334 THE GLACIAL LAKE AGASSIZ. 



Cousiderable cliunueling of the valleys iu which these streams flow appears 

 thus to have been accomplished before the land was uiillfted and the lake 

 receded to its Norcross and lower shores. This delta accumulation, consist- 

 ing partly of alluvium from stream erosion after the departure of the ice, 

 but evidently in far larger measure of modified drift supplied by streams 

 from the melting ice in which it had been held, occupies a width of 6 to 12 

 miles, and stretches about 35 miles southward from McCanna, by Larimore, 

 Northwood, and Hatton, to the vicinity of Portland. Its thickness at 

 Lai'imore, as shown in fig. 14, is 60 feet, and doubtless its average thick- 

 ness is as much as 30 or 40 feet upon its area of about 300 square miles. 

 It was deposited in the edge of Lake Agassiz during the first and second 

 Herman stages, for these shores marked by beach ridges, are above the 



Fig. 14. — Scctiun across the delta of the Elk Valley. Horizontal scale, 3 miles to an inch. 



delta; but the third and fourth Herman beaches extend across it, passing 

 close east of Larimore. The Norcross and Tintah shore-lines lie near its 

 eastern boundary, for the greater part upon its edge, but it has not been 

 conspicuously eroded. Farther east the surface is mainly till for the next 

 15 miles or more, descending toward the Red River, which is bordered on 

 this latitude in North Dakota by a belt of alluvial clay and silt only a few 

 miles wide. 



A section of the beds forming this delta is furnished by the well at the 

 Sherman House, Larimore, which was dug 20 feet and bored 40 feet, as 

 follows: Soil, 2 feet; fine sandy and clayey silt, without coarse sand, 

 gravel, or stones, 5 feet; fine yellowish sand, with less clay, being mainly 

 siliceous, 13 feet; and dark sand, very soft to bore through, two-thirds 



