Additional sediment data in the form of core logs and granulometric 

 characteristics are contained in Appendixes B and C. 



2. Segment Description . 



The study area is divided into 20 segments (for convenience of de- 

 scription) , each of which is fairly uniform in bottom topography, sub- 

 bottom reflector patterns, and sediment characteristics (Figs. 8 to 13). 

 A brief segment-by-segment description of the geologic character of the 

 area and assessment of the availability of offshore sand resources 

 follows. High potential areas are designated in places where the sand 

 deposits are judged to be of large volume, readily accessible, and with 

 textural and minerological characteristics suitable for beach fill. 



a. Segment 1 . This segment is dominated by a large north-south 

 trending linear shoal that fronts the northern part of the segment and 

 merges with the shoreface in the southern half (profile 1, App. A). No 

 cores were obtained from the segment; thus, the character of the sediment 

 is uncertain. If the surficial layer contains suitable material, an anal- 

 ysis of the seismic data indicates that the thickest deposits probably 

 occur along the western margin of the shoal near the north end of the 

 segment. 



b. Segment 2 . Segment 2 includes Big Sable Point and peripheral 

 areas to the north and south. Seismic records did not show subbottora 

 reflectors in this area, suggesting the surficial layer is probably very 

 thick off the main part of the point. In any case, dredging is not rec- 

 ommended off Big Sable Point because of the steep bottom slope and possi- 

 ble adverse effect on slope stability. The best prospects for obtaining 

 sand are judged to be near the northern and southern ends of this segment 

 where the bottom slopes are gentle and there are several ridges which may 

 contain suitable sand. Cores 4 and 5 from the southern part of the seg- 

 ment contain clean, fine sand which is very uniform in size and character 

 throughout the cores . 



c. Segment 5 . A smooth to jagged bottom topography prevails in 

 segment 3 (profile 3, App. A). The blue reflector crops out or is only 

 a few feet below the lake floor on all profiles; thus, the surficial 

 layer appears to be thin and discontinuous. All of the cores taken in 

 this segment (cores 1, 2, 3, 6, and 7) contain soft reddish-brown clay 

 which either crops out or is thinly mantled by sand. The thickest sand 

 layer occurs at the site of cores 1 and 2 where 0.6 and 1.8 meters (2 

 and 6 feet), respectively, of clean, medium sand overlies the clay layer. 

 On the basis of present information the best area for further exploration 

 in this segment is in the locale of cores 1 and 2. 



d. Segment 4 . The lake floor in this segment contains a number of 

 broad smooth-surfaced ridges up to 3.0 meters (10 feet) high (profile 4, 

 App. A). The blue reflector crops out or is very shallow in the swales 

 between these ridges. The most promising locale for sand resources is 

 in the southern part of the segment where the ridges have the greatest 



