Response of deep-sea ostracod assemblages to Late Cretaceous palaeoceanographical changes: ODP Site 689 in the Southern Ocean

Twenty-six deep-sea ostracod species are described from the late Campanian to late Maastrichtian of ODP Site 689 in the Southern Ocean. Three are desc ribed as new: Cytherelloidea megaspirocostata, Agulhasina sudoceanica and P ennyella foveolata. Correspondence analysis identified three faunal sample groups. The first is mainly characterised by A. sudoceanica, Krithe sp. and Cytherella sp. This is replaced, first temporarily (between c. 71 and 69 M a) by a group mainly characterised by Argilloecia spp. and C. megaspirocost ata, possibly a consequence of a short-lived global palaeoceanographic even t marked by increased ventilation and cooling of intermediate waters at Sit e 689. It then reappears before finally being replaced by a third group lar gely characterised by Eucythere cf. circumcostata, P. foveolata and Dutoite lla minica Dingle. This final change is coeval with a marked increase in th e faunal density of ostracods, probably owing to an increase in food supply . However, the oxygen isotopic records of benthonic foraminifera suggests t hat the replacement of the first ostracod group by the third is a result of the long term Maastrichtian cooling of intermediate waters at high latitud es. This replacement is also coeval with a gradual change in benthonic fora miniferal assemblages at Site 689. It is suggested, therefore, that Pennyel la and Dutoitella had a greater potential of adapting to successively colde r palaeoceanographical conditions than Aguihasina. The former genera have a cosmopolitan deep-sea distribution today. (C) 1998 Academic Press Limited.