240 H. L. FAIRCHILD PLEISTOCENE UPLIFT OF NEW YORK 



waters were excluded ; and this raises the isostatic problem, the rate and 

 manner of uplift during the waning of the ice-cap. 



No one is likely to hold the view that a large continental area would 

 rise indifferent to the ice-load, or that the northward differential uplift 

 occurred beneath the ice-body, for that would imply that the ice-bur- 

 dened area rose faster than the unloaded region. The causal relation of 

 the glacier to the land movement seems to be well grounded in geophy- 

 sical philosophy. 



The alternative to such conception is that of a wave uplift responsive 

 to the unloading. We can not postulate a small or local uplift immedi- 

 ately at or beneath the edge of the ice-sheet. Some considerable depth 

 of the earth's crust is involved, and time is required to establish the 

 elastic reaction and isostatic movement and the flow of the deep-seated 

 material. The uplift wave must be dilatory. If the earth wave of uplift 

 ever overtook the receding glacier margin, the amount of rise there must 

 have been very small as compared with the subsequent uplifting. 



All the facts from field study and all the philosophy based on them 

 (largely suggested in the tabulated data, plate 11) lead to the conception 

 of a wave uplift subsequent to the removal of the ice. The isobases almost 

 certainly represent the total land uplift and will be so regarded in this 

 paper. 



Marine Plane 



In the northern edge of the State the most critical locality is the Covey 

 pass, the second outlet of Lake Iroquois. The summit marine level is 

 there 740 feet. On either side of the salient, of which Covey Hill is the 

 point, heavy gravel bars are found in close set series. On the east these 

 stretch for miles south and north of Cannon Corners, in the northeast 

 corner of the Mooers quadrangle. Woodworth saw and mapped part of 

 these bars (103, map), but did not correlate them. The highest of these 

 splendid cobble bars are about 4 miles southeast of Covey outlet and about 

 a mile north of Cannon Corners, by the White school, with altitude 735 

 feet. On the west side of the promontory a fine display of cobble bars 

 lies about 6 miles northeast of Chateaugay village, in the extreme north- 

 east corner of the Chateaugay quadrangle, and three-fourths of a mile 

 north of the Irish school and one-fourth mile south of the International 

 Boundary monument, No. 70 6 A. The summit altitude of this series has 

 not been determined with great precision, but it is 730 to 735 feet. As 

 : bars, cliffs, or deltas, the marine shore is strongly developed in the Cha- 

 teaugay district. It passes into Canada just west of Frontier and follows 

 the land slope northeast, past the west end of the Covey outlet channel. 



