2. Falrport Harbor . 



a. Bathymetry and Bottom Sediment . An irregular and arcuate bathymetric 

 high up to 5 kilometers wide that extends northwest of Fairport Harbor for about 

 10 kilometers roughly defines the lake floor expression of the sand deposit (Fig. 

 13). Specifically, the high consists of up to three poorly defined ridges 2 to 



3 meters high that trend in an east-west direction along the eastern part of the 

 deposit and change to a southeast-northwest direction along the western flank of 

 the deposit. Water depths range from about -7.5 meters near the shore to about 

 -20 meters offshore. The lake bottom adjacent to this feature is irregular near- 

 shore and becomes uniform and flat farther offshore where modern fine-grained 

 sediments have been deposited. 



The cores show that the sand at the surface of the Fairport Harbor deposit 

 is relatively well sorted and medium grained, and is exposed between trackline 

 fixes 657 to 662, 665 to 675, and 719 to 729 (Fig. 13). Cores 62, 65, and 66 

 and the seismic profiles (fixes 652 to 657, 675 to 703, and 729 to 748) show 

 that mud borders the sand to the northeast of the deposit; jetted holes 58, 62, 

 and 66 and the seismic profiles (fixes 662 to 665, 704 to 719, and 748 to 761) 

 show that a poorly sorted mixture of silty sand and gravel lies to the southwest 

 of the deposit. 



b. Subbottom Sediment and Sand Volumes . The seismic reflection records 

 and vibracores indicate a 2- to 3-kilometer-wide subbottom deposit of sand rang- 

 ing from about 1 to 7 meters thick is present at Fairport Harbor. The sand is 

 composed largely of quartz grains and rock fragments; the rock fragments are 

 largely shale and make up to 50 percent of the sand (Hartley, 1960) . The 

 deposit is divided into two areas on the basis of sand thickness and textural 

 characteristics as seen in the cores (Fig. 14). Area A consists of two zones: 

 the upper zone is well-sorted, medium- to coarse-grained sand, and the lower 

 zone is moderately sorted, silty, fine- to meditim- grained sand. This sand, 

 which essentially underlies the ridges, has a mean thickness of 4 meters and a 

 range of 2 to 7 meters. The upper, medium-grained sand zone has a mean thick- 

 ness of 2.5 meters and a range of 1.5 to 5.0 meters; the lower, finer grained 

 sand zone has a mean thickness of 1.5 meters and a range of 0.5 to 2.5 meters. 

 The volume of the upper zone, based on the mean thickness of 2.5 meters, is 

 about 82 million cubic meters; the volume of the lower zone, based on a mean 

 thickness of 1.5 meters, is about 52 million cubic meters. 



The sand in area B, on the southwest flank of area A, is well sorted and 

 fine grained and has a mean thickness of about 1.5 meters. The volume of sand 

 in this area, based on the mean thickness of 1.5 meters, is about 12 million 

 cubic meters. 



Hartley (1960) reported considerably larger sand volumes for the Fairport 

 Harbor deposit than have been estimated in this report. He interpreted jetted- 

 hole data to show sand thicknesses on the order of 6 to 13.5 meters and cal- 

 culated almost 317 million cubic meters of sand in the deposit. However, 

 comparisons between logs of nearby vibracores and jetted holes indicate that 

 sand thicknesses based on jetting are too large, probably because sand cascading 

 down the hole makes the differentiation of sedimentary contacts in finer grained, 

 noncohesive sediments quite difficult. 



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