GLACIAL EROSION IN THE FINGER LAKE REGION 19 



interglacial conditions the older gorges were cut; with return of glaciation the 

 valleys were deepened still further. During as many glaciations as this region 

 experienced this process was continued. On this basis the older gorges are 

 interglacial; their cause is the lowering of their base level by the overdeepening 

 of the valleys to which they were tributary. Since facts sufficient to establish 

 or to overthrow this explanation are not yet at hand, it must stand at present 

 merely as a working hypothesis. ^ 



Work done since the publication of this paper strongly supports 

 the theory of double glacial origin for at least the Seneca valley. In 

 this valley there is a general condition of remarkably perfect, broad, 

 mature tributary valleys hanging several hundred feet above the 

 lake level, at about the 900-foot contour. They are truncated by 

 the straight, smooth, lower steepened slope of the main valley, so 

 that they stand out prominently, with open mouths, clearly discord- 

 ant with the main valley, and about 1,500 feet above the rock floor 

 of the Seneca valley at Watkins. 



These hanging valleys are trenched in their bottoms by gorges 

 partly buried in Wisconsin drift. The buried gorges are both broader 

 and deeper than those of postglacial origin. Along the western shore 

 of Seneca Lake from Watkins to the northern edge of the Watkins 

 topographic sheet, a distance of eight miles, there is absolutely con- 

 tinuous rock, proving that the gorges have not cut below lake-level. 

 Yet the rock-floor of the main valley is 1,000 feet below lake- level 

 at Watkins. The gorges are therefore also hanging valleys, and a 

 double period of glacial erosion is indicated, with an intermediate 

 condition of interglacial stream erosion. 



On the eastern side of the Seneca valley the evidence is almost 

 as clear, though there are some short gaps in the rock- wall. In the 

 Cayuga valley there are gaps in the rock which may possibly be on 

 the sites of the buried gorges, so that the evidence from this valley 

 is not convincing. 



In my previous paper it was pointed out that there is a marked 

 discordance in the hanging valley levels of neighboring valleys, and 

 this fact was then considered to be evidence opposing the glacial- 

 erosion theory. Both Salmon and Six Mile Creek valleys hang at a 

 much lower level than their neighbors (for example, Fall, Casca- 

 dilla, and Buttermilk (Ten Mile) ). I am now convinced that the 

 interpretation that this discordance is opposed in the glacial-erosion 



I Ibid., p. 284. 



