j6 LA TOUCHE : GEOLOGY OF WESTERN RAJPUTANA. 



pink felspar and grains of quartz. Flow- structure is frequently met 

 with among them, and some of the flows are spliaerulitic. A reJdish 

 brown, more strongly porphyritic rhyolite is found in places, especially 

 in the neighbourhood of Barmer itself. 



There do not appear to be any beds of tuff intercalated with the 

 lava flows, and it is generally impossible to make out any regular 

 bedding among them. They seem to have been erupted from a net- 

 work of fissures and to have been heaped together without any delinite 

 arrangement. No trace of anything like a vent is ..to be seen any- 

 where. Near the village of Jesai, about ten miles west of Barmer, a 

 thick bed of conglomerate, consisting of well rolled pebbles of the 

 rhyolites imbedded in an ashy matrix, is interstratified with the flows. 

 The bedding of this is inclined to the west-south-west at an angle 



of 30°. 



The western portion of the large hill at Jesai, rising to an altitude of 

 2,073 feet above the sea, consists of a rather coarse hornblendic granite 

 without mica, similar to the granite of Siwana. The relations of this 

 granite to the rhyolites are not so clear as they are in the Siwana 

 country, for no sections were found in which the granite could be seen 

 to throw off veins into the rhyolites, while on the other hand the latter 

 in a few places appeared to be intrusive in the granite. I have already 

 pointed out * that the granite of this area was probably intruded into 

 the lavas before the period of volcanic activity came to an end, and 

 thus it came to be pierced by dykes of the rhyolites. 



The same granite occurs again in the hill west of Taratra, ten 

 miles south of Jesai, and clear sections of the junction with the rhyo- 

 lites are exposed at the head of a ravine just west of the village. 

 Here the granite is distinctly intrusive, sending off veins and tongues 

 into the rhyolites ; it also includes masses of the latter. The western 

 portion of the hill is composed of rhyolite dipping away from the 

 granite towards the north-west. ' 



1 Supra, p. 24. 

 ( 76 ) 



