Sample composition was strongly related to bluff type. Almost pure sand 

 was found on both the backshore and foreshore at profile lines 4, 6, 8, 9, 11, 

 and 14, all of which are backed by sand bluffs. Similarly, only profile lines 

 10, 13, 15, and 17, which have till bluffs, had high silt concentrations on 

 the backshore (greater than 50 percent). 



While gravel was found in varying amounts at all profile lines, high and 

 low concentrations were characteristic of specific lines. High percentages of 

 gravel (geater than 40 percent) were found on the foreshore at profile lines 

 1, 3, 5, and 13. Gravel concentration was not necessarily related to bluff 

 type. For example, the beach at profile line 1 is covered with pebbles even 

 though it fronts a sandy dune area (Davis, 1976). 



A not unexpected finding is the linear relationship between (profile 

 average) sample gravel content and median sand size shown in Figure 17 for 

 both the foreshore and backshore data from Table 5. 

 0.8 r- 



50 



60 



30 40 



Gravel Content (pet) 



Figure 17. Linear relationship between median sand size and percent 



gravel by weight. 



When the data are averaged' monthly, as shown in Figure 18, the backshore 

 median sand size is fairly uniform throughout the year. However, the fore- 

 shore shows an increase during the fall months, peaking at 0.48 millimeter. 

 This trend is similar though out of phase with the lake level variations. An 

 examination of the variation for individual profile lines indicated that this 

 seasonal increase occurred to some extent only at profile lines 2, 5, 8, 10, 

 11, and 12. Seasonal variations in sample content are also shown in Figure 

 18. 



70 



From the visual estimates of heavy mineral content, it was determined that 

 heavy minerals, predominantly magnetite, were most commonly found on the back- 

 shore. Only 6 percent of the foreshore samples had significant amounts of 

 magnetite compared with 13 percent of the backshore samples. The average 



34 



