LOWER TRANSITION ROCKS. 



125 



Manganiferous bed. 



Madras Survey map) and extend to the north of Tonashagiri village, 

 beyond which their course becomes quite obscure, probably because 

 they thin out. I could not trace their continuation round the Tona- 

 shagiri corner into the Appianhalli ridge. 



Above and overlying these two beds, which I will call the lower 

 Tonashagiri beds, another haematite bed crops 

 out, and where it is crossed by the path from 

 Tonashagiri to Kammataravu it contains numerous thin lenticular 

 concretions of a manganese ore similar to that seen on the ghat 

 west of Raman Drug Similar concretions occur in the same bed 

 about half a mile further westward, where it is crossed by the direct 

 path leading from Kammataravu to Somahalli. The concretions in 

 this upper Tonashagiri bed are not so black in colour as those seen 

 near Raman Drug, and are more earthy looking and therefore probably 

 poorer in quality. 



Owing to the great spread of lateritized detrital haematite 

 on the very level of the southern part of the plateau the stratigraphical 

 relations of the Tonashagiri and Raman Drug series of haematites 

 could not be determined in that quarter. As seen in the spur north- 

 west of the iron mine valley, the former certainly appears to be simply 

 a lower series which is widely overlapped by the upper one. 



The iron mine series of red argillites is underlaid by a series of 

 grey ones, which is crossed by the path leading from the mine to 

 Kannevihalli. 



About a mile below the Adar Gani mine the path, which has been 

 Manganiferous nodules running down the eastern side of the spur, crosses 

 in argilhte. a s iight saddle and passes along a bed of drab 



argillite, in which occur numerous large and small concretionary 

 nodules of a black manganese ore (see Chapter on Economic Geology). 

 The nodules are larger and of much deeper black colour than those 

 met with to the west of Raman Drug and constitute a richer ore 

 which from its situation could be very easily and cheaply mined. 

 The argillite bed has a dip of 40 N. E. 



Iron and manganese are the only metals that were met with by 



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