relief and the surface layer is thickest. Core 9, from a ridge cresting 

 at 16.8 meters (55 feet) below lake level, contains 2.6 meters (8.5 feet) 

 of clean, medium sand which may be characteristic of other ridges in the 

 segment as well. Core 8, which lies farther seaward and to the north, 

 contains 4.9 meters (16 feet) of clean, medium sand. The bottom topog- 

 raphy at core 8 is seaward of the surveyed zone and is unknown. 



e. Segment 5. Except for one low ridge and sets of sand waves with 

 up to 1.5 meters of relief, the lake floor of segment 5 is essentially 

 featureless (profiles 5A and 5B, App. A). Inshore, the blue reflector 

 is generally no more than 1.5 meters below the lake floor, but becomes 

 deeper offshore as shown in profile 5B. At the southern end of the sec- 

 tor (profiles SB and 6, App. A) a reflector, which apparently lies at 

 considerable depth to the north, appears to rise to the level of, and 

 merge with, the blue reflector. This indicates that the rock unit which 

 underlies the blue reflector to the north is succeeded at this point by 

 another rock unit. Core data are not sufficient to reliably determine 

 the lithologic character of the units directly underlying the blue re- 

 flector to the north and south of this transition point; however, from 

 the" limited data available it seems likely that the underlying unit to 

 the north of the transition is clay while that to the south is probably 

 glacial drift or relict lake floor sand. 



f. Segment 6 . Segment 6 includes Little Sable Point. The lake 

 floor in this segment is steep, smooth to irregular, and includes several 

 large ridges. The blue reflector lies mostly at 6.1 to 18.3 meters below 

 the lake floor but comes closer to the surface in an offshore direction. 

 Cores 10 and 11 in the segment both contain clean quartz sand ranging in 

 size from fine to medium (core 11) to medium to coarse (core 10). Pros- 

 pects for obtaining suitable sand are good throughout the segment; how- 

 ever, as at Big Sable Point, the steepness of the bottom slope may 

 dictate limitations on offshore borrow operations. For this reason 



the southern third of the segment, where milder inshore bottom slopes 

 prevail, is considered the best area for potential offshore sand sources. 



g. Segment 7 . Segment 7 contains a series of ridges having 1.5 to 

 4.6 meters (5 to 15 feet) of relief. The blue reflector is shallow or 

 crops out between the ridges but is buried as much as 6.1 meters beneath 

 the ridge sediments. Cores 12 and 13 taken in this segment contain pre- 

 dominantly fine sand. Many ridges in this area may contain abundant 

 sand; however, most lie in more than 18.3 meters of water. 



h. Segment 8 . This is a short segment of smooth lake bottom with 

 a 3.1- to 6.1-meter accumulation of sediment above the blue reflector. 

 No cores were taken in this segment; however, if the surf layer is sand, 

 a large volume of material might be obtained in the area. 



i. Segment 9 . Bottom topography in segment 9 varies from smooth to 

 irregular. Several large ridges of up to 6.1 meters relief occur seaward 

 of the 15.2-meter (50 feet) isobath (profile 9, App. A). The blue reflec- 

 tor increases from less than 1.5 meters below the lake floor out to about 



26 



