128 



WYNNE: GEOLOGY OF THE SALT RANGE IN THE, PUNJAB. 



Thickness. 



The following" is the estimated thickness of each 

 of the groups : — 



Siwalik sandstones and clays, grey, brown, and red zones 



Nahan zone 



Nummulitic limestone 



Salt-pseudomorph zone, variable 



Magnesian sandstone 



Black shaly zone (silurian) 



Purple sandstone group ... 



Red salt-marl with gypsum ... ,., 



Feet. . 



1,200 



800 



15 to 30 



80 to 20 



150 to 200 



100 to 180 



170 to 250 



50 and upwards. 



Nara glen. 



Immediately to the south-westward of the summit two deep ravines 

 Magnesian sandstone, ©xpose sections in the beds as low down as the pur- 

 pie sandstone, the magnesian sandstone forming a 

 narrow edge above a vertical precipice formed by this and the under- 

 lying rocks. The same group undulates over a large lobe of the moun- 

 tain, between some ravines and the more open glen north of Nara, edged 

 by precipices. At the base of these the salt-marl makes its appearance, 

 while from their crest the steep north-western 

 slopes of the mountain commence. The salt 

 marl here is, as usual, accompanied by gypsum and white calcareous bands 

 (probably magnesian limestone layers), which contain very perfect casts 

 of hopper-crystals of salt.* These are rather numerous close to the 

 Mount Tilla experimental shaft, sunk in this gypsum and marl to seek 



the salt which ought to occur beneath it. The site 

 Salt marl. 



chosen for this shaft or driving seems to coincide 



exactly with the run of a fault or extensive slip. Appearances outside 

 would lead to the expectation that the solid rock should be found much 

 within the length the driving has been carried to, instead of which the 

 ground it has passed through exhibits a most heterogeneous accumu- 

 lation of detrital fragments, of the local rocks. From this fact it 

 would seem that the line of division between a great subsided mass 



* First obsei-ved by Dr. Warth. 



( 1^8 ) 



