32 LA TOUCHE: GEOLOGY OF WESTERN RAJRUTANA. 



of supposing that two exposures of such similar beds, separated by 

 so short a distance horizontally, should belong to such different 

 periods as pre and post-Vindhyan, makes it almost certain that the 

 boulder beds at Pokaran are faulted down against the Vindhyans. The 

 sandstones of the latter formation form a scarp rising above the low 

 ground in which the boulder beds are exposed, and the apparent 

 superposition of the sandstones on the Talchirs may be due to masses 

 of the sandstone having slipped bodily down the scarp. 



Mr. Oldham describes the boulder beds of Bap as consisting of 

 " a matrix of fine grained marl through which fragments of felsite, 

 syenite, limestone, gneiss and granite of all sizes from a few inches 

 to in one case over 10 feet across, are scattered; and many of these 

 are smoothed and striated in the peculiar manner characteristic of 

 glacier work." 1 These beds extend from Shekasar to Nokra, both 

 villages near the eastern boundary of Jaisalmir, a distance of about 

 35 miles. 



Another instance of a boulder bed of probably the same age may 

 be mentioned here, since it contains boulders of the Malani lavas and 

 granites, though it occurs far beyond the limits of the area now dealt 

 with. This is the well-known boulder bed of the Salt Range in the 

 Punjab, which has been shown to be of upper Palaeozoic age and to 

 rest unconformably and transgressively on all the older Palaeozoic 

 strata of the range. 2 Mr. Middlemiss has described microscopically 

 several specimens of the boulders from this bed, and though he cou'd 

 not specifically identify any of his specimens with the few examples of 

 Malani recks available, he notes the existence of a certain family 

 likeness between them. 3 These boulders were probably carried across 

 from what must have been the high glacier covered land of the Malani 

 area by floating ice. 



1 Loo. cit. 



2 Manual, Geology of India, 2nd Ed., p. 120. Rec. Geol. Surv. Ind, Vol-; 

 XXIV, Pt. 1, p. 22. 



» (bid, Vol. XXV, Pt, 1, p. 20,. 

 ( 3-' ) 



