502 G. H. CHADWICK^GLACIAL LAKE PROBLEMS 



(at M5Tenae) considerably above the level of the Eome outlet, or higher 

 than the free drainage channels. The inevitable conclusion is that they 

 discharged into a restored Lake Amsterdam, due to reblocking of the 

 Mohawk at its lower end (Schenectady). It is reasonable that any re- 

 advance of the ice at Syracuse sufficient to restore the Grand River outlet 

 must have been accompanied (or slightly preceded) by a powerful thrust 

 in the Hudson Valley, of which we here have the confirmation. Appar- 

 ently this forward shove was felt also (a bit later?) at Batavia, thus 

 sundering Warren and Vanuxem as above intimated. 



Eastward Reach of Lake Arkona 



More puzzling questions revolve around earlier reexpansions of the ice. 

 Taylor thinks that Lake Arkona invaded central New York before the 

 readvance extinguished it. The position of the overriding Alden moraine 

 in the wider portion of the Genesee Valley (where the Warren beach is 

 strong but single), and thence eastward to the Seneca Valley, is well 

 above the Warren level and shows that the ice must have there destroyed 

 any Arkona beaches, except far south up the valleys, where they would 

 necessarily be weak. Careful search may yet reveal these; probable 

 beaches and notches occur, 20 feet above the Warren shore, at and east 

 of Geneseo, but the best record is found in the large 8 50 -foot delta terrace 

 at the mouth of the Mount Morris canyon, which could not have been 

 built in Warren waters, because the canyon had been cut far back and 

 deepened in the stage of lowered escape preceding Warren. The fact that 

 the moraine of readvance barely sunders the Mount Morris and N"ew- 

 berry levels at the critical points near East Bloomfield, Reeds Corners, 

 and Gorham is evidence that even Newberry had been swallowed down 

 into Arkona before that readvance occurred. (See the chart, page 506.) 



Westward Reach of Lake Newberry 



In his later writings and maps^° Fairchild carries Lake Newberry into 

 the Genesee Valley from the east at this same moment in the history 

 preceding Lake Hall. While the overriding ice has destroyed the records, 

 making it impossible to say that Newberry did not have such an exten- 

 sion prior to Arkona, yet it seems to the writer unlikely that the New- 

 berry level entered the Canandaigua Valley before its restoration, and 

 not immediately even then, being momentarily excluded by a restoration 

 of the Potter Lake wdth new outlet east of Gorham. This presently fel] 

 to Newberry, and when the latter almost immediately coalesced with the 



"Bull. 306, N. Y. state Museum, p. 32; BuU. 127, N. Y. State Museum, pi. 35; etc. 



