INFRA-TllAPPEAN ROCKS. 16'9 



been but little weathered since its deposition on this spot, and was, there- 

 fore, probably only liberated from the matrix at a comparatively recent 

 period, and from a matrix of much softer character than that of the 

 enclosed pebbles. 



Of similar pre-trappean origin is perhaps another patch of quartzite 



.. ,, , , and jasper gravel met with at Idubhavi (Idoo- 



At Idubhavi. ^ ^ 



bhawi), eleven miles north-north-east of Ling Sugur^ 

 at an elevation of about 200 feet above the present bed of the Krishna;, 

 an elevation the flood waters of the river cannot be supposed ever to. 

 have attained. The jasper pebbles are to all appearance of gneissic- 

 origin. 



Some other cases of shingle deposits of doubtful age, but which 

 may possibly have been of pre-trappean origin, will be mentioned ia 

 Chapter X» 



Thin beds of sandy marl, semi-compact sandstone,, and rather soft 

 sandstones were found in many places along the boundary af the trap- 

 flows ; but nowhere exposed over more than a few dozen yards, and rarely 

 so much, beyond the edge of the trap. In almost all cases they are 

 much reddened near the point of contact with the trap,, by the presence 

 of quantities of bright-red bole. 



The most extensive exposure of these infra-trappean beds is near 



the village of Sigihalli (SeegeehuUee), about ten 

 Sigihalli section. 



miles east-south-east of Belgaum. The sand- 

 stones are here seen in very thin courses^ — in soft sandy marl resting on 

 hornblendic schistose gneiss. The thickness af these infra-trappean beds 

 may here amount to 8 or 10 feet at the utmost.. No fossils were found in 

 any case. The presence of bole in so many of the pre-trappean deposits 



Occurrence of bole in appears to be due to the heating action of the 



contact with the trap. i. a j iiipni mi 



trap-flows, poured on to beds oi fine clay. The 



quantity of the bole is always largest close to the trap, where it occurs 



X ( 169 ) 



