l6S FOOTE: GEOLOGY OF THE BELLARY DISTRICT. 



Grom> W * ] I# The Venkata P ur W. dyke . Hospet area. 

 W. by S. I. The Kabingudda (Cubbingooda) 



dyke .... Kudligi area. 



Each of the abovenamed dykes forms in some part or parts of 



its course one or more important and conspi- 



the S dykes nd ^^ ^ CU0US h ' lU y M % eS 0r bosses > but als0 man > T 

 others of small size and length which are per- 

 fectly inconspicuous. Many of the larger dykes are by no means 

 continuous in their courses, but sink down at intervals below the 

 surface, and are hidden by superficial deposits for considerable dis- 

 tances, making it difficult to decide in some cases whether the 

 detached lengths should be regarded as extensions or as separate 

 dykes. Unless there was a striking identity in their petrological 

 characters, I have treated them as separate in cases where their 

 respective ends were more than 2 miles apart. In the majority 

 of cases great size and great length of the dykes go together, but 

 in some instances this is not so. A striking example of this is to 

 be seen in the dyke lying half way between the villages of Bantanhal 

 and Chippagiri, about 3 miles north-west by west of Guntakal Junc- 

 tion, where the dyke, which cannot be traced for more than a mile 

 in length, measures apparently some 200 yards, or more, across. 

 Another good though less striking example of this is the great dyke 

 crossing the Tungabhadra at Modalkutta. 



One of the most interesting of the many dykes mapped is the 

 Harappanahallidyke. Iar § e one crossing the crystalline rocks to the 

 north of Harappanahalli in a north-west to south- 

 east direction. The special interest attaching to this dyke, which is a 

 very large one, forming several hilly ridges along its course, which 

 measures close upon 8 miles, arises from the fact that it has cut through 

 the great brecciated quartz-run lying half way between Harappana- 

 halli and Bagali (Baugaly), and thus shows that it was itself irrupted 

 at a period subsequent to the formation of the quartz-run. It cuts not 

 only the quartz-run itself, but also a large cross- vein (of very blue quartz) 

 from the main run to a yet larger run half a mile to the southward of 

 it ; the intersection in this case is however much less distinctly seen. 

 ( 168 ) 



