LATE PLEISTOCENE OSCILLATIONS. 
13 
overlain by the upper clay, and the occurrence of abundant 
remains of Macoma Bakhica in the littoral deposits in the district 
at altitudes of 470 feet and lower, and of Mytilus edulis Lin. at an 
altitude of at least 325 feet above the sea, shows that the climate 
was not high-arctic during the time of emergence of the land as 
Mytilus edulis on high-arctic shores is not a littoral shell and 
Macoma Balthica is more characteristically boreal than arctic. 1 
The occurrence of the clays at high altitudes far up the Ottawa 
and Gatineau valleys also shows that the ice-sheet had retreated 
a considerable distance before emergence of the land had taken 
place to any great extent. Both the physical character of the 
clays, and the character of the fauna, therefore, seem to show 
that the sea must have risen on the land as the ice-sheet with- 
drew; that at first it stood at about 300 feet or possibly lower 
and later rose considerably higher. 
This is exactly what has been shown by Brogger to have 
taken place in southern Norway. Brogger has held that the 
oscillation of sea-level was due to a depression of the land. 
Wright, 2 however, has pointed out that it is more probable that 
the sea rose on the land owing to the return to the ocean of the 
water which had been bound up in the ice-sheets, for the depres- 
sion of the sea-level was “an absolutely necessary result of 
glaciation,” as has been shown by the investigations of Penck, 
Woodworth, and Daly. 
The rise of the sea on the land which, apparently, took 
place in the Ottawa valley was preceded by uplift which affected 
the Great Lakes region; for the Ottawa valley must have been, in 
part at least, occupied by the ice-sheet during the existence of 
Lakes Iroquois and Algonquin and at least a small amount of 
uplift affected the region at the foot of Lake Ontario during the 
life of Lake Iroquois. 3 Uplift also affected the northern portion 
of the Great Lakes region and probably included the upper 
portion of the Ottawa valley near Mattawa during the existence 
of Lake Algonquin and while the ice-sheet still occupied the upper 
1 Brogger, W. C., Ibid, p. 693. 
s Wright, W. B., “The Quaternary Ice Age.” 
*Coleman, A. P„ “The Iroquois Beach in Ontario,” Bull. Geol. Soc. Am., vol. XV, 1903, 
pp. 347-368. 
