25. Most existing data on lithology of subaqueous areas consists of the 

 description of surficial samples obtained with a primed lead (adhesive -coated 

 sounding weight) or by grab and dredge samplers. While helpful, surficial 

 sediment characteristics cannot be reliably projected downward. For example, 

 in a study of 1,240 ICONS cores obtained from the Atlantic shelf, Meisburger 

 and Williams (1980) found that major changes in lithologic character occurred 

 within 2 m of the surface in 48 percent of the cores and within 1 m in 31 per- 

 cent of the cores. In-depth sampling, using coring devices or soil boring 

 techniques, is expensive and an often difficult operation. Consequently, 

 existing core and boring data are relatively sparse and widely scattered. 

 Probably the largest single collection of such data is the 1,240 cores 

 obtained by the Corps of Engineers under the ICONS program and now archived by 

 the Office of Energy and Marine Geology.* These cores are available for Corps 

 use upon request. 



26. Inferences concerning the lithology of surficial and sub-bottom 

 sediments and rocks can be made by analysis of the side scan and seismic 

 reflection records. However, these inferences are in broad general terms such 

 as distinctions between sand and clay and are tenuous at best. Direct means 

 such as in situ testing procedures are more useful, but in general do not 

 provide definitive information on the size distribution characteristics of 

 material, a crucial factor in evaluating fill suitability. In addition, core 

 data are more useful in correlating between data points and developing sub- 

 bottom stratigraphy and geological history than remote sensing methods. 



Stratigraphy 



27. Stratigraphy deals with the nature and sequence of stratified rock 

 and sediment bodies. The main function of performing stratigraphic analysis 

 is to identify, delineate, and describe various rock and sediment bodies 

 (stratigraphic units) into a coherent system that shows the relationship of 

 each unit to surrounding units. Stratigraphic units are usually defined by 

 lithological characteristics; however, units can also be defined on the basis 



* Office of Energy and Marine Geology, US Geological Survey, National Center, 

 Reston, Virginia 22092. 



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