Late Cretaceous ostracods recorded from ODP Hole 113-689B

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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 described as new: Cytherelloidea megaspirocostata, Agulhasina sudoceanica and Pennyella foveolata. Correspondence analysis identified three faunal sample groups. The first is mainly characterised by A. sudoceanica, Kirthe sp. and Cytherella sp. This is replaced, first temporarily (between c. 71 and 69 Ma) by a group mainly characterised by Argilloecia spp. and C. megaspirocostata, possibly a consequence of a short-lived global palaeoceanographic event marked by increased ventilation and cooling of intermediate waters at site 689. It then reappears before finally being replaced by a third group largely characterised by Eucythere cf. circumcostata, P. foveolataand Dutoitella mimica Dingle. This final change is coeval with a marked increase in the faunal density of ostracods, probably owing to an increase in food supply. However, the oxygen isotopic records of benthonic foraminifera suggests that the replacement of the first ostracod group by the third is a result of the long term Maastrichtian cooling of intermediate waters at high latitudes. This replacement is also coeval with a gradual change in benthonic foraminiferal assemblages at site 689. It is suggested, therefore, that Pennyella and Dutoitella had a greater potential of adapting to successively colder palaeoceanographical conditions than Agulhasina. The former genera have a cosmopolitan deep-sea distribution today.

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