ABSTRACT

Chemical analysis of dust which fell on the S.S. Dunstan when about 400 miles southwest of the Canary Islands on February 6, 1962, shows essential differences (in SiO₂, Al₂O₃, MgO content and in the Fe: Ti ratio) between the dust and the nearest analysed deep-sea sediment, and indicates a means of recognizing aeolian material in such sediments. The presence of clear, uncoated quartz grains in the Dunstan dust shows that quantitative estimates of wind borne dusts in ocean sediments cannot reliably be obtained from counts of coated quartz grains in these sediments.

One-third of the Dunstan dust is composed of "aggregate" particles, which, on the basis of chemical and X-ray work, are thought to consist of quartz, mica, and a clay mineral. Organic matter is relatively abundant. More than four-fifths of the dust particles have diameters of between 5µ and 30µ, which is a little greater than the average grainsize of other dusts falling in this region. The origin of the dust is believed to be the coast of Spanish Sahara, where long shallow depressions may act as suitable gathering grounds for both the minerals and the organic matter.