138 DR. E. H. PASCOE OX THE EARLY HISTORY [vol. lxxv, 



8. The Early History of tlte Indus, Brahmaputra, and Gaxges. 

 BvEdwlxHall Pascoe, M.A.,D.Sc, F.G.S., Superintendent, 

 Geological Survey of India. (Bead March 12th, 1919.) 



"Plate X— Map.] 



The ideas expressed in this paper are the outcome of a study 

 of the Punjab oil-belt. The principal hypothesis proposed has 

 been advanced simultaneously by Dr. H. G. E. Pilgrim, F.G.S., in 

 a paper still in manuscript, to explain the formation of the Siwalik 

 boulder-conglomerates. That paper will, I hope, soon be pub- 

 lished, 1 but 1 have taken the liberty of following up an interesting 

 point to which Dr. Pilgrim has drawn attention : namely, the 

 frequent V-shaped course of the north-bank tributaries of the 

 Ganges where they leave the belt of Siwalik deposits. 



Briefly, the hypotheses that I desire to bring forward may be 

 summarized as follows : — 



(i) That in Eocene times a gulf extended from Sind northwards as far as 

 Afghanistan, and thence curved eastwards and south-eastwards through 

 Kohat and the Punjab to the neighbourhood of Nairn Tal. 



(ii) That this gulf gave place to a great river, the head-waters of which 

 consisted of the portion of the Brahmaputra flowing through Assam. This 

 river flowed westwards and north-westwards along the foot of the Himalaya 

 as far as the North- West Punjab, where it turned southwards along a line 

 not very different from that of the modern Indus, and emptied itself into the 

 Arabian Sea. In other words, the Assam Brahmaputra was once the head- 

 waters of the Indus. 



(hi) That two separate rivers or two branches of the same river, debouching 

 into the Bay of Bengal, cut back and beheaded this old Indus, the eastern 

 capturing the Assam portion to form the Brahmaputra, and the western cap- 

 turing gradually piece by piece the portion that intervenes between Assam 

 and the present Jamna. 



(iv) That in the meantime this old river was being still further reduced by 

 the piecemeal capture of the portion lying between the Jamna and the Jhilam 

 by its own tributaries, the Jhilam. the Chinab, the Ravi, the Beas, the Sutlej, 

 and the Ghaggar. 



(v) That the Attock part of the present Indus was a tributary of this old 

 river, which at a comparatively early period cut its way back into Kashmir, 

 where it captured the upper waters of a large river that flowed north-west- 

 wards, and either found its way into the Oxus, or curved south-westwards into 

 Eastern Afghanistan. 



The second hypothesis seems to me to be adumbrated in the 

 second edition of the 'Manual of the Geology of India' 1893 

 (p. 141) by Mr. B. D. Oldham, who concludes that there are good 

 rounds for supposing that 



: the great bulk of the Himalayan drainage once found its way to the sea 

 by a single delta, instead of two, and this must have been either at the head of 

 the Arabian Sea, or of the Bay of Bengal.' 



He then goes on to say that 



• the indications of the sea having extended up the Indus valley within the 

 recent period, and the absence of any similar indications in the delta of the 



1 This paper has since been published in Journ. Asiat. Soc. Bengal, n. s. 

 vol. xv (1919) pp. 86-99. 



