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Source Areas and Transport Mechanisms for Freshwater and Brackish-Water Diatoms Deposited in Pelagic Sediments of the Equatorial Atlantic 1

  • Edward M. Pokras (a1)

Distributions of freshwater and brackish-water diatoms from dust samples and modern sediments of the equatorial Atlantic demonstrate different transport mechanisms and source areas. Both Melosira spp. and Stephanodiscus spp. are transported via winds from the southern Sahara and Sahel in Northern Hemisphere winter. The core-top distribution of Cyclotella striata delineates the extent of the low-salinity plume formed by runoff from the Zaire River into the extreme eastern Atlantic. The transport mechanism and source areas for Melosira spp. during arid phases have not changed appreciably in the last 130,000 yr. There is no evidence for long-distance transport of freshwater diatoms by the southeast trade winds. This study confirms the validity of paleoclimatic research which inferred eolian transport of Melosira spp. in the winter dust plume from source regions north of the equator, although fluviatile input of Melosira valves into nearshore sediments cannot be ruled out.

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Lamont-Doherty Geological Observatory, Contribution No. 4698.

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Quaternary Research
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