Biometric analysis of Eocene and Oligocene calcareous nannofossils

Four Eocene to Oligocene calcareous nannofossil species groups were analyzed biometrically from DSDP and ODP Sites 366, 549, 558, 563, 628, 647, and 748. Integrated biostratigraphic and magnetostratigraphic data established the age of each sample in order to compare biometrically established events between sites.; Principal Component Analysis (PCA) and Discriminant Function Analysis (DFA) of Cyclicargolithus shows that no significant differences in shape occur with changes in size, age, or latitude. Size increases are asynchronous between sites, and are not biostratigraphically useful within the Oligocene. All species of Cyclicargolithus are synonymized with C. pseudogammation n. comb.; Development of a large sized (mean {dollar}>{dollar}11 um) population of the Reticulofenestra umbilica/R. hillae group occurred between 45.0 and 42.8 Ma in three sites. The first occurrence of specimens {dollar}>{dollar}14 um in size is highly asynchronous and not biostratigraphically useful. A continuum between large and small holed forms indicates that R. hillae should be considered as a forma of R. umbilica. This forma is more abundant in the uppermost Eocene to lower Oligocene.; Principal Components Analysis of the Reticulofenestra bisecta complex revealed an overall gradual size increase from middle Eocene to Oligocene, and a rapid increase in hole size beginning in early Oligocene in high latitudes. R. bisecta subsp. filewiczii is synonymized with R. bisecta subsp. lockeri n. stat., and R. scrippsae is synonymized with R. bisecta.; Principal Components Analysis of the Chiasmolithus expansus/C. oamaruensis/C. altus lineage revealed large fluctuations in the width of the central 'X' structure from upper middle Eocene to Oligocene, possibly related to changes in water masses. The narrowing of the 'X' is due mainly to narrowing of the central bar connecting the cross bars of the 'X'. A trend towards smaller relative hole sizes occurred from the Eocene to Oligocene. Both C. oamaruensis and C. altus may have evolved from C. expansus in the upper middle to lower upper Eocene. End-member forms were geographically separated, with transitional forms occurring between them through the lower Oligocene. C. altus may be a colder water form than C. oamaruensis.