atteeememmenn ie ace eee

12

merging gradually into the other. Between Athabaska and Great Slave lakes
there is also no marked change of slope along the contact of the two provinces
because of the thick deposits of alluvium that have been spread along that contact
by the Peace and Slave rivers. North of Great Slave lake, however, the contact
appears to be well defined by a low but abrupt escarpment, facing eastward and
built of the flat-lying sedimentary rocks that underlie the Great Central plain.
Whether or not this escarpment is continuous is impossible to say at present, but
from the canoe route between Great Slave and Great Bear lakes it was noted
by J. M. Bell* and Preble at a number of points. North of Great Bear lake
enough information is not available to define the nature of the contact between
the two provinces. :
The physical features of this province are typical of the whole Laurentian
plateau generally. When viewed broadly the topography is that of a broad plain
sloping gradually to the west and north with a gradient towards the great lake
depressions which rarely exceeds 6 or 8 feet tothe mile. Here and there residual
round-topped hills or monadnocks rise a few hundred feet above the general level,
but these ‘hills are not aga rule connected into. definite ranges nor aligned in any
particular direction. In detail, however, the plateau is very irregular, broken,
and rocky, with an uneven hummocky or mammillated surface (Plate II A).
The surface of the plateau is nowhere broken by any prominent ranges of
hills and the vertical relief is nowhere so great as that which obtains in the
Cordilleran province. The greatest relief is found on the shores of the great lakes
where it reaches a maximum of about 1,000 feet. On the north shore of Atha-
baska lake at Black bay a group of irregular, round-topped hills rises 800 feet
above the level of the lake”, and on the northeast end of Great Slave lake, R. Bell®
describes hills of granite and gneiss rising “as a sea of half-rounded hummocks to
a general height of nearly 1,000 feet all along the northwest side of this part of
the lake and also around the northeastern extremity.” Again, on the eastern shore
of McTavish bay on Great Bear lake, steep cliffs rise abruptly from the lake
shore to heights of 600 and 700 feet, and a few miles inland they reach a maxi-
mum of about 1,000 feet.4
Little is known of the character of the Laurentian Plateau province inland
from the shores of the great lakes, except along a few canoe routes that have been
traversed by Hearne, Franklin, Petitot, Tyrrell, Bell, Preble, Camsell, and a few
others. From reports of these men it appears that the whole country is of a
generally uniform level rising as a rule not more than 200 feet above the adjacent
stream or lake levels and only at wide intervals is the evenness of the sky-line

‘broken by any outstanding eminences. Instances of such eminences are, however,

reorded by J. M. Bell® and E. A. Preble® in the country between Great Slave and
Great Bear lakes where isolated peaks of conical or rounded outline rise as high
as 1,000 feet above the level of the adjacent lakes. These higher hills are
invariably composed of solid rock and usually of the harder igneous varieties;
but lower hills of glacial origin and composed of sand, gravel, or boulders are
described by J. B. Tyrrell’, in the region southeast of Athabaska lake. Such
hills, however, rarely exceed 200 feet in height. Ea

1Geol. Surv., Can., vol. XII, p. 20 et seq.

2Camsell, Charles, Geol. Surv., ‘Can., Sum. Rept., 1914, p. 57.

’Bell, R., Geol. Surv., Can., vol. XII, 18919, p. 106 A.

4Bell, J. M., ‘Geol. Surv., Can., vol. XII, 1899, p. 18 1c,

5Geol. Surv., Can., vol. XII, 18919, p. 23 iC.

SNorth American fauna, No. 27, U.S) Dept. of Agric, 1908, p. 114 et seq
7Geol. Surv., Can., vol. VIII, 1895, pt. D. :