The relative abundances of 18 selected taxonomic groups of Radiolaria were determined for 145 trigger-weight core-top samples collected between long 80°E and 55°W and lat 35°S and 60°S. Seventy-two samples were considered to represent nonreworked recent sediments. A factor analysis of these 72 samples resolved Antarctic, subantarctic, and subtropical assemblages, with distributions closely corresponding to the main surface water masses in the area.
Using the technique of Imbrie and Kipp, paleoecologic equations have been developed to estimate surface-water temperatures for August (winter) and February (summer). Estimated temperatures range from near 20°C in the northern parts of the area to 0°C at the location of the southernmost cores. The standard error of estimate of the equations is less than 1.5°C. The CaCO3 content of the 145 surface-sediment samples shows that variations in the calcite compensation depth (CCD) for locations north of the Antarctic Polar Front depends mainly on varying dissolution. The CCD is about 4,800 m in the western basin of the Atlantic Ocean but is deeper than 5,200 m, at least locally, in the Indian Ocean. South of the Antarctic Polar Front the CCD is shallower than 3,700 m.
Radiolaria are common in most samples, with the maximum number per gram of sediment being found in samples collected near or beneath the Antarctic Polar Front.