LATE PLEISTOCENE OSCILLATIONS. 
3 
resembling the underlying fluvioglacial deposits. These masses, 
in some cases at least, appear to be “boulders” incorporated in the 
till sheet by the ploughing up of the underlying deposits by the 
ice; for they are irregular in shape and the underlying sands are 
in places disturbed as if by the overriding of the ice. 
There are at least two distinct sets of stria in the district, 
as has been noted by other writers . 1 One set, which is the more 
pronounced, trends nearly south; the other, which is the later, 
trends nearly southeast. This shows, at least, a marked change 
in direction of movement of the ice-sheet during the closing stage 
of glaciation. 
No well marked terminal moraines occur in the vicinity of 
Ottawa; but, between Ottawa and Montreal, a strongly marked 
kettle moraine or series of moraines, showing characteristic knob 
and basin topography, extends southwestward from a point on the 
Ottawa river a few miles below Hawkesbury, through Alex- 
andria and beyond, towards the St. Lawrence river. This 
moraine or series of moraines appears to mark the culmination of 
a slight readvance of the ice during the latest stage of Pleistocene 
glaciation. 
No marine sediments are known to be overlain by glacial till 
in the Ottawa valley and no deposits which might be regarded 
as interglacial are known to occur. It is possible that the 
region was invaded by ice-sheets during early stages of Pleistocene 
glaciation; but, if so, no definite records have been left, so far 
as is known. It is probable that the glacial deposits in the region 
all belong to the latest or Wisconsin stage of glaciation. 
EXTENT OF THE CHAMPLAIN SEA. 
It is impracticable to definitely trace the northern boundary 
of the Champlain sea at its maximum extent in the Ottawa valley 
because of the weakness of development of the highest shore-line 
and because of the character of the rocky upland area which is 
unfavourable for the development of shore-line features; but 
Wilson, W. J., "Notes on the Pleistocene geology of a few places in the Ottawa valley," 
The Ottawa Naturalist, vol. XI, No. 12, 1898, pp. 209-220. 
Ella, R. W„ “Report on the geology and natural resources of the area included in the map 
of the City of Ottawa and vicinity," Geol. Surv., Can., 1901, p. 18G. 
