GEOLOGY. 38 



the salt and gypsum lie buried below some five thick palaeozoic and 

 mesozoic groups (from the base of the nummulitic downward), forming 

 many hundreds of feet of rocky strata. Here in the Kohat district, 

 however, the salt and gypseous series is only separated by a band of red 

 clays, averaging about 250 feet, from the fossiliferous basal beds of 

 apparently the same nummulitic limestone as that of the Salt Range 

 series. No unconformity is observable in the sections here, nor is there 

 any established in those of the Salt Range above mentioned either. 



Further than this there is not alone presumable parallelism of posi- 

 tion from the Kohat nummulitic series downwards, but in tracing the 

 boundaries of the formations at least one thin band of salt was found, 

 separated by a thicker layer of dark bituminous gypsum from the mass 

 of the salt below. Again, the gypsum was found to alternate with 

 limestone beds or thin layers in some places, and even above the red 

 clay zone succeeding the mass of the gypsum, strong bands of the latter 

 were found locally interstratified with the basal portion of the nummu- 

 litic series. These alternations would appear to indicate a long period of 

 tranquil conformable deposition extending from that during which the 

 salt was formed up to the time of the nummulitic limestone, a period 

 in the course of which the conditions necessary to such alternations were 

 partially or locally recurrent. 



Throughout this lower part of the Trans-Indus series the evidence 

 of organic existence is scanty and uncertain. The fine gray clays asso- 

 ciated with the gypsum here and there contain small fragmentary 

 traces of grass-like plants, and a few obscure shell impressions occur in 

 some of the accompanying limestone layers close to the gypsum ; while 

 further up in certain bands of sandstone near the top of the overlying 

 red clay zone some broken fragments of bones have been detected, but 

 none of these afford any grounds on which to separate the saline lower 

 part of the series from the nummulitic rocks above. 



Dr. Verchere, while leaving the age of this salt undecided, seems 

 to have followed others in assuming that it formed a continuation of that 

 e ( 137 ) 



