DETAILED DESCRIPTIONS OF ROCKS. ^^ 



The large hills at Chotan, which is situated just outside the south- 

 western corner of the map, are all composed of a similar granite, 

 traversed by numerous east and west dykes of basic rock. A few 

 masses of rhyolite are seen in contact with the granite of the hill 

 north-west of Chotan, and are apparently included in it. 



The isolated hill at Radhana, 27 miles west of Barmer, is also 

 composed of this coarse grained granite. Here it is broken through 

 by several broad dykes of a dark coloured eurite indistinguishable in 

 appearance from the rhyolites. 



The mode of occurrence of the Barmer sandstones at Barmer itself 

 has already been described. 1 A clear section showing the uncon- 

 formability between the sandstones and rhyolites is exposed in a 

 small hill at Lunu, about five miles north west of Barmer. Here the 

 sandstones dipping to the north-east at 26 are banked up against 

 and cover up an old ridge of the rhyolites, which runs from north to 

 south through the middle of the hill. The sandstones are also exposed 

 in several places on the plain to the north. At Bhadres they form a 

 low rise entirely covered with blown sand, but the sandstone is found 

 in wells. At Sondri and Bonthia they rise above the sand into low 

 scarped hills dipping in an easterly direction at low angles. 



1 Supra, p. 33. 



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