THE NINTH OR LEAF HILLS MORAINE. 167 



In North Dakota the ice barrier of Lake Agassiz during the accumu- 

 lation of the Leaf Hills moraine is believed to have curved to the north- 

 west, extending upon the area of till along the eastern side of the sand and 

 silt delta which reaches fi'om McCanna 35 miles south to Portland. The 

 existence of this large delta, evidently due to drainage from the melting 

 ice-sheet without dependence on the aid of any of the present streams 

 having been deposited by a glacial river flowing southward from the Elk 

 Valley, implies that north of it the ice front was deeply incised. The 

 reentrant angle probably moved gradually toward the north from near 

 Hatton to Larimore and McCanna and along the whole extent of the Elk 

 and Golden valleys, and the ice-lobes stretched southward on each side of 

 the delta, but were, like the angle, slowly undergoing change in their posi- 

 tion by a steady or mostly intermittent recession from south to north. 



The islands of morainic till which rose above the surface of Lake 

 Agassiz at its highest stage along a distance of more than 30 miles east of 

 the Elk and Golden valleys, between McCanna and Edinburg, were accu- 

 mulated during tliis time on the west margin of the Minnesota ice-lobe. 

 Their material and that of the beach ridges formed from their erosion were 

 derived from the north and northeast, and contain scarcely any Cretaceous 

 shale from the Pembina Mountain area. No glacial cun-ents coming from 

 even a few degrees west of north seem to have contributed immediately to 

 the formation of this moraine, although during earlier stages of the glacia- 

 tion currents from the north-northwest mingled their diift with that from 

 the northeast upon this region. Numerous detailed notes of the Elk and 

 Golden valleys and of the narrow series of morainic hills on their east side 

 are given in Chapter VI, in connection with the description of the asso- 

 ciated delta and beaches. 



Rising from beneath the Elk Valley delta, which occupies the Avestem 

 margin of Lake Agassiz between the Turtle and Goose rivers, the Leaf 

 Hills moraine seems to be represented by a succession of several more or 

 less morainic belts, formed on the southeastern side of the Dakota ice-lobe. 

 Subordinate stages of the glacial retreat are thus indicated, belonging to 

 the time of progressive accumulation of the delta and of the moraine 

 formed east of the Elk and Golden valleys, both of which, as well as the 



