2.4 FOOTE : GEOLOGY OF MADURA AND TINNEVELLY DISTRICTS. 



the great tank east of the villag-e. It is fully 20 feet thick, but exposed 

 only for a few yards distance in the bank of the channel. The lime- 

 stone occurs intercalated with dark green hornblendic beds which 

 contain numerous laminae of pink calcspar. From its course (north- 

 west-by-north to south-east-by-south) and its easterly dip this bed would 

 appear to belong to the same series as the Pantalagudi beds. To 

 the same series belongs also, to all appearance, the coarse reddish 

 semi-granitoid gneiss seen at and north of Nagalapuram (Naugala- 

 poorara). 



The most southerly outcrops in the gneissic area east of the Vaippar 

 are a black hornblendo-micaceous gneiss at Kodangeputty and a show of 



Bommayapurara gra- gvanular quartz rock at Bommayapuram which is 



quai z IOC . exposed only in the roadside ballast pits. Some 



connection will probably be traced eventually between this and the 



broad belt of granular quartz rock which rises out of the great cotton soil 



plain to the north of Ettiapooram (Etteyaupoorum) and forms the 



Kovilpatti granular Minachipuram and Lyungumpatti hills which joia 

 quai z an . ^^^^ Kovilpatti ridge. This ridge trends south for 



several miles parallel with the railway, and then strikes south-eastward 

 for fully 12 miles, when it again turns south, but after a course of some 

 3^ miles further again trends south-east and appears to curve round and 

 form the southern end of an elliptical synclinal basin, the eastern limb 

 of which runs northward through the taluq-town of Ottapiddaram and 

 disappears some 4 miles further on under a great spread of regur. 

 Several ridges of granular quartz rock are to be seen at some distance 

 to the west of the railway between Kovilpatti station and the INIauiachi 

 junction, while two or three small granite gneiss hills rising out of the 

 cotton soil plain to the north of Kaddambur station show the granular 

 quartz rock to be here also interstratified with granite gneiss. 



The relations of several detached and isolated outcrops of granular 



Outcrors of granular ^"'^^'^^ ^'^^^^^ Occurring south of the Ottapidaram- 

 qnartz ro<k south of Kovilpatti band such as that lyino- west of Kil- 



Ottapidduraui. ... . 



Mauiachi village (about a mile south-west of the 

 ( 21' ) 



