94 BLANFORD : GEOLOGY OF WESTERN SIND. 



If to the above, 150 feet be added for the thickness of the beds 



T t 1 thickness of Gai omitted at the top of the measured section, the 



g r( > u P- whole vertical development of the Gaj group in 



this locality will be 1,500 feet. This is, perhaps, rather over than 



under the truth, but the amount in excess must be very trifling. 



There are two points in this section deserving of notice. Although, 



wherever the Gaj beds are exposed on hill sides, 

 Prevalence of shales. . . . _ . . . . 



they appear to consist chiefly ot limestone, here, 



where all the beds are equally well seen, the greater portion is shown to 

 be composed of sandy clays and shales, the hard limestone beds, although 

 far more conspicuous, being only subordinate. It will be shown farther 

 on in Chapter VIII, that this is not the case in the Habb ' valley and the 

 country near Karachi. 



The second is the interesting circumstance that in the lowest 

 Estnarine fossils in G »j beds, as in the highest, there is some 

 lower Gaj heds. evidence of estuarine conditions, the mollusca 



found in the lower strata comprising Corbida trigonalis and Twrritella 

 angulata, two of the most typical fossils of the passage beds between Gaj 

 and Manchhar, This is quite in accordance with the resemblance between 

 Nari and Manchhar sandstones and the probably fluviatile origin of the 

 upper Nari beds. 



There is no marked break at the base of the Gaj beds, and, so far as can 

 Nari beds, Gaj river *>e 3 u(1 ged, n0 unconformity. The calcareous bands 

 section. disappear in the lower group, and so do the clays, 



but there are sandstones in both, quite undistinguishable from each other 

 mineralogically. The line of division has been drawn where the Gaj 

 marine fossils disappear. Below the Gaj beds, the characteristic thick 

 brown sandstones of the Nari group appear in force. The boundary 

 of the two groups north of the river is complicated by irregular dips, and 

 has been sketched in from the peaks near the Gaj, so it may not be 

 quite correct. In general, the hard limestones near the base of the Gaj 

 group can be traced with certainty for many miles, but near the river 

 a roll in the strata interferes with the regularity of the outcrop. 

 ( 94 ) 



