1070 THE BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER 1957 



Television is being used in shallow waters by various organizations. 

 However, picture resolution is poorer than that obtained photographi- 

 cally, and nothing has been done in depths greater than 110 fathoms. 



Physical sampling is accomplished by corers, grab samplers, and rock 

 dredgers. Earliest samples were obtained by "arming" a sounding lead 

 with tallow, to which some of the bottom sediment would adhere. Coring 

 is the most important source of bottom composition data. Specimens up 

 to 70 feet in length are obtained by dropping a weighted tube vertically 

 into the bottom sediments. About 1,200 sediment cores have been ob- 

 tained in the Atlantic. The locations of most of these stations are shown 

 in Fig. 10. Rock dredging has produced much evidence on the nature of 

 the continental slope, the Mid-Atlantic Ridge, and on the various sea- 

 mounts. Lamont's rock dredge stations are shown in Fig. 10. Not shown 

 are a large number taken by French workers off the Bay of Biscay and 

 off Georges Banks. 



Sounding data can provide a wealth of detail in addition to the depth 

 if an experienced operator evaluates the fathogram. The least skilled 

 operator can differentiate between rough and smooth bottoms, while the 

 most experienced can interpret a fathogram in terms of bottom smooth- 

 ness, sediment thickness, and the location of interfaces in the sediment. 



3.2 Present Knowledge 



3.2.1 General Characteristics 



Navigation charts sometimes include a short notation alongside a 

 sounding, indicating the type of bottom, ranging from common terms 

 such as sand, mud, or ooze, through the less familiar foraminifera or 

 globigerina ooze (shells of microscopic marine life). These notations are 

 most abundant in shallow coastal waters where they provide informa- 

 tion for piloting and anchorages. In the less frecjuented depths, bottom 

 notations on navigation charts are very rare — charts of bottom sediments 

 commonly published are based on sparse and incomplete data and, as a 

 result, are generalized. 



Deep sea sediments have been divided into two main classes, terrig- 

 enous and pelagic. Terrigenous sediments are those derived from the 

 erosion of the land and are found adjacent to the land masses, while the 

 pelagic deposits are found in the deep sea and are distinguished as either 

 organic ooze or inorganic clay. The organic oozes are composed princi- 

 pally of fossil remains of planktonic animals. Distribution of types of 

 sediment is by no means static. Such factors as deposition by turbidity 

 currents, land slides or slumps, bottom scour by ocean currents, and 

 climatic changes continually cause changes. 



