During phase II, the vessel GS-1 was used to relocate fix positions 

 selected as coring sites by duplicating the range values from the shore sta- 

 tions. The GS-1 first maneuvered until one of the ranges was duplicated and 

 then an arc was run on that range until the other range was intersected, at 

 which time an anchored float was used to mark the core location. Core sites 

 were located and marked in this manner because of the limited maneuverability 

 of the scow. The GS-1 crew located a core position in minutes and dropped a 

 float marker; the tug and scow then moved in on the marker, anchored, and the 

 core rig was lifted from the deck of the scow and set on the lake bottom. 

 Meanwhile, the GS-1 proceeded to the next core site. Once the core rig was on 

 the bottom, the core barrel was driven into the lake bottom sediments; within 

 about 15 minutes the coring was completed and the apparatus was lifted back 

 onto the scow. The core liner containing the sediment was removed from the 

 barrel and small reference samples were obtained from the top and the bottom of 

 each core. The liner was then capped and sealed, labeled, and a general de- 

 scription of the samples was made. The scow was then moved to the next coring 

 location. While underway, the corer was reassembled and loaded with a new 

 liner. In general, the corer penetrated the lake bottom deposits quite easily; 

 however, penetration in stony till and in some well-sorted, medium-grained 

 sands was poor. 



3. Office and Laboratory Procedures . 



After completion of the data collection, the navigational fix marks, ship 

 trackline positions, core sites, and shore stations were plotted to show the 

 coverage in the survey area (Figs. 2 to 7) . The cores were split longitudinally, 

 using a circular powersaw to cut the plastic liner and a piece of thin wire to 

 cut the sediment. As soon as the core was opened it was color typed using the 

 Munsell color system (Munsell Soil Color Charts, 1954 ed., Munsell Color, Inc., 

 Baltimore, Md.). Color typing was immediately followed by sampling for 

 natural water determinations (sample is weighed, dried, and reweighed) , by 

 unconfined compressive and shear-strength measurements (using hand-held Soiltest 

 instruments), and by detailed descriptions (see App. A). The unsampled half of 

 the core was wrapped in plastic for storage. After the sampled half had par- 

 tially dried (a day or two), the description was checked, photos of representa- 

 tive units were taken, and additional sampling was done if necessary. 



Three principal techniques were used for the grain-size analyses: rapid 

 sand analysis (RSA) for the finer sands (U.S. Army, Corps of Engineers, Coastal 

 Engineering Research Center, 1977), sieve analysis at 0.5-phi intervals for the 

 coarser sands and fine gravel (Folk, 1974), and pipet analysis for the samples 

 containing appreciable clay- and silt-size particles (Folk, 1974) (App. B) . 

 In addition, 22 clay samples were analyzed by X-ray diffraction (App. C) , and 

 general sand-grain mineralogy was determined with a binocular microscope using 

 a feldspar stain technique (Gross and Moran, 1970) . Atterberg limits were 

 determined for 29 fine-grained samples (App. D) , and two radiocarbon-14 ages 

 were determined from wood samples in core 62. Mollusks from selected samples 

 were identified generally to species level (App. E) . 



4. Seismic Interpretation . 



Seismic reflections from the shale and till surfaces were extensive enough 

 in the subbottom to be mapped throughout most of the study area. The shale 

 reflector generally is broken and irregular but well defined with closely 



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