G-EOLOOY OP THE UPPER PUNJAB. 353 



Cambrian and Silurian. 





6. Succeeding the more crystalline rocks are masses of contorted 

 azoic slates in the outer Himalayan regions, some of which are semi- 

 crystalline or metamorphic, and alternate with quartzites or trappoid 

 rocks on the Pir Panjal. These slates have not been found in a 

 highly metamorphosed state within the range of my observations ; 

 but silky slates and beds decomposed to a substance like porcelain 

 clay have been found in Hazara. Greenstone dykes and masses 

 were also met with. 



A portion of this slate series has been classed as Cambrian by 

 Mr. Lydekker, and another, less metamorphic, containing coaly 

 shales and limestones, as Silurian. 



I have provisionally referred the slates and limestones of Attock, 

 and the slates of ISTowshera and Hazara, to the Silurian period, for 

 the reason given in a footnote at p. 65 of my former paper*. 



Yery different from these is the older portion of the extra-Hima- 

 layan series of the Salt flange. Here a thin group of less than 

 200 feet of dark clunchy shales, in which I found numbers of little 

 Oboli (or Siphonotretas) of two species, represents the Silurian rocks. 

 Below these is a thick group of dull purple sandstones, without 

 fossils, the place of which is taken in some western parts of the 

 range by dark-coloured conglomeratic shale enclosing quantities of 

 crystalline boulders of kinds not recognizable among the Himalayan 

 detritus. The lower part of this " Purple-Sandstone " group becomes 

 earthy, and passes downwards into the great red gypseous marl and 

 salt-bearing group of the range, present almost everywhere along 

 its southern foot. The salt-marl has been estimated at more than 

 1000 feet in thickness ; and where the section is best known, the 

 upper 500 feet of it is occupied by massive alternations of rock-salt 

 beds overlain by thick beds of white gypsum, 250 feet of the salt- 

 beds (some of them in solid zones 200 feet in thickness) being almost 

 chemically pure saltf. 



A small lenticular deposit of potash salt (sylvine with kieserite :£) 

 was found some time ago in one of the more earthy saline layers by 

 Dr. Warth, Collector of Customs, in charge of the mines. It is 

 possible that other deposits of the kind may exist and yet remain 

 unknown ; for the ease with which the common salt is obtained in 

 so many places close to the surface seems always to have rendered 

 it unnecessary to explore the ground §. 



It would appear that there were at this Silurian or Cambro- 

 Silurian period seas depositing silts, sandstones, and limestones in 



* The discovery of Silurian fossils in detritus from the Khybur range &c. 

 Quart. Journ. Geol. Soc. vol. vii. p. 38. 



t None of this Salt-range salt has, so far as I know, been examined for the 

 rare metals. 



| See Kecords Geol. Surv. Ind. vol. vii. p. 64, 1 874. 



§ At least until Government had a shaft and drift made to seek for the 

 common salt beneath Mount Tilla, nearer to the railway than the present 

 mines at Khewra, and not carried to a conclusion, so far as I know. 



