GEOLOGY OF THE LAKE PLACID QUADRANGLE /I 



PLEISTOCENE GEOLOGY 



BY HAROLD L. ALLING 



INTRODUCTION 



In the detailed mapping of the quadrangles in the Adirondack 

 region more attention has usually been given to the crystalline 

 rocks than to the Pleistocene geology. The glacial phenomena, 

 however, are clearly discernible and promise to add materially to 

 the knowledge of the Pleistocene history of the State of New York 

 when fully worked out. Besides the usual types of glacial deposits 

 the Lake Placid quadrangle exhibits deltas, terraces and shore-line 

 features of a succession of extinct glacial lakes whose history can 

 be traced with a fair degree of accuracy. Unfortunately for con- 

 cise description, the lakes were not confined entirely to the quad- 

 rangle so it is necessary in many cases to examine adjacent 

 topographic sheets in order to appreciate the extent and history of 

 each during its initiation, life and extinction. Nevertheless only 

 those lakes which formerly covered some portion of the Lake Placid 

 quadrangle will be described. 



Although positive evidence of multiple glaciation in the Adiron- 

 dacks is not, as yet, forthcoming, Prewisconsin glaciation in Penn- 

 sylvania, New Jersey and on Long Island^ has been established so 

 as to lead us to the conclusion that this area has been subjected to 

 continental ice bodies more than once. In some of the stream 

 valleys the depth of the drift is enormous and a difference in the 

 character of different levels can often be detected. If evidence is 

 to be found of Prewisconsin ice action in the Adirondacks, it is 

 in such deposits. 



But as the surface deposits are chiefly due to the last or Lauren- 

 tian lobe of the Wisconsin ice, we shall confine ourselves to its 

 effects. 



Wisconsin Glaciation 



Without much doubt the entire Adirondack region was com- 

 pletely buried by the ice, which has been estimated to have been 

 9000 to 12,000 feet in altitude over the central Adirondacks.^ To 

 this enormous load upon the land surface is attributed the well- 

 observed phenomenon of deformation, to which we will return 

 later. 



jT 



*Fairchild, H. L. Bui. Geol. Soc. Amer., 24:134. 



^Fairchild, H. L. Geol. Soc. Am. Bui., 24:136. After Shackleton. 



