316 THE GLACIAL LAKE AGASSIZ. 



or more above tlie averag-e height of its expanse. Fig. 13 presents a section 

 crossing this deka from east to west. 



The deposition of the deha proper, and also of the fine lacustrine silt 

 extending beyond its plateau to the Red River, took place mainly during 

 the upper Herman stages. The plateau, gently descending eastward, is 

 crossed by the Herman and Norcross shore-lines, and in part by the Tintah 

 and Campbell shores on its eastern and southeastern border. From the 

 Maple River 8 miles east to Leonard, however, and thence southeasterly 

 about 25 miles, its margin lias been eroded and changed to an abrupt 

 escarpment, or at least a somewhat steep slope, by the lake waves during 

 the Tintah, Campbell, and McCauleyville stages. This front of the delta, 

 75 to 25 feet above the flat low land of the Red River VaUey adjoining its 

 base, decreases in prominence as it is followed southward. It passes close 



FlQ. 13.— Section across the delta of the Sheyonne Ei' 



north of Leonard and within a few miles west of Kindred, Walcott, Colfax, 

 and Barrett, gradually ceasing as a notable feature farther south. 



A great portion, probably exceeding a half, of the Sheyenne delta, as 

 of all the other large deltas of this glacial lake, is modified drift, which 

 was brought down by glacial streams fr(im tlie melting surface of the ice- 

 sheet. The coarser gravel and much sand that were supplied from the 

 ice to the head streams of the Slieyenne during the time of formation of 

 its delta were deposited along the outer side of the great moraines soutli 

 of Devils Lake; the finer gravel and a great volume of sand were carried 

 by the Sheyenne to this delta; and the finest silt and clay of the great 

 glacial river were spread in the quiet water of the lake, ()^■('r a nuu-h larger 

 adjoining area of its bed, from near Breckenridge northwai-d beyond the 

 motith of the Sheyenne. 



