526 A. G. LEONARD 



be described later, which probably accounts for the exceptional 

 thickness of the pre-Wisconsin drift at this point. 



Another excellent drift section occurs in this same morainic 

 area 3 miles west and one-half mile south of Charlson, or 5 miles 

 south of the Missouri River on a tributary of Sand Creek (Fig. 5). 

 Here the following section appears in the steep bluff which rises 

 abruptly from creek-level : 



Ft. In. 



Sandy clay and soil 2 



Sand and clay in alternating bands 8 



Gravel 8 



Sand and clay in alternating layers 3 



Gravel, coarse 8 



Sand 2 4 



Gravel 7 8 



Till or bowlder clay, dark gray in color, and containing large numbers 

 of pebbles and bowlders imbedded in the tough, hard clay. A 

 large proportion of the bowlders and pebbles are composed of 

 compact limestone and the till contains considerable blue shale 

 (Pierre ?). Thickness of till exposed above the creek 61 



85 4 



The sand and gravel forming the stratified drift of the foregoing 

 section are light yellow in color. The drift hills just back of the 

 bluff rise 50-60 feet above the top of section, so that the total 

 thickness of the drift above creek-level is from 140 to 150 feet. 



BOWLDER BED ON THE MISSOURI RIVER 



An interesting bowlder deposit belonging to the pre-Wisconsin 

 drift is found along the Missouri River just above water-level, 

 2 miles below the Nesson Ferry and one-half mile below the mouth 

 of Tobacco Garden Creek (Fig. 6). This bed of bowlders shows a 

 thickness, above the normal stage of the river, of 12-14 feet and 

 its depth below water-level was not determined. The deposit 

 is well exposed along the water's edge for a distance of nearly 100 

 yards, and scattered bowlders and ferruginous gravel occur at 

 intervals for another 200 yards. Overlying the bowlders is 15 

 feet of gravel, which is overlain in turn by silt and fine sand extend- 

 ing to the top of the terrace, 100 feet above the river. The bowlder 



