
GLACIAL PHENOMENA AND SUPERFICIAL DEPOSITS. 21 
Figure 2. Plate XIII. illustrates diagramatically the structure of the 
Coteau, Xc., in localities north-east of Wood Mountain. 
532. The Coteau itself, and the degraded northern edge of the Lignite 
plateau are equally characterized by the abundance of Laurentian and 
Limestone fragments, the drift being in fact chiefly composed of northern 
travelled matter. On ascending toward the summit of the plateau, 
however, the drift rapidly changes its character, the rocks previously 
abundant becoming comparatively scarce; and on reaching its upper 
surface, it is found to be but scantily covered with drift deposits of any 
kind, and the material of these to belong to the Quartzite drift with 
but avery slight intcrmixture of Laurentian. South of the Tertiary 
plateau, and where it is broken down toward the tributaries of the 
Missouri, the country still remains but thinly covered with drift. 
Fragments of Laurentian origin and Limestone are rare, and quartzite 
abundant. 
533. The Quartzite drift, where typically developed, differs not only 
in its composition, but in its appearance and mode of deposition, from 
that of north-eastern origin. The fragments composing it, while of very 
resistent rocks, are not of great size, and rarely show any evident marks 
of glacial polishing or scratching. They are rounded and smooth, like 
beach pebbles, or shingle, and appear to have been for a long time subject 
to the action of the waves. They do not generally form thick deposits 
or banks, but are pretty uniformly spread, and often form a bed only a foot 
or eighteen inches in thickness, with little admixture of clayey matter, 
which rests on the eroded surface of the Lignite Tertiary beds, and in- 
tervenes between them and the soil. Sections in Porcupine, and 
Pyramid Creeks, and in the Great Valley, all showed a capping of this 
material, and the mode of its occurrence may be seen in some of those 
represented. The quartzites and similar rocks forming this drift, which 
are here classed together, are often very varied in appearance, though all 
agreeing in the preponderence of fragmental silica. In colour, the pre- 
vailing tints are yellowish and brownish, sometimes verging on red. In 
texture, rocks may be found from those of a compact jaspery appearance, 
to others in which the grains of sand are coarse, and still plainly 
distinguishable from each other, Fragments of silicified wood also 
occur. 
