| Summary: | No page 69 Six distinct benthonic foraminiferal assemblages are recognized in the Dumont D'Urville Sea of Antarctica on the basis of the common occurrence and predominance of taxons. The distribution of calcareous and arenaceous faunal facies on the continental shelf coincides remarkably with the relative distribution of reworked glacial sediments and organic-rich biogenic muds. Surface productivity, seafloor topography, and bottom current velocities are thought to control the distribution of these biogenic muds, which are restricted to shelf depressions, and the surface sediments themselves are thought to control the relative distribution of arenaceous and calcareous populations on the shelf. Depth is a subsidiary factor in controlling faunal distributions on the continental shelf. A mixed calcareous and arenaceous fauna defines the contact of the lysocline with the continental slope, below which lies the oceanic CCD at 19m and a slope arenaceous fauna. Shelf assemblages are generally of low diversity, but high diversity populations underlie upwelling nutrient-rich plumes of modified Upper Circumpolar Deep Water, which have been injected along an isopycnal between underlying dense shelf water and overlying surface water. Benthonic foraminifera are therefore useful as indicators of hydrographic conditions, and models relating the distribution of high diversity standing crops of benthonic foraminifera to such upwelling plumes are discussed.
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