20 LA TOUCHE : GEOLOGY OF WESTERN RAJPUTANA. 



lavas are bent up into an anticlinal, the axis of which runs north and 

 south, and the flows rise iD steep scarps on either side of the valley 

 On the west side, at the base of the scarp, a band of conglomerate 

 some 20 feet thick is interposed between the lavas and the slates, 

 resting on the upturned edges of the latter. The boulders and 

 pebbles in this are frequently well rolled and consist of quartzose 

 grit, quartz, schist and slate, evidently derived from the underlying 

 slaty series. The strike of the slates is fairly steady, from north-east 

 to south-west, the lavas and associated beds passing transgressively 

 across their edges, and the evidence of unconformability is very com- 

 plete. On the east side of the valley the slates appear to dip beneath 

 the lavas and the conglomerate is not visible, but the ground is covered 

 with talus and thorny scrub. The angle of dip of the two series of 

 rocks is however quite different, and at the north end of the valley on 

 this side the lavas are again found resting directly upon the upturned 

 edges of the slates. I found several exposures of micaceous schist 

 with exactly the same strike as these slates, in the plain to the east of 

 this section, and J have no doubt that the slates do belong to the Ara- 

 valli series. 



At one or two places to the north of this, viz., on the western edge 

 of the group of hills at Khairla, a station on the Jodhpur railway to 

 the north-west of Pali, and again at Rajpura on the left bank of the 

 Luni, about half way between Khairla and Jodhpur, nearly vertical 

 slates are seen within a few hundred yards of outcrops of the Malanis, 

 and in these instances the lava sheets are quite unconformable both in 

 dip and strike to the older rocks. Mr. Hacket says that the schists 

 at Khairla are " undoubted Arvali rocks." 



The lavas of the Malani series are for the most part rhyolites of a 

 highly acid type, varying greatly both in colour and texture. The 

 most common variety is of a rich brown colour tinged with red or pur- 

 ple, with a stony texture and studded with porphyritic crystals of pink 

 or flesh coloured felspar and minute blebs of quartz. Other colours, such 



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