2 LA TOUCHE : GEOLOGY OF WESTF.RN RAJPUTANA. 



already been noted further to the west in Jaisalmir, and it was 

 therefore thought that the coal measures of the lower Gondwanas 

 might be found in the intervening ground. After making a preliminary 

 examination of the country, Mr. Oldham suggested that boring? should 

 be put down in the area west of Bap, but subsequent investigation led 

 him to modify his opinion, as he found that there was strong evidence 

 that the boulder beds were unconformably overlaid by sandstones of 

 upper Gondwana age, and that in consequence the existence of the 

 coal measures in this area was purely a matter of speculation. 1 



So the matter remained until the year 1896, when 1 was sent to 

 survey the country to the south of the Jodhpur-Jaisalmir road, the 

 geology of which was till then only slightly known. So far as the 

 presence of the coal measures in that direction is concerned, I may say 

 at once that my investigations have been completely barren of results. 

 Not only are there no exposures of the Talchir boulder beds to the 

 south-west of Pokaran, but the country in that direction is so buried 

 in sand that no rock is visible until the old land surface of the volcanic 

 rocks in the Barmer desert is reached. All the rocks met with 

 during my three seasons' field work, with the exception of the Vindhyan 

 sandstones of Jodhpur and a few isolated exposures of sandstone of 

 upper Mesozoic age in the Barmer desert, belong to various crystalline 

 types. They include schists, quartzites and granitoid gneisses belong- 

 ing to the Aravalli system, ancient volcanic lavas and tuffs of extremely 

 acid composition, intrusive granites, and dykes of basic rock. 



As regards the rocks that may be concealed beneath the sand, little 

 or no information is available. Nothing can be learnt from well sec- 

 tions, for where the wells are sunk close to the hills, as is usually tl.e 

 case, the rocks pierced by them are naturally the same as those form- 

 ing the hills themselves, while those that have been sunk further out 

 in the plain either do not pierce the alluvium or are lined with cement or 

 otherwise protected to prevent the sides falling in, so that nothing can 



1 Rec. Gcol. Surv. Ind., Vol. XXI, Pt. 1, p. 30. 



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