GEOLOGY OF THE AREA. 21 



Sometimes the upper broad part of the valley is very broad 

 indeed ; and instead of one gorge, a number of channels of various 

 depths are cut in its floor. At last the original floor of the valley 

 is so much cut up as to leave only a number of low hills capped with 

 laterite, quite isolated from each other. The caps are the remains of 

 the laterite that once covered the bottom of the broad valley. In the 

 section from Pandalur Hill to Kurnad Hill (Section II, PI. VIII) one of 

 these broad valleys is shown . 1 he dotted line shows the original surface 

 of the valley, which is now cut up by numerous rivers and streams. 



In this region (gorge region) several high gneissic hills rise far 

 above the highest laterite. They have already been alluded to. 



The plain near the foot of the Ghats is to a great extent covered 

 with laterite ; but the covering is thin and incomplete. The valleys 

 are cut down into the gneiss and many low gneissic hills rise above 

 the level of the laterite. 



From the sections and descriptions just given, it is clear that the 

 laterite may be divided into three groups, viz. : — 



(i) Plateau laterite, 



(2) Terrace laterite, 



(3) Valley laterite, 



and as the plateau must be older than the valleys cut in it, it appears 

 that this is also the order of age. But the plateau near the coast being 

 newer than the higher part, some of the valleys may be older than 

 some parts of the plateau. 



As we have already seen (Fig. 2) that the terraces (including 

 the isolated hills of Section II) are the remains of the floors of old 

 river valleys, so is the terrace laterite an older valley laterite. 



The plateau laterite has been formed on a plain of marine 

 denudation, and the other two in river valleys. 



Plateau laterite. — This is almost always of the vesicular type. 

 Occasionally it includes angular quartz and gneiss masses, usually of 

 small size. They have already been mentioned as occurring at 

 Pandik£d, and they also occur on the high conical hill two miles south- 

 west of Cherpalcheri, and in many other places. Sometimes, as in the 



( 221 ) 



