In contrast to Eocene and Oligocene radiolarian stratigraphy for low latitudes, which is well understood and documented in a number of deep-sea sequences (for details see Sanfilippo and Nigrini, 1995, 1998), few studies document late Paleogene radiolarians in middle and high southern latitudes. Deep Sea Drilling Project (DSDP) Leg 28 provided a good composite sequence of sediments for constructing a Neogene radiolarian biostratigraphy, to extend earlier Pliocene and Pleistocene zonations, and it was the first opportunity to examine Oligocene radiolarians from the Antarctic (Chen, 1975). The late Paleogene assemblages from DSDP Leg 28 were, as expected, found to be very different from low-latitude faunas, and Chen (1975) did not attempt to establish an Oligocene radiolarian zonation. During the last decade, our knowledge of southern high-latitude radiolarians has improved markedly. Reports of the sporadic presence of Paleogene radiolarians reported from early DSDP Legs 28, 29, 35, 36, and 71, combined with observations from more recent ODP legs, have shown that the Paleogene radiolarian fauna is different from that of the low latitudes, and a separate zonation was needed. ODP Legs 113 and 114 (in the south Atlantic) and Legs 119 and 120 (in the southern Indian Ocean) have provided sediment sequences containing well-preserved radiolarians useful for establishing a Paleogene biostratigraphy for this region. In addition, work on land-based sequences from the Eocene and Oligocene of New Zealand has resulted in integrated Paleogene biostratigraphies, including foraminifers, calcareous nannofossils, radiolarians, dinoflagellates, and palynomorphs (e.g., Strong et al., 1995; Hollis et al., 1997; O'Connor, 1999, 2000). Figure F2 provides a correlation of the tropical south Pacific, and Southern Ocean radiolarian zonations to the geochronometric timescale (for further details see Takemura and Ling, 1997; Hollis et al., 1997; O'Connor, 2000).
The goal of investigating the radiolarian assemblages from Site 1128 of ODP Leg 182 in the Great Australian Bight was to interpret the Oligocene and Eocene biostratigraphy where the calcareous microfossil record is too sparse for stratigraphic interpretation. The lack of southern high-latitude and tropical index species in Hole 1128C, however, has prevented biostratigraphic interpretation on the basis of previously published zonations of the lower Oligocene-lower Miocene sediments recovered from Sections 182-1128C-8H-1 through 26X-CC. This does not preclude future development of a zonal scheme from this intermediate latitude sub-Antarctic band as more comparable material becomes available.