Abundance ofBulimina exilis andMelonis barleeanum: Relationship to the quality of marine organic matter

Studies on diatoms showed that locations of Mauritanian coastal upwellings during the last glacial and deglaciation epochs were More westerly than present-day sites, i.e., off the continental shelf, rather than nearshore. Benthic foraminifera revealed a stratigraphic coverage from the present to the last glacial maximum (0 to 18000 yrs BP). Factor analysis produced four factor assemblages that account for 95.4 percent of the variance. Two factors are dominated by eitherBulimina exilis orMelonis barleeanum. The quantitative stratigraphic distribution of these two deep-sea species is related to the quality of marine organic matter derived from surface upwellings.B. exilis develops only when organic matter reaching the bottom is relatively unchanged;M. barleeanum prefers organic matter in a more altered form.