THE CHAMPLAIN SEA IN THE LAKE ONTARIO BASIN 549 



features have been described recently by Taylor 1 and Johnston 2 

 and need not be dwelt upon here. Briefly, Algonquin River carried 

 the overflow from Lake Algonquin to Lake Iroquis and, after its 

 extinction, to Gilbert Gulf. A large delta in the Rice Lake region 

 marks the point at which the river debouched into Lake Iroquois. 

 It is now approximately 620 feet above sea-level. The spillway 

 channel continues down Trent Valley past the Gilbert Gulf shore 

 line (320 feet) to the present level of Lake Ontario (246 feet) near 

 Trenton. The channel below the summit marine plane apparently 

 differs in no way from the portion above that level. 



To explain these features by postulating a continuance of the 

 Algonquin River now until after the lower portion of Trent Valley 

 had been lifted above the level of Champlain Sea is obviously 

 difficult. Neither Taylor nor Johnston is satisfied with that 

 explanation. In the light of the conclusions resulting from the 

 study of Napanee Valley, the difficulties met with in Trent Valley 

 are removed. Algonquin River carried its large volume of water 

 to, and below, the present level of Lake Ontario before, rather than 

 after, the Trenton neighborhood was submerged beneath sea-level 

 waters. The delta which must have been built at the outlet of 

 the river into Gilbert Gulf is now hidden beneath the lake. Sound- 

 ings in the Bay of Quinte may some time reveal its hiding-place. 

 By the time the Gilbert strand had crept above the present lake- 

 level retreat of the ice in the Nipissing region had uncovered a new 

 outlet for the upper Great Lakes, and the Lake Algonquin overflow 

 was diverted from the Fenelon Falls outlet. 



Confirmatory evidence. — Physiographic features in Napanee and 

 Trent valleys are thus explainable by postulating a positive move- 

 ment of the strand line in the Ontario basin during the final stages 

 of the waning ice sheet. A similar advance of marine waters in 

 Ottawa Valley has been suggested by Johnston 3 to explain the 



1 F. B. Taylor, "The Pleistocene of Indiana and Michigan and the History of 

 the Great Lakes" (Leverett and Taylor), U.S. Geol. Survey Mon. 53, 1915, pp. 445-46. 



2 W. A. Johnston, "The Trent Valley Outlet of Lake Algonquin and the De_ 

 formation of the Algonquin Water-Plane in Lake Simcoe District, Ontario," Canada 

 Geol. Survey Mus. Bull. 2j, 1916. 



3 W. A. Johnston, "Late Pleistocene Oscillations of Sea-Level in the Ottawa 

 Valley," Canada Geol. Survey Mus. Bull. 24, 1916. 



