MULTIPLE GLACIATION 647 



It has fallen to the writer to attack the problems of the glacial geology 

 of the central Adirondacks and to attempt to present, as best he can, 

 something of the wonderful history there to be deciphered. In such 

 pioneer work many mistakes and false conclusions are apt to appear, for 

 it is impossible to avoid errors in an undertaking of such magnitude and 

 complexity as is there found. 



The great variety of glacial deposits and the interesting series of local 

 glacial lakes, with their attendant deltas, beaches, and outlets, are sure 

 to attract the glacial geologist when the region is better known. Espe- 

 cially striking are some Pleistocene cataracts in a number of the outlet 

 channels, that remind us of Cataract Lake Park, in the neighborhood of 

 Syracuse. 



Multiple Glaciation 



Although positive evidences of multiple glaciation in the Adirondacks 

 are not forthcoming, pre-Wisconsin glaciation in Pennsylvania, Xew 

 Jersey, and ISTew England has been established so as to lead us to the 

 conclusion that this area also 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 character of different levels can 

 be detected. If evidence is to be found of pre-Wisconsin ice-action in 

 the Adirondacks, it is in such deposits. 



The Laurentian' Ice-body 



extent and thickness 



It is generally conceded that at the maximum extent of the ice the 

 Adirondacks were completely buried, and it has been estimated that this 

 ice must have been 8,500 to 12,000 feet in altitude 2 over the central 

 Adirondack region. To this enormous load on the land surface is attrib- 

 uted the well observed phenomenon of deformation, to which Ave will 

 return later. 



MOVEMENT 



It is generally accepted that the ice-sheet moved across the area in a 

 southwesterly direction, although very few stria? have been observed within 

 the area itself. In the table given below the glacial scratches are pre- 

 sented as noted by a number of geologists and are also indicated on the 

 accompanying map. In the Champlain Valley the direction was south- 

 ward, but farther to the west the stria? swing to the Avest of south Avith 



- H. L. Fairchild : Bull. Geol. Soc. Am., vol. 24, p. 136. After Shackleton. 



