

CRETACEOUS AND TERTIARY—WHITE MUD RIVER. 113 
276. The valley of the White Mud River, where crossed on this 
northern route; is very broad, but the banks are much reduced in height, 
as compared with those on the Line, and are not of the same precipitous 
character. The bottom of the valley is flat, and the soil being based on 
the Cretaceous clays without the intermediation of drift material, is 
barren in the extreme, and supports a scattered growth of Artemisia, and 
some salt-loving plants. The Cretaceous clays are seen in the banks, but 
are not well exposed. 
Cretaceous and Tertiary Rocks, from White Mud River to Milk River. 
277. On the western side of White Mud River, hilly ground occurs, 
in which some of the lowest Tertiary beds may be represented; but, 
which I am inclined to believe, is due entirely to accumulation of drift. 
The banks of the two branches of Cottonwood Coulée, next met with, do 
not appear to yield any exposures, but the country, from its character 
and elevation is, no doubt, based on the dark Cretaceous clay-shales, to 
about the 505 mile point, where the prairie which has been gradually 
becoming more undulating and hilly, makes a very definite rise, and 
forms a plateau, which extends along the Line, to the 534 mile point. 
278. This plateau like that near Wood Mountain, is found to be 
composed of Tertiary beds, but is not so well defined. Its surface is 
always undulating and often quite hilly, large quantities of drift having 
apparently, been piled upon it. The underlying rocks are seldom seen, 
and its age might have remained a doubtful question, but for the sections 
occurring along its abrupt western front. On coming to this edge, a 
great area of barren and arid prairie, at a lower level, and based on Creta- 
ceous No. 4, is seen stretching westward toward the Milk River. The 
Three Buttes or, Sweet Grass Hills, the Bear’s Paw, and Little Rocky 
Mountains, are also here seen for the first time, at a great distance, 
rising above the level horizon. The exposures are not very clear or 
extensive, but indicate the existence near the foot of the escarpment, 
of a considerable thickness of greyish and brownish arenaceous clays, 
forming rather massive beds. Some distance above these, a well-marked 
red zone occurs, and can be traced at various points along the edge of the 
escarpment, as far as the eye can reach. It is due to the combustion, in 
situ, of one or more lignite beds; portions of which were found in one 
place, unaffected by the fire, but not sufficiently well exposed to enable 
measurements to be taken, or any estimate of their quality formed. The 
metamorphism produced, has been very extensive, and rocks are found 
8D 

