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NEW YORK STATE MUSEUM 



Across the main divide to Allegany drainage 



The reader should clearly appreciate the relation of the ice body 

 to the general land surface. While the ice margin was lying on 

 ground having free southward drainage the waters utilized the 

 valleys leading south and away from the ice front and they had no 

 occasion for making new channels. The copious waters from the 

 summer melting of the ice mass, combined with that from the 

 local rain and snow fall, produced heavy floods in the south-leading 

 valleys; and vast quantities of debris from the ice were swept 

 far down the valleys and filled them to great depths. This is 

 well illustrated in the valleys of Cassadaga and Conewango creeks 

 as shown in plates 2-3. The present creeks meander listlessly 

 over the broad plains of valley-train drift left by their larger 

 glacial predecessors, and are contributing only a surface layer 

 of fine materials or are intrenching themselves in the older deposits. 



When the ice front receded to the northward of the divide the 

 waters which were then ponded in the valleys facing the ice had 

 to escape across the divide, through the lowest passes or cols, 

 which were often deepened or cut down by the water flow. The 

 divide was usually formed, at least in the valleys, by the moraines 

 left by the ice, and in our district the transverse channels are in drift 

 and not in rock. 



The general ice front adapted itself to the larger land configura- 

 tion, and lobations of the ice pushed forward into 'the greater 

 valleys, as shown in figure 1 for the Erian lobe. It will be seen 

 that the broad relation of the ice and land was such that the south- 

 leading channels were, in general, opened successively from west 

 to east; but the precise relation in time is uncertain and is not 

 important here. These channels will be enumerated here very 

 briefly and discussed again in a later chapter in connection with 

 the local lakes which they drained. 



The south-leading outlets for the glacial waters held in the basin 

 of the Genesee were described in 1896. 1 The Genesee lakes lay 

 on the eastern border of the territory described in the present 

 paper, and the more southerly of the Genesee outlets were probably 

 effective while the ice was yet lying over all of our area. Probably 

 some of the small primitive lakes held by the ice in the eastern part 

 of the Cattaraugus basin were tributary for a time to the Genesee 

 waters, but these details have not been studied. 



The easternmost channel which carried only Erie basin waters 

 is probably the one at Machias, in Cattaraugus county, with eleva- 

 tion of 1646 feet. This was the outlet of the glacial lake in the upper 



'Glacial Genesee Lakes. Geol. Soc. Am. Bui. 7:423-52. 



