





150 B. N. A. BOUNDARY COMMISSION. © ie 
of the Fort Pierre group, probably occupy nearly the whole area of the 
second plateau, south of the North Saskatchewan, and between it and 
the Boundary-line. Eastward, they terminate in the escarpment over- e) 
looking Manitoba Lake, and the low lands of the Red River Valley. I uy 
is possible, however, that future explorations may bring to light, —— a 
this great area, many places where the beds of No. 5 have been 
preserved, from their superior hardness, especially in such high-lands as 
the Touchwood Hills, and parts of the so-called ‘mountains’ of the 
eastern escarpment. Outlyers of the Lignite Tertiary may even yet be © 
found. 
364. The rocks of the earlier Cretaceous do not seem immediately to 
underlie any great area on the eastern edge of the formation, but to occur — 
merely along the base of the high-lands formed by No. 4. In the 
vicinity of the forty-ninth parallel, they are completely hidden by 
alluvial deposits. If it be supposed that No. 4 is shown nearly to its 
base, in Pembina Escarpment, on the Line; allowing the two lower 
divisions the same thickness assigned to them by Meek and Hayden in 
Nebraska, and taking the general slope of the prairie surface toward & 
Red River, as representing that of the denuded edges of the rocks below, 3 
—suppositions, none of which are probably far from the truth—then, 4 
rocks of the 3rd Group, with a thickness of 200 feet, would have their : 
eastern limit about twenty miles from the base of the escarpment, while a 
those of the two lowest groups, would pass below the bed of the Red a 
River, with a thickness of about 1,000 feet. This would allow them to MG 
abut directly on the older Silurian or Laurentian rocks of the east. my. 
Rocks apparently belonging to this formation, as proved by boring, i 
} 
underlie the alluvial and glacial drift deposits of the Red River Valley, “ae 
at Morehead, 180 miles to the south; and are also now known to overlap 
Laurentian and Silurian rocks in south-western Minnesota.* While it is 
probable that they exist below the Red River prairie on the Line, at = 
least as far east as the river, and very likely to the eastern paleozoic 
boundary of the valley; it is hardly probable that they do so in such 
force as above indicated. The basin of older rocks containing those of 
the Cretaceous, probably shoals rapidly eastward, and would cause these 
marginal beds to be thinner than those of the Nebraska section. It is 
also probable, that their eastern edges may have a pronounced westward = : 

dip, which would cause them to run out more rapidly. As a a proctor: the 
* Prof. N. H. Winchell, Second Annual Report Geol. Surv, Minn., 1874. 

