B. Published Survey or Laboratory Data 



Descriptions and analyses of large numbers of sediment 

 samples appear in scientific journals, cruise reports, progress reports 

 of research contracts, and published data reports. Data are reported 

 in an infinite variety of tables, lists, graphs, histograms, profiles, 

 sections, summaries, and descriptions. The reported data often are 

 incompatible because they have been derived through many different 

 methods of analysis and are described in terms of different systems of 

 classification and units of weights and measurement. One example is 

 the basic classification of sediments in terms of mud, sand, gravel, 

 and rock which is subject to the following difficulties: 



1. These terms may describe quantitatively measured and 

 computed grain size composition,or the observer's opinion based upon 

 the appearance of the sample (wet or dry) or the feel of the sample, or 

 both. If the classification is based upon appearance and feel, its 

 accuracy depends upon many varying and indefinable factors such as 

 the observer's bias, knowledge, and experience; the type and amount of 

 organic material; and the homogeneity of the sample. Experiments have 

 shown that even experienced geologists permit a small (less than 10 

 percent) proportion of clay, dark color, or stickiness to obscure the 

 dominajit coarseness of a sand sample and will classify it as mud or 

 mud- sand. 



2. If the grain size of the sediment is measured in the labora- 

 tory, classification of the sample still is complicated by determination 

 of the range of grain sizes which defines a mud, sand, or gravel. Such 

 definitions are arbitrary, and no single system of classification has 

 become widely accepted. Attempts to equate English, metric, and 

 logarithmic (phi) scales of measurement cause additional complications. 



3. A third source of disagreement in sediment classification 

 is in selection of the statistical parameters (mean, median, or mode 

 of the frequency distribution of grain sizes) used to classify a sample, 

 and the effect of the type and amount of deviation of the grain size 

 distribution from the normal (sorting, skewness, kurtosis). Some 

 geologists describe a sample composed of 70 percent sand sized 

 grains and 30 percent or more silt as a silty sand, while others would 

 classify the same sample as only a sand. Others adopt 20 or 10 percent 

 as the minimum proportion of silt to be classified as silty sand. 

 Some geologists use an elaborate descriptive system, using and often 

 noixing English terms with others of Latin and Greek derivation such 



