
86 B. N. A. BOUNDARY COMMISSION. 
division into two parts above indicated, is so distinct as to be of much 
stratigraphical importance, or of a nature to be constant over great areas. 
It expresses merely the composition of the series at the Pembina Mountain 
localities. 
Lignite Tertiary Rocks on the Souris River. 
201. In proceeding westward across the drift-covered region above 
referred to, the upper beds of the Cretaceous are passed over. The 
Lignite Tertiary rocks next appear, and are first seen in the valley of the 
Souris River at a point 250 miles west of the Red River, and about four 
miles east of the tributary from the south known as Short Creek. These 
beds may underlie the prairie some distance east of this point, but the 
banks of the Souris Valley near this place show a remarkable change, 
presenting numerous exposures of the Lignite Tertiary to the west, while 
eastward they are gently sloping and grassed from top to bottom. This 
change probably coincides with the eastern edge of the Tertiary basin. 
The line of junction runs north-westward, and from the contour of the. 
surface of the country, and other considerations, I have been led to 
indicate it on the map as crossing the Boundary-line near the 230 mile 
point. 
202. From the point where the Lignite Tertiary beds are first seen, 
exposures occur at frequent intervals in the banks of the Souris Valley, 
westward, to the position occupied in the summer of 1873 by Wood End 
Depot Camp, a distance of about twelve miles by the Line, and consider~ 
ably more by the river. 
203. The hard sandstones of the base of the Lignite Tertiary, fringe 
the Souris Valley near the mouth of Short Creek, and give it a pictur- 
esque appearance. These are not, however, the very lowest beds of the 
formation, as some miles east of this point, and underlying the sand- 
stones, whitish and purplish clays, and arenaceous-clays occur; and in 
one place, a small bed of lignite was found.* 
Se, 204. On the south side of the Souris Valley, and a short distance to 
the east of the valley of Short Creek, the Roche Percée group of rocks is 
situated. This locality has already been described by Dr. Hector and 
Captain Palliser, who made a branch expedition to it from the north, in 


* The sections and details of exposures of the Lignite Tertiary rocks of this part of the Souris River, 
and westward to the 393 mile point, were published in a separate form, as a part of the Report of Progress 
of Geological Work in connection with the Boundary Commission, in 1873. They are here repeated, in so 
far as is essential, asa part of the general section on the forty-ninth parallel; beiag rearranged so as to 
follow the general order of description, from east to west, 
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a eee Se 



