location was usually made before attempHng to sample. In areas where the surface 

 sediments were coarse grained, the deposits were found lying on bedrock. The high 

 reflectivity of the coarse sediments and of the bedrock generally obscured the Sono- 

 probe record, and the resolution was poor, and thicknesses could not be determined 

 accurately. Where the sediments were thick penetration was good, but in these 

 locations, the sediments were usually fine groined. A prominent subbottom reflection 

 was found on most of the runs, but it was largely unverified by sampling be- 

 cause of the short length of the corer and the excessive depth to the' layer. Where 

 the subbottom sedimentary layer was sampled, the sample contained coarse material, 

 but the exact position of the reflecting horizon relative to the coarse material could 

 not always be determined. Only cores 136, 137, 201, and 211 penetrated the sub- 

 bottom layer as recorded on the Sonoprobe . 



Core 136 apparently consisted almost entirely of sediments from below the sub- 

 bottom horizon. (See Figure 15 for the Sonoprobe runs over the coring sites and the 

 Appendix for the analysis sheets.) The core was poorly sorted, muddy sand with the 

 percentage of sand increasing toward the bottom. The core was pebbly at the top 

 and at the bottom . 



The bottom of core 137 probably represents the top of the subbottom layer in 

 this area. The core was silty and sandy to about 25 inches. Below this depth the 

 core became moderately well sorted sands which increased in coarseness to the bottom 

 at 108 inches . 



At location 201 the sediments were sandy muds and muddy sands becoming sand- 

 ier toward the bottom. The material was all poorly sorted. The subbottom reflection 

 at 4 to 5 feet below the bottom was reflected in the core by an increase in the median 

 diameter of the sediments. Below this depth the sediments became muddy sands again. 



Core 211 probably just penetrated the subbottom layer. The core increased in 

 coarseness from top to bottom . The top was silty clay, gradually becoming pebbly 

 and sandy at the bottom. The lowest portion of the core was slightly disturbed owing 

 to the sucking action of the piston when a piece of wood became firmly wedged into 

 the core retainer preventing further entry of sediment Into the core barrel . 



Sandy cores showing fairly close correlation with the Sonoprobe reflections are 

 130, 148, and 207. Table 2 presents a description of the core data and the corre- 

 sponding Sonoprobe record for comparison. Generally the comparison is good for 

 uniform cores and in areas where there were coarse sediments or bedrock at the water 

 bottom . The sandy laminae and layers In cores consisting mostly of finer material 

 did not show up on the records. These beds were usually too thin to be detected, 

 and they contained high percentages of finer material which reduced the acoustic 

 contrast between the sandy layers and the silty clays above and below. One reason 



37 



