242 Report on the Geological Structure of the Salt Range. [No. 3. 



presents in the western part of the Range negatives the idea. It is 

 probable however, that it has undergone metamorphism from 

 igneous influence, the exact nature of which it is difficult to ascer- 

 tain. In no one locality in the Salt Range is there any evidence of 

 the existence of plutonic or volcanic rocks by which this metamor- 

 phism could be effected, or the great disturbance produced, which is 

 apparent every where. In addition to the brick red colour of the 

 marl, which at once associates itself with the aspect of a well-burnt 

 brick-kiln, the contained gypsum in many places and particularly on 

 its surface, is converted into a powder-like plaster of Paris, which 

 can only be prepared artificially by baking gypsum. This appearance 

 is most common towards the upper parts of the marl, on which at 

 Kewrah, Mukrach and Nurpur patches of a most singular choco- 

 late-coloured argillaceous rock of a somewhat trappian aspect occur, 

 just at the point where the marl passes by fissile argillaceous beds 

 into the red sandstone. It every where appears broken up into 

 small masses, which sometimes present a scoriaceous aspect, and in- 

 clude a curious radiated mineral not unlike some varieties of Tremo- 

 lite, nodules of green clay, and nests of talc. The patches of this rock 

 are quite superficial, and do not extend beyond twenty or thirty feet, 

 except in the gorge above the Kemah village, where it seems to form 

 a bed about L| feet thick, which may be traced on the West side of 

 the gorge for about 80 yards, when it thins out, passing apparently 

 into argillaceous sandstone, a metamorphosed portion of which it 

 appears to be. 



It effervesces slightly with muriatic acid, which dissolves a little 

 peroxide of iron, alumina and carbonate of lime with a trace of 

 magnesia. 



In addition to the above indications of the marl having been sub- 

 jected to a high temperature, we would add the fact that the fissile 

 sandstones resting on the marl are every where rent and shivered 

 into small fragments, which appearance gradually vanishes as we 

 leave the marl. The beds of chert and sinter before noticed as 

 occurring in it, could only have been deposited by thermal waters, 

 silica being only soluble in water (generally alkaline) at a high tem- 

 perature and under high pressure. 



