208 



PROP. P. M. DUNCAN ON THE 



There is another argument which has not hitherto been employed 

 and which favours this theory. 



The Sivalik strata rest on, or are in contact with (along a line of 

 fault), certain plant-bearing strata of the Sirmur series which are 

 associated with the underlying Nummulite-bearing Eocene rocks of 

 Subathu. 



The nature of the flora, so far as it has been examined, is not 

 very foreign to that of India at the present time ; and by the same 

 kind of reasoning which asserts the separation of other terrestrial 

 and underlying marine strata, these beds, called Kasaoli and Dugr'hai, 

 may well be the remains of the Miocene land. 



Whence were the vast thicknesses of the sands, clays, and con- 

 glomerates of the Manchhar-Sivaliks derived? They represent a 

 ruined mountain-chain in bulk ; and they are found not only on the 

 flanks of, but also within, the orographical systems of which they 

 form parts. 



It appears from the study of the history of the Himalayas by 

 Strachey, Stoliczka, Medlicott, and those Indian Geological Sur- 

 veyors who have laboured so industriously of late years, that a low 

 mountain- chain existed on the area after the jSTummulitic age — the 

 results of a post-JSTummulitic earth-movement. It was probably 

 a broad chain, and not a suflicient barrier to prevent the roaming of 

 the animals on and over it in the subsequent geological age. This 

 chain appears to have had an axis of old rocks; and the whole 

 suffered denudation during the age of the Sivalik Mammalia. In 

 Hundes Strachey found the great tableland (now at an altitude of 

 from 14,000 to 16,000 feet) to consist of sediments filling up a basin 

 in old rocks to the depth of 3000 feet — sediments which included 

 osseous remains of animals that could not have traversed high and 

 difficult mountain-ground. 



Part of the Sivalik sediments were formed out of low mountain- 

 ground by fluviatile denudation; but to account for the vast deve- 

 lopment of the rest on the flanks of the present mountain- system, it 

 is necessary to admit that the upheaval, and much of the north- and- 

 south crush of the Himalayas, occurred pari passu with the slow 

 accumulation. Elevation and diminution of the breadth of the area 

 progressed ; and doubtless much of the great crush which folded and 

 often reversed the flanking strata was final. 



The Sivalik strata rest on the flanks of the chain and on old rocks 

 within the range ; and they were the youngest deposits affected by 

 the mountain-making. Hence the Himalayas, as a grand system, 

 culminated during and subsequently to the collection of these strata, 

 which have been pronounced to be Pliocene in age. 



The Sivalik deposits in the tableland of Hundes are overlain by 

 relics of the great glacialization of the Himalayas. Hence, before 

 the vast glaciers of the glacial period accumulated, valleys had been 

 worn out and denudation had proceeded. So it is necessary to 

 recognize that the culmination of the movements which developed 

 the height of the Himalayas occurred in preglacial times and 

 during the Pliocene age. 



