48 MALLET: GEOLOGY OF DARJILING AND WESTERN DUARS. 



the junction is primarily a line of original contact, possibly modified by sub- 

 sequent faulting/'* — that the original limit of deposition of these rocks 

 was a steeply escarped coast line, against which the sands and mud were 

 banked. By subsequent tangential pressure the consolidated strata were 

 crushed up so as to present a pseudo-underlie towards the older forma- 

 tions ; whilst the steep original contact gives the junction the appearance 

 of being a faulted one. The direction of such an escarpment as the above, 

 in highly inclined strata, would generally be determined by the strike 

 of the bedding ; and in the Darjiling district, the persistent parallelism 

 of the Tertiary-Damuda and Damuda-Daling boundaries would seem 

 to indicate that such an escarpment may have been determined by the 

 outcrop of the upturned Damudas. 



The Tertiaries are wanting for some miles eastward of the Lehti 



„ , , ., ,. naddi : they occur again in the Ma-chu, but are 



Break in the conti- ' J ° ' 



unity of the Tertiary a ,g a i n absent for forty miles eastward of the 



fringe. 



Jaldoka. Their absence along this part of the lower 

 hills was first pointed out by Major Gowdin-Austen ; and, as observed 

 by Mr. Medlicott,t it is the only known instance of the kind from the 

 Indus to the Brama Khund. With respect to the question whether their 

 absence is due to denudation or to their never having been deposited 

 along this portion of the hills, I think the former is decidedly the more 

 probable explanation. The thickness of strata exposed in the Ghish 

 river is as great as anywhere to the west ; the group does not show any 

 sign, of diminishing thickness; yet three miles further east it has 

 entirely disappeared. The older formations do certainly stretch further 

 south here, owing mainly to a change of strike, and it is possible that 

 they originally ran still further south as a promontory in the Tertiary 

 basin of deposition. There is, however, no evidence that they did so; 

 and it is more difficult to explain the removal of such a promontory, than 

 it is to explain the removal of the softer Tertiary rocks on the alternative 

 supposition. 



* Vol. HI, pt. 2, p. 102. f Vol. IV, p. 436. 



( 48 ) 



