Middle Eocene to early Pliocene Bolboforma from the Kerguelen Plateau

Bolboforma were recovered from all sites of Ocean Drilling Program (ODP) Leg 120 to the Central Kerguelen Plateau in the southern Indian Ocean. Eight Paleogene taxa, ranging from middle Eocene through early Oligocene, and nine Neogene taxa, ranging from late middle Miocene through earliest Pliocene, were recognized. A Bolboforma zonation recently proposed for the middle Paleogene of the Leg 114 sites from the southern Atlantic Ocean is applicable to the Leg 120 material from the southern Indian Ocean. The age of zonal boundaries is consistent within a resolution of +/- 1 m.y. The ranges of some marker species have been extended, causing a redefinition of some late Eocene zonal boundaries. The revised zonal scheme agrees well with the Paleogene occurrence of Bolboforma species from the Leg 113 sites in the eastern Weddell Sea. This and the consistent presence of Bolboforma in Paleogene cores from the Antarctic ODP legs promise that Bolboforma stratigraphy will become a useful tool for the subdivision of sequences across the Eocene/Oligocene boundary from southern high latitudes. The stratigraphic subdivision of the Miocene and Pliocene based on a Neogene Bolboforma zonation from the Norwegian Sea proved to be difficult and of limited stratigraphic value for the Leg 120 sites