PHYSICAL GEOLOGY. ]3 



depth of at least 3,000 feet, thus leaving a deep, though wide, upward 

 sloping V-shaped pass or gorge of about 2 miles in length through the 

 Eastern Ghats. 



The late Dr. Oldham long ago communicated the view that the great 

 Approximate age of drainage basins of India were on the large scale 

 nver valley. marked out and existed as drainage basins at the 



enormously distant period which marked the commencement of the depo- 

 sition of what we now call the Gondwana formation, and he considered 

 the Penner valley as one of these larger basins, though no traces now exist, 

 and perhaps never did, in its valley of any Gondwana strata. There are, 

 it is true, the patches of Rajmahal (Jurassic) shales occurring out on. the 

 plains towards the coast, to the north and south of the river, but these 

 do not necessarily bear on the age of its basin. I have, however, already 

 shown how the plains and ghat step of the Coromandel probably existed 

 in early mesozoic times, and this, taken in connection with the occurrence 

 of the plant-remains, seems to favour the view that the Penner valley was 

 then in existence also. This is, I think, all that can be safely said of the 

 age of the Penner valley in reference to Dr. Oldham's generalization, 

 though as regards the marking out of that valley in the Cuddapah dis- 

 trict and in the eastern portion of the Bellary district covered by the 

 same transition rocks, it is possible to conceive a much earlier time, fol- 

 lowing almost immediately on the elevation of these supposedly very 

 early palaeozoic rocks. 



The Penner has a narrow strip of alluvium along either bank as far 



back as the Somasilla pass or gorge, but the first 

 The delta of the Penner. . 



spreading out of its deltaic deposits occurs at San- 

 gam. There is, however, really very little of a fair delta at the mouth 

 of this river, for it does not sub-divide into two or more streams until 

 within about 10 miles of the seashore, a feature which seems to me to 

 indicate that the alluvial deposits must after all be greatly eroded, and 

 that we have here only a portion of the original delta. The Swarna- 

 mukhi and the Kaiidleru have nearly as large deposits of alluvium spread 

 out around their mouths, and they join with the Penner and the other 



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