THE CHAMPLAIN SEA IN THE LAKE ONTARIO BASIN 



KIRTLEY F. MATHER 



Queen's University, Kingston, Canada 



INTRODUCTION 



The retreating front of the Labradorian ice sheet late in the 

 Wisconsin glacial stage rested for a time against the northwestern 

 slopes of the Adirondack Mountains. Between the ice front in the 

 upper St. Lawrence Valley and the southern rim of the Ontario 

 basin in New York state, the waters of Lake Iroquois were ponded. 

 The history of this lake, with its outlet down the Mohawk Valley 

 past Rome, New York, has been deciphered by Fairchild, Taylor, 

 Spencer, Coleman, and others. Further withdrawal of the ice 

 margin permitted the escape of the Iroquois waters through 

 " Covey Gulf," southwest of the summit of Covey Hill, the north- 

 ernmost hill on the west flanks of the Adirondacks, a mile north 

 of the international boundary. The altitude of the Covey outlet 

 at the present time is about 1,000 feet, while that of the Rome out- 

 let is 460 feet, but, according to Fairchild, 1 the altitudes of the two 

 outlets during Iroquois time were very similar, "if not practically 

 identical" (see Fig. 1). 



North from Covey Hill the land drops rapidly away to the broad, 

 low valley of the St. Lawrence. As soon, therefore, as the edge of 

 the ice sheet had withdrawn a mile or two farther northward, Lake 

 Iroquois was drained. The water in the Ontario basin and the 

 St. Lawrence Valley rapidly fell to sea-level, for the land stood at 

 a much lower altitude then than now. Differential uplift of the 

 Great Lakes region had commenced long before the extinction 

 of Lake Iroquois, and it is commonly held that the Champlain Sea 

 was then at its maximum extent. It has been more or less uncon- 

 sciously assumed that the history of these sea-level waters in the 

 upper St. Lawrence Valley was simply a slow but progressive 



1 H. L. Fairchild, "Pleistocene Uplift of New York," Geol. Soc. Airier. Bull., 

 XXVII (1016), 235-62. 



542 



