Late Eocene to Recent deep-sea benthic foraminifera from the Central equatorial Pacific Ocean

Many species are cosmopolitan and probably have wide environmental tolerances. Fluctuations in frequency of some taxa (e.g., Nuttallides umbonifera, Epistominella exigua, and Uvigerina spp.) cannot be correlated from one site to another. Several common species (e.g. Oridorsalis umbonatus and Globocassidulina subglobosa) range from late Eocene to Recent.

First and last appearances are generally difficult to define precisely because many species are rare. For some species these datums differ from one site to another, but several datum levels are within 1 m.y. at all sites. First and last appearances are most numerous in two intervals, the late Eocene to early Oligocene (about 32 to 37 Ma) and the early to middle Miocene (about 13 to 18.5 Ma).

Isotopic events occur within each of these periods of benthic faunal change, but the isotopic events have a shorter duration and start after the initiation of the changes in the fauna. Changes in deep-sea benthic faunal composition are not directly related to short-term oceanographic changes as expressed in isotopic records.