
CHAPTER X. 
GLACIAL PHENOMENA AND SUPERFICIAL DEPOSITS—(Continued. ) 
MArGin AND EASTERN REGION OF THE THIRD PLATEAU (Continued)—Drift deposits 
near Wood Mountain—Northern extension of the Coteau—Southern extension 
of the Coteau—General aspect of the Coteau—Methods of accounting for the | 
formation of the Coteau—Drirr Deposits OF THE THIRD PLATEAU WEST OF 
Woop Mountatn—Boulder-clay of East Fork of Milk River, &c.—Compo- 
sition of the Drift near Milk River—The Three Buttes—Western limit of 
Laurentian drift— GLACIAL ACTION IN THE Rocky Mountains — Former 
glacier of Waterton Lake—Terraces in the mouth of the 8. Kootanie Pass— 
Origin of gold—Moraines and lakes—Cirques—GENERAL COMPOSITION OF THE 
Drivt—THE Rep River Vautey—Its character and inclination—Alluvial 
deposits—Sections from borings at Winnipeg and Fargo—Yellow marl deposits 
—Connection of deposits of Red River Valley and Missouri Country—PRE- 
GLACIAL ASPECT oF THE CouNnTRY—Former southern flow of Red River— 
First stage in depression—Correlation of levels of plateaus and terraces—Depth 
of submergence when greatest, and action at this time—Emergence of the 
continent— Difficulties met with in explaining the phenomena—PostT-GLACIAL 
PHENOMENA—Possible existence of a pluvial period—Great river vallies— 
Alternative vallies—Valley of the Red River—The formation of coulées. 
Margin and Eastern Region of the Third Prairie Plateau to Wood 
Mountain (continued.) 
534. Following in the description of the drift deposits, as nearly as 
possible, the order pursued in systematically describing the older forma- 
tions, it will next be necessary to consider the region westward of Wood 
Mountain, and between it and White Mud River. The three belts of 
country already defined, are here not so distinctly marked, as the watershed 
plateau turns north-westward, and does not maintain its elevation so 
uniformly as before. The third region, or that sheltered by the plateau, 
consequently shows a somewhat greater admixture of foreign matter, 
though the preponderance of the Quartzite drift is still remarkable, and 
the size of some of its component fragments is greater than in any 
locality previously observed. After passing the 425 mile point, it rests 
upon the surface of the clay-shales of No. 4 of the Cretaceous formation. 
The average elevation of the region above the sea is about 3,000 feet. 
535. A numerical examination of the pebbles of the drift, near the 450 
mile point, gave the following ratios for its constituents :— 
1. Quartzite drift, brownish, yellowish, purplish, and dark grey, 
and varying in texture as already described....... erp’ 40°66 
2. Granitic and gneissic rocks. ... 1.1.6.0 ese cece eee eee ee eens 25°83 
4, White limestone... ,.,cccrrrcvevcvevvcccccssssecssosces 19°95 
