RB-Sr, Sr87/Sr86 Isotope System as an Index of Provenance of Continental Dusts In the Open Atlantic Ocean.

摘要

The Rb-Sr, Sr-isotope system technique was applied to samples of water-insoluble atmospheric dust to test its utility in determining: (1) The continental provenance of the dust; and (2) The relative importance of eolian vs. other contributions to deep-sea sediments. Samples of atmospheric dust were taken on Whatman filters during two Atlantic cruises and from the Equatorial Atlantic; and mesh samples from Barbadoes were analyzed. The overall pattern of dust concentrations is consistent with the known strong Saharan plume at 10-15 deg N latitude and extends westward to the Caribbean with average concentrations in excess of 10 micrograms/cu m. From the Sr87/Sr86 ratios the dusts from the Saharan can be distinguished from a second plume, probably from the Kalahari Desert. The ratios of dusts in the Saharan plume are indistinguishable from deep-sea sediments in this latitude band. Adding Rb/Sr to the Sr-isotope ratios in an isochron plot, permits distinction between the dusts and deep-sea sediments east of the Mid-Atlantic Ridge, and from the sediments underlying the Saharan plume but west of the Ridge. It is concluded that, west of the Ridge, the eolian dust contribution to the sediments is strongly diluted by non-eolian sediment sources, confirming conclusions derived from sediment mineralogical data.