52 LA TOUCHE : GEOLOGY OF WESTERN RAJPUTANA. 



than the rhyolites, and is usually very rotten in texture so that it is 

 difficult to procure a good hand-specimen. Owing to this difference 

 in weathering the rhyolites generally stand up on either side of the 

 dykes in the form of vertical walls, and the eye can easily follow the 

 course of the dykes along the hill side. 



About four miles to the south-west of Jasol is a very large mass 

 of hills, extending for about seven miles from east to west and rising at 

 its highest point to an altitude of 1,354 feet above the sea. The 

 village of Nagar is situated at the base of the range on the north 

 side, at about its centre. The whole of this range is composed of the 

 Malani rhyolites, in great variety, interbedded in places with breccias 

 and tuffs, and traversed by numerous dykes of dolerite. 



Towards the eastern end of the range the rhyolite is of the 

 common dark grey or reddish brown porphyritic variety, but towards 

 the western end, and in the detached ridge to the south-west, the 

 prevalent rock is a dark green highly porphyritic rhyolite with very 

 conspicuous flow-structure. Where the lava sheets are not horizontal 

 they are inclined to the south or south-west at various angles up to 

 about 30° Some brecciated beds occur on the crest of the range a 

 little to the south-east of the survey mark near its western end, 

 associated with tuffs. These beds are also exposed on a low pass close 

 to the western end of the range, where they are brought down by the 

 south-westerly dip. The most conspicuous is a band of light yellow 

 colour containing scattered angular fragments of a dark brown 

 rhyolite. A band of breccia beneath this is dark coloured, containing 

 in places large blocks of rhyolite up to a foot in diameter. These 

 breccias underlie the dark green porphyritic rhyolites at the western 

 end of the range. 



Breccias are also exposed at the base of the range, about a mile 

 east of Nagar. The matrix of these includes small fragments of rhyo- 

 lite as well as large blocks up to three feet in diameter. They appear 

 to have undergone some denudation before being covered up by the 

 ( 52 ) 



