Radiolarians vary in abundance from barren to common and are moderately diverse throughout the Oligocene and upper Eocene at Site 1128, suggesting bathyal water depths and high rates of biological productivity on the continental slope during the latest Paleogene. Tropical taxa (notably the genera Podocyrtis, Thyrsocyrtis, Lithocyclia, and Eucyrtidium) are nearly absent in the Australian Bight; whereas, actinommids, spongodiscids, porodiscids, litheliids, and cornutellids, considered the major component of high- to midlatitude faunas, predominate. The marker species for the Paleogene Southern Ocean are mostly absent. The concurrent presence of Aphetocyrtis rossi, Eucyrtidium spinosum, Lophocyrtis (Paralampterium) dumitricai, Periphaena decora, P. heliastericus, and Prunopyle hayesi indicate that the age represented in Samples 182-1128C-9H-1, 25-27 cm (74.75 mbsf), to 26X-CC, 20-22 cm (240.21 mbsf), is Oligocene, approximately equivalent to the Axoprunum (?)irregularis to Eucyrtidium spinosum Zones in the sense of Takemura and Ling (1997) and Hollis et al. (1997). The Oligocene/Miocene and Eocene/Oligocene boundaries cannot be placed using radiolarians.