GEOLOGY OP THE UPPER PUJNJAB. 373 



stance that the mountainous ground adjacent was perhaps not sub- 

 merged beneath the water which deposited the post-Tertiary silt, 

 or the glaciers of the Kashmir, Kishengunga, and Nainsook valleys 

 may not have extended downwards, or been so large as those of the 

 Indus valley and its tributary from Kabul. 



Besides the erratics in the neighbourhood of the Indus there are 

 others, locally distributed, on the eastern part of the Salt Range, or 

 scattered over the country in that direction. They are mainly 

 composed of a red granite, the source of which is unknown ; and the 

 largest of these blocks now lying on the red salt-marl near the Mayo 

 salt-mines at Khewra, has been estimated from measurements taken 

 by Dr. Warth, to have a weight of about 9 tons. 



Prom the similarity of this granite to blocks contained in the 

 Cretaceous, or supposed Cretaceous, boulder-clays, both may have 

 come from the same source originally, in which case the ice-scratched 

 block found by Mr. Theobald possesses an important signification 

 with regard to glacial action having operated upon a former land 

 surface, the only traces of the existence of which here are the indi- 

 cations afforded by the foreign materials of the Salt-Range series 

 and neighbourhood. 



Recent. 



23. During and since the post-Tertiary period denudation has 

 been most actively at work forming the present features of the 

 ground. Since some of the post-Tertiary pebble-beds were deposited 

 the forces of denudation have lowered the hanging level of the Indus 

 2000 feet, and reduced the softer Tertiary ground to the lower 

 altitude of the Rawal-Pindi plateau. They have also cut out the 

 deep glens among the hills around, eaten this plateau into a laby- 

 rinth of vertical-sided ravines, strewed the whole southern face of 

 the Salt Range with great dislocated portions of its rock groups by 

 removing the soft marl or salt beneath, and they continue to supply 

 the bed of the Indus with the same hard Himalayan boulders which 

 found their way downwards by the same channel in later Tertiary 

 and post-Tertiary times. 



In doing this, however, denudation has not followed, but produced 

 the ridge-and-valley form of the ground. The principal rivers, as 

 well as many of the minor streams, intersect the ridges and ranges 

 in more or less directly transverse directions, showing that the 

 general elevation of the whole country towards the Himalayan axes 

 gave the initial direction to its drainage, the courses of which, being 

 fixed at an early post-Tertiary or even Tertiary period, denudation 

 has since revealed the forms which the stratigraphic structure of 

 the ground, influenced by elevation and disturbance, induced the 

 erosive agency to display. 



Over most of the country this agency, in Recent times, has been 

 destructively employed ; but in some spots construction of calcareous 

 tufa or deposition from rivers has been taking place, the largest 

 deposits of the latter kind being the alluvium of the Jhelum and of 



