32 THE NAVY OCEAN SCIENCE PROGRAM 



and the types of mineralogical and biological materials. The 

 objective is to understand the mechanisms which are responsible 

 for the movement and deposition of sediments so that their 

 influence on existing and future Navy systems may be predicted. 

 One of the more significant recent discoveries from cores in high 

 latitudes is that successive layers of clays exhibit reversed 

 magnetic polarization. The clays were deposited over a time when 

 the earth's magnetic field apparently reversed polarity several 

 times. The reversals in the cores have been correlated with 

 reversals of known age in lava beds on land. The core reversals 

 may thus have application to dating ocean sediments. This 

 finding has inspired renewed activity in magnetic studies of 

 sediment. 



Sediment transport occurs by a variety of mechanisms. Many 

 sediments are turbidites, which were transported by turbidity 

 currents for extraordinarily long distances. Sediment is also 

 being found suspended in layers in ocean water. Optical measure- 

 ments in the deep sea have shown that a very small amount of 

 suspended sediment exists in these (nepheloid) layers, particu- 

 larly near the bottom. These layers appear to provide an im- 

 portant and previously unknown process for sediment deposition 

 in the deep oceans. Such layers have been identified in various 

 regions, but particularly off the east coast of the United States, 

 the Aleutian Trench, and the eastern Pacific. Wind-carried dust 

 also provides a transport mechanism. This comparatively recent 

 series of findings provides new insight into sediment transport 

 processes, the full effect of which can be assessed only as the 

 program is continued. Analysis of dusts collected in the At- 

 lantic in low latitudes shows them to correlate with terrestrial 

 samples from Europe and Africa. In the Atlantic at low latitudes, 

 these materials appear to be transported by trade winds. Sedi- 

 ment cores that include materials deposited prior to and fol- 

 lowing the last ice age have been analyzed to determine indicated 

 climatic conditions and variations in composition and deposition 

 rates. 



Sediment ages are determined primarily by the potassium- 

 argon method, by fossils, and by correlation of volcanic ash 



