Radiolaria and diatom stratigraphy of ODP Hole 182-1128C sediments

Eocene and Oligocene radiolarians were recovered from Site 1128 on the slope of the upper continental rise during Ocean Drilling Program (ODP) Leg 182 in the Australian Bight. The early Oligocene radiolarians cored at Site 1128 vary considerably in abundance and preservation. Many intervals are barren or contain only rare fragments of radiolarians. Early Oligocene assemblages are dominated by sponge spicules and diatoms, similar to faunas of modern cold temperate shelf waters, and age diagnostic radiolarians useful for stratigraphic determination are rare. The interval is characterized by abundant actinommids and a dominance of robust artostrobiids representing the genus Siphocampe. In contrast, tropical taxa are present sporadically in rare abundance in the Eocene sediments. The radiolarian assemblages from the Eocene-Oligocene sequence at Site 1128 lack zonal marker species reported from regions further south or north, and thus, age estimates cannot be made using previously published zonations. However, the presence of diverse and well-preserved radiolarians in these assemblages indicates that it should be possible to establish a zonation for this intermediate latitude sub-Antarctic region as more comparable material becomes available. […]