62 NEW YORK STATE MUSEUM 



GLACIAL GEOLOGY 



BY HAROLD L. ALLING 



Introduction 



The crystalline rocks of the Adirondack quadrangles have usually 

 received more attention than the Pleistocene geology, yet glacial 

 phenomena of the Mount Marcy quadrangle are so striking that 

 they can not fail to impress the summer visitor or resident. When 

 the terraces and beaches of former but now extinct lakes are traced 

 and their various outlet channels are located and correlated, it is 

 possible to decipher a history of glacial times that is full of interest. 

 The responsibility for the presence of several groups of glacial lakes 

 must be ascribed to the damming of valleys by the ice sheet. In the 

 two parallel valleys, the Keene valley, with which we have much to 

 do, and the Elizabethtown-Pleasant valley to the east, the drainage 

 was northward, but the ice body, preventing the normal escape to the 

 sea, flooded these depressions with standing waters. Each definite 

 pause assumed by each level was controlled by lateral outlet channels. 

 As the ice retreated northward, lower and lower spillways were 

 opened, with a consequent lowering of the waters, initiating lakes of 

 lower altitudes. 



In order to follow the succession of the glacial waters in the 

 Mount Marcy sheet with any satisfaction it is necessary to describe 

 briefly some of the glacial phenomena of adjacent quadrangles, but 

 such excursions will be liinited to features of the lakes that in whole 

 or in part once covered portions of the quadrangle. 



Although positive evidences of multiple glaciation in the Adiron- 

 dacks are not forthcoming, pre- Wisconsin glaciation in Pennsyl- 

 vania, New Jersey and New England has been established so as to 

 lead us to conclude that this area has been subjected to continental 

 ice bodies more than once. In some of the brook valleys the depth 

 of the drift is enormous and often a difference in the degree of 

 weathering of different levels can be detected. In the valley which 

 extends from the slopes of the Cascade-Porter mass northeastwardly 

 to the East branch of the Ausable, the thickness of morainal material 

 is certainly not less than 200 feet and is one of the most promising 

 deposits harboring evidence of pre-Wisconsin ice action within the 

 quadrangle. 



All evidence points to the conclusion that at the maximum extent 

 the Adirondacks were completely buried by the ice, which spread 



