142 
The American Geologist. 
March, 1905 - 
ECONOMIC GEOLOGY OF THE PEMBINA REGION OF NORTH 
DAKOTA. 
Bt CHABLB8 P. Bbrkkt. New York City. 
PLATE XII. 
Prominent es- 
carpments form 
the western mar- 
gin of the Red 
river valley in the 
vicinity of the in- 
ternational boun- 
dary, in both N. 
Dakota and Mani- 
toba. These are known locally as 
the "Pembina mountains." A maxi- 
mum development is reached near 
the Pembina river where elevations 
of 600-700 feet above the adjacent 
plain are common and form a strik- 
ing relief from its monotony. 
Streams entering the Red river 
valley in this region have in all cases 
cut deep gorges into the margin of 
these escarpments and have worked 
back variable distances into the 
highlands beyond. By far the most 
important of these is the Pembina 
river. The Little Pembina is its 
main tributary and this together with the Tongue river lo 
miles farther south completes the list of streams to which 
frequent reference will be made. 
The Pembina has cut a gorge 500 feet deep and half a 
mile wide. Relief resulting from the work of this river 
and its tributaries forms the most prominent physiographic 
feature of Cavalier county, North Dakota. At many places 
along the gorges the blufifs are bold and bare exposing all 
rock formations in detail. At all other points a moderate 
covering of glacial drift and soil conceals the underlying 
rocks. The covering is seldom more than 20 to 30 feet 
thick on the highland country. In places large granite 
