THE INTERGLACIAL GORGE PROBLEM I 39 



origin, and this explanation seems, at present, the most probable; 

 but all that can now be said with certainty is that they antedate 

 the last advance of the ice. The question of these gorges has a 

 very important bearing upon the whole subject of the drainage 

 history of central and western New York. Were the gorges due 

 to interglacial conditions or to an uplift of preglacial times ? 

 Leverett refers to similar gorges in his monograph^ on TJie Gla- 

 cial Formations and Drainage Features of the Erie and Ohio Basins. 

 The valleys of this hilly country present marked differences in topography. 

 In some valleys the slopes from top to bottom have a mature aspect, while in 

 others the upper part of the slope is mature, but the lower part is gorge-like 

 and youthful in appearance. The phenomena suggests at once that some val- 

 leys have remained below the level of stream-cutting, while others have been 

 undergoing a marked trenching. In these which have been deepened, the 

 old valley bottoms are traceable along the brow of the rock gorges or canyon 

 valleys, for the old valleys are generally broader than the new ones. In some 

 cases, however, the new valleys occupy the whole width of the bottoms of the 

 old ones, and there is only the change in the angle of the slope of the valley 

 bluff to mark the depth of the old valley. There is, in some valleys a series 

 of complex terraces or rock shelves, of which one set or system stands at the 

 brow or border of the canyon valley, and the others at higher altitudes. There 

 are also, in some cases, rock shelves inside the trenches of the canyon val- 

 leys. The set of trenches standing at the brow of the canyon valley is, how- 

 ever, a far more persistent feature than any of the others, and it is this set 

 which receives chief attention in the ensuing discussion of drainage systems. 

 It seems to mark a true gradation plain, formed when the stream was in con- 

 dition between degrading and aggrading its bed. 



All the preglacial tributaries of Cayuga Lake Valley which 

 have been examined have gorges cut in their bottoms, and these 

 gorges are wider, and in many cases deeper, than the postglacial 

 gorges. The approximate width of the drift-filled gorges can 

 usually be ascertained without much difificulty. On account of 

 the drift-filling, the depth is not readily determined ; however, 

 Evans, who studied Taghanic carefully, mapped the old valley 

 bottom as continuous above the level of Lake Cayuga.^ 



Ten Mile Creek. — Ten Mile Creek, despite its name, is only 

 about six miles in length. It rises near the village of Danby and 

 flows a little west of north, entering the Inlet about two miles 



' Monograph XLI, U. S. Geological Survey, p. 80. 



'^ R. M. Evans, Thesis on Taghanic (1897), Map. II. 



