LOWER TRANSITION ROCKS. 129 



In the centre of the trap area the trap rises into hills from 300 to 

 400 feet above the surrounding plain. 



The trap is generally a very dioritic rock of very black colour and 

 medium texture. Here and there it is coarse grained. A slight 

 tendency to prismatic (columnar) jointing is not uncommon, but the 

 columns are rarely more than a foot long and rather rude in shape. 



A narrow margin of the basement trap along the western side 

 of the area has been included in the fold of the Sandur synclinal, and 

 on the edge of this margin stands the village of Joga, which is one 

 of the most interesting centres for the study of the Dharwar rocks, 

 as is clear from a consideration of the three important sections in the 

 three ravines opening south of the village (see pages 101-106). 

 These do not exhaust the geological interest in the environs of Joga, for 

 within a few yards of it to the north runs one of the largest and most 

 important trap-dykes in the Bellary district forming two elevated 

 ridges crested with great piled-up masses of intensely black rock 

 which present quite dominant features in the Joga valley ; while imme- 

 diately north of the great dyke rises a considerable and important hill 

 mass which, for want of a local name, I will call the Joga hills. 



These hills consist of thick beds of schist and haematite quartzite 

 underlying the great trapflow, which may very conveniently be termed 

 the Joga flow from the important position it occuoies in the valley 

 and along the southern slopes of the Joga hilis. 



The section afforded by a traverse over the 

 Joga hills section. 



Joga hills from north to south is the following:— 

 12. Trap-flow, "Joga flow". 

 u. Schists. 



10. Haematite quartzite, very thick. 

 9. Trappoid. 

 8. Haematite quartzite. 

 7. Chloritic schist. 

 6. Hornblendic schists. 

 5. Chloritic schists, ferruginous. 

 4. Trappoid, very thick. 

 3. Haematite quartzite, poor. 

 . Hornblendic schist, thick. 



Haematite, rather earthy, very thick, dark colour 

 Gneiss. 



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