HEEMAN BEACHES ALONG PEMBINA MOUNTAIN. 355 



Along- the western border of Lake Agassiz here and northward into 

 Manitobti extends a prominent wooded bhifF, the escarpment of a treeless 

 plateau which from its crest stretches with slow ascent westward. This 

 escarpment, commonly called tlie Pemljina Mountain (described in pages 

 40-42, 93-97), is a very marked feature in the topography for about 75 

 miles. It is caused by the outcrop, mostly overspread by glacial drift, of a 

 continuous belt of nearly horizontal Cretaceous shale, several hundred feet 

 thick, usually so hard and enduring that it is popularly termed "slate" 

 Its course coincides laearly with the west line of Gardar and Thingvalla 

 townships. Thence it continues in an almost straight course, a few degrees 

 west of north, to the international boundary, beyond which it runs north- 

 northwest nearly 50 miles to the vicinity of Treherne. The base of the 

 ascent is about 1,225 feet above the sea, and its crest approximately 1,500 

 feet, northward to the Pembina River, beyond which the base sinks to 

 1,150 and 1,100 feet and the crest to 1,400 and 1,300 feet. The width 

 occupied by the slope varies from a quarter to a half of a mile. 



Natural surface at the quarter-section stake on the north side of section 

 32, Thingvalla, 1,178 feet above the sea. Sections 32, 29, and 20 of this 

 township are mostly till, smoothed by this glacial lake, the depressions hav- 

 ing been filled by leveling down the higher portions, where many bowlders 

 partially embedded testify of considerable erosion. A broad ridge of beach 

 sand and fine gravel 3 to 5 feet high extends from south to north tln-ough 

 the center of section 29, its crest being at 1,180 to 1,182 feet. This is the 

 thu-d in the series of foiu- Herman beaches observed near ]\Iaple Lake, near 

 Larimore, and in Lampton. The higher beaches are probably also recog- 

 nizable 1 to 1 J miles farther west, near the base of the Pembina escarpment 

 or -"second mountain," which is 1,220 to 1,230 feet above the sea; but it 

 is impracticable to trace their course and determine their exact elevation, 

 because woods reach from the base of this escarpment a half mile east, 

 where these beaches belong. 



Fourth Herman beach, a broad, low swell of sand and gravel, extending 

 north-northwesterly through the east half of section 20, Thingvalla, 1,166 to 

 1,172 feet; through sections 17 and 8, an eighth to a quarter of a mile wide, 

 1,161 to 1,173 feet, having in some places a depth of at least 10 feet, as 



