ARAVALLI SYSTEM. 13 



and the various calc-ferro-magnesian silicates (especially diopside) 

 are more strongly developed. It is helped out by the interleaved 

 white bands of aplite. The banding is frequently puckered after 

 the manner of contorted mica-schist. 



A particularly clear and interesting section in the railway 

 cutting, 1 mile south of Khed Brahma, is illustrated in PI. 1, 

 fig. 2. It is there seen that the streaky banding of the calc- 

 gneiss is exactly comparable, in the mode of arrangement of (he 

 minerals, to that of many forms of Archcean schists or gneisses : 

 that is to say, the layers are sometimes due to differently pro- 

 portioned amounts of one or more of the dark minerals among 

 the light minerals, or (within limits) to different degrees of coarse- 

 ness of grain, and lastly these layers may vary in thickness. Thus, 

 as in the hand-specimen from the locality referred to above, one may 

 detect a J inch layer of very pure calcite with just a few grains of 

 coccolite scattered through it. There may be others of closely packed 

 coccolite, and other subsidiary bands where biotite is prominent 

 forming | inch, very dark layers. Others again with pyrite, graphite 

 and so on. There is endless diversity in detail as we progress from 

 band to band, and the same is true when quartz and felspar play a 

 more Leading role. A similar diversity on a larger scale is also found 

 among more thickly bedded masses and between nearly related 

 outcrops of still wider dimensions. 



As regards the other Aravalli areas characterised by calc-gneiss, 



a brief reference is all that will be given here 

 Other calo-gneiss areas. . 



before proceeding to the penological de- 

 scriptions of characteristic varietal forms. In the neighbourhood 

 of Golwara, near the Sabarmati R., occur first some little 

 isolated hills of the calc-gneiss. These coalesce at Golwara into 

 a well-developed branching ridge which passes northwards, via 

 Chandap and Nawawas, into a set of low-lying and more straggling 

 groups which in turn veer to the N.X.E. towards Babsar and 

 Mhor. The alluvium of the flarnav and Sabarmati junction 

 hides their further continuation in this direction until in the 

 neighbourhood of Gadra they once more emerge, first in straggling 

 low ridges, and then coalescing into the fairly continuous exposures 

 in the country between Khed Brahma and Kherod. 



Over all these areas the general type of rock is very similar as 

 a whole, although diversified in detail— so uniform in fact that no 

 further subdivisions of the series can be made for mapping purposes, 







