DESCRIPTIVE GEOLOGY: GENERAL CONSIDERATIONS. 267 



that at least several thousand feet of Murree sandstones were 

 once superposed on them, and forces the natural conclusion that at 

 or about the beginning of the Murree stage, at a time when little 

 more than the purple and gypsiferous Kuldana beds had been spread 

 over what is now the Nummulitic zone, the latter was gradually 

 upheaved, and a limit of deposition formed for the succeeding thick 

 beds of the Murree sandstones. At the same time the preliminary 

 phase of the main-boundary fault began. As the Nummulitic zone 

 grew in height, the undulating strata wrapped the Kuldana beds 

 in synclinal folds and the boundary fault became more marked as a 

 line of differential earth movement, on one side of which the undulating 

 Nummulitics were forced southwards and upwards, and on the other 

 side of which the accumulating Murree sandstones were forced 

 northwards and downwards. 



How long a time, geologically speaking, a boundary fault such 

 as this took to form, cannot be very accurately gauged, but that it 

 began in early Murree times, and practically ended when the younger 

 Siwalik sand-rock and conglomerates were depositing, seems a 

 safe conclusion. Apart from the special case here considered, I take 

 it for granted that a fault of this description cannot be of a paroxys- 

 mal kind; it has nothing in common with a normal fault ; it bears no 

 relation whatever to a rock-fissure or crack that we might conceive 

 of as having been formed by a sudden snapping or rupturing of the 

 rocks. It seems to me a weak point in geological nomenclature that 

 such lines of relative earth-movement were ever classed with faults 

 at all ; but that they have been makes it all the more necessary to 

 scrupulously define them. 



Turning our attention now to the next boundary fault to the north- 



„ , . west, namely, that between the Nummulitic 



Boundary fault be- J 



tween the Nummulitic and the Slate zones, we find, from the presence 

 and Slate zones. f _- ... .. . .- ,, f ., 



of Nummulitic limestone to the north of it as 



outliers in the Slate zone, that that fault cannot be regarded as a limit 



of deposition for the Nummulitic limestone. On the other hand, 



from the absence of Kuldana beds north of the fault, it seems pro- 



( 267 ) 



