GEOLOGY OF THE LAKE PLACID QUADRANGLE 73 



the slopes of Whiteface, Sentinel and especially Esther mountain. 

 The origin of rocky pockets, now occupied by ponds, on the south- 

 western slopes of some of the mountains is not clearly understood, 

 but plucking action of the ice may be regarded as a contributing 

 cause. 



In pushing through the major fault-line valleys, such as the 

 Pitchoff " pass," the Wilmington Notch, and also the Aliddle Kilns 

 valley, the ice carried with it the talus material that had accumu- 

 lated during interglacial periods, freshened out the valley walls and 

 left U-shaped valleys, blocking both ends with crescent-shaped 

 moraines as it retreated. 



The occurrence of glacial boulders is quite common, some of 

 which appear to have been transported from great distances while 

 others can be traced to parent ledges in the neighborhood. Rounded 

 boulders of Potsdam quartzite have been noted all over the quad- 

 rangle. Large irregular slabs of Potsdam sandstone and quartzite 

 are encountered in some of the brook valleys where the drift is 

 abnormally thick. To the north of the road running from Upper 

 Jay to Wilmington, some 2 miles directly south of the latter, irregu- 

 lar nonglaciated flagstones were encountered in such numbers as 

 strongly to suggest that a ledge of the Potsdam existed here before 

 the ice invasion broke it up. Similar occurrences in the Elizabeth- 

 town^ and Mt Marcy quadrangles,^ together with outliers,* point 

 to the conclusion that the Adirondacks were submerged in the 

 Potsdam sea to a much greater extent than was formerly considered 

 to be the case. 



Moraines 



There is but little true morainal material to be found in the Lake 

 Placid quadrangle, for most of it has been modified by water f the 

 movement of the ice during the maximum advance having evidently 

 been too vigorous for deposition and the material that was deposited 

 as the ice retreated having been sorted by the waters of the glacial 

 lakes. 



The recessional moraines appear to be largely confined to the 

 fault-line valleys, being formed by the ice-tongues as they with- 

 drew from the narrow defiles. At the southern ends, in the broac 



^ Kemp, J. F. The Geology of the Lake Placid Region, N. Y. State 

 Mus. Bui. 21, p, 21. 

 ^ Rudemann, Rudolf, N. Y. State Mus. Bui. 138, p. 62. 

 * Ailing, H. L., Bui. Geol. Soc. Amer. 27 1650. 

 ' Miller, W. J., N. Y. State Mus. Bui. 182, p. 44- 

 'Gushing, H. P., N. Y. State Mus. Bui. 115, p. 496. 

 Ogilvie, I. H., Jour. Geol., 10:406. 



