On the benthonic bathyal-zone foraminifera as stratigraphic guide fossils

A study of benthonic foraminifera in 837 samples from the U Cenozoic deposits of 9 DSDP holes located in the middle bathyal zone of the S Atlantic, S Pacific and Indian Oceans revealed that the Oligocene and Quaternary assemblages consist of nearly all the same species. These species do not show any important morphological changes. This means that the Quaternary fauna developed not later than the Oligocene. Late Cenozoic benthonic foraminiferal assemblages contain, in total, more than 400 taxa; however, less than 5% of them can be used as stratigraphic guide fossils and even those with some reservations