180 foote: geology of the bellary district. 



CHAPTER VIII, 

 Alluvial Deposits. 

 The alluvia formed by [the principal rivers draining the Bellary 

 District are of limited proportions when compared with the size of 

 the rivers themselves, a fact that must be attributed to the rapid 

 fall of the river beds in most parts. The alluvia are not shown to 

 any extent on the map accompanying this memoir, for in many places 

 they are so much mixed up with protruding masses of the more im- 

 portant Archaean and Transition rocks, that it would be impossible 

 to show both clearly except on a much larger- scaled map ; and in 

 many other places the alluvia are so much covered up by subaerial 

 deposits that it is impossible to trace their boundaries. 



Except in the case of the Tungabhadra the alluvia do not attain 



to any notable thickness. In this case, however, 

 High-level shingle t 



beds. there is abundant evidence that the river at 



At Makrabbi. . . , 



some not very remote period occupied a very 



much larger channel than its present one. The evidence of this con- 

 sists in the existence at many places along its banks of well-marked 

 and important beds of coarse but well-rolled shingle consisting chiefly 

 of quartz pebbles, and showing generally a pale cinnamon-brown 

 colour from the predominance of the quartz pebbles. Gneissic and 

 granitic pebbles come next in quantity, while quartzite and jasper 

 pebbles are less common. Trap pebbles are rather rare. The 

 greatest development of these high-level shingle beds is met with 

 along the right bank of the river between the Mysore boundary 

 north of Harihar (Harryhur) and the barrier formed at the northern 

 end of the Sandur Hills. The shingle beds attain their greatest 

 height over the present bed of the river at Makrabbi in Haddagulli 

 taluq, where they form a regular plateau several hundred acres in 

 extent and of conspicuously reddish colour. The surface of the 

 plateau at Makrabbi village must be close upon 100 feet if not more 

 above the general level of the Tungabhadra in the reach immediately 

 to the north. Higher up the river much high-level shingle of the 

 ( 180 ) 



