REPORT OF THE DIRECTOR AND STATE GEOLOGIST 1900 rl3S 



In cases where the head of the valley is a deep col which is the 

 lowest outlet southward of a capacious north-sloping yallej, it 

 is evident that a considerable flow of water must have passed 

 through the col while the ice front was damming the waters in 

 the north valley. The Tully lakes col at: the head of the Onon- 

 daga valley is a good example of such relationship, and yet it has 

 an uncut moraine divide like the Cassadaga col here mapped. In 

 the case of the Cassadaga col the volume of water ponded north 

 of the divide was not relatively great, but the lake w^as however 

 of sufficient size to require a distinct outlet channel, which is not 

 found. 



Two features of this map of the Cassadaga phenomena do not 

 harmonize with the theoretic requirement. One is the absence 

 of a well defined channel across the divide, and the other is the 

 presence of lakes or depression® in the head of the valley. The 

 latter inconsistency is not difficult of explanation. The valley 

 was filled with the drift, by the glacier and the stream, from the 

 south toward the north, or up stream, following the retreating 

 ice front. The lower stretches of the valley were uncovered by 

 the glacier and filled with the drift sooner than the upper sec- 

 tions. At the head of the valley the supply of drift or filling 

 material gave out rather suddenly as the glacier front passed to 

 the north of the divide, as a lake was then formed which became 

 the catchment basin for the glacial debris. Thus the head of the 

 valley did not receive so much drift as the lower sections, but it 

 would reasonably seem as if it should have received sufficient to 

 fill such shallow basins. And now the question arises, what 

 agency produced such basins in the path of stream action? They 

 evidently are not moraine depressions or kettles, as they do not 

 lie in moraine drift, but do lie in stream-spread deposits. The 

 explanation of these lake basins is that they are ice-block kettles, 

 or areas occupied at the time of the stream work by blocks of 

 glacier ice. When the glacier front receded over the divide, 

 masses of ice became detached from the body of the ice lobe and 

 became surrounded or even buried by the stream deposits. With 

 the ultimate melting of the buried ice, the basins were produced. 



