within a Narrow Area. 155 



greatly deepened by the ice scour that tributary valleys, 

 having- an east-west axis, were left hanging high above 

 the new valley bottoms. These tributary streams flow- 

 ing down the newly steepened rock slopes and encounter- 

 ing horizontally bedded strata of varying degrees of 

 resistance to water erosion, developed falls. The reces- 

 sion of these falls created gorges at the lower ends of the 

 hanging tributaries. 



There is evidence for postulating a second advance of 

 the ice, known in this region as the late Wisconsin 

 advance. While such an advance may have accentuated 

 the phenomena resulting from the earlier ice occupation, 

 it is now considered to have been of meager erosive effec- 

 tiveness in this area. However, during the retreat of this 

 second sheet the valleys were graded up with drift, out- 

 wash deposits, and lacustrine sediments, and there is no 

 doubt that these deposits are chiefly responsible for the 

 present relatively flat-bottomed topography of the 

 through valleys common in the Finger Lake District. 



Since the time of the several glacial occupations the 

 tributaries of the overdeepened north-south valleys have, 

 in places, been engaged in cutting gorges at their lower 

 ends, as indicated above, and also along their upper 

 courses where diversion from the axes of the preglacial 

 valley bottoms results from the irregular dumping of 

 glacial deposits. At some points, both in the case of the 

 gorges at the lower ends of the valleys and of those along 

 the upper courses, these gorges have developed on the 

 sites of earlier interglacial cuttings ; at other places they 

 represent wholly post-glacial rock cuts. 



Previous Investigations. 

 The first detailed examination of Sixmile Creek as a 

 whole was made by Lockhead (3) 2 who, in 1895, pointed 

 out that its early mature valley, with a hanging termina- 

 tion where it enters the. Cayuga Valley, is occupied in its 

 lower course by a stream that is now apparently flowing 

 in a post-glacial gorge, and that, previous to the Wis- 

 consin advance of the ice, had earlier occupied another 

 gorge in the mature valley bottom. In 1898 Tarr (6) 

 wrote: "In the case of Sixmile Creek . . . the post- 

 glacial stream occupies the preglacial valley throughout 

 its distance, but, because of the drift filling it is not now 

 flowing at all places along the lowest part of the old yal- 



2 See bibliography at end of article. 



