148 H. L. FAIRCHILD PLEISTOCENE GEOLOGY OF NEW YORK STATE * 



ously erode their beds. However, a few peculiar channels or "dead" 

 creeks have been noted which have such form and relations as to suggest 

 erosional flow beneath the stagnant margin of the ice. One of these 

 bayou-like channels is that of Dead Creek, a tributary of Seneca River, 

 lying southwest of Baldwinsville and mapped on the Baldwinsville sheet. 



Marginal drainage. — This class of drainage phenomena includes many 

 of the most conspicuous and interesting features connected with the dis- 

 appearance of the ice-sheet, and they have been the subject of much work 

 by the writer. The ice-border drainage channels are important, as they 

 locate ice-front positions and determine the altitude of the glacial lakes 

 which they drained. They are humanly or economically important, since 

 they have graded the ways for many lines of communication or trans- 

 portation. And they are specially valuable for geologic instruction, since 

 they are widely distributed and easily recognized products of long extinct 

 agencies. 



It is evident that stream-flow along the ice-margin could occur only 

 where the land surface sloped toward the ice, and consequently only 

 north of the divide. The remarkable physiography of the western half 

 of the State favored the production of glacial lakes, which required out- 

 let channels for the imprisoned waters. 



The most notable series of ice-border drainage channels occur in five 

 districts. (1) On the south slope of the Erie Basin, where the ice-im- 

 pounded waters in the north-sloping valleys escaped westward into the 

 Erian glacial lakes. (2) Along the south slope of the Ontario Basin 

 the glacial waters found eastward escape toward the Mohawk-Hudson 

 depression. (3) On the Helderberg scarp, west of Albany, the waters 

 of the Ontario and Mohawk basins escaped southward into the Hudson 

 marine inlet. (4) In the district about Rome, at the east end of the 

 Ontario Basin, the waters both from the north and the west flowed along 

 the sides of the ice-lobe to reach the Mohawk Valley. ( 5 ) On the north 

 and west sides of the Lowville highland the waters of the southwestern 

 Adirondacks and the Black Valley forced their passage into Lake Iro- 

 quois. 



The channels leading east through central New York, more conspicu- 

 ously developed in the Syracuse District, were the predecessors of Ni- 

 agara River in their function, the equal of Niagara in volume and the 

 rival of Niagara in cataract phenomena. 



The successor of the Iromohawk and the immediate predecessor of the 

 St. Lawrence was the outlet river of the second Lake Iroquois. This 

 flowed across the north point of the Adirondack highland, at Covey Gulf, 

 on the international boundary, with further flow in ice-border channels 



