by the cores. The thickest sand deposits are probably in the ridges of 

 the northern part of the segment. 



o. Segment 15 . The lake floor in segment 15 is relatively smooth 

 and featureless. Only a few short and discontinuous subbottom reflectors 

 appear on profiles 15A and 15B (App. A). Cores 53 to 61 were obtained in 

 this segment. Core 54 contains very fine gray sand. The remaining cores 

 all contain fine to medium sand with layers of sandy granules and pebbles. 

 In cores 58 to 59 the surficial sand layer is less than 1.2 meters thick 

 and is underlain by gray silty clay and till. The best prospects for 

 suitable sand are near the north end and the southern third of the 

 segment. 



p. Segment 16 . In segment 16 the lake floor is also relatively 

 smooth and featureless (profile 16, App. A). The blue reflector appears 

 to be at or very near the surface in most places. A deeper reflector 

 which rises to the lake floor on this segment is probably the top of a 

 shale unit cored in segment 17. All but one core from this segment 

 (cores 62 to 66) contain a thin sand layer less than 0.5 meter (1.5 feet) 

 thick overlying gray clay. In core 64 the sand layer is 1.7 meters (5.5 

 feet) thick and the locale of this core site is probably the best area 

 for potential sand borrow. Elsewhere, prospects for obtaining large 

 volumes of sand appear to be poor. 



q. Segment 17 . The dominant feature of segment 17 is a low mound 

 with an extremely jagged surface characterized by a shale outcrop. The 

 surface of the shale creates a strong subbottom reflector in places 

 peripheral to the outcrop where it is buried beneath younger sediments 

 (profile 17, App. A). All three cores (cores 67, 68, and 69) from this 

 segment were in the shale outcrop area. None penetrated more than 0.5 

 meter into this highly resistant material. Little or no sand occurs in 

 the shale outcrop area, but sand deposits may exist around the periphery. 



r. Segment 18 . A series of low ridges 1.5 to 3.1 meters high 

 characterize the lake floor in this segment (profile 18, App. A). The 

 blue reflector crops out between the ridges, but lies up to 3.1 meters 

 beneath the ridge areas and is occasionally incised by 4.6-meter-deep 

 channellike depressions (profile 18, App. A). Cores 70 to 73 were 

 obtained in this segment. Core 73 contains only sand; the remaining 

 cores contain sand overlying gray silt and clay. Limited quantities of 

 clean sand can probably be obtained from the ridge areas. The cleanest 

 and coarsest sand occurs in core 73 from the southern part of the segment. 



s. Segment 19 . The bottom topography in this segment varies from no 

 relief to low undulating ridges and swales of about 1.5 meters relief. 

 The blue reflector crops out in most places but may lie as much as 2.4 

 meters (8 feet) below some of the ridges. Cores 74 to 79 and core 85 

 contain mostly gray clay and silt with a surficial sand layer of 0.6 

 meter or less in thickness. Prospects for recovering large quantities 

 of sand in this segment are poor. The best places for further investi- 

 gation are the ridge areas in the southern part of the segment. 



28 



