110 SUB-HIMALAYAN ROCKS OF N. W. INDIA. [CHAP. IV. 



through slow lateral compression, in such a section as that in Fig. 15, 



Fig. 15. 



Possible effects of compression in producing folded flexure and apparent reverse faulting, 

 which is very like that seen in the Markunda. The younger strata being 

 softer, and also probably less weighted, would yield most, thus inducing 

 the reversion of the line of contact. There can be no hesitation as to the 

 existence of the cause to which I have appealed ; for, the prodigious 

 contortions of the strata in these disturbed regions admit of no doubt 

 that boundless tangential forces have acted upon the earth's crust, one 

 vera causa for which forces we find in the more or less local depression 

 of that crust. 



The section at Tib is illustrative from another point of view, — it exhi- 

 bits the initial stage of dun formation. It is, in 



Dun formation. " . 



fact, the geological limit of the Kyarda and 



Dehra duns, these two forming but one geographical feature. A few 



score yards to the east of Tib the boundary retreats rapidly northwards, 



and at several places, as on the bank of the Markunda, near Kujurna, 



the slightly inclined conglomerates are found resting on the Nahun 



beds. At Simbuwala, a mile and a half to the 

 Section at Simbuwala. . 



east, the feature is more completely developed , 



here the Markunda runs along a miniature dun ; the conglomerate 

 beds of the contact-section in the lower Markunda continue steadily 

 along the same strike, and with about the same dip beyond the 

 deflection of the boundary near Tib, and from this point they form, 

 more or less continuously, the crest of the Sivalik range of hills. In 

 the ridge just south of Simbuwala, these thick clay and sand conglo- 

 merates dip at 40° to north 30° east; in the banks of the river, about 

 100 yards to the north, the dip is reduced to 20° and 1 5° ; and further 



