68 NEW YORK STATE MUSEUM 



and smoothed by lake waters. The Boreas ponds — Elk lake areas 

 in the southern portion of the sheet are similar. 



Conditions Favorable for Glacial Lakes in the Region 



A number of important factors favored the formation of several 

 series of local glacial lakes in the east-central Adirondacks which 

 formerly existed in the area covered by this bulletin. Among the 

 conditions we note : ( i ) northward draining valleys, sloping toward 

 and blocked by the ice lobes; (2) the complete isolation of such 

 valleys by mountain ranges; and (3) the presence of a huge ice ring 

 that completely surrounded the Adirondack highlands impounding 

 vast quantities of water. The Mount Marcy quadrangle was situ- 

 ated close to the northeast rim of this ice ring. The large amount 

 of sand and gravel for the formation of deltas, terraces and beaches, 

 makes possible the recognition of the different lake levels in the 

 valleys. The cause of the great quantities of sand is discussed 

 later on. 



As noted above, Taylor ^ was one of the first to describe a number 

 of glacial lakes in the east-central Adirondacks, although he did not 

 attempt to separate and correlate the different levels with any great 

 care. A year later Kemp ^ noted two or three sets of deltas in the 

 Keene valley. 



In dealing with the glacial lakes the writer has for convenience 

 classified them in three sections : ( i ) the western section, which 

 included the area around Lake Placid, west of the Wilmington 

 notch; (2) the eastern section, or the Keene valley division in the 

 valley of the East branch of the Ausable ; and (3) the EHzabethtown- 

 Pleasant valley group. The last section does not come under discus- 

 sion here. 



Upper Series 



Western Section 

 As the ice sheet began to wane, the highest peaks of the Adiron- 

 dacks were the first to be uncovered, playing the role of islands in a 

 sea of ice^ (see figure 8). Slowly these islands became larger, sur- 

 rounded by a growing accumulation of water impounded by the 

 ice. These waters found escape over the ice to the south and eventu- 

 ally passed to Susquehanna drainage. This progress of melting was 

 continued until entire mountain ranges were exposed. 



1 Taylor, F. B., "Lake Adirondack," Am. Geol., 19:392-96. 1897. 



2 Kemp, J. F., N. Y. Mus. Bui. 21, p. 60. 1898. 

 ^Fairchild, H. L., N. Y. State Mus. Bui. 160, pi. 11. 



