BORDER OF THE WISCONSIN DRIFT. 227 



the border of the late Wisconsin swings southeastward with the glacial 

 boundary or takes an eastward course toward the southern ends of the 

 Finger Lakes, leaving a strip of early Wisconsin drift exposed in northern 

 Pennsylvania and the adjacent portion of New York. 



In the vicinity of the reentrant angle in southwestern New York the 

 border of the Wisconsin drift is very attenuated on the uplands and some- 

 what difficult to locate, but in the valleys it is marked by morainic ridges 

 and knolls of considerable strength. The influence of topography has 

 been very marked, there being pronounced lobation in the valleys and low- 

 lands, and a falling back or northward recession of the border on the 

 uplands. This is well shown in the map of the Olean quadrangle (PL IV). 

 How far eastward these characteristics of the Wisconsin drift border extend 

 has not been determined. They are known to prevail at least to the point 

 where the glacial boundary passes into Pennsylvania, and they may be 

 prevalent over the crest of the Allegheny Mountains. 



From the reentrant angle in New York southwestward the Wisconsin 

 drift presents a definite terminal moraine on high uplands as well as in 

 valleys. The sinuosities of its border are also far less striking than in the 

 vicinity of the reentrant angle. It exhibits pronounced lobation in the 

 broad lowlands, such as the Grand River, Scioto, and Miami basins, but 

 the ordinary valleys of the hilly country were occupied only a very short 

 distance beyond the position of the border on neighboring ridges. 



There is a well-defined terminal ridge or moraine marking the border 

 of the early Wisconsin drift in Ohio and Indiana as well as that of the late 

 Wisconsin drift. It is therefore only on elevated uplands in the hilly coun- 

 try of southwestern New York and northern Pennsylvania that the border 

 of the Wisconsin drift is not marked by a definite ridge. The terminal 

 ridge or moraine is a far more conspicuous featiu-e of the Wisconsin glacia- 

 tion than of any earlier glaciations, not only in the region under discussion 

 but throughout the glaciated portion of the United States. 



