Figure 13. Schematic profile showing primary and secondary 

 reflectors and reflection units (Meisburger 1979) 



155. The scope of preliminary core and sample analyses in the field is 

 limited by three factors, as follows: (a) only partial visual and physical 

 access to the cores for preliminary logging and sampling is usually possible; 

 (b) the type and extent of sample analysis possible in the field is in many 

 respects not comparable to laboratory analysis; and (c) in order to keep pace 

 with the progress of the survey, the field analysis for each core must be com- 

 pleted in a limited time frame. 



156. Many large vibratory corers such as those commonly used for borrow 

 source investigations have plastic tube liners inserted in the core barrel to 

 contain the sediment. After each core is taken, the liner containing the 

 cored materials is removed and replaced by a fresh liner. Usually the liners 

 consist of clear acrylic plastic that allows observation through the wall. 

 However, in some cases heavy scratching by granular material or silt and clay 

 coatings of the inner wall obscure the contents. Where the cored material is 

 visible, logging and selection of samples representative of the cored section 

 can be made by direct visual inspection. Some vibratory corers use aluminum 

 or opaque plastic tubing as core barrels without liners and use the core bar- 

 rels themselves as the containers using a fresh core barrel for each core run. 

 This procedure presents a problem in field logging and sample selection since 

 only the material in the top and bottom of the core tube is visible. For this 



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