
GLACIAL PHENOMENA AND SUPERFICIAL DEPOSITS. 239 
Drift Deposits of the Third Prairie Plateau West of Wood Mountain. 
549. On the western side of White Mud River, is a region of gentle 
hills somewhat elevated above the prairie to the west of it, and which 
ten miles north of the Line, is about ten milesin width. From the contour 
of the surface it would seem that this is in great part caused by an accu- 
mulation of drift, though it may also be connected with the occurrence of 
outlyers of Cretaceous No. 5. From the 505 to the 535 mile points, an 
outlying portion of the Tertiary plateau extends, and runs north-westward 
to an unknown distance. Its eastern edge is somewhat cut up by old 
disused vallies, in one of which a large saline lake occurs. These may 
be of pre-glacial age. The western front is comparatively little broken 
by vallies, and is abrupt and escarpment-like. No sections or features of 
interest in connection with the drift were observed, though some parts 
of the region show many boulders of mixed origin. 
550. Westward, a flat, arid plain stretches to the East Fork of Milk 
River. It is very stoney in many places, and an examination of the con- 
stituents of the drift near the 540 mile point gave the following result :— 
eR MPUMEDC TET se ch a He's i SET as ole wad oh sla ee 57°14 | 
2. Granitic and gneissic rocks......-......--+0+se00s-sseees 23°07 
3. Limestone, some of it resembling that of the Rocky Moun- 
ST FOR CPE ERT a BPS . 15°02 
ge eee enna WARS SANTA a1 s ne ae Estas fe Mae We en's ERO Oe sw 1°83 
Se MIe a is MRGMELERCUEIINIS 5 CERIO Ba) oer onl os wt xe ~ 0 we ade nee rer ol J vw weve BU Oa 1°09 
So Bregman of Osirea- (locales. . i3).'s Sn as eee. 0°36 
er aati a shls rad a sense Aaraterdisr ole x >, 5 naigin ¢ TLE RE LL SEG PE 0 36 
8) Wood, patily siliethed,. 5.20 66. ee TY 2 eee & 0°36 
ee ees ee ee Se? 2 0:73 
551. In the valley of a stream near the 547 mile point, good sections 
of the drift appear. The material is a rather hard arenaceous clay, of a 
general brownish-grey colour, and some appearance of rough stratifica- 
tion. It shows stones of all sorts irregularly imbedded in it, many of them 
very evidently glaciated ; and also contains specimens of a Cretaceous or 
Tertiary fossil Ostrea, crystals of selenite, and small angular fragments of 
a material more resembling true coal than lignite. 
552. The surface of the country, before reaching East Fork of Milk 
River, again rises somewhat, and is very thickly strewn with erratics, 
which show a mixture of northern and western drift. In the valley of 
East Fork, though there are no sections of the Cretaceous or Tertiary, 
very interesting exposures of true boulder-clay, resembling that last 
described, are found. The banks in some places, where the stream has 
cut away their base, are nearly vertical, and about forty feet in height. 
(Plate XII., Fig. 1.) The material is a very hard sandy clay, varying in 
