Late Cretaceous and Cainozoic bathyal Ostracoda from the Central Pacific (DSDP Site 463)

Cainozoic deep-sea ostracod assemblages from the summits of Mid-Pacific guy ots point to high levels of endemism possibly as a result of their bathymet ric separation from the surrounding sea floor. However, the interpretation of these fossil assemblages is hampered by the paucity of comparative mater ial from surrounding non-guyot sites. Fifteen ostracod assemblages from DSD P Site 463 (Late Cretaceous-Pleistocene) were studied to compare with those from nearby guyots. Three distinct faunal assemblages are recognised at Si te 463: Assemblage A (Maastrichtian-Eocene), Assemblage B (Oligocene-Upper Miocene) and Assemblage C (Upper Miocene-Pleistocene) although the palaeoen vironmental significance of these units is unclear. Sixty-two ostracod spec ies are identified, the thirteen most abundant are discussed in the taxonom ic section, five of which are described as new. Between 30 and 100% of the species encountered in each sample are considered as endemic to Site 463, w hile some of the remaining species were previously thought to be endemic to individual guyots. Similarly high levels of endemism on nearby guyots prob ably reflect an incomplete knowledge of deep-sea ostracod faunas rather tha n the establishment of geographically or bathymetrically restricted populat ions. The presence of globally pandemic and geographically widespread taxa on sites such as the Mid-Pacific Mountains, surrounded by abyssal depths wh ich lie below the CCD indicates that some faunal exchange or migration of o stracods does take place. This must be achieved within the intermediate wat ers and probably occurs passively. (C) 1999 Elsevier Science B.V. All right s reserved.