56 WYNNE : GEOLOGY OF KUTCH. [PAET i. 



dykes seems hardly adequate to the result, has become as completely 

 and regularly columnar as any igneous rock might be ; the columns 

 having sometimes a length of some feet, but varying much in size. They 

 occur both vertical to the bedding, and inclined at various angles. Por- 

 tions of the Jurassic rocks not unfrequently are completely enveloped in 

 the trap, or perched as cappings upon its hills ; and in some places the 

 alteration is so intense that the aqueous beds appear to have passed by a 

 process of complete fusion into the trap ; while in others the trap and 

 sandstone are so intermingled that hand specimens may be found nearly 

 all trap on one side and sandstone on the othei', the passage being 

 indefinite as if the base (probably fel spathic) had been metamorphosed 

 first and the grains afterwards ; a few refractory quartz particles still 

 lying in the trap at some distance from the nearest portion of the 

 altered sandstone. 



The visible portion of the formation has been estimated to reach 



a thickness of 6,300 feet, of which 3,000 may be 



allowed for the upper portion; but it should be 



remembered that neither the base nor the uppermost limit of the group 



is visible. 



Infea-Teappean Geits. 



These form a peculiar, soft, loosely granular, and obscurely stratified 

 o-roup of earthy and sandy rocks largely composed of trappean materials, 

 which by weathering out give the stone a spongy aspect and assist in its 

 disinteo-ration. These beds rest uneonformably upon the Jurassic rocks, 

 and are freqiiently associated with the base of the stratified traps ; but 

 they also occur in separate patches over the country and sometimes at a 

 considerable distance from them. They are clearly beneath the trap 

 in some localities ; in others they fill up hollows in the Jurassic beds, 

 the planes of stratification not being conformable even to the surfaces 

 of the hollows which they occupy. 



( 56 ) 



