54 MIDDLEMISS: PHYSICAL GEOLOGY OF SUB-HIMALAYA. 



dip amounting to 40 . At the same time, the single great flexure, 

 into which the Upper and Middle Siwaliks are thrown, indicates earth 

 movements and subsequent denudation on a scale much above that of 

 the Kotah dun. 



The Nahan sandstones, on the other hand, lie in an elevated zone 

 by themselves, and are marked unmistakeably by their greater hard- 

 ness and jointed appearance, by their being folded into several flex- 

 ures w-ith resulting dips of 70 , 8o°, and 90° and by inversion at the 

 main boundary fault. They have thus a more ancient appearance 

 than the rocks of either of the other stages, and show signs of lateral 

 compression of greater intensity than has influenced the latter in the 

 same area. In this respect they bear the same relation to the Upper 

 and Middle Siwaliks that the Himalayan rocks bear to them. We see 

 also that this contrast is most probably due to the difference in the 

 lengths of time in which each formation has been subjected to moun- 

 tain-forming and indurating causes. 



It is essential to bear this in mind when considering the date of 

 the upheaval of the Himalaya as a whole ; for, so long as local sections 

 show these different amounts of compression in neighbouring zones 

 of different age, we shall not fall into the error of dating the whole 

 of the Himalayan disturbance from late Tertiary times, on the insuffi- 

 cient ground that in one locality the Siwalik conglomerate is verti- 

 cally inclined. 



A similar contrast to the above is of course very noticeable in the 

 Kotah dun ; but I forbore from pressing the point there, as the 

 Middle Siwaliks were invisible, and the only real conclusion to be 

 drawn would have been that the Nahan sandstone zone had been 

 much more disturbed than the uppermost Siwalik conglomerate. 



There seems no room for any doubt whatever, therefore, that the 

 disturbances which have affected the rock stages which have so far 

 come under our cognisance cannot be imputed to one or more 

 paroxysms acting in post-Siwalik times. It can with no truth be baldly 

 stated that the " Siwaliks have been involved in the last colossal 

 movements whereby the Himalayas have been upheaved." The 

 ( «ia ) 



