of Himalayan geology will be aware. Its production 

 has been accounted for in a variety of ways. Some observers see in it 

 an entirely inverted state of the rocks ; others would represent it 

 as the effect of a gigantic fault ; whilst others again throw doubt on the 

 fault theory, and regard the main boundary as an original limit of de- 

 position, complicated by crushing. It would be premature to discuss 

 the subject here, more especially as, in the process of describing the 

 country bit by bit, its full meaning will more clearly unfold itself. 

 Whatever be the nature of this boundary, it has always claimed an 

 important share of attention, as being the greatest master-feature of 

 the south face of the Himalaya ; inasmuch as it relentlessly divides in 

 a natural way the Sub- Himalayan from the Himalayan region. 



At the foot of the Nahan sandstone spurs the winding edge of the 

 dun marks the in-coming of the great chaors, or plateaux, forming 

 the Kotah dun. They are uniformly composed of slightly coherent 

 coarse gravel, or torrent-boulder beds, and sandy clays, which lap 

 round the eroded edges of the Nahan sandstone, just as the deposits 

 of the plains lap round the edges of the still younger rocks. There 

 is every reason for supposing the greater part of these beds to be 

 uppermost Siwalik in age, the section being a parallel one to that at 

 Simbuwala described in Mr. Medlicott's memoir (p. in). At first 

 sight, their level arrangement, as exhibited in some parts of the Dabka 

 and the Baur (Bhaol) 1 rivers, inclines one to the only other belief 

 tenable, namely, that they are still more recent gravels than the 

 Siwalik, which might be expected to be found overlying unconform- 

 able the real Siwalik conglomerates. This idea was the first to ob- 

 trude itself on my mind. Detailed work, however, showed me the 

 following excellent reasons for discarding it, and assimilating them 

 with the Siwaliks, even though that assimilation should bring the 

 top of the Upper Siwalik stage much higher in the scale than is com- 

 monly supposed, and within measurable distance of the Recent river 



1 Wherever names of villages and rivers differ, the first written in the text is the 

 more correct or more modern one, and is so marked on the 4-inch Forest Survey maps ; 

 the name in brackets is that marked on the older i-inch Trigonometrical Survey maps. 



( 90 ) 



