VOLUME XXIV NUMBER 6 



THE 



JOURNAL OF GEOLOGY 



SEPTEMBER-OCTOBER igi6 



THE PRE-WISCONSIN DRIFT OF NORTH DAKOTA 



A. G. LEONARD 



North Dakota Geological Survey 



Considerably over one-half of North Dakota is covered by 

 Wisconsin drift, which is found east of the Missouri plateau and 

 also occupies a belt of country along the eastern margin of the 

 plateau. The western border of the Wisconsin drift is marked by 

 the wide, massive Altamont Moraine which crosses the state 

 diagonally from northwest to southeast and has a width in places 

 of 20 miles. West of this moraine there is an older drift sheet 

 which extends from 70 to 130 miles beyond the Wisconsin drift 

 and in North Dakota covers an area at the surface of approxi- 

 mately 19,000 square miles. The border of this older drift crosses 

 the Montana boundary about 30 miles north of the Northern 

 Pacific Railroad. This older drift undoubtedly underlies the Wis- 

 consin drift of eastern North Dakota, but with possibly one excep- 

 tion it has not been observed in outcrops or recognized in wells. 



East of the Missouri River the pre-Wisconsin drift, while covered 

 in many places by outwash silt from the Altamont Moraine, is 

 present in Emmons, Burleigh, eastern McLean and Mountrail, 

 and perhaps in Williams and Divide counties. West of the Mis- 

 souri River the older drift covers most of Morton, Dunn, and 

 McKenzie counties, a corner of Stark, and all of Mercer and Oliver 



Vol. XXIV, No. 6 521 



