438 THE GLACIAL LAKE AGASSIZ. 



A belt of low dunes in sections 28, 21, and 16, township 161, range 

 55, running along the eastern base of the great Campbell embankment 

 that was built out to the south from the front of the Pembina delta, prob- 

 ably records the McCauleyville stages, approximately at 1,000 to 980 feet. 

 North of the Tongue River the McCauleyville shores lie a third to a half 

 of a mile east of the Campbell embankment and beach ridge along a dis- 

 tance of 5 miles. Thence through the next 6 miles, extending northwest 

 to the Pembina River and Walhalla, they run along the base of the "first 

 Pembina Mountain," which is the very steep ascent, 100 to 175 feet high, 

 of the eroded east border of the Pembina delta plateau. 



The road from Olga to Walhalla, coming down from this plateau about 

 a mile southeast of the Pembina River, crosses at its foot a terrace of sand 

 and gravel, 30 to 50 rods wide, having an elevation of 1,000 to 1,004 feet 

 above the sea, which was formed during the upper McCauleyville stage. 

 The highest part of the terrace is where it rests against the "mountain," 

 and its surface descends a few feet to its northeastern verge. There is 

 next a somewhat rapid slope to 985 feet at the bottom of a depi'ession 

 about 15 rods wide, beyond which the road passes over the beautifully 

 developed lower McCauleyville beach. This ridge is 20 to 30 rods wide, 

 with smoothlv rounded top at 990 to 993 feet, very level along a visible 

 distance of a third of a mile or more of its course from southeast to north- 

 west, but hidden farther away by trees and bushes scattered here and there 

 on its otherwise prairie surface. Its lakeAvard northeastern slope falls 

 about 20 feet within 25 rods, and from its base a slower descent continues 

 eastward. 



All the land of this vicinity, including the plateau and front of the 

 delta, the terrace and beach ridge, the intervening hollow, and the flat 

 country on the east, consists of gravel, sand, and fine silt, belonging to the 

 delta as it was originally deposited, or as it has been worked over by 

 the lake waves during later stages. Indeed, proceeding eastward 30 miles 

 to the Red River at Pembina, St. Vincent, and Emerson, one crosses only 

 the fine silt which was of like origin with the delta, but was carried farther 

 into the lake, or the similar alluvial lieds that have been laid down from 

 floods of the Pembina, Tongue, aud Red rivers since Lake Agassiz was 

 di'ained away. 



