From the study of the ostracodes of Sites 516, 517, and 518 in comparison with those of Sites 21, 22, and 357, we can show that a time lag (early to late Oliogene) existed between the formation of the deep water masses (mid-bathyal ± 2000 m) and those of intermediate depths (upper bathyal ± 1000 m). The ostracode faunas suggest that while the Antarctic Intermediate Water (O2 = 4.5 to 5 ml/l) was flowing through the Vema Trough to fill the northern basins, the returning less-dense, warmer water (O2 = 3.5 to 5 ml/l) originating in Tethys was being gradually displaced upslope. Efforts to identify shallow (less than 200 m) faunas were unsuccessful. No evidence of significant changes in paleodepth or close proximity to islands could be found that could not be better explained by water-mass changes. Studies of the genera Poseidonamicus and Krithe suggest an important water mass change at about 14 Ma (late-middle Miocene), but the cause of this event is not yet understood.

? = species uncertain.

Supplement to: Benson, Richard H; Peypouquet, Jean Pierre (1983): The upper and mid-bathyal Cenozoic ostracode faunas of the Rio Grande Rise found on Leg 72 Deep Sea Drilling Project. In: Barker, PF; Carlson, RL; Johnson, DA; et al. (eds.), Initial Reports of the Deep Sea Drilling Project (U.S. Govt. Printing Office), 72, 805-818