SECT. 2] INSOLUBLES 299 



in Atlantic deep-sea cores has invited thought as to a process of wind conveyance 

 from land. These plant remains were found in Atlantic deep-sea cores but not 

 in the Pacific and Indian Ocean sites traversed by the Swedish Deep-Sea 

 Expedition, according to Kolbe {op. cit.). In the Atlantic, over 60 freshwater 

 species, belonging to various ecological niches, were found. 



Kolbe suggests that the transporting agency might be the "Harmattan 

 Haze", an atmospheric disturbance resulting from the Northeast Trade Winds. 

 Investigations preceding the work of Kolbe had found that the haze was com- 

 posed primarily of diatom shells and their fragments. Of the 51 freshwater 

 diatoms identified in the haze, 25 were found in Atlantic sediments. The 

 components of the haze apparently originate in the arid, but periodically 

 inundated, swamp districts of the Niger and its tributaries. In addition to the 

 diatoms, the Harmattan dust also carries ashes of burnt plants resulting from 

 prairie fires fanned by the Northeast Trades. 



C. Continental and Volcanic Components 



An initial entry into the problem of the identification of wind-borne materials 

 in marine sediments was made by Radczewski (1937, 1937a) who was impressed 

 by the rather common occurrences of dust falls observed as far as a thousand 

 nautical miles from land. The rather reddish coloration in such clouds resulted 

 from the preferential loss of the larger yellowish quartz grains to near-coastal 

 areas. Particles found in the dusts included quartz, clay minerals, calcite, iron 

 oxides, feldspars, with minor quantities of green hornblende, biotite, tourmaline, 

 garnet, epidote, titanite, rutile and zircon. 



Radczewski was stimulated to seek out a material, diagnostic of the source 

 area, which was a major component in the dusts and which could be readily 

 identified in the sediments. His area of study was the Cape Verde basin and the 

 most probable source for eolian material was the Sahara desert. The mode of 

 transport was presumed to be the equatorial easterly winds. 



Quartz grains, coated with a red-brown hematite, proved to be an excellent 

 mineral indicator, characteristic of the desert material. This material, named 

 "Wiistenquarz", represented between 3.1 and 39% of the quartz in the 10-50 

 micron size range and between 5 and 22% in the 5.5-10 micron size range. 

 These percentages decreased in those deposits farthest from shore and the 

 highest values were found in the inshore coarse fractions. Finally, the Wiisten- 

 quarz was found in all samples of the last glacial and interglacial stages. 



In the Pacific, Rex and Goldberg (1958), on the basis of a marked latitudinal 

 dependence of quartz in surface sediment samples, suggested a windborne 

 origin for this material. Quartz is a mineral nearly alien to the basaltic rocks of 

 the Pacific basin, and its distribution provides a key to the transporting 

 processes. It shows a maximum concentration (on a calcium carbonate free 

 basis) around 30°N and somewhat less distinctly around 35°S (Fig. 2). The 

 particles occur in the deposits as chips and shards in the silt range with 2-10 

 micron particles most abimdant. Highest concentrations occur in a region 



