GLACIAL WATERS IN BLACK AND MOHAWK VALLEYS 2)7 



'from morainal drift and lake deposits. Later study makes that 

 conclusion seem improbable. 



The lacustrine plains and terraces in the upper Mohawk and 

 north of Rome are now found to correlate with the glacial lakes 

 held in the whole extent of the Mohawk valley by the Hudsonian ice 

 lobe. While the ice lay over Rome there was drainage past its 

 northern edge at as low elevation as 500 feet; and as early in the 

 glacial lake history of central New York as the close of Lake 

 Vanuxem (see title 19, page 57 and plates 37, 38) there was free 

 eastward flow through Syracuse as low as 400 feet, present altitude. 

 The low altitude of the Syracuse passes as compared with the Rome 

 col, 430 feet, seems partly due to the northerly position of Rome, 

 some 12 miles, which gives at least 25 feet of relative uplift for the 

 Rome parallel. 



In plates 15 and 16 of this paper we make the low Syracuse drain- 

 •age correlate with Lakes Amsterdam and Albany. It could not 

 have been earlier than this stage, unless in some deglaciation interval 

 as yet unrecognized. It does not seem probable that it was later, 

 because lying in time between this and Iroquois time in central New 

 York is the readvance of the ice at Syracuse and the considerable 

 period of Lake Warren and the Hyper-Iroquois waters. We must 

 not assume too great difference between the waning of the ice 

 fronts in the Syracuse and the Albany districts. 



It does not seem possible that any considerable lowering of the 

 hard rock barrier at Little Falls could have been accompHshed by 

 the moderate flow during merely the closing phase of the Amsterdam 

 lake. But this seems imperative if we attribute all the cutting to 

 that one episode of lowering waters ; for when the outflow on the 

 Rotterdam salient was under 600 feet the Little Falls pass was 

 under Amsterdam lake water, and at what now appears to have been 

 the end of the Amsterdam stage the pass was as low as it is now. 



It is believed that the glacial phenomena in New York are not the 

 work of a single ice invasion but the product of two or more 

 invasions. This being conceded it follows almost certainly that the 

 production of glacial lakes must have been repeated, and the prob- 

 able outflow have been similar to the latest. In this view the large 

 drainage channels were not wholly cut by the latest rivers. In 

 accordance with the above it seems altogether probable that the rock 

 barrier at Little Falls was chiefly or entirely cut by Prewisconsin 

 drainage, and that the Glaciomohawk and Iromohawk^ rivers had 



1 These names for the glacial river were given in 1904. See title 17, 

 p. 38. 



