A CONTRIBUTION TO THE STUDY OF THE INTER- 

 GLACIAL GORGE PROBLEM.^ 



Topography of the Finger Lake regioji. — The topography of the 

 Finger Lake region is too well known to American geologists to 

 require any detailed description here. The rocks, which are 

 almost wholly Devonian, consist of great deposits of shale and 

 sandstone, with a few thin beds of limestone. These rocks have 

 never been greatly disturbed and lie nearly horizontal, with a 

 slight southward dip. In the Cayuga Lake district there is a 

 series of gentle folds which cross the lake valley in the east-west 

 direction. A glance at the even sky-line presented by the hill- 

 tops shows that the region is a great plateau. This plateau has 

 been so deeply dissected that it resembles a mountainous coun- 

 try, with the hills often rising several hundred feet above the 

 valley bottoms. About fifteen miles south of the heads of the 

 lakes is a dissected divide that Professor Tarr^ has characterized 

 as being "high and diverse in topography." From the divide 

 the plateau slopes northward and merges into a drift-filled region 

 at the northern ends of the lakes. Here, doubtless, there was 

 an escarpment in preglacial times, but it is now nearly obscured 

 by drift. 



Cayuga Lake valley. — From the divide at Spencer Summit the 

 valley of Lake Cayuga extends northward a distance of nearly 

 fifty miles, when it is lost beneath the drift. Professor Tarr^ has 

 called the divide at Spencer Summit a divide of "destructional 

 origin." He considers the depth of the drift here to be slight; 

 and from the steepness of the walls he infers that the divide 

 must have been higher in preglacial times, "having been lowered 



'This paper was originally written as a thesis for the master's degree at Cornell 

 University. Since the preparation of the original manuscript enough new informa- 

 tion has been secured to warrant a slight revision, and therefore some changes have 

 been made. The writer is indebted to Professor R. S. Tarr for many valuable sugges- 

 tions concerning the field investigations and the preparation of the original paper. 



^R. S. Tarr, Bulletin No. j, Geological Society of America, p. 340. 



'^Ibid., p. 341. 



133 



